www.UsHumans.net
The Story of Us Humans,
From Atoms to Today's Civilization
Robert Dalling
For my parents, family, friends, and community and the comprehendible fortune of being a certain collection of molecules, with certain ways, for a few decades.
Part One
How and when the universe and the Earth began
Scientists measure everything from motion to society, even love
Newton's motion equation, and the gravitational force
The electric force and light waves
Chapter 3
How and when the Universe began
Measuring the distance, speed, and chemical composition of stars
Gravitational formation of stars and planets
How and when atoms first formed
Star formation and stellar fusion
Chapter 4
How and when the Earth began, and the effects of its moving continents on life
Initial formation of the Earth
Moving tectonic plates and the factors that affect climate
Liquids and gasses in the development of life on Earth
Part Two
The nature of a human
Electrical binding in atoms is the physical basis of the molecules of life
DNA naturally duplicates itself
DNA naturally builds and operates entire individuals
Science, living matter, and religion
The sequence of life forms that have evolved on the Earth
Chapter 6
The emergence of humans
The transition to the human variety of ape
Food packet size determines social size
Behaviors associated with mating
Chapter 8
Primate social systems, and the origins of our emotions, morals, and language
Social system of nonprimate mammals
Complex social systems promote bigger brains, sympathy, empathy, and self-awareness
The social systems of common chimpanzees and Bonobos
What do these primate social systems tell us about ourselves?
Matrilineages, patrilineages, and cross-cousin marriages
Scientific studies of language ability in apes
Origin and purpose of our feelings and emotions
Origin and purpose of our morals
Chapter 9
The gatherer-hunter way of life, and some cultural details of the Canela Indians of Brazil
Food getting, and agricultural ceremonies
Shaman cure, but witchcraft causes misfortune
Part Three
Origin and development of religion, government and civilization
Chapter 10
The religion of gatherer-hunter peoples: the power in the bush
Deities and the power in the bush
Chapter 11
Human Political Forms: bands, tribes, chiefdoms, and states
Ranked and socially stratified society
Chapter 12
The origin of farming, cities, and civilization
Plant and animal domestication
Farming villages and irrigation
King and queen, palace, and government
Invention of war: by the leader, for the leader
Our modern religions of moral behaviors
Some views of the people of the Hindu faith
Some views of those of us humans who are Christian
Some views of those of us humans who are Buddhists
People who are humanists celebrate humanity
Chapter 14
Our civilization, from ancient to modern
Astronomy, mathematics, and reading tea-leaves
The Ancient Greeks present our first explanations of nature not given in terms of deities
Confucian respect for helpful elders binds families, society, and government
Emperor, administration, and a bureaucratic system based on merit
Religious festivals, deities, and the ancestor cult
Bathing, cosmetics, and clothing
Servants, laborers, and peddlers
State monopolies, taxes, and currency
Old age, death, and inheritance
Holidays, entertainment, and clothing
The feudal and manorial system, the Baron’s revolt and Magna Carta, and the peasant’s revolt
Growing wool industry expands trade
Europeans inherit knowledge expanded in Islamic lands
Our ideas for specific liberties resulting from specific injustices
Worth of individuals over states
Government by and for the people
Balancing the spread powers of government
Constitution of the United States
Numerous travelers talk of other cultures
Social affects of factory life
Colonial beginnings and immigrants from the world
Rapid westward expansion of twenty miles per year
Social and economic classes and enslaved people
Food, food-storing, and cooking
Families bartered goods at the General Store
Agricultural and social events
Mutually beneficial exchange of help among community members
Mining, ore processing, and blacksmithing
Lead, tin, pewter, copper, brass and silver working
English mechanics were sought to build the first U.S. factories
Debate of benefits and drawbacks of industrialization
Debate over the role of government in any coming industrialization
Production techniques mixed as industrialization requires power and decades to mature
No employees exist for the first factories
Corporations for pooling business funds
Lowell mills operated by northeastern girls, then immigrants
Factory clothing replaces homemade
Handmade shoes and instruments
Varieties of products fill our homes
The South chooses to remain agricultural
Many of us factory workers struggle to earn money for bread and rent
Interrelated elements of the economy
Exchanges and occupations change
Peddlers, freight haulers, and entertainers
Canals transport people and goods between east and west
Cities and industry grow and spread Westward
Industrialization, urbanization, and commercialization
Labor strikes of the 1880s and 1890s
The role of government and courts in industrialization
When a nation chooses to industrialize today
Movies, sports, and other entertainment
Part Four
Today's society, business, and government
Chapter 17
The computer and its uses
Chapter 18
Today's global business
Global corporations from Europe, Japan, and the U.S.
Global manufacturing blurs imports and exports
Political power of global corporations
Global corporations and governing one's national economy
Global corporations search the world for the cheapest labor
Products of global corporations sold mostly to people within the richest nations
Entertainment, book, news, and record businesses
Electrically measuring customer and voter emotions
Monitoring and analyzing each customer's purchases
Today's worldwide migration of 75 million job-seekers per year
Franchises and preferential agreements between corporations
Global products but not global culture
Globalization is not yet global
Governing global corporations with independent, sovereign nations
Reasons for a people to change their political leadership
Authoritarian governments of Eastern Europe from 1945-1989
Taiwan's conversion from authoritarian to democratic government
African government before, during, and after independence
Guiding principles for U.S. foreign policy
A global, democratic assembly of democratic nations
Chapter 20
How Washington shares power today
Branches of government in the U.S.
Political power and legislation through consensus-building, exchanges, and pressure
The president can set the agenda
Abuse of presidential power and legislative reactions
Congress and its recent further spreading of power, and the power of congressional staff
Role of television and marketing in politics
Campaign marketing, and the talents needed to campaign compared with those needed to govern
Lobbies, political action committees, and issue marketing
Chapter 21
Today's big-city way of life for two boys in Chicago
Chapter 22
The science of government through measurements of the success of government's efforts
Some specific social health indicators
Rates of child neglect and abuse
Putting the indicators to work measuring the success of our efforts to govern
National and global surveys of social-health indicators
Social and economic indicators in the daily news
Importance of social-health indicators
Well-being and the quality of life in the past
Acknowledgments
A special thanks to the students of the Maine School of Science and Mathematics for improving the text. I want to thank Megan Gill for creating the artwork of the cover. Humans enjoy making and experiencing art; it’s one of the things we do.
Ralph Linton's 1932 description of the global diffusion of techniques and inventions is quoted below. What has taken me five hundred pages to say, Dr. Linton accomplished in about five hundred words. I thank John Azer of Normandale Community College for bringing Dr. Linton's article to my attention.
This book consists of nothing but summaries of other books written by experts describing their own fields (their books are listed in the chapter sources). Each of these books provides a portion of our story and is simply combined here to give a glimpse of the whole at once. Reading this book is an incomplete shortcut to reading fifty or so of the books that these specialists have written.
The facts presented in this book have been taken directly from these other books. I have not created any of the understandings presented here, I simply serve the role of the reporter–except that this book is a less accurate summary of the material presented by these experts. As I remove the technical terms from the writings of these experts, I am also removing the precise meaning of their statements. The authors have very clearly presented their fields of study. I apologize to them now for not presenting their understandings as well, or as accurately, as they had earlier expressed them. I decided that it would not be appropriate in this book to quote the page numbers from which each fact has been taken because every sentence here would then have such a reference. I have instead acknowledged sources within the text of the paragraphs. It is hoped that the reader will become interested in reading some of their books in order to gain a more complete understanding of the story of all of us humans.
I insert occasional paragraphs to emphasize the human aspect of these facts. Whenever I have done this, I have tried to make it obvious that the statement contains my own interpretation. I am sure those summarized specialists will not want anyone thinking that they had made such a silly statement. In such cases, I often state that the sentence contains my own guess about a possible detail of life by using the phrase "I can guess." The reader is encouraged to make further studies to increase the details of the existing facts. At best, my wrong guesses may serve the purpose of spurring further discussion. The discussion needs your investigations and contributions, too.
In addition, these authors have shown that they are wiser than I am by sticking to their own field. They know that persons who write about subjects not within their own specialty always make fools of themselves. But it is also true that nonspecialists have no career to risk and are free to rush into areas that the specialist avoids. This means that I am more free to state silly guesses, hoping to spur debate among the readers.
You might like to visit www.UsHumans.net to download the latest internet version of this text.
Robert Dalling,
January 2007
Namaste. As my friends Prem and Raz say, the humanness in me greets the humanness in you. This is the story of us humans: we’ll discuss how we got here, what we are, and where we are today. Knowing something about what we are and where we've been helps us choose where next to take our civilization. An outline of this story is presented through brief descriptions of the natural universe, the nature of a human, human culture, and the flow of civilization. I'll describe the stepping stones of our development including the beginning of the universe, the formation of the Earth and its sequence of plants and animals, including parenting mammals, social primates, and then cultural humans with our three ways of life–gathering-hunting, farming, and wage-earning–and our civilization of farming, cities, business, religion, and government. This book contains a description of the emotions and behaviors of us parenting and social humans and a description of the origin, development, and current ways of our neighborhoods, religion, government, science, and business because these things form the largest aspects of our lives, our history, and our future. This book contains a summary of our understanding of nature, of our own nature, and of our societies, history, and civilization. An improved understanding of the natural universe and of the nature of a human leads to more accurate notions of what it means to be human and of our own place in the universe. We can then see that our religions, governments, and other institutions are necessarily matched to our own human nature and we can then see that the goals we are choosing for our 10,00-year-old human civilization are becoming increasingly matched to the nature of a human.
This book is a celebration of the peoples of the Earth and tries to be about all of the humans of the world. Humanity consists of 10,000 cultures, past and present, see http://en.wikipedia.org/wiki/List_of_ethnic_groups, but we have had just three basic ways of life: gatherer-hunters, farmers, and wage-earners. The ways of representative people from each of these three lifestyles will be described to illustrate our nature, our idea of civilization, and something of the flow of civilization through its 10,000-year development. For brevity, the peoples of just a handful of representative times and places of the world receive a detailed description. I'll describe the way of life of a group of gatherer-hunters because we humans lived this way for millions of years–with incremental changes that made this lifestyle increasingly sophisticated. We are biologically prepared to be gatherer-hunters and to live in small social groups of a few nuclear and extended families. For most of our past we have lived in groups of twenty to one or two hundred persons, and we knew each of those persons well enough to be able to predict their behavior. (It is no coincidence that still today, this is the number of persons that we can know that well.) These groups would include a handful of unrelated, extended families. Neighboring groups frequently met to hold ceremonies and such; we often first met our spouse during such a meeting. For millions of years our way of life did not fundamentally change until we became full-time farmers about 10,000 years ago. For this reason, I'll describe the first farmers and city-builders of Ancient Mesopotamia. We’ll look at the democracy and rational thought of Ancient Athens and then the ways of Medieval China and Europe. Nothing about today's neighborhoods, business, or government makes any sense until we understand the social changes that occur as a people switch from working their own family farms to working in factories. As an example of this transition, we'll look closely at the changing way of life for the people of the United States in the early nineteenth century.
People everywhere, and at all times in the past, have asked the following questions. How and when did the world begin? Where did we come from? How did we learn to make tools, use fire, grow crops, build homes, and find and prepare food? How did we learn to perform the ceremonies and rituals for births, weddings, cures, and deaths? These things make up our daily life. For each aspect of our daily life we have had a creation myth that explains its origin. Each group of persons have had their own collection of unique myths. These colorful myths have been handed down and modified through the generations. They are accepted as sacred truths and form the basis of our oldest religions. In past centuries, as our children became old enough to ask about our origins we would teach them those mythical stories. Lehmann explains that these myths give meaning to a people and satisfy certain basic emotional needs for security in an insecure world of mysterious phenomena, food collecting needs, illness, enemies, and death.
More recently, we have come to understand much of the workings of nature and have developed a more accurate picture of our origins. This emerging picture turns out to be much more incredible than any of the myths that our imaginations had produced in the past and is the subject of this book. Through our own efforts, we now have a general understanding of how we got here: from the beginning of the universe and the formation of atoms–including the atoms inside your body at this very moment–to the formation of the Earth with its moving continents, changing climates, and liquid seas leading to life forms (little molecule machines) changing through time in order to remain matched to their surrounding but ever changing environment of climate, predators, and food. We now understand much of our own nature and much of our own history.
In the last five hundred years, but especially in the last one hundred years, tens of thousands of scientists have spent their entire lifetimes measuring literally billions of facts about millions of natural phenomena. (Whenever you hear the word "science" you should think of "facts and understandings learned from repeatable measurements.") As each new fact is found, it is shared with everyone on the planet by being recorded in one of the scientific magazines–for example, the Philosophical Transactions of the Royal Society of London began publication in 1665, see www.bodley.ox.ac.uk/ilej for on-line copies. Today’s scientific and technological knowledge consists of all of the facts that have been gathered by all of the people of the world along with the sum of all the procedures that all of the world's people have developed. This book consists of a summary of just those facts that have been found to be directly related to the development of humans and of human civilization. Our entire story is explained in this report through nine thousand ideas or paragraphs consisting of about 27,000 facts or sentences.
At first those millions of studied phenomena seemed to be unrelated but they are now understood to be different aspects of a few more-fundamental phenomena and are explained by just a few laws of nature. In fact, there may be just one law of nature. It will be explained below how all physical phenomena may be described by a single law of nature and how this law also governs the chemical and biological processes that occur within the atoms of our bodies. We have begun to see the simple underlying principles of nature and have begun to understand the nature of our own past.
What is our own nature? We find that people everywhere and at all times of the past are the same in that we simply want to care for our children and spouse, the members of our extended family, our friends and neighbors, and for our community and its health. That is, we just want to laugh and joke with our spouse, family, friends and neighbors, pursue life and the limits of our talents, and raise children. We live in social groups glued together by our innate agreement to do as the other did. In practice, this occurs as we exchange help to accomplish most any daily task deemed larger than can be handled by the efforts of one individual. We expect our society to be mutually beneficial for all of us and we will react against any unfairness or injustice in any interaction within our community. We live for our children. We gauge success in life in terms of healthy and happy children and communities. What is a human? Most every thought or action of every human involves his or her children, spouse, family, community, and justice. That’s about all there is to us.
We better understand our own nature by considering those things that we are able do without having to first think about them. We do not have to decide that these are things we want to do, we just do them. We realize the core nature of a human by noticing the things that come naturally to us without having to first struggle learning to perform them. One purpose of this book is to give you a chance to think carefully about what is a human. Can you think of any things that are as important to you as are your children, extended family, friends, community, and justice? You might like to stop now and make a list of the most important things in your life. You might also like to list those things you find are effortlessly accomplished. The largest elements of our naturally evolved heritage are most apparent while doing those activities found to be the most effortless to do, and so they are also those activities being the most taken for granted, from breathing to the production and comprehension of speech. (While traveling in foreign countries, I’m amazed at the rapid rate at which one person produces strange sounds and another person comprehends them.) We effortlessly notice social incidents, including things like the sudden increase in time that two particular persons are spending together or simply the simultaneous absence of two particular individuals. Without any mental concentration, such as that needed to arithmetically divide two numbers, you know how far each member of your extended family and group will go for you, how far you will go for each of them, and how much each person will let you get away with. While you and another person are interacting as a pair of individuals, we know how the presence of any third person will change that interaction and how that change differs for each specific third person. We readily notice when we are in danger of being socially swindled by other persons. We are uplifted when singing at the top of our lungs. We are happiest when our family and group members are happiest and when we have their approval. We effortlessly recognize a face or learn a new geographic layout. We observe the details of the natural world around us, including such things as plant cycles and animal behaviors. Beginning a few million years ago, our intelligence enabled us to be successful gatherer-hunters. While other animals hunt with their feet and teeth, we find exploitable behaviors in our prey. We don’t hunt by simply wandering a field while carrying a club and hoping to come across an animal; we notice the exploitable behaviors of the animal residents of our neighborhood and continue to take a portion of their population. In the example of the animal harvesting tactics of the Amahuaca hunter given in Chapter 8, we’ll see how our brains have evolved to readily notice the exploitable behaviors of other animals. (“Harvesting,”not hunting, may be a more accurate description of our food-getting technique, making the term harvester more accurate than the term hunter-gatherer.)
Whenever unequipped for the task at hand, we naturally look around for something to fashion into a tool. We create a tool for every need, and each new tool invented means that our way of life has changed a little. Our first tools were sticks and stones. Later on, we modified rocks to cut, poke, and scrape. Since then, farming and industrialization have been our two most life-altering tools. As the human species spread throughout the world, nomads became sedentary and began obtaining a small portion of their food by planting seeds around their home. It takes considerable knowledge of plants for farmers to successfully live off their cultivated plants, as we began to do some 10,000 years ago. We’ll see that it took a few thousand years for farming to spread around the planet and that it has taken the last two hundred and fifty years for industrialization to spread throughout much of the planet. The knowledge and use of each newly invented tool quickly spreads around the planet to everyone else experiencing a need for that solution. Today’s science and technology is the combined sum of all the facts, tools, and procedures ever discovered or invented by anyone throughout the planet. What will be our next life-altering tool?
We form a community or society because of the unspoken certainty we have that the mutually beneficial exchange of help makes for a better life than going it alone; it is unspoken because it is innate. We don't have to think about it first and then decide to be a member of society: this is what we do naturally. Today, our society is beginning to include everyone on the planet in a single group. Our global civilization is another name for our most inclusive society.
We all agree about the proper behavior between the family, friends, and neighbors forming our society. This proper behavior is often described as the predisposition to do as the other did and to expect the other to do what you did (as we'll see is explained by De Waal). This agreement is synonymous with our primate social system because it is the social glue that creates that system. It is no accident that it forms the basis of the major religions of today's groups of millions of persons. You might like to stop now and describe the most important elements of "proper behavior" and then compare your description with that from each of several other persons.
There are also fascinating differences in the details of the ways of life (the culture) of each group of persons. We want to put ourselves in the place of our past ancestors, and we want to learn something of the way of life of our fellow humans. We will meet a few groups of persons in this book. When we understand the ways of others then we better understand the uniqueness and arbitrariness of our own ways. We can then begin to see our own culture from the eyes of an outsider and gain more respect for ourselves and for all other humans. It has been said that the best hope for humanity is a respect for humanity along with a belief in the fundamental good of each human. In the coming chapters we will see how "good behavior" simply means the behavior that is common to all of us because of our common humanness. “Bad behavior” is that which is uncommon or aberrant. (Notice that one bad person can kill ten others: If we were all bad by nature then our species would not be here.) Good behavior falls in the middle of a bell-shaped occurrence curve, while bad behavior falls on the edges–no matter the species.
There are two points to this book: first, to understand how humans are a natural result of the simple, fundamental workings of nature, and second, to see that our civilization is an extension of human nature. Together, we control every aspect of our mutual civilization. It is built by us and will be anything we choose to make of it. We choose first to make of it a tool to care for our children. (This is not yet fully the case because of our being occasionally sidetracked into less meaningful pursuits benefitting fewer of us.) Understanding our own nature, along with something about the flow of civilization, helps us form a more clear idea of our place in the universe and helps us to together choose where next to take our civilization by choosing goals that best match our own nature. Civilization is our mutual collection of tools and procedures meant not only to make life better for all of us but to better-enable us to pursue the limits of human potential. What do you want out of life? How do you gauge success in life, and what priorities and goals do you have for your own life and for your community, nation, and planet-wide civilization? How should we measure the success of our attempts to reach these goals? Our children should be continually asked to think about what they want out of life and what they feel are meaningful priorities and goals for themselves and for the mutual efforts of our civilization. You might like to write down your answers to these questions and discuss them with your family and friends. In fact, we might like for each of us to periodically submit answers to be combined into a public report to help prioritize our goals. (Today, a small computer has the capacity to do such a chore as this.) Democracy works best with such public debate. Most everyone agrees that, first of all, we want healthy and happy children and communities. About 10,000 years ago, people's farming practices allowed population increases that led to cities, states, and our civilization. The combined efforts of all of us humans have produced our rapidly developing civilization (which has also been our tool for organizing numbers of us greater than our innate band of twenty to one or two hundred persons). It is an increasingly larger-scale, social community. Nature made us human and made us able to form culture and civilization but it has less control over the details of the culture or civilization that results; that is up to us. The only limits on our choice occur because we cannot act outside our own nature. Our current civilization includes the ideas of history, mathematics, science, technology, the factory, business, economic and social justice, and government that protects our liberty. What sorts of changes will occur in our civilization in the coming decades and centuries and which goals will we choose for it? Together, we will choose our future.
We will see that, at any time or in any place around the planet, whenever hundreds of us humans get together to form a tribe or chiefdom we will build structures like earthen mounds, irrigation systems, and stone monuments. One of the first things such a group of people will do is to try to find how big a rock they can carve or move or how large a mound of earth they can create. Whenever tens of thousands of us get together we build temples, palaces, cities, and city-states. The earth and rock structures we build express our inner drives and our inner view of the world. During construction, each person within the group typically spends one week per month working on these structures. After finishing these structures we all stand back and admire our accomplishment. What can billions of us build? Make a list. Discuss your list with others. What are we now building?
The following snapshot of today's understanding of nature and of the nature of a human begins with a description of the underlying physics of the atoms of biology and then proceeds with a discussion of our own biological ancestry and development. We'll especially compare the characteristics and behaviors of humans, primates, and mammals. As we begin to see the differences and similarities between ourselves and these other animals we gain a more accurate idea of what we are–and also what are our family, religion, and civilization.
In this book, we will look at what astronomy, physics, geology, biology, chemistry, anthropology, history, religion, social science, and political science tell us about ourselves. This is a summary of everything in our world, including the history of civilization. The origins, history, and current ways of our neighborhoods, government, business, science, technology, and religions is described so that we can better understand today’s world. We begin the story of our origins with the observations that astronomers have made about the origin of the universe, the formation of molecules, and the formation of the Earth. A summary is given of the geologist's understanding of the Earth's moving continents and changing climates, the biologist's findings concerning the origin and evolution–from molecular forms to mammals–of life on Earth, and of the anthropologist's story of the evolution of primates and humans. The behaviors of mammals and of primates are described so that we have a better picture of the similarities and differences between us and these other animals. We will look closely at the origins of our emotions and at our increased intelligence and language abilities, and we will look closely at the way of life of people at representative times and places around the world. Onto these things, we’ll add some history.
The first two chapters of this book contain a description of science and of the scientific method. We want to know about science because much of our understanding of our nature has been obtained through its approach, results, and conclusions. We will also discuss the way in which many seemingly unrelated phenomena are described by a single law of nature. This helps us to see how each fundamental aspect of nature is simple and that each complicated end product–for example, a human–consists of a large number of these more-simple underlying phenomena. I will often point out the tremendous number of facts accumulated by our scientific studies. You will then know that when a scientist states a conclusion–for example, that the Earth's continents are slowly moving around the surface of the planet–that it is based on the results of millions of observations and measurements. It is not merely a statement that scientists think would be neat if it were found to be true. After the discussion of science, the remaining sequence of chapters is arranged to follow the historical order of the events of our past.
The evolution of living matter began with the first self-duplicating molecule. Life consists of collections of molecules that naturally operate and duplicate themselves and that also produce the sequence of chemicals that grow an entire individual out of its surrounding and ingested chemicals. Life grew from an initially-molecular size. For a few billion years, the molecules of life increased in length at a rate of about one additional atom per year. (By the way, in the United States–and in this book, too–the number "one thousand-million" is referred to as "one billion," while in England the term billion refers instead to one million-million.) Bacteria were the first single-celled organisms to develop and are too small to be seen without a microscope; soon after they first developed, the size of living creatures grew rapidly. The sequence of stepping-stone animal forms that have developed in the last 750 million years includes non-boned invertebrates with eyes and a sense of touch, fish with bony skeletons and hearts and brains, amphibians who left the oceans for the land, egg-laying reptiles, parenting mammals, social primates who cooperate as extended families, and then us humans with our increased language and culture, and our civilization.
We will see that we naturally have the feelings and emotions to go with our animal, mammal, primate, and human heritage; our biological heritage includes each of these elements. Many of our behaviors are common to all mammals or to all primates. We are mammals with a monogamous parenting strategy and a nuclear family. Again, we live for our children. We are social primates who care first for our extended family and then for the other members of our society, and we care for our society. We are aware of who is related to whom and which persons are the friends of which others. Both parenting and the extended family form a large part of being human, as do our senses and emotions. We humans are naturally equipped with the feelings, behaviors, emotions, and morals to go with our animal, parenting, extended family, and social ways. These things form the core of what it is to be human. We'll also see how they necessarily form the core of our religion and government.
Today, most of us live in a city and do not understand the cultures of the rest of the world's people–even the culture of our great-grandparents can be mysterious. Though culture changes every one hundred years and every one hundred miles (160 km), we'll look closely at the way of daily life for a just few of our past times and places. We’ll look at illustrative, specific groups of gatherer-hunters, village farmers, and factory workers, including the Amazonian Canela, the Ancient Mesopotamians, the democrats of Ancient Athens, the Medieval Chinese and Europeans, the Cahokians and Yoruba, and the people of nineteenth-century New England.
The way of life of gatherer-hunters is first described so that we might know something about how all of us lived before we developed farming (about 10,000 years ago) and then cities (about 5,000 years ago). We’ll see that we lived in bands of a few extended families who cooperated in life, that everyone made their own tools and clothing from readily available materials, that most of our food was obtained by gathering plants, and that our hunting techniques relied on finding exploitable behaviors of other animals. The religions of our gatherer-hunter times concerned the mysterious powers of the world.
We’ll see that the Mesopotamians of Ancient Iraq were the people who first began to build our civilization because they were the first to became full-time farmers and the first to build cities. The early forms of government emerged, often as bands became tribes and chiefdoms to handle surplus crop (or in response to one of many other causal agents). These governmental forms will be described so that we know something about how our political units began and matured. Since farming turns out to be the key to abundance, the Mesopotamians were also the first to build cities, states, and written history. The development of cities and states is synonymous with the beginnings of business, technology, religions of morals, and of our political systems that would eventually develop into nations. (We are beginning to make continent-wide economic and political structures and will no doubt form global structures within a number of decades.) We’ll look closely at the way of life in Mesopotamian cities and find that we share much in common with them as we live in today’s big cities.
We’ll see that it took 5,000 years for Mesopotamian farming villages to grow from hamlets of a few extended families to cities of 100,000 persons and that people lived in peace throughout this span of time. War and its mass murder was not invented until we invented the empire, about 4,000 years ago, as city-states began interacting and overlapping. It is not a coincidence that this is also the time in which our religions began to concern moral behavior rather than the powers of nature. The populations of our largest cities grew from 300 persons 7,500 years ago, to 30,000 persons 5,000 years ago, to 300,000 persons 4,000 years ago, to one million persons 1,000 years ago, and to ten million today. Still, about 90% of us lived in small villages working as farmers until about 250 years ago when we began to become factory workers (in the U.S. today, just 1% of us are farmers).
After a glance at democracy in Ancient Athens and a medieval sojourn, we’ll see how our invention of the factory around the year 1760 began the Industrial Revolution. We’ll look closely at the changes in the way of life that occurred when the people of early nineteenth-century New England switched from farming to factory work. Nothing about today's business, government, and neighborhoods makes any sense until we see the changes in our way of life that occurred as we made this switch. We’ll see that wage-earners both produce and purchase factory goods and that this system results in increased numbers of tools, utensils, and decorations for our homes but that it also decreases the directly visible social ties within the community. Our civilization today operates only through the combined efforts of each and every one of us working our daily jobs–as is made visible by the traffic that occurs as we all go about our daily business. Our switch from farming to factory work also meant that each of us individuals came to hold less-control over our own continued well-being. We’ll see that the role of government increases in an always reluctant and late-in-coming response to the social consequences of the shift from self-reliant farming to wage-dependent and economic-cycle-dependent factory work dominated by our ever-larger business organizations geared mainly to increase profit. Keep in mind that these profits are simply the income of those of us who own the corporation and whose income is among the upper 1% of us. Social and economic inequality grows first with urbanization and greatly increases with industrialization. These changes are rapidly occurring in those nations making this switch today.
Not many decades ago, one in six of us died before reaching the age of one, and many of us died in early adulthood from minor ailments, such as simple cuts that became infected. In recent decades, we have become more likely to survive our first year of life and then live a healthier and longer life because of our newly found practice of sanitation and use of simply antibiotics and such. One hundred years ago, if a person made it to age twenty then they were likely to live to age sixty or so. The scientific and technological knowledge that we have accumulated in the field of medicine, now means that instead of dying of our first serious illness at age sixty, we now undergo a life-saving operation that enables us to live another ten years. (This operation typically costs $50,000 in the U.S. but in other nations it might cost one-half or one-tenth that amount.) Some meaningful goals for the mutual efforts that form our civilization include access to water, food, shelter, toilets, health care, and education. But more than that, we want to be able to pursue the limits of our individual–and combined–talents and passions so that we can continually improve ourselves and our mutual civilization..
Through much of history, the concerns of our governments of kings and queens have often been nothing except the concerns of kings and queens: the maintenance or expansion of their own territory, wealth, and power. In response to particular injustices of certain medieval kings and queens, we demanded written, institutionalized lists of rights and liberties. It is in our social nature to demand a mutually beneficial community and it is in our nature to react against any injustice within our community. Through the last few centuries of effort, we have been redirecting the concerns of our leaders from the maintenance and expansion of their own power and territory to the concerns of a person: having a quality life for ourselves and for our children, spouse, extended family, and community. For example, today our governments more often debate healthcare rather than the annexation or colonization of foreign lands. Most of us measure success in life simply in terms of happy and healthy children and communities–not wealth or power. How do you measure success in life?
We'll have a glimpse of government in today's nations and examine the cultural ingredients for initializing and maintaining a stable democracy. We’ll see that democracy is more than just voting and free speech; it is a spread and balance of power among many persons, and it is a blending of views and priorities that partially satisfies everyone. Since nothing happens without a sufficient consensus, much of daily politicking involves the attempt to persuade a portion of the population over to one’s side. In contrast, authoritarian governments outlaw all views besides their own; imagine the direction your nation would take if only one of its parties were allowed to choose priorities and actions. As for our future, is it likely that we will develop a global, democratic assembly of democratic nations in order to solve today's global problems that are beyond the control and borders of a single nation.
We'll have a glimpse of the social life of our elite and also of the everyday life of some of our children who live in poverty today. We will look at the ways of business and government today and see how the interacting components of our whole society are involved in our well-being and in the quality of our lives. We can now measure hundreds of aspects of our well-being and of the quality of our lives, and these measurements can help to verify the success of our efforts in building the mutual civilization we choose for ourselves.
To choose goals for our civilization we have only to decide what are the most important things in our lives. You might like to make a list of what you feel are the most important things in life. To decide what life is about we examine ourselves and the nature of a human. The goals of human civilization can be nothing else than the goals of a single human: the care of our family and society, to pursue life and the limits of our talents, and to raise children. We simply want to be able to laugh and joke with our spouse, family, friends, and neighbors, to pursue life, and to raise children.
As you read of the development of our civilization try to gauge our progress in technological matters, business practices, the maintenance of social and economic justice, equal access to education and the benefits of civilization, having healthy lives that are not unnecessarily shortened from a simple illness or accident, having a sense of belonging to a community, maintaining our family's quality of life, and having a feeling of control over our own lives and over our own continued well-being. Do you think the things in life that are most important to us depend on the century in which we live or on the level of our technology? Has the level of our happiness changed with technology and time? What makes you happy? How do you measure your own well-being and the quality of your own life? As you read on, you might like to compare these aspects of life for gatherer-hunters, the first farmers of Ancient Mesopotamia, the people of Medieval China and Europe, the Yoruba people and the people of Cahokia, and today's factory workers. How do we maximize the benefits of civilization for as many of us as possible?
If a chapter contains more facts than are of interest for an initial reading then you might choose to read just the first and last pages of that chapter, or just the first sentence of each paragraph, and save the remainder for a second reading. The large number of facts presented here are not meant to be memorized; they are meant to illustrate the depth of our scientific, social, and historical knowledge.
The chapter questions are meant to help you gain an understanding of the "big picture" of the story of us humans and do not ask you to have memorized every fact given in the text. The questions are mostly meant to encourage further thinking and study. Some might help you form a better idea of what it is to be human and what it is not to be human–for example, by asking you to compare humans with other things. The questions are not meant for you to repeat the statements of the text but as a place for you to write down your own conclusions so that you can begin to further test your own conclusions. As you answer the questions, try to decide what you should next measure to test your answers. We have all heard that each newly answered question leads to many additional questions. If a specific aspect of our past doesn't have a clear answer then it will appear in this report as a question. This means that many of the questions do not yet have an answer, which is all the more reason for you to be thinking about them; you might choose to contribute in finding their upcoming answers.
Suggestions for further reading
For an earlier summary of "how we got here," see The World and Man As Science Sees Them edited by Forest Ray Moulton, 1937, The University of Chicago Press. The general picture has hardly changed since its publication in 1937, but some finer details are now known. The expansion of the universe was measured by Edwin Hubble and published in 1929. This measurement led to the Big Bang scenario but it was too new to be mentioned in that book.
A summary of events from the Big Bang through the beginnings of history is given in A Short History of Nearly Everything, Bill Bryson, 2003, Broadway Books, New York, New York.
The Human Story, Our History, From the Stone Age to Today, James C. Davis, 2004, HarperPerrenial, New York, New York.
You might follow that book with The Human Story, Our history from the Stone Age To Today, James C. Davis, 2004, HarperCollins, New York, New York.
The Sciences, An Integrated Approach, James Trefil and Robert M. Hazen, 2004, John Wiley & Sons, Inc., Hoboken, NJ. This is a one-year college course in the fundamentals of physics, astronomy, chemistry, geology, and biology.
For the discussion of the functions of religion and the value of understanding other cultures, read the forward and the first chapter of the book Magic, Witchcraft, and Religion An Anthropological Study of the Supernatural 4th Edition Edited by Arthur C. Lehmann and James E. Myers, 1997, Mayfield Publishing, Mountain View CA. Also read the introduction to The Spanish Frontier in North America, David J. Weber, 1992, Yale University Press.
A Briefer History of Time, From the Big Bang to the Big Mac, Eric Shulman, 1999, St. Martin’s Press. For more information, visit http://members.bellatlantic.net/~vze3fs8i/bhtes/index.html. A one-minute video can be seen at http://real21mt.audiovideoweb.com/ramgen/nj20real2550/nsf/universe.smi.
Questions
1. Make a list of the thoughts and actions you have today and then decide which of these are or are not motivated by your concern for your children, spouse, extended family, or your community.
2. We insist that our community is mutually beneficial and just. This means that love and children, family and friends, community and justice cover about every thought we have and every action we take. Do you agree?
3. To begin thinking about "what a human is" you might like to begin listing things you see many persons do in a similar manner. In the same way that we see many cats behaving similarly while in similar situations–they exhibit "catness"–we wonder what would they see to be typical human behavior or "humanness."
Do many of us act in similar ways whenever we unexpectedly meet a friend, as we inhale to speak, or as we are about to yawn or sneeze? Do we act similarly in the way we quickly look around for the source of an unexpected sudden noise, or the way we drop open our mouths when surprised, or the way we raise our arms upward as we take large downward steps, or the way we step away from a potentially harmful animal? Is it in our nature to look around for something to fashion into a tool when unequipped for the task at hand? In what situation will many of us roll-up our eyes? Do we all throw our sleeves in the same way to look at our wristwatch? Do we act the same when we first push on a door that needed to be pulled and then stand back to determine whether or not the store is open for business? What is it in our nature that makes us do that one-eyed open-mouth lip-curl when aiming cameras and such? Do we all carry our infants on our hips? Do those infants all rub their eyes in the same way when they are sleepy?
In certain ways, the members of some age groups act in similar ways. For example, we often speak of "the terrible twos," or the "what is that years," or the "teenage years." Is there infantness, parentness, older brotherness, or older sisterness? We also talk of bullies, do-gooders, know-it-alls, phony kiss-ups, and kind people. What sorts of behaviors can be fairly uniform among the humans of the world?
How and when the universe and the Earth began
Science
The purpose of this chapter is to describe something about scientists and to explain the scientific process. The facts given throughout the first two parts of the book have been obtained through science, so we want to know something about the technique of science. We may then be better able to determine the general validity of the scientific process and of its results. The general public is already familiar with the practical benefits of science because, every few minutes, each of us reaches for a machine or a medicine. In addition to those benefits, the knowledge and understanding obtained from science is mentally and spiritually rewarding. Science and art are both intellectual pursuits that are rewarding in themselves. They are things we humans do as we celebrate life. We humans are curious creatures. We have an innate capacity to notice, remember, understand, and predict patterns. These things are often described as memory, learning, and reasoning and are large parts of what it is that makes us human.
We have heard of those funny people called "scientists," but the only scientists most of us know are those strange persons found in a movie. What percentage of scientists dress funny and are forgetful, socially awkward, and unaware of the weekday? It is natural that those of us who make movies know far more about other movie makers than we do about scientists or of the scientist's passion for the knowledge of nature. Scientists show the same range of personalities and characteristics as occurs in all other persons.
Our understandings of nature and of us humans have been obtained by these scientists. Each scientist takes the results of the previous generation of scientists, adds something to it, and passes the increased knowledge on to the next generation. As we strive to understand a newly discovered aspect of nature, we usually fumble around in the dark for a while as we try to make sense of it. Once it is understood, soon everyone else on the planet also knows about it, and we never un-learn anything. Throughout history, the use of each new tool soon spread around the planet. Today’s science and technology is the sum of all the facts, procedures, and understandings ever obtained by any person on the planet.
Scientists do science because they want to understand how the world works. More than that, they feel that they cannot live without coming to understand the world. They are happy only when they are learning more. Many scientists work to acquire knowledge and understanding much more than they work to acquire money. You might suspect that your children will become scientists if you often see them intently observing "simple" things such as a butterfly or a drop of water. (In the past such behavior might have seemed strange enough to get some of us locked in the attic.)
Many scientists will work eighty hours per week for years with a single-minded obsessiveness in pursuit of this knowledge. You know that feeling of confusion you have as you are trying to figure out a complicated problem; it is like a painful knot inside your head. The obsessed scientist has this feeling throughout most of the day and sort of becomes addicted to it. The end of a good day's work means that you are so mentally exhausted that voices dance on their own through your head (this is nirvana). These obsessed workers are aware of each minute that they are not working and become panicked if just a few minutes are spent away from their work for "no good reason." Such an obsession is not anything new. For example, it was the cause of the death of Archimedes. He lost his life while working on a mathematical problem and refusing to pay due attention to a Roman soldier who was anxious to question him (see Watchers of the Sky, by Patrick Moore).
After a scientist has seen important questions–for example, the question of the origin of the universe–then everyday questions like getting there via Main street or Broadway, or the color of today's shoes and shirts, even material pursuits, become unimportant. In fact, the scientist sees that her own life is but a very small part of the universe. This is a very humbling experience and often results in the scientist's behavior being mistaken for either boredom or arrogance. The scientist prefers to spend time only on the most important questions.
Those of us humans who build roads and construct buildings feel a sense of accomplishment when we see the results of our work. We hope that it will last for decades, even centuries. Scientists build understanding, and hope that it will be useful for people for decades, even centuries, to come. For example, electricity and antibiotics will be useful for all humans for centuries to come. An explorer wants to go where nobody has ever been. A scientist wants to know and understand what has never been known or understood–to think what has never been thought. Scientists feel as explorers do when they are the first to understand a phenomenon. They jump up and down and scream and shout when they have come to understand a piece of the universe. They also scream and shout when they break their instrument just before they would have been able to understand a new piece of the universe. And they scream when politicians close down projects, like the Texas Supercollider, with the result that they can't even search for the still-undiscovered phenomena of nature.
The current state of our understanding of the universe is the result of the lifetime's efforts of thousands of scientists who have been working for the last five centuries. These scientists have studied–that is, they have measured–millions of species of plants and animals, millions of stars, millions of physical phenomena, millions of chemicals, millions of fossilized bones, millions of archaeological artifacts from previous cultures, and they have observed millions of facts concerning living cultures. For example, in the Human Genome Project, biologists have just recently finished the Herculean task of studying the 3.6 billion letters in human DNA. Scientists completed this task in just twelve years.
By the way, the PBS televison series Race, see www.pbs.org/wnet/dna/episode3, discusses genes and race: a person's appearance–ear shape, hair color, height potential, skin color, nose size, and eye shape and such–is determined by perhaps one part in one-thousand of his or her genetic makeup. Where we instinctually place much weight on the outer appearance of an individual, we are analyzing but a small fraction of that individual's genetic makeup. The vast majority of our genes produce our bodies with cells, arms, legs, eyes, hearts, and livers and the other organs. This means that two human individuals are 99.9% genetically identical. Two unrelated individuals differ by only about 30 out of 30,000 genes, which is a difference of 0.1%. This is true whether or not those two individuals are of the same race, come from the same hometown, or come from opposite sides of the Earth. We now know how thoroughly we share the genes that make us human. Two siblings differ by half of that 0.1%. This also means that a stranger from the other side of the planet is only twice as different from you as is your sibling. Gathering five persons from throughout the planet produces no more variety than gathering five siblings. What is the percentage difference in genetic makeup between men and women, between members of an extended family, or between humans and chimpanzees? It is often mentioned that humans and chimpanzees share 97% of their genes. This means that the two species differ by only about nine hundred genes. The 0.1% difference between unrelated human individuals is 3% as great as the 3% difference between humans and chimpanzees. Even humans and mice share 85% of their genes because most genes make lungs and livers and such. We animals are not all that different from each other, we mammals are even less so, and we primates have the least differences of all.
Scientists have gathered billions of facts. At first, many of these facts seemed to have no relation to any of the others. Eventually, scientists were able to deduce a handful of basic, underlying principles of nature that explained all those facts and revealed their interrelations. In the next chapter we will see how all phenomena involving motion, heat, electricity, magnetism, light, sound, and energy are simply different manifestations of one underlying aspect of nature. In Chapter 5 we’ll see that evolution explains all biological phenomena. Much of psychology and anthropology are different manifestations of the biology of the brain.
Scientists make measurements, form conclusions, and then make additional measurements to further test and refine those earlier conclusions. They will repeat endless cycles of measuring, concluding, and further testing as they move ever closer to understanding. They continually decide what should be next measured to further test conclusions. Every conclusion is tentative because the next measurement might prove it to have been incomplete or even wrong. As soon as a scientist believes something to be 100% true then that person is no longer a scientist. Each measurement and conclusion is reviewed by other interested scientists and is subject to verification or disagreement. The goal is continually to refine measurements and conclusions to gain a more accurate understanding of a phenomenon. “Truth” and our level of understanding is measured by counting the number of significant figures in repeatable measurements.
Scientists operate from a fundamental base of well-understood phenomena. These are the things that they all agree on. Luckily, there is also a never ending list of newly discovered phenomena that are incompletely understood. When scientists recognize a new phenomenon of nature they will make a list of things that might produce or affect that phenomenon and then do experiments designed to vary just one listed item. In this way they measure each listed variable's affect on that new phenomenon. This tells them if any of the items did cause, or at least affect, that new phenomenon. The measurements from each new experiment reveal clues to the nature of the phenomenon.
Scientists show every human characteristic and emotion as they debate and compete at the frontiers of knowledge. They will always argue and disagree about the not-yet-understood aspects of nature. There is disagreement while measurements are revealing more of the true nature of the phenomenon. For example, look at a picture that is hanging on the wall, except, imagine that most of the picture has been covered by hundreds of little square tiles. Each scientific experiment reveals more about a phenomenon in the same way that more of that picture is revealed by removing a randomly chosen square. Until enough squares have been removed there will be a debate about the contents of the picture. Some might argue that it is a picture of a giraffe eating a railroad car while others think the picture shows a bush listening for a bee. One feature of doing science is that the pieces of the picture are revealed in random order. The full picture is not understood for days or weeks–in fact, it usually takes many years. If you like mysteries, then you might enjoy a career in science. Nature provides the most interesting mysteries.
An example will help to illustrate this "scientific process." Let’s make a pendulum by attaching a weight to the end of a string or rod. Hold the string while letting the weight hang straight down. If you next pull the weight to one side, keeping the string taught, and then release it from an initial angle, it will swing back and forth in a repeating motion under your hand. When you first release the weight, it has a speed of zero. Gravity pulls it down and it begins to speed up as it falls. However, it does not fall straight down because the string is also pulling on it, causing it to take a circular path. The weight’s speed is greatest as it passes through the low point in its motion and then decreases back to zero as it rises. The falling and rising motion repeats. The combination of the downward force of gravity and the upward force of the string causes the weight to swing back and forth in a periodic motion. The "period" of the pendulum is the time it takes for it to make one complete cycle of motion. A scientist begins to study the phenomenon of the periodic motion of the pendulum by making a list of variables that might affect the pendulum's period. Its period might be affected by the length of the string, the angle at which it is initially pulled aside, the size of the weight, or how heavy it is. First we guess which things might affect this phenomenon and then we make measurements to find out if any of them in fact do so; we’re often surprised to find that nature behaves differently then we had naively guessed. We also find out the relative sizes of any affects. Through measurements we find that as the size of the weight increases there is an increase in the force of air resistance that acts to stop its motion. (Since air resistance is really a separate phenomenon from the repeating motion of the pendulum, its study is left for another experiment seeking to understand air resistence, not pendulums). Next we will determine if any of the three variables–length, weight, and initial angle–have an affect on the period of the pendulum. We will look at just the first few oscillations of the pendulum so that the frictional force of the air resistance, which eventually stops the pendulum, will not swamp the affects of these other three variables. First, we will keep the length of the string, and the initial angle constant but measure the period for various weights. You might like to try this. Surprisingly, it turns out that the period is the same for large and small weights. You may have heard about large and small weights falling at the same rate; the pendulum's weight is similarly falling though it happens to be tied to a string that makes it fall in an arc instead of falling straight down. Next, the weight is kept constant while the period is measured for many different string lengths. The scientist searches for a mathematical relationship between the measured string lengths and periods. It is found that the period increases as the square-root of the string's length: a long pendulum swings more slowly than does a short one. Lastly, the pendulum's period is found to be unaffected by the initial angle as long as that angle is kept below about 10 degrees. For larger angles, a mathematical "elliptical function" relates the period to the initial angle. By the way, the period of the pendulum is also found to vary inversely with the square-root of the planet’s force of gravity; pendulums swing more slowly on the moon than they do on the Earth.
In this example, we have used the scientific process to determine the relations between the period of a pendulum and its weight, string length, and initial angle. Everyone who repeats this experiment will obtain the same results because nature always behaves in the same manner. People do get different results when they try to build machines–a clock for example–out of pendulums. This happens because each engineer has a different amount of success at canceling the effects of friction and of temperature change (the length of the pendulum changes as its temperature changes).
Pendulums have been observed for centuries. In 1583, Galileo (see http://galileo.rice.edu) used pendulums to time the motion of spheres rolling down inclined planes. He first got the “clocking” idea while watching the swinging motion of church chandeliers. To time the duration of events he also counted heartbeats or counted water drops emerging from a small hole in the bottom of a container. In 1657, Christian Huygens first made a clock out of a pendulum.
The pendulum example involves just a few variables. Each variable's affect on the period is directly–and independently–measured. Sometimes a physical system is difficult to understand because it involves several heavily interacting components that are not as easily isolated as were the variables in the pendulum experiment. In these more complicated situations, we can often gain understanding of the whole by finding less complicated regions of the system where only two of the components interact heavily while the others interact just slightly. This approach begins to reveal how all of the components interact.
Physical phenomena are the easiest to study because they usually involve a small number of variables, while biological, economical, and sociological phenomena involve thousands–or even billions–of variables. For example, when scientists try to determine the cause of cancer they are faced with countless variables, and it is more difficult to isolate single variables than could be done with the simple pendulum. Even the tiniest biological phenomenon is incredibly complicated. But it is understandable when its entire process is broken into a series of smaller, individual steps. Each biochemical phenomenon involves a long list of complicated chemical reactions. The operation of your thyroid gland, or its reaction to an increase in the level of any single chemical, involves a series of many interacting chemicals.
Scientific results often include estimates of the accuracy of the conducted experiments. This is done because there is always an uncertainty in the last measured digit whenever one makes a measurement. For example, measure the length of a pencil with a ruler. The ruler's smallest division might be one-sixteenth of an inch (or it might be one-tenth of a centimeter) and the end of the pencil might fall about one-third of the way along one of those smallest divisions. But it is hard to tell exactly because sometimes it looks like it may be one-quarter of a division instead of one-third of a division. The usual rule-of-thumb is to take the experimental uncertainty to be one-half of the smallest division of your measuring instrument. The measurement of the length of the pencil might be written as 6.33 plus or minus 0.05 centimeters–that is, its length is measured to be within 0.05 cm of 6.33 cm. In the same way, you can read your car's speed meter, and your bathroom scale, accurately to about half the smallest division of the scale. If you weigh yourself before, and again after, drinking a glass of water then you will find that the scale has trouble distinguishing that change in weight. Most scientific measurements are accurate to about one-tenth of a percent, but today's best measurements are accurate to one part in one hundred billion. In comparison, one hundred billion seconds is a 30,000-year time span. It's hard to imagine measuring a 30,000-year time span and being accurate to within one second.
Scientists are concerned the accuracy of their measurements for a few reasons. They want to compare their results with those of other scientists, and they want to compare their measurements to the numbers obtained from theoretical equations. For example, if one can measure accurately to 0.1% then the results are expected to be within 0.1% of theoretical predictions; otherwise, something is wrong with either the theory or the experiment. Another use is that if one can measure accurately to just 1% then it is meaningless to worry about affects accounting for less than 1% of the system’s development. This is the reason we were able to ignore air resistence in the pendulum experiment above.
A mathematical square-root was mentioned in the above discussion of the pendulum. When the ancient Greeks found a mathematical relationship for the ratio of the lengths of two wires that produce successive musical notes they were surprised that nature could be modeled by mathematics. (For more about this, visit www.aboutscotland.com/harmony/prop.html.) Why can nature be modeled mathematically? Is nature mathematical? In addition, some scientists wonder whether mathematics exists on its own or if it is simply invented. Humans model the universe with mathematics because this allows them to more accurately understand nature and to build more useful machines and medicines. The beings who might live in the Andromeda galaxy will use very different mathematics. We use forms of mathematics like arithmetic, calculus, group theory, and topology. There is no way to predict the Andromedian's approach. We all wish we had more imagination in developing additional forms of mathematics. Humans will benefit greatly–after they learn to stop staring–when they first get to discuss mathematics with that Andromedian mathematician named Greshkwag.
As much as we hate to admit it, our imagination is limited. An example of our limited imagination is that we cannot think of a new color–not simply "sand-dab melon chardonnay" but a new color, one that does not contain red, green, orange, violet, or blue. Even more telling about ourselves is the fact that we cannot think of new emotions or behaviors for ourselves that are not already innate to a human. (We also have trouble imagining how a being could think or could choose behaviors without using language to do so.)
Scientists test our assumptions about nature by making numerical measurements of phenomena. For thousands of years, we have sat in our "arm chairs" imagining how nature works. We tried to reason logically and to keep our newly developed deductions logically consistent with our previous deductions, but we have been constantly surprised to find that nature behaves very differently than we had naively expected. Quite often, nature has been found to behave in a way that nobody had imagined. For example, no physicist could have guessed how either atomic-sized or fast-moving objects interact. ("Fast" objects are those moving at more than 90% of the speed of light; they are also said to be moving at “relativistic” speeds because they are in the realm of Einstein’s theory of relativity, see www.einstein-online.info/en.) Instead, we find out the actual ways of nature as we make measurements. The equations of quantum mechanics and relativity numerically describe the way nature was found to behave when scientists measured these things, just as was done for the pendulum. No matter how many logical reasons we can think of that objects should be able to move faster than the speed of light, we have never observed any object doing so in nature despite the fact that millions of high speed particles are observed in elementary particle accelerators every single day. (For information about quantum mechanics, visit http://vmsstreamer1.fnal.gov/VMS/Samples/particles.ram.)
Throughout history the operation of the brain has been subject to much arm-chair debate. Today’s scientific measurements are finding that the operation of the brain is very different from the expectations produced from our previous, logically-deduced, arm-chair debates. The actual operation of the brain is being found to be much more incredible than any arm-chair philosopher had imagined. This is another example of how we are surprised when we make measurements and find out how nature actually functions. Just recently we have become able to make measurements on brains as they are in the process of thinking, feeling, and remembering and such, as will be further described in Chapter 8.
A scientist studies one of the following four fields: matter and its motions and interactions, plants and animals, chemicals, or people and our societies. From these studies emerge an understanding and appreciation for nature and for human beings along with clues about our place in the universe–along with some useful machines and medicines. A scientist will learn the general, underlying principles that explain the millions of previously-measured facts within one of these fields, and then become an expert at a more specific aspect of that field. A single scientist knows a tiny, tiny fraction of all of the known facts of a given field, but will know a meaningful percentage of the facts within one specific aspect of a field. For example, a particular biologist learns the general principles of plants and animals, then thoroughly studies hundreds of species and becomes an expert in a small number of them or of a certain aspect of them.
Science is done by performing repeatable experiments. An experiment is repeatable if everyone who does the same experiment obtains the same result. It then means that the aspect of the world just studied is in fact an aspect of the world and not just a figment of our wishful imagination. In addition to the reward that comes from understanding the world, this will then mean that a machine or a medicine can be built that makes use of this repeatable aspect of nature. It used to take decades before a machine might be based on a new understanding. Today there are business persons who are more quick to make machines that are based on each newly understood phenomena. Whenever you hear the word "science" you should think of "facts and understandings learned from repeatable experiments." When you see scientists explaining a fact or a phenomenon that they think they learned from doing experiments you should decide if others can repeat those experiments and come to the same conclusion.
If a proposed process cannot be repeatedly measured despite sufficient attempts then that process is probably does not happen in reality. For example, one might propose that migrating birds navigate by detecting the gravitational pull of the stars. The complete lack of repeatably-measurable results is the reason that scientists complain about such things as paranormal phenomena, extra sensory perception (ESP), and communication with the dead. Scientists have never been successful in their attempts to measure these phenomena. If they cannot be repeatedly measured then they cannot be understood as real events or used to make machines or medicines. Many persons (like my friend John) like to point out that as much as we would like for ESP, telekinesis, mind-reading, astrology, and paranormal phenomena to be real things, none of these have improved the quality of life of the general population. They have not solved a single social problem or even built a single building. In contrast, science and technology have enabled our modern civilization.
Whenever an object's motion is changing there is always a force responsible for that change in motion. Physicists have found only five forces in nature: gravity, electricity, magnetism, and the weak and strong nuclear forces. If there was a force that could allow a person to move an object by mental concentration then that force would most likely have revealed itself long ago. For telekinesis to be a real phenomena, it would have to operate through a force that has not revealed itself in any other way. This is unlikely. Physicists spend their entire lives doing nothing except studying forces and would be thrilled to find a new force to study. Does this “telekinesis force” do nothing except move objects by mental concentration. We will see that the electrical force is responsible for millions of different phenomenon, from rainbows to x-rays, and governs all of chemistry. In particular, it holds together the molecules of life and governs much of the interior workings of our bodies. This means that a human is just an example of one of nature's electrically governed molecule-machines. The existing forces of nature make the operation of the molecule-machine possible. Every force that is present today has existed since the beginning of the universe and evolution has been making use of all of them since its beginning.
Since we have no experience with extra sensory perception, it is hard to even imagine what it would be like to have an additional sense. It is much easier to imagine what it would be like if we had fewer senses; this exercise may broaden our understanding of our own senses. If you take away our sight, hearing, sound, and senses of touch and smell, then you are left with a life-form such as a plant or a tree. A plant would consider sight or touch to be a case of extra sensory perception. Plants have never seen, heard, or felt an animal; yet they have developed thorns to keep them away and fruit to entice them to carry away their seeds–and stickers to force them to do so. Their seeds also blow away in the unseen, unheard, and unfelt wind. Though plants do not see, one has grown an appendage that has the appearance of a bee; this attracts bees that the plant then eats. This plant has no sense of sight. It has never seen a bee but it has managed to evolve such that it takes full advantage of light. In the same way, flowers attract insects with light–that is, with their appearance–even though flowers cannot see. (Visit www.pbs.org/wgbh/nova/orchid/smarts.html to view the PBS video A Plant with Smarts, explaining how the appearance and released odors of orchids entice insects and other animals to help it reproduce.) To a plant, light is another sense. If there were other, useful ways that we animals could take advantage of natural phenomenon then it's likely that we would have already done so–just as plants have taken advantage of light. Plants are actually evidence against the existence of extra sensory perception in humans. We would all have these extra senses already. There is no reason that just a few members of our species would be so different.
When scientists talk of things that are well understood, it means that their statements stand on the evidence obtained from thousands to billions of measurements. They are often describing unbelievable but true phenomena. When people describe paranormal phenomena they are talking about something that stands on the testimony of a single person and is often contradicted by many scientifically repeatable measurements. It is something that would be neat if it were true but it is never as interesting as the phenomena that the scientists have found to be true. The actual workings of nature are always more interesting than our imaginary devices. For example, the intricate workings of quantum mechanics, relativity, and DNA are far more interesting than are “magic wands."
In the following chapters, I will often stress the large number of facts from which scientist's statements have derived, and mention the lifetime's of effort involved in the study of these facts. The purpose of this is to show that the basic statements of scientists stand on thorough understanding and firm ground. This is stressed so that the reader will be aware of the difference between the measurement-backed statements made by scientists and the non-measurement-backed statements made by someone describing paranormal phenomena and such. For example, it is fun to hear of the lost continent of Atlantis. An "Atlantis researcher" will present a dozen logical explanations and describe possible locations. But this meager amount of information does not compare to the millions of facts that a geologist can present concerning the well-understood positions, features, sizes, and movements of the continents, oceans, and ocean floors throughout the history of the Earth. In fact, today's satellites "see" the entire ocean floors and watch the continents slowly move around the surface of the Earth. To see images and movies of the ocean floor, you might like to visit the National Oceanic and Atmospheric Administration’s (NOAA) websites at www.ngdc.noaa.gov/mgg/announcements/announce_predict.html, www.ngdc.noaa.gov/mgg/image/2minrelief.html and www.oceanexplorer.noaa.gov/gallery/maps/maps.html. Global topography data, images, and movies are available at www.ngdc.noaa.gov/mgg/global/global.html. If you are wondering if a scientist is talking about something that "stands on firm ground" just ask that person "Is this something that is well understood and generally agreed upon, or is this something that is incompletely known and still subject to opinion?" That scientist will be happy to explain further about the range of opinions and the nature of the accumulated evidence.
What are the differences between scientists, artists, and engineers? Scientists perform experiments in an attempt first to discover and then to understand new aspects of nature. A physicist might make a new machine or measuring device that has never existed before and use it to measure a newly reachable part of nature. They then find equations that describe the measurements. Physicists don't make equations for everyday machines; that's what engineers do. Engineers make machines that are based on existing understandings. They imagine new uses for old understandings.
After a particular scientist has measured a new aspect of nature, this new information becomes part of our base of knowledge and serves as a springboard in searching for additional aspects of nature. Scientists use their imaginations first to figure out what should next be measured and second to guess the results of those upcoming measurements. As they repeatedly guess and measure, they are refining their understanding of the phenomenon. If a particular scientist had never lived, those aspects of nature will still be measured by someone else–and probably within a few years because it often occurs that most everyone's efforts are directed at the current frontier of understanding. Nature has many aspects, each of which still exist even if we never measure them. Individual scientists alter the timing of discoveries and the naming of newly measured phenomena. Scientists use their imagination in building knowledge that has never before existed.
Artists use their imagination to create things that would have never otherwise existed in the universe. Art bounces back and forth between individual artists and gets changed during the process. An individual artist can alter the direction of flow in a specific art; sometimes one artist will create an entirely new form of expression. Art and science are both intellectual activities but art more often involves physical talent, too. All of the understandings, procedures, and arts of humans change through time as they bounce between individuals. The physicist Richard Feynman explains that scientists use their imagination to guess the true reality of nature while artists use their imagination to invent a reality that does not otherwise exist. Feynman says he once tried to write a novel but found himself to be a very mediocre writer.
My friend Justin Hoenke creates music (to hear some samples, visit www.rockerie.com/thescene/bands/225 and www.myspace.com/belsapadore). When I asked him how he creates something out of nothing he answered that he sometimes wonders if he should more often “focus on things that do exist instead of living as he does in a pseudo dream world.” He said that time and time again he has thought about how and why he creates but the more he searched the further he was from the reason he started in the first place. He started making music because he loved to hear music. Since he had always been a creative kid, music and his creativity just fell together. Justin likes how music brings a smile to a person’s face as they hear it. He likes how it makes the hairs on his arm stand up when listening to something he really enjoys and wants to do that for everyone with his own music. He explains that a lot of the first songs he wrote were based on positive and negative experiences he had had. Since he wasn't an open person and held things in, music was a way of saying things. During his Zomo days, see (hear) www.myspace.com/zomo, he let “all that he wanted to say stay inside until he wrote those angry songs.” Then, “Belsapadore started off as me trying to find my footing in the world and slowly it's becoming me saying what I want to say when I want to say it and not letting it boil up inside of me. I guess it's all some kind of journey that I'll understand someday.” When I asked about creative techniques, Justin said that each artist has their own method in which they feel most comfortable working, but the goal is really never to feel comfortable in the way you create or you might get into some kind of routine that just leads to the same thing over and over again. Justin says that through a several-year period he relied on the pure emotion of a moment to craft a song. He said that he would wait around for or even create incredibly intense, emotional moments and then capture them in song. He wrote a few hundred songs this way. But after awhile, it got to be a real drag on his personal life because, as he lived for these moments he was in turn killing himself for art. He realized that he wasn't happy with the newer songs because most of them were created out of habit. He then began working in isolation on new songs that didn't rely on these moments of intense experience. He says that “The only thing that could then inspire me would be me.”
Scientists measure everything from motion to society, even love
Scientists measure many details of our own emotions and behaviors–but not how to behave. They study everything, even love is a topic of scientific study. The topic of our own emotions and behavior is subject to many rumors, partially true stories, and guess work by each of us. This happens because we accumulate our own experiences and form our own descriptions of these things. A scientific study can add to our own somewhat vague notion of love by providing concrete facts determined by measurement and by discussion with many different persons. It's also fun to find out how similar or different we are from others and about the range of characteristics in people. It's fun for us to learn about the amount of variation in these things from one person, or one culture, to the next. The scientist also has fun making measurements to learn more exactly what is occurring. It should at least be fun for us to know that there are people who actually think such a study is fun. For example, see www.psychology.sunysb.edu/attachment/danfords2002/documents/fraley1.pdf.
A scientist will ask specific questions like how many times does a person fall in love, how do we fall in love, and what sorts of chemicals are going through our brains while this is happening. For example, it has been found that we have elevated levels of certain chemicals during the first two years we are in love with a person. Do you think you feel differently during the first two years of being in love? Every child asks his or her parents how to know if he or she is in love. Scientific studies make more concrete our vague notions, sometimes verifying what we already suspected about ourselves. Have you noticed that we often fall in love in steps. First, we enjoy this certain person's company. We begin to pay attention to every detail of their movement and behavior, and soon, we can think of nothing else besides this person. We have a tender first-kiss which we might replay in our mind every few seconds through the next week. During each replay in our mind, we see the other’s face and feel the soft press of lips. We are unable to focus on our work except for ten seconds out of every three minute period, and we can’t sleep. Scientists find that the chemical oxytocin is being produced and released within our brains. It is enabling this extraordinary power of concentration and is forging our love. We are now fiercely smitten. The beauty of this person becomes more pronounced and we become unaware of the existence of all other persons. Everything around us that used to be dull and boring suddenly takes on a new brightness; an old familiar song now sounds different. Finally, we never want to be away from this person. We feel that the universe was made for the two of us and that compared to love, what does the universe matter; without our love, their would be no universe. Did you experience any of these steps? In what way is falling in love different for you?
Notice that as you replay in your mind the sight of this person’s face and the press of your lips that no words are being spoken: the feeling you are experiencing is older than words. For a few million years, our ancestors were falling in love–and being in love–without holding a single conversation. Did they communicate with tender tones? As you hug your loved one, you feel as if you have everything needed in life. Everything else in the world seems to evaporate and your troubles disappear. The comfort you feel at that moment has been occurring during such hugs for millions of years. Do the members of every hugging and nudging species experience the same feeling? In the following chapters, we will be looking into our biological past to gain insight into human nature. There is evidence to suggest that we developed full speech, consisting of thousands of words, only about 50,000 years ago but we have been a monogamous species for more than one million years. As you fall in love with your lifelong spouse, which of the above steps to falling in love do you think could happen without any words at all? Which steps could not be accomplished before our communication abilities had grown to include fifty words and gestures? What would have been the fifty most important things in life, and so would have been among the first fifty things to have been verbally named? What are the fifty most important things to you? Would our first fifty words have included such things as hello, mom, yes, love, food, group, war, and profit? Did love not exist before fully formed speech had developed? Is there love today?
Scientists also find that there are changes in internal chemical levels during these processes, as there are during every other process. There are countless, published volumes of measurements involving the process of love. Are these measurements useful? Will we be able to make a machine or medicine from these studies? Certainly we want to know more about ourselves and to understand ourselves more accurately and more completely–whether or not this understanding can be used as the basis of a business that might earn great profits. Scientists study love because the more thoroughly we understand it, the more beautiful it becomes. Our poets will never stop describing love. Love is a large part of what it is that makes us human. For many of us, it is our most precious part.
The range in cultural influences of love gives us clues about human nature. Some of today's Western people are confused by the arranged marriages of some of the world's cultures in the East. The arranged marriage is a social union between two extended families, not just two individuals. The goal of the marriage arrangers is to improve the lot of the extended family relative to that of all other extended families. The arrangers have in mind that the extended family of the selected spouse will be good for our extended family, so we’ll marry our child and theirs. As my friend Anti likes to explain, a person of a culture employing arranged marriages might describe love as a pot of water that slowly comes to boil, while a Western person might instead describe a marriage as a flare that starts very bright and then subsides in time. Do you agree with these descriptions? You might like to compare your description with that from other persons.
Scientists also make measurements that give us a more accurate notion of our social systems. Some of these measurements involve the following aspects of society. How many times per day an individual laughs and jokes, smiles and cries, fights and makes up, feels empathy or sympathy, thinks about reproduction, helps friends and strangers, is proud or shameful, decides if a potential behavior will be right or wrong, considers the impact of an action on others, acts in a dominant or submissive manner, forms an alliance with someone against another individual, feels like a member of a group, decides what is good for the group, makes a decision based on morals, follows the dictates of culture, speaks to another individual, or uses a tool.
To give us a more accurate notion of what is a human, these measurements are repeated for countless animals of all types, including other primates, other mammals, birds, fish, reptiles, amphibians, and insects. The measurements are more difficult and indirect for these other animals and so are subject to very careful interpretation. The scientist obtains these measurements after becoming familiar with many individual animals and by knowing which individuals are related by family. Observations of one group of individuals are made for many years, and thousands of interactions between individuals are recorded. It's easy to see that these measurements can go on for much of a scientist's lifetime.
Scientists also measure answers to difficult questions like the following: the portion of persons who don't have enough money to eat properly, have been sick in the last month, changed jobs this month, have a child who died before age ten, have been in jail, live below the poverty line, earn more than four times the average annual income for the country, use more than one ton of wood per year, finished high-school, are able to read, or have been sick from pollution. They also study the cultural similarities among different groups of peoples who choose to adopt a democratic form of government. In these types of questions, conclusions about cause and effect are the most difficult to make because millions of variables are involved. (We see that physicists have it easy with their systems involving just a few variables, as in the pendulum above.) Many of these measurements concern the economic and social justice of our civilization.
There are many popular misconceptions and complaints about science. For example some complain that the scientist's laboratory is nothing like the "real world." The fact is that scientists observe nature; nobody can get nature to act differently then it wants. That is, nature will act the same out in a forest as it does inside a room–even if the door on that room happens to say "Albert's Lab." For example, if you drop a ball outside then it will fall down. Nature will also have the ball fall down when you drop it inside of a laboratory. You cannot get nature to operate "unnaturally." In the laboratory, scientists often try to arrange a natural setting in which they can isolate single variables in order to study them one at a time.
Another complaint is that scientific research is useless. Sometimes people say "What use can that be?" or "How can you make a machine from that?" The trouble is that no one can guess ahead of time how many machines will result from a particular research project. No one can predict its potential to improve the quality of our lives. For example, for a few centuries people laughed at the scientists who played with the funny little rocks that "magically" pushed and pulled each other. Eventually this was described as electromagnetism and led to many of today's most important machines, such as the electric letter opener. Some people do science just because they want to understand the universe. These scientists simply enjoy understanding and are less concerned about possible profits from future machines. Curiosity is also a human trait. We celebrate our humanity in many ways: by dancing, singing, making art, climbing mountains, creating buildings or organizations, or by being curious.
There is a common misconception that a scientist's "theory" is the same thing as a "wild guess" that has little to do with the real world, and that a theory has to sit alone and wait unused for a long time before someone finds a way to relate it to something in the real world. To a scientist, a theory is an explanation that is consistent with all previous measurements of a phenomenon. It is referred to as "theory" rather than "fact" because it isn't known if it will be consistent with the next measurement that is either more accurate or concerns a slightly different but revealing aspect of the world. (Since religion does not involve measurement, one can not say that Genesis is another “theory” of the origin of the universe and require that it to be taught in a science classroom alongside the “wild guess” of the Big Bang; similarly, science is not taught in a course on religion. Religion teaches us how to behave in life’s situations. The closest science comes to the concern of religion is in its study of what is behavior. Science never tells us how to behave. Since science and religion concern different things, there is no conflict between them.) Sometimes a theory is given in terms of a mathematical equation that produces the same numbers as have been previously measured for a certain phenomenon. Since the theoretical equations are designed to produce the same numbers as had been previously measured it means that the theory has an "application" from the start. The first job of the theory's equation is to match those previously measured numbers. For example in the 1920s, one of the first applications of the newly developed, theoretical equations of quantum mechanics was to give the same numbers as had been measured for the colors of light emitted by a hydrogen atom.
How many scientists are there? The number of scientists per million persons in 1996 was 1900 in the EU, 3800 in the U.S., 4700 in Japan, 500 in Latin America, and 100 in India and Sub-Saharan Africa, as given in http://enreca.pubhealth.ku.dk/1997_Danish_Research.pdf. There is a misconception that all scientists are atheists. (Visit www.adherents.com/largecom/com_atheist.html for information about the number of atheists in various nations.)
The more we understand about a phenomenon the more incredible it becomes. Closely studying nature is one way that some scientists worship. In this way, both the scientist and the priest are pursuing the same goal. Each of us has our own interests. Some of us have no interest in nature. Others care only to understand that a particular natural phenomenon is the way it is because "God made it that way." Rather than stopping at an explanation of a phenomenon in terms of being part of "God's creation," some scientists want to understand the tiniest details of every phenomenon in an attempt “to know the mind of God." Rather than only worshiping God, some scientists seek to know His mind.
By the way, I estimate that about one-third of my science friends are very religious in that they perform religious activities regularly. Another one-third have spent years in internal deliberation about the assumptions of their culture as it has come down to them from their grandparent's grandparents and have come to the conclusion that there is no God or that the evidence is not yet sufficient to be able to decide either way (of course these persons have the same moral behavior as does everyone else). The remaining one-third simply do not care to expend much energy thinking about such things.
The topics of scientific study are discussed in only a few paragraphs of our ancient and most precious religious documents. For example, the Bible mentions the planet Venus only a few times. These religious documents explain proper behavior in terms that we could understand many centuries ago–and today, too. They are not encyclopedias of physical and biological knowledge and do not contain blueprints for technical devices. Since there is little science discussed in our scared documents there is little reason for conflict between science and religion. In the end, both have the same goal of understanding a human and the relations among humans. Scientists are not out to disprove our religious documents. They are instead investigating, for example, why humanity is so well matched to the teachings of these documents. Some scientists do not say that the observation of the Big Bang disproves Genesis but that it allows us a glimpse of the details of how God created the universe. Others ask if God created us simply by creating the natural laws of the universe that resulted in the Big Bang. That is, God knew that the Big Band would occur and that a little while later you would occur. There are some scientists who wonder if God is the Big Bang.
Each of the six billion of us share humanness, but each of us has different interests. Scientists show the same range of personalities found within the rest of society. For example, some scientists feel that, compared to the universe, what does the color of shoes matter and that without love, what would the universe matter. The following websites have more information about science, scientists, and research. Meet several scientists at www.askascientist.org/meet-scientist. Visit www.hhmi.org/becoming to see interviews with several scientists each describing scientists and the ingredients for scientific success. You might like to visit the Royal Society at www.royalsoc.ac.uk and the Association for the Advancement of Society at www.aaas.org . Also visit the Research Channel at www.researchchannel.org and the Archaeology Channel at www.archaeologychannel.org.
The two points of this chapter are that "science" means "facts and understandings learned from repeatable measurements" and that today's scientific knowledge is the result of billions of these measurements. Any explanation of nature must be consistent with each of these previously measured facts. Scientists build a more accurate understanding of a phenomenon by first questioning their naive, initial assumptions about that phenomenon and then making measurements and temporary conclusions. This cycle of questioning, measuring, and concluding is continually repeated until a phenomenon is understood and more-permanent conclusions can be made. Conclusions are never permanent because a refinement in our measurement can lead to improved conclusions. Science progresses closer to the complete story by continually refining measurements and conclusions.
In their intellectual pursuits, scientists, artists, and engineers use their imagination to create new understandings, beauty, and machinery–sometimes all at once. In the next chapter we will see how scientists have found that many seemingly different phenomena are merely different aspects of a small number of more-fundamental elements of nature. Does a mathematician invent or discover understandings? That is, does mathematics exist on its own or is it invented by us? What do parents, families, and societies create? These are some of the things we humans do because it is in our nature to do them, as will be described below in Chapters two through eight. What do generals, politicians, priests, farmers, parents, workers, and business persons create? These are some of the activities that humans do within our civilization, as will be further discussed in Chapters nine through twenty-two. You might like to view the streaming video What is Science by Douglas Duncan at the Fermi Lab website http://vmsstreamer1.fnal.gov/Lectures/NatureofScience/Dunca/f001.htm. At http://vmsstreamer1.fnal.gov/Lectures/NatureofScience/Quigg/f001.htm you can view The Nature of Science by Chris Quigg. You might like to visit www.scienceonline.org.
Questions
1. What is science? Who pays for it? Who benefits from it? How many scientists are there? What portion of science is funded by government or business? Do we need science?
2. How much does your country spend on each of science, art, sports, education, health, and the military?
3. What is the difference between science and technology? What has been the role of science in building roads, boats, cars, planes, buildings, cities, electronic gadgets, business procedures, political campaigns, home appliances, and farming techniques?
4. Should science provide understanding, or just practical tools, or both? Should we stop doing science?
5. Is it important for everyone to understand the science behind the machines that we use every day? Is it important for everyone to understand the natural world? What do we need to understand about science before we vote on scientific issues?
6. List some fields of science.
7. Discuss the personality of some movie characters that were scientists.
8. Weigh yourself once every hour for a few days.
9. What is the width of the characters on this page?
10. List some things that would affect how far you could throw an object? How can you measure some of these things?
11. What is the number of things that might affect your health? How can you measure some of these things?
12. How many facts do you think have been measured about each of the following: bees, the human heart, the human body, flowers, iron, water, earthquakes, nuclear radiation, stars, fossil skeletons, primate behavior, human emotions, satisfaction in the workplace, the economy, and ancient Mesopotamia?
13. List some evidence for ESP. How many facts have been measured about ESP? Which is more interesting, ESP or the psychology behind our desire for it to exist?
14. Does a plant hear? When is it happy? How can we measure these things?
15. Toss a coin 100 times. For each toss, try to predict if the coin will land heads or tails. How many times were you right? Count the number of heads and tails and compare the difference in counts to the square root of 100, which is ten.
16. Is scientific understanding important? Is art important? Are sports important? Are material possessions important? Who is to decide if these things are important to a person or to a group of persons?
17. Is astrology a science? Does it involve repeatable measurements?
18. Think of a statement that you were told as a child, whose truth you have taken for granted your entire life. Since the evidence for this statement is nothing but hearsay, what should you research or measure to determine whether this statement is in fact true. For example, many of us have heard the following claims. Cats eat mice, sugar is bad for you, elephants fear mice, feed a fever but starve a flu, baldness comes from your uncle, muscle turns to fat when you're lazy, red headed people have tempers, blonds are dumb, all persons born under the astrological sign of Aries act smukely, the Earth is round, lightning never strikes the same place twice, radiation from plutonium kills people, all politicians are crooks, all poor people are stupid and lazy, scientists are atheists, atheists are immoral, you can't teach an old dog new tricks, we use only 10% of our brain, people act differently during the full Moon, criminals have bad genes, the people on the other side of the Earth are inferior, and animals can't think and don't feel emotions.
19. During each day you hear many statements made by persons who simply claim that the statements are true. List some of them, and describe what you should research or measure in order to determine whether this statement is in fact true.
21. How can you determine if a news story is true? List a sentence from a news report, or from a person you had talked with today, that you knew was true because it was supported by measured facts.
21. One example of science rumor versus science fact is given by the nuclear debate. How can we choose the best source of energy for our civilization? What are the factors in this decision and the relative importance of each factor? What should you measure to determine the best energy source? We have all heard that nuclear energy is "just plain evil" and should never be used. Did you know that a single nuclear-powered, electric generating plant produces about 1,500 megawatts of power, which is enough for one million persons, and that it gets all of this energy from a piece of uranium the size of a basketball? (It seems like science fiction that we could obtain that amount of power from such a small volume material.) Nuclear-powered electrical generating plant emit no smog while coal-fired electrical generating plants emit tons of smog because it burns a tons of coal every year–typically, two trainloads per day. How many persons get sick every year from the smog emitted from coal-fired plants, and how many persons get sick every year from the radiation emitted from nuclear-powered plants? To put the "hand on the other foot," how much smog is released from a nuclear plant and how much radiation is emitted from a coal-fired plant? (Coal, dirt, bricks, and many other materials from the Earth naturally emit radiation.) We often hear that electric cars will be smog-free but this will not be the case if they get their electrical power from our coal-fired generating plants. Did you know that a grain-sized piece of uranium could power your automobile for your entire lifetime without producing the tons of smog that your gasoline-powered car creates during your lifetime? Imagine driving your entire lifetime without having ever gone into a gas station. This indicates that we might be choosing our energy source with our emotions instead of carefully weighing facts. Is the public debate being fought with emotions or facts? Are groups trying to persuade you to their side by evoking your emotions or your mind? The energy debate is important. We need to carefully weigh all of the facts before making our decision because we don't want to make the wrong choice. Could it possibly be true that nuclear plants do less harm to the environment than do coal-fired plants?
22. Statistical conclusions about entire populations can not be obtained from the characteristics of just ten of its members. A conclusion based on those ten persons will have little relevance to the entire population. How many persons have to be considered before percentages become repeatable?
23. Do you dream in color? Do your dreams include smells, tastes, emotions, or social situations? Do other animals dream? Does your dog's dream involve smells? Would a snake’s? Does a spider feel web vibrations in its dreams? Does a bird hear songs in its sleep? How can we measure these things?
24. How does a dog feel as it sings or as it holds its head out of the window of a moving car? Do birds or fish enjoy flying or swimming around in gymnastically-moving groups? Does a mother bear enjoy her children? Does a spider enjoy waiting in its web? Can we measure these feelings?
25. To experience the thrill that scientists feel as they explore the world you might try looking at a drop of water with a microscope–its abundance of living things will surprise you. You might look at the Moon or the rings of Saturn in a telescope. Since we see it most every night, we think we are familiar with the Moon until we see the detail visible in a telescope. You might be thrilled to see three-foot long (one meter) lightning bolts shoot out from a Tesla coil, see www.teslascience.org and www.teslasociety.com.
26. Are triangles, circles, and spheres just "theoretical" shapes? Does anything in nature have the shape of a perfect triangle, circle, or sphere? Have we built anything that has such a shape? Do molecules form these shapes? Does the Earth or the Sun have the shape of a perfect sphere?
27. What is the difference between science and religion?
28. Have you heard the rumor that bees are able to sense your fear? Would this mean that bees feel emotions of their own if they can understand ours?
29. Interview a scientist to find out about his or her life and research.
30. What have been the most important experiments of one of the fields of science?
31. Do either scientists, teachers, priests, politicians, dictators, or business operators ever change our way of life?
32. Is mathematics real in that it exists on its own so that we simply discover new aspects of it or do we instead invent mathematics as the need arises? Do natural phenomena exist on their own? Does either art or understanding exist on its own?
33. How many factors might affect the weather, the economy, our behavior on Tuesday, a nation's decision to convert their political system, global warming, the causes of famine, the causes of poverty, or the brain's operation? Which of these things is well understood? Are radiation, nuclear energy, and genetic engineering well understood?
34. Secretly write a numeral on a sheet of paper and cover it up with a dozen squares. Then remove squares, one by one, in random order while other persons try to guess which number had been written down. (Watch out for foreign, ancient, or backwards and upside-down numerals.)
35. Name a scientific study that is useful and one that is useless. Does everyone agree with you? How can we gauge the "usefulness" of a study?
36. Compare a scientist's and a poet's description of love, roses, gnats, and a sunset. What is the difference in motivation of these two persons? Why do we ponder love, roses, gnats, and the sunset?
37. Can you prove or disprove that bras and wallets do or do not cause breast and prostrate cancer? Do white fence posts, green homes, or trees cause cancer? Has the use of saccharin as a sugar substitute increased the occurrence of cancer? How many persons per one-thousand of us get cancer? Does everyone who smokes cigarettes get cancer? In the ancient past, did we get cancer from our incessant campfire smoke?
38. Place the following items into some categories: hat, horn, blue, rat, running, tag, bat, volcano, cow, dog, Jupiter, algae, Saturn, ape, knee, algae, whale, liver, heart, Asia, Africa, Tuva, Brian, Greg, knife, arrow, Kari, clamp, home, tribe, chiefdom, farmer, teacher, DNA, happiness, smelter, anger, justice, play, eat, hydrogen, carbon, sleep, neon, gazelle, toaster, radio, Islam, x-ray, Hinduism, thunderstorm, computer, Napoleon, shoe, steam engine, chocolate, tire, music, governor, debt, and nothing. A physicist might categorize these items by electrical resistance and mass-density. What sort of categories might a biologist, geologist, psychiatrist, political scientist, politician, pastor, bureaucrat, business person, gatherer-hunter, ancient farmer, or a sociologists use?
39. List some artistic forms that are purely intellectual, others that are purely physical, and some that are both. Which sciences involve physical talent? How is sports different from art?
40. If two people measure the same event will they both obtain identical measurements? While driving a car, if one drops a rock out of the window onto the road, does the rock fall straight down? Would a second rock fall straight down if it is dropped onto the floor of the moving car? Would a person standing on the curb watching the moving car and the dropped rock think either rock fell straight down?
41. Logically deduce answers to the following questions and then go measure the answer to see if you were right. Can you make any conclusions from these measurements, and what should you next measure in order to test these conclusions?
i) How many times per day an individual laughs and jokes, smiles and cries, fights and makes up, feels empathy or sympathy, thinks about reproduction, helps friends and strangers, is proud or shameful, decides if a potential behavior will be right or wrong, considers the impact of an action on others, sticks up for themselves or gives in to another's request, forms an alliance with someone against another individual, feels like a member of a group, decides what is good for the group, makes a decision based on morals, follows the dictates of culture, speaks to another individual, or uses a tool. Repeat these questions and measurements for a chimpanzee.
ii) the portion of the persons in the room or in the region, who like coffee or chocolate, don't have enough money to eat properly, has been sick in the last month, changed jobs this month, has a child who died before age ten, have been in jail, are Catholic or Buddhist, work in agriculture or industry, live below the poverty line, earn more than four times the average annual income for the country, use more than one-ton of wood per year, finished high-school, are able to read, or have been sick from pollution. Is there any relation between a nation's high-school drop out rate, suicide rate, average lifetimes’ income, happiness, marriage and divorce rates, and the average height of its citizens?
iii) What is light? We see the stuff as if it is something real but if we cannot hold it in our hand can it be real? How fast does it move? Why can you see through glass but not wood? What are the differences between water, glass, wood, iron, electricity, and air? What happens to wood when it burns? Where does it go? Is it still wood? What is sound, and how fast does it move? What's the difference between music and noise? What is an echo? When a whistling train or police car passes you, why does the whistle's tone change from high to low? How do you hear, see, smell, taste, and feel? Why do different things smell, taste, sound, appear, and feel different? Why is it so hard to force a ball to stay completely under water? Why do balloons float? When you spin a glass of water why does the center of the water move downward and its edges upward? How does a lever work? When you drive your car and turn a corner, why does all that stuff slide toward the side of the dash? How did that stuff know you had turned around the corner? What is the difference between ice, water, and steam? When you stretch a ruberband and release it, what makes it snap back? Why doesn't a bent wire snap back into place? If you bend a wire back and forth it gets hot and breaks. Why? How does a magnet attract things? What is gravity? Does it pull in one direction or does it pull sideways, too? Is gravity the same thing as magnetism? How are mountains formed? Why does the Moon go around the Earth? Why don't we fall off the Earth? Why doesn't the Earth's atmosphere leak off into space? How big is the Earth? Where do clouds and the Sun go at night? Where do the stars go during the day? What are stars? Where has the Moon gone when we can't see it? Why does the Moon's shape change from night to night? Why are the Sun and Moon larger while they are rising and sitting? Do the Moon, Sun, clouds, and stars follow you as you walk down the street? Where does the sky end? Is it taller than it is wide? What is electricity? How is it different from magnetism and gravity? How does a gun make a bullet move? How do binoculars make things appear to be larger? Why does a pencil appear to bend when you put it into a glass of water? Is it bent? When you spill water on your shirt why does the shirt then appear darker? If the "darkness" is in the water, then why isn't a glass of water dark? When you slam on the brakes why do you fly forwards? Why doesn't the dust blow off your car when you drive down the highway at twice the posted speed limit? Why doesn't the dust blow off your home cooling fan? (Those things are always full of dust.) How does a drinking straw work? What in the world is a fire flame, and why does it rise? Why is the sky blue, and why does it turn red at sunset? What is lightning? What is thunder? Does one cause the other? What causes tornadoes and hurricanes? Why do the ice skaters spin faster when they pull their arms inward? What is heat and just how is it different from cold? What are the coldest and hottest temperatures that exist? Does hot flow toward cold or does cold flow toward hot? How does heat get into things? How does a coat keep you warm? How does sweating cool you off? When you place clothes in the dryer, where does the water go? When water boils, where do the bubbles come from? What is a cloud? Why are some clouds bright while others are dark? While driving, why does that little patch of winter ice always form in the car window? How does the glass of ice-water get wet on the outside? What keeps a car window from frosting over when you park under a carport? How do geysers like "Old-Faithful" work? (Visit www.nps.gov/yell/oldfaithfulcam.htm for a webcam view.) When you hold a spoon in the stream of a water faucet, sheets of water shoot out. What does this have to do with Space Shuttle engines? What is the difference between green and blue? The hairs of a paintbrush spread out when placed underwater but cling together when taken out of the water. Why? What is a rainbow? Why do camera lenses appear blue? Why does the doorknob sometimes give you that electric shock? What determines the color of an object? What are the Moon and the Sun? What are those funny little points of light in the nighttime sky? Why does a mirror reverse right and left but not up and down? Jearl Walker gives hundreds of examples of physics in everyday phenomena in The Flying circus of Physics. For example, hot water running into the sink doesn't splash as much as cold water, and it sounds different. Why? Water falling out of a slightly-on faucet narrows as it falls? Why?
42. Create a piece of art that explains how you feel about science.
43. Which other animals have a capacity for memory, learning, and reasoning? How can we measure their feelings?
Suggestions for further reading
Watchers of the Stars, Patrick Moore, 1973, G.P. Putnam's Sons, New York.
The Demon Haunted World Science as a Candle in the Dark, Carl Sagan, 1996, Ballantine Books, New York.
The Skeptical Enquirer. The articles in this magazine contain descriptions of attempts by scientists to verify unusual claims.
The Structure of Scientific Revolutions, Thomas S. Kuhn, third edition 1996, The University of Chicago Press, Chicago.
The Scientific Revolution, Steven Shapin, 1996, The University of Chicago Press, Chicago.
Why We Love: the Nature and Chemistry of Romantic Love, Helen Fisher, 2004, Henry Holt & Company, Ltd., New York, NY.
The Philosophy of Science, Peter Caws, 1965, D. Van Nostrand Co Inc, Princeton NJ.
For a discussion of the relationship between pure science and technology, see: To Light Such a Candle, Keith J. Adler, 1997, Oxford University Press, Oxford.
The Matter Myth by Paul Davies and John Gribbin, 1992, Simon & Schuster, New York, ISBN 067172840-7 or -5 for hbk or ppbk, discusses theory and reality.
Weird Water and Fuzzy Logic–More Notes of a Fringe Watcher, Martin Gardner, 1996, Prometheus Books. In this book Gardner debunks pseudoscience.
In the first section of this book, Feynman describes the scientific method in The Meaning of it all, Thoughts of a Citizen-Scientist, Richard Feynman, 1998, Addison Wesley, Reading MA.
Science For All Americans, F. James Rutherford & Andrew Ahlgren, 1990, Oxford University Press, Oxford and New York. This is a report about the need for increased science education in our schools.
The Educated Child, William J. Bennett, Chester E. Jr. Finn, John T.E. Jr, Cribb, 2000, Simon & Schuster, New York, New York.
Science, Steve Fuller, 1997, University of Minnesota Press, Minneapolis, MN.
The Scientific Revolution, Steven Shapin, 1996,The University of Chicago Press, Chicago, Il.
Science and Human Values, J. Bronowski, 1956, Harper & Row, Publishers, New York, NY.
Early Greek Science: Thales to Aristotle, G.E.R. Lloyd, 1970, W.W. Norton & Company, New York.
Hellenistic Science and culture in the last three centuries b.c., George Sarton, 1959, Dover, New York.
The Beginnings of Western Science, David C. Lindberg, 1992, The University of Chicago Press, Chicago.
The Exact Sciences in Antiquity, O. Neugebauer, 1969, Dover Publications, New York, NY.
Science in Medieval Islam, Howard R. Turner, 1995, The University of Texas Press, Austin, Texas.
Science and Civilization in Islam, Seyyad Hossein Nasr, 1992, Barnes and Nobles Inc, New York.
Science and Creation in the Middle Ages, 1976, University of Notre Dome Press, Notre Dame IN.
The Measure of Reality, Quantification and Wester Science, 1250-1600, Alfred W. Crosby, 1997, Cambridge University Press, Cambridge.
Science, Its History and Development among the World's Cultures, Colin A Ronan, 1982, The Hamlyn Publishing Group Limited, New York.
Servants of Nature, A History of Scientific Institutions, Enterprises, and Sensibilities, Lewis Pyenson and Susan Sheets-Pyenson, 1999, W.W. Norton & Company, New York.
Facing Up, Science and its Cultural Adversaries, Steven Weinberg, 2001, Harvard University Press, Cambridge, Massachusetts.
Science in History (4 volumes), J.D. Bernal, 1971, MIT Press, Cambridge, Massachusetts.
The Journal of Irreproducible Results, Improbable Investigations & Unfounded Findings, Edited by Dr. George H. Scherr, 1983, Workman Publishing Company, New York.
The Flying Circus of Physics With Answers, Jearl Walker, 1977, John Wiley & Sons, New York.
Nature has but a few fundamental rules; today, millions of natural phenomena are understood to be different aspects of these few rules
Physicists have studied millions of phenomena, including heat, light, motion, gravity, electricity, magnetism, gases, fluids, solid materials, sound, radiation, atoms, and nuclei. At first it seemed like the world was full of millions of unconnected phenomena, but we now understand how each of these is just one of multiple aspects of a few more-fundamental phenomena. As Richard Feynman says "The adventure of our science of physics is a perpetual attempt to recognize that the different aspects of nature are really different aspects of the same thing.," see http://photos.aip.org/exhibits/feynman.jsp. This chapter contains a few illustrations of this reduction along with an explanation of how it may even be possible to explain all physical phenomena with a single law of nature. We will see how these few but fundamental laws govern the chemical and biological processes that occur within the atom's of our bodies. We will then begin to see that the fundamental aspects of nature are simple, that nature exhibits endless variety, and that each complicated end product–for example, a human–consists of a large number of these more-simple underlying phenomena.
This chapter also contains a description of atoms, the electrical force, radioactive dating, and the unpredictable uses of today’s science. These topics are important in our understanding of what is life and how life works. We are made of atoms. The electrical force is important to us because we are made of atoms held together by this force. Every chemical reaction–including those within our bodies–occurs through the electrical forces exerted between neighboring atoms. It is also the force behind many material interactions that you see every day, from rubber bands to light and even our sense of touch. A description of radioactive dating is included in this chapter because this technique is used to tell us the age of the Earth and the age of many materials that we find on the Earth. It also tells us the age of the first appearance of many of the different species of life and the age of many of our cultural objects, too. An accurate measurement of these ages allows us to more precisely determine the order in which interesting evolutionary steps have taken place. The power and endless usefulness of science is illustrated in this chapter by discussing the impact that 100- and 300-year-old science has on our lives today. In the same way that the people of those times could not imagine the machines that have resulted from the research of those years, nobody can imagine the machines that will soon result from today's scientific research.
Newton's motion equation, and the gravitational force
Around the year 1687, after the motion of enough systems had been studied by previous scientists, Isaac Newton (see http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Newton.html for his biography) deduced a single rule of nature, in mathematical form, that describes the motion of each of these special cases. He was able to begin with that single, mathematical rule of nature and, after applying a sequence of mathematical steps, obtain each of the distinct equations previously found to describe just one system. This made us understand that all of those systems previously thought to be distinct were actually just variations of the single phenomenon: motion.
Many physicists believe that all natural phenomena are governed by just one rule of nature: if you push on an object it will speed up. This is Newton's law of motion (or motion equation) which he published in 1687 in the mathematical form “force equals mass times acceleration.” For any object, this law numerically specifies its location, speed, and acceleration through time that will result when any set of forces are applied to it. The mass of the object resists this change in speed: it has inertia and momentum that make the object prefer to continue moving in the same direction at the same speed. (To accelerate means to change either your speed or your direction of movement.) The law can be written in terms of either force or energy. Today, this law is written in a relativistic, quantum-mechanical form. Visit www.pbs.org/wgbh/nova/elegant/program_d_t.html for the PBS video The Elegant Universe. Visit www.mine-control.com/sand.html for an example of motion as art.
Newton's motion equation describes the motion that results from applying forces to masses. Objects are pushed or pulled with a force. Only five forces have been found to exist in nature: the gravitational, electric, magnetic, and the strong and weak nuclear forces. Gravity is the attractive force that pulls two masses toward each other. In this way, it keeps the Moon in orbit around the Earth and the Earth in orbit around the Sun, and it also holds us to the surface of the Earth. In the year 1680, Newton obtained the equation that describes this gravitational force. Electricity and magnetism are the forces between charges and magnets. These forces can be either attractive or repulsive. As mentioned above, all of chemistry results from the electrical force. The short-ranged, weak nuclear force is involved in the process of radioactive decay. The strong nuclear force holds together the particles, called protons and neutrons, found to makeup the nucleus of an atom, and it also holds together the three quarks that are the particles forming a proton or neutron. The weak and strong nuclear forces were found only in the last century as we became able to measure atomic-sized processes.
Recently the electric, magnetic, weak, and perhaps the strong forces have been shown to be different aspects of a single force. There have not yet been any measurements of the gravitational interactions of atomic matter, so we do not yet know how to describe gravity on an atomic scale. Many physicists hope to unite gravity with the other four forces, resulting in a single equation that describes the interactions of all the particles of the universe in a “theory of everything.” This is called the Grand Unified Theory.
The single equation describing the gravitational pull that the Earth exerts on the pendulum's mass also describes the gravitational pull that the Earth exerts on the Moon's mass. The two systems, Earth-Moon and Earth-pendulum, are just two different variations of a system of gravitationally interacting masses. Some differences between the two systems include the lack of a string in the Earth-Moon system and that the Moon has enough speed or inertia to continue its motion all the way around the Earth. Instead of releasing the pendulum from rest, you could instead choose to throw it downward and sideways with some speed. If it is thrown with enough speed, it would spin all the way around your hand.
I want to stress the power of Newton's law of motion by pointing out that it describes any motion by any object that you see. If you list every object you have ever seen in motion, the motion of every one of them is described by this single equation. For example, the equation mentioned above relating the period of a pendulum to its length can be obtained from Newton's motion equation. The motion of the pendulum is what results when the force of its string and the force of gravity both act on it at the same time. Remove either the string or gravity and the motion will not be that of a pendulum. The pendulum is one example of a system of motion. That its equation of motion can be obtained from Newton’s equation is an example of the way in which Newton's single, but general, force and motion equation describes each particular system. All we do is add up the forces and apply a sequence of mathematical steps to obtain a final equation. A person could list millions of different systems that undergo motion, and distinct equations could be found that would describe the motion of each of these distinct systems. Since the entire world is the sum of these possible systems, our description of the entire world–that is, nature–would be a complicated mess if we had to use millions of unrelated equations for each of these millions of possible systems. All motion is instead described by a single, universal equation, making the universe a simpler place.
By the way, some persons enjoy applying sequences of mathematical steps to obtain the distinct equations for various systems like the pendulum. If you think this might be fun then you might become a physicist. We can summarize a physicist's college years in two sentences: A college student becomes a physicist through six years of course work and a few years of experimental work. During each day the student obtains the distinct equation for several additional systems, adding up to several thousand systems by the end of college. (I always wonder what are the major features of other person's occupations, so I'll mention this in passing.)
Newton's law is used daily by scientists and engineers. For example, it is used to determine the motion of your car as it moves and turns, the motion of the fluids in a car's fuel and hydraulic systems, the motion of the air that flows around airplanes and lifts them into the air, the movement of the Moon around the Earth, and the trajectories that take spaceships from the Earth to the other planets. In the year 1687, nobody could imagine the endless applications of this equation. The equation is a few hundred years old and will continue to be used for all centuries to come. It is a fundamental truth of nature. (Truth is measured by counting significant figures in repeatable measurements.)
When Newton first published his equation, many persons were surprised that one equation could describe both the motion of everyday objects, like pendulums, and the motion of heavenly bodies. In fact, they were astonished that a mere human could find an equation that even the heavens obeyed. Before then they had considered the heavens to be of a separate reality with its own behaviors. After Newton’s success, many scientists set out to find equations describing everything from human behavior to economics and society.
To prepare us to see the role of the electrical force in the orbital motion of two charges about each other, I want to further describe the role of gravity in the orbital motion of two masses about each other. The orbital motion of the Earth and the Moon, due to the gravitational attraction between the Earth and Moon, is similar to the way in which two persons sort of spin around each other while facing, holding hands, leaning backwards, and running sideways. If the two persons let go of each other then they will fly apart. The two skaters can sort of "orbit" each other, see http://paer.rutgers.edu/PT3/experiment.php?topicid=5&exptid=58. They can continue in this circular motion because of the mutual pull of each other's hands. If one skater is one hundred times heavier than the other, then you will hardly notice the motion of the larger person. The Earth and the Moon are similarly held in their circular orbit by their mutual gravitational pull; gravity enables them to pull on each other without having to hold hands. They orbit each other but the Earth moves little since it is about one hundred times as massive as the Moon.
The gravitational force is so tiny that it takes a lot of mass before it amounts to anything. We feel our own weight because that is how strongly the Earth is pulling on the matter of our body. If you stand on a scale to weigh yourself but have somebody pull down on your feet then the scale will read as if your weight has suddenly increased. When you stand on the scale, the Earth is pulling on your feet with the force indicated by the meter. It is an attractive force between each of the pieces of your body and each of the pieces of the Earth. The more pieces either you or the planet have, the larger will be the force and the higher the scale reading.
The electric force and light waves
The electric force is created either by an electric charge or by a changing magnetic force. Electric charges come in two varieties, which Ben Franklin named "positive" and "negative” in the year 1747. (For biographical information, see www.pbs.org/benfranklin/exp_shocking.html, www.soul.org/Ben%20Franklin.html and www.mos.org/sln/toe/kite.html, which has a video of lightning striking his kite.) We all remember from grade school that like charges repel and unlike charges attract. There is no magnetic charge that creates a magnetic field; it is instead created either by a moving charge or by a changing electric field. We occasionally experience electrical charges (electrons) and the electrical force as a slight shock when we touch metal objects on a hot, dry day. Lightning is an example of the flow of electricity.
The electric force is very strong. It is a zillion (1045) times stronger than the gravitational force. (This means that you would have to be able to measure about forty-five decimal digits before you could see the tiny change in motion that gravity causes between two objects that are also interacting electrically.) All matter is composed of these electrical charges. Most everyday objects have equal mixtures of positive and negative charges, making them electrically neutral. In 1785, a person named Coulomb (for his biography and portrait, visit http://en.wikipedia.org/wiki/Charles-Augustin_de_Coulomb) made measurements that resulted in the equation describing the electrical force between two electrical charges.
The electric force holds together atoms and molecules, including those within your body. (Remember that there are about one hundred different kinds of atoms, from hydrogen to uranium, and that a molecule is a collection of atoms.) In the same way that the gravitational force can pull two masses–the Earth and Moon, for example–into a circular orbit around each other, the electric force can pull two or more electrically charged atoms into a circular orbit around each other. Since the electrical force is sometimes attractive and sometimes repulsive, depending on whether the involved charges are alike or unlike, all molecules do not electrically attract all other molecules. This is in contrast to gravitational attraction, which is always attractive. If two atoms, or collections of atoms, electrically repel each other then they will not join together. Those atoms electrically attracting each other will join together–indeed, they must.
It turns out that a close examination of the atoms within the pendulum's string shows that the tension in the string is transmitted along the string's length through the electrical interactions of neighboring pairs of atoms. We also see the electric force at work in springs and rubber bands. It provides the "static cling" of clear food-wrap, and it keeps you from falling through the floor. Electric charges serve many purposes in industry. They are used in Xerox machines, in electroplating, to remove pollution from smoke stacks, to separate nuts from shells and chaff from wheat. (You might like to read Electrostatics, Scientific American March 1972.) Our bone growth is electrically controlled through a pressure sensitive, piezoelectric effect. Electricity consists of moving charges and is found in nerves, muscles, eyes, brains, hearts, eels, lightning, and in the electronic machines that we use every day.
All electronic circuits make use of the electrical force. A battery contains separated positive and negative charges. The negatively charged side of a battery produces a repulsive force on negatively charged electrons, forcing them to flow through the circuit toward the other, positively charged side of the battery that is attracting the electrons. The earliest usable batteries were made in 1800 by AlessandroVolta (for his biography and portrait, see http://en.wikipedia.org/wiki/Alessandro_Volta). So, in his honor, we rate battery strengths in "volts." The electric force pushes charges, causing them to flow through an engineer's circuits as a "current." One of the first persons to make measurements of electrical current was Andre Marie Ampere (1775-1836). Today, we measure the size of electrical current in units called "amperes" that are named after him.
It was soon found that each material has a characteristic resistance to the flow of electrical current. This was studied by in 1826 by Georg Simon Ohm (see http://en.wikipedia.org/wiki/Georg_Ohm). The unit of electrical resistance is named "ohms" in his honor. It took several years of research to find a way to cause an electrical current to flow through a material for distances of just a few yards (meters) and even more years to get electricity to flow through wires for distances of kilometers and miles. This research lead to the development of the telegraph machine, which occurred in the year 1844. The trans-Atlantic cable was completed in 1857.
In 1864, James Clerk Maxwell (see http://en.wikipedia.org/wiki/James_Clerk_Maxwell) wrote a set of four equations describing all electric and magnetic phenomena. These four equations, which are called "Maxwell's equations," describe a fundamental truth of nature and will be useful for all of us humans for the rest of time. They describe every electrical and magnetic machine that will ever be made including generators, streetlights, radio and television sets, motors, MRI and CAT medical imaging devices, the circuits of a computer, and toasters. Maxwell's equations also made it clear that the electric and magnetic forces are two different aspects of a single phenomenon of nature, called electromagnetism, and that light too, is an electromagnetic phenomenon.
It was found that whenever an electric charge is wiggled it sends out electromagnetic "light waves" that move away at the speed of light. For an animation of waves emanating from wiggling charges, visit the Iowa State University website at http://www.ee.iastate.edu/~hsiu/movies/dipole.mov.The frequency with which the charge is wiggled determines the "color" of the light. Blue light has a higher frequency and more energy than does red light. (It also occurs that a hot object that glows with blue light is at a higher temperature than an object that glows with red light.) The electrical charges that make up matter are caused to wiggle whenever a light wave passes by, and this in turn causes them to emit light waves of their own. Light waves come in many colors, most of which are invisible to us. Some of these are called radio, microwave, infrared, ultraviolet, radar, x-ray, and gamma-ray. This means that the operation of lenses, mirrors, cameras, optical fibers, infrared remote control devices and nighttime viewers, radar detectors for the weather and the speed of automobiles, microwave ovens, medical x-rays, and other such devices are also described by Maxwell's equations because they involve electromagnetic waves. In addition, it has been found that each chemical element wiggles at uniquely different frequencies and that these characteristic frequencies increase as the temperature of the chemical increases; scientists have already measured millions of these frequencies. When astronomers look at the light coming from a star, they measure the received frequency and then know that star’s chemical composition and its temperature, too.
We see the Sun because its wiggling charges emit light, and since these charges wiggle at many frequencies, the Sun emits many different colors of light. But because of its temperature, the Sun emits most of its light between the red and blue colors and much less beyond the infrared and ultraviolet colors. This is the reason our eyes are sensitive to the red through blue colors. It wouldn't help for Earthlings to see colors that our Sun doesn't produce. Since many other stars emit most of their light in colors not emitted by our own Sun, the eyes of creatures who might live around those stars would be more sensitive to those other colors, which might be infrared, ultraviolet, or even x-ray. The eyes of the nighttime creatures of the Earth–snakes, for example–are more sensitive to infrared light than are those of daytime creatures. Flowers are brightest in the ultraviolet colors because the eyes of their "partners," the bees, are most sensitive to these colors.
At the time of the publication of Maxwell's equations in 1864, it became clear that it was possible to generate electromagnetic "radio waves" using oscillating, electrical circuits in which current flows back and forth between capacitors and inductors (in many ways, this oscillatory motion is similar to that of the pendulum). It took about twenty years before Heinrich Hertz was first able to do so, and we have named the unit of frequency after him. We hear television and radio station frequencies given in terms of kilohertz, megahertz, and gigahertz. (My computer keyboard is operated at a speed of three nanohertz.) In 1888 Marconi was able to invent the machine we call a "radio-frequency detector" or "radio" by electrically producing an electromagnetic wave in one place and detecting it in another. The detector is nothing but another circuit containing the same capacitor-inductor combination. The frequency to which the circuit reacts is adjusted by altering the circuit components, which we are doing as we turn the radio knob. (In Chapter 16 we will see that the radio business did not blossom until the 1920s.)
The first radios consisted of a number of vacuum tubes, see http://en.wikipedia.org/wiki/Vacuum_tube, in which electrons are greatly accelerated before they are suddenly stopped by a collision with metal tube-components. Since the sudden stop is equivalent to a very high frequency wiggle, the stopping electrons emit high frequency light. In the year 1895, research involving the light emitted from vacuum tubes accidentally stumbled across the ability of certain frequencies to pass through body-sized pieces of matter. This was the discovery of x-rays by Wilhelm Roentgen, see www.xray.hmc.psu.edu/rci/ss1/ss1_2.html.
It was claimed above that many seemingly unrelated phenomena are simply different aspects of a more fundamental law of nature. The above list of electrical machines and the following list of light-phenomena illustrates this point. Some examples of light phenomena described by Maxwell's electromagnetic equations include polarized sunglasses, the rainbow patterns seen on spilled oil sheets and soap bubbles (see www.geom.uiuc.edu/graphics/pix/General_Interest/Digital_Art/sullivan-120cell.html), the highly reflective paint used on highway signs, telescopes, binoculars, a mirage on a hot day, the colors separated by water drops and the resulting rainbow, the halo that is sometimes seen around the Sun or the Moon, the blue sky, the red sunset, the color of every object, and the streaks of light you see when you squint your eyes while looking at a lightbulb. Each of these is simply a different aspect of electromagnetism. Each is described by Maxwell's equations and results from pushing on an object with the electromagnetic force. It is impressive that humans figured this out–in the year 1864, no less. There is no end to the usefulness of this understanding and its applications. In fact, humans are another example of this fundamental law of nature at work in that the atoms within our body are held together by the electrical force.
In the year 1864, nobody could imagine what sorts of machines would be made using the electromagnetic equations. In the same way, we cannot imagine the future machines that will result from today's scientific research. What sort of machines and medicines will be developed 150 years from today that are based on the just-completed human genome project, or that are based on the quark research of today's elementary particle accelerator projects?
Phenomena that involve heat are now seen to be yet another example of motion and so are not a unique or independent aspect of nature. The equations for phenomena involving heat were obtained in the last three centuries. These equations provide mathematical relationships between an object's temperature, pressure, volume, and its type of material and physical structure. It has been found that a material's temperature is a measure of the speed of its constituent atoms. The atoms of a gas bounce around, colliding with other atoms and with the walls of the container. The pressure of a gas is due to the force of the atoms colliding with the container walls. In this way it has been found that heat phenomena are also described by Newton's motion equation. That is, heat is not a separate phenomenon but is another aspect of motion. The atoms of a hotter material are jiggling faster than are those of cooler ones. When a fast moving atom runs into a slow moving atom, it is slowed by the collision; the slower atom’s speed is increased. This transfer of the speed-of-motion from one atom to another is the flow of heat. Your food heats as its slower-moving atoms are brought in contact with the more energetic atoms of the surrounding fire or air. (A microwave oven passes electromagnetic waves through food in order to make the atoms of the food wiggle more quickly and become hotter.) Other examples of heat machines include steam, gasoline, and diesel engines.
About the year 1900, scientists began to be able to measure nature on an atomic scale. Examples of atoms include the basic and familiar chemicals hydrogen, helium, carbon, and oxygen. It has been found that atoms consist of a massive, central core or nucleus composed of positively-charged protons and a number of uncharged neutrons. This nucleus is orbited by negatively-charged electrons, see www.lbl.gov/abc/Basic.html. The electrons are held in orbit around the protons by their mutual electrical force in a manner analogous to the way in which the Earth and Moon are held together by their mutual gravitational force. Visit VisionLearning at http://web.visionlearning.com/custom/chemistry/animations/CHE1.3-an-animations.shtml for animations of various atoms) It takes some force to pull an electron away from the nucleus to which it is electrically attached. Protons and neutrons are about 2,000 times more massive than electrons.
This picture of electrons orbiting a massive clump of protons and neutrons was determined in the year 1911 by Ernest Rutherford. He passed a beam of low-mass helium nuclei through a thin sheet of high-mass gold atoms and measured the resulting trajectories of the helium nuclei. Gold can be hammered into very thin sheets; Rutherford's sheet was so thin that it contained only a few layers of gold atoms. Usually the beamed helium nuclei passed right through the thin gold sheet but sometimes they struck a gold nucleus and bounced straight back toward the incoming beam. This revealed that a nucleus consists of lumps of mass and that there is mostly empty space between the adjacent nuclei of the sheet. The mass and charge of these lumps can be measured in many ways. The lumps were later named protons and neutrons. For an animation of this scattering process visit http://galileo.phys.virginia.edu/classes/109N/more_stuff/Applets/rutherford/rutherford.html
Inside the nucleus, the positively charged protons are repelled from each other by the electric force; this is a tremendously large repulsive force. Despite this large repulsive force they are held together by the even-stronger but short-ranged and attractive "strong nuclear force." That is, the protons are subject to both the electrical and the strong nuclear forces. This nuclear force is about a million times stronger than the electrical force with which the orbiting electrons are held to the nucleus (this is also the reason nuclear explosions are a million times stronger than chemical explosions). When a nucleus is split into two pieces, say by the collisional force of an incoming projectile particle, the two separated pieces are no longer close enough to each other to be held together by the short-ranged and mutually attractive strong-nuclear force. The separated, positively charged pieces will then fly apart due to their mutual electrical repulsion.
Normally, atoms are electrically neutral because they have equal numbers of protons and electrons. When an atom is heated, its electrons gain speed. When sufficiently heated they will gain enough speed to break free from their electrical bond with the nucleus and move away, leaving behind a positively charged atom. The positively charged atom is called an ionized atom, or ion. This means that the atom is now electrically charged instead of being neutral because it is missing some negatively charged electrons. The temperature at which each chemical element ionizes has already been measured.
The nucleus of each type of atom always contains a fixed number of protons but it can have a bit of a range in its number of neutrons. Each variation will then have a different mass and is called an isotope of that particular type of atom. For example, a carbon nucleus always contains six protons but has either six, seven, or eight neutrons. Uranium has ninety-two protons, ninety-two electrons and 140 to 150 neutrons. Isotopes and their variations in mass make possible the techniques of radioactive dating and such that are used to study our own history..
Scientists have found that only ninety-two different atoms or chemical elements–from hydrogen to uranium–occur in nature, see http://education.jlab.org/itselemental/index.html. Each different chemical element contains from one to ninety-two protons inside its central nucleus and an equal number of orbiting electrons–unless sufficient heat is added that the electrons begin escaping. The number of neutrons varies for each particular chemical atom but the number of protons does not. That is, hydrogen always has one proton, helium always has two, and uranium always has ninety-two.
Hydrogen atoms are the smallest of all and consist of a single proton orbited by a single, electrically-bound electron. Hydrogen atoms are so small that 100 million of them fit across the width of your finger. Most often, hydrogen nuclei have no neutrons, but about 0.8% of them are found to contain both a proton and one neutron. Since the mass of protons and neutrons are about the same, this variety of hydrogen is twice as massive as the form that contains no neutron.
Helium is the next largest atom and contains two protons, two electrons, and usually two neutrons. It has been found that about 0.3% of helium atoms have three neutrons instead of two. (Helium is the gas inside a child's balloon; it also makes your voice sound funny when you breathe it.) If you press two hydrogen atoms together with a megaton force then they will merge into a single helium atom and release a lot of previously-stored nuclear energy.
Atoms can become electrically attached to other atoms. We use the term molecule to refer to any collection of two or more atoms. Large molecules can be built by combining many smaller ones. The molecule's collection of atoms remains electrically stuck together unless it is sufficiently heated or comes into contact with another molecule that has the right charge distribution to disrupt it.
Each atom within a solid piece of material, such as a block of iron, behaves as if it is attached to each of its neighbors with little springs, see www.physics.brocku.ca/courses/1p21_reedyk/images/F09001.jpg; the springs represent the electrical force. As this material is heated, the atoms are seen to jiggle more rapidly, see http://vis.lbl.gov/Vignettes/vanhove-98.ijs/output.mpg. At a certain temperature the atoms are no longer able to hold each other in place and the material melts. The melting-point has been measured for thousands of types of atoms and molecules.
Those one hundred or so varieties of atoms combine into endless varieties of molecules. A molecule consists of two or more atoms that are electrically bound together. For example, we all remember that water, H-2-O, consists of two hydrogen atoms and one oxygen atom. The largest molecules within our bodies consist of billions of atoms and are electrically neutral because they contain equal mixtures of positive and negative charge. Chemists study the ways atoms interact with each other. They have found many rules that help them figure out which final chemicals will result after several chemicals have been mixed together. (During each day of an eight-year college curriculum, a chemistry student will study many different chemical reactions; by graduation, the properties of thousands of chemicals have become familiar.) We use many chemicals in our daily lives. The most familiar everyday uses include medicine, soap, glue, oil, paint, and cleaning products. Our bodies consist of millions of interrelated chemical reactions.
What's the difference between chemistry and physics? Physicists are interested in the nature of the electrical force between atoms. Some chemists might think this is an interesting aspect of interacting atoms but they are usually more interested in the properties of the millions of chemicals that result from these electrically bound combinations. Chemists want to know how atoms interact and how more-complex molecules can be formed. They study the properties of known chemicals and look for uses for them. They also look for new chemicals to serve specific purposes. Physicists want to know why atoms and molecules occur. They look for the fundamental building blocks of atoms instead of new combinations of atoms.
The electrical bonding between the atoms of a molecule occurs in a few ways. In one situation, the electrical binding-force occurs when an electron simultaneously orbits two nearby atoms. In another situation, two neutral atoms can become electrically bound when their component charges become displaced. This happens, for example, when a charge is placed near an electrically neutral block. When that neutrally charged block is undisturbed, it consists of little packets–its atoms–of equal amounts of positive and negative charge. When an exterior positive charge is held near the block, the block's positive charges are slightly repelled while its negative charges are slightly attracted toward that exterior charge. This makes a slight separation between the positive and negative charges within the block. The near side of the block is then slightly negative, while the far side is slightly positive. The result is that the neutrally charged block is slightly attracted toward the exterior charge, see http://courses.science.fau.edu/~rjordan/rev_notes/movies/EFA03AN1.MOV. The same thing can occur in nearby molecules. The electrical charge of a large molecule is unevenly distributed about its three-dimensional shape. When two multi-atom molecules face each other, a slightly positive charge of one side of the first molecule and a slightly negative charge of one side of the second molecule can result in an electrical force that holds the two molecules together. We will see that, inside our bodies, this process builds very large molecules containing thousands to billions of atoms.
The difference in the mass of different chemicals also allows us to identify substances. To do this, a small amount of an unknown substance is heated until it is vaporized into a gas of ionized molecules. The gas molecules have varying speeds and bounce around within a container. The container has a tiny hole that allows those molecules moving in the right direction to escape into an adjacent tube. There are both magnetic and electric fields within the tube and each exerts a force on the moving molecules. The magnetic field does not exert an equal force on every molecule; instead, its force is larger on faster-moving molecules. The force of the electric field does not vary with molecular speed. Those molecules moving with a certain speed will experience a force from the magnetic field that is exactly counterbalanced by the force of the electric field. These molecules then move straight down the tube while all others are pushed into the walls of the tube. The combination of these two fields has the property that it allows only those molecules with a certain preselected speed to pass along the tube. The researcher selects the desired speed by altering the ratio of electric and magnetic fields. Those molecules having non-selected speeds will not traverse the entire length of the tube. This means that each molecule emerges from the end of the tube with the same speed. Those emerging molecules next pass into an area containing a second magnetic field forcing them into a circular orbit. For each different molecule, the size of its circular orbit depends on its mass: more-massive molecules move in a larger circle than do less-massive molecules. Measuring the radius of motion allows the mass of the molecule to be measured. This so-called mass spectrometer is used to identify a chemical by measuring its mass and then comparing it with previously known molecular masses. The mass of tens of thousands of different molecules have been measured and tabulated.
The mass spectrometer has many uses. It can be placed on a rocket and used to identify the chemicals of the upper atmosphere or of the atmospheres and surfaces of other planets and moons. Also, differences in the chemical contents of different geological sources of obsidian and such can be measured and tabulated. When archaeological excavations find an obsidian artifact, the artifact’s chemical composition can be compared with those tabulated sources to determine its geographical source. This tells much about the people who used the artifact, including their trading patterns. Criminal investigators use mass spectrometers to identify the tiny chemical remnants found in clothes, cars, rugs, hair, poisons, pencil marks, and arson materials gathered at the scene of a crime. The mass spectrometer is also used in the radioactive dating procedure.
Our knowledge of the nucleus has given us lots of useful machines. The medical imaging process called Magnetic Resonance Imaging (MRI) is an important example. To understand the operation of these imaging devices recall that the magnetic needle of a compass always points toward the north pole of the Earth. It has been found that the moving, positively charged protons inside each nucleus act as a pointing magnet and will line up with an external magnetic field. If that external magnetic field is suddenly turned off, each different nucleus–that is, each different chemical–will take a different amount of time to become unaligned from that previously existing field. MRI machines makes use of the alignment and un-alignment times of different nuclei in order to determine the types of material found inside your body. Some of these materials include bone, tissue, normal cells, and cancerous cells. This allows a picture to be made of your interior without sawing you in half.
If energy is added to a nucleus, it will soon re-emit that energy to return to its less-energetic state. Since the nucleus of each chemical emits a different spectrum of energy, a chemical can be identified by measuring the energy emissions of its nucleus. This is called neutron activation analysis. For example, after you fire a gun there is an invisibly tiny amount of gunpowder left on your palms. The personnel in a crime lab can collect a remnant from the palms of a suspect and then examine the spectrum of that heated remnant to determine if that person had recently fired a gun.
Quantum Mechanics is the description of nature on the atomic level. It was developed in the 1920s (quantum mechanics is what happens when nobody in the U.S. is allowed to drink for ten years) as a necessary refinement of Newtonian mechanics. For large-scale objects, Newtonian and quantum mechanics agree to about thirty decimal places. In 1926, Erwin Schroedinger found the version of Newton's equation that describes atomic-sized particles. Schroedinger's equation describes the behavior of the atoms inside all materials. After a few decades, people learned to use the equation to make lasers and transistors and such–like those used inside computers and cd-players. Nobody in the 1920s could imagine the machines that would result from the application of Schroedinger's equation.
Electric charges were found to come in two varieties, positive and negative, but the carriers of the strong-nuclear force have been found to come in three varieties. During this century, we will begin to make machines that use the strong nuclear force. Nobody today can imagine the future machines that will be made whose operation will be governed by the strong nuclear force. The strong nuclear force is not yet fully understood, in fact, there is much left to be learned–you might like to join in the research.
The age of many objects can be measured by the technique of radiocarbon dating. This physical process will be described here so that we can refer to it throughout the remaining chapters. As mentioned above, the nuclei of a particular chemical element can contain a small range in its number of neutrons. The number of neutrons in a given nucleus can change when an external neutron collides with it and either knocks away others or becomes absorbed. That colliding neutron may have been emitted by the chemicals of the Earth, the Sun, or even another star. Certain numbers of neutrons result in an unstable nucleus, like having an overcrowded house. Stability is reestablished when the nucleus emits "radiation." This radiation has been found to occur in three forms: an electron (named beta radiation); a light wave, like an x-ray (named gamma radiation), or a helium nucleus (named alpha radiation) that consists of two protons and two neutrons. The proper mispronunciation of "helium nucleus" is "helius nucleum."
X-rays, electrons, and helium nuclei are often useful, and like everything else, they can also be harmful. One hundred years ago, Madam Curie was one of the first scientists to study radiation. From the studies of these early scientists, we began learning the hard way about the dangers of radiation. During the last hundred years, physicists have measured millions of facts concerning radiation. Today, the most familiar use of radiation is to create monster movies. Radiation can also be used to fight cancer. It can be used to kill microscopic germs in newly harvested potatoes, fruit, and meat and such. This process is called pasteurization and gives food a longer shelf life. Radiation is used to provide power in spacecrafts and in heart pacemakers. Radioactive tracers are used in medical tests. For a list of additional uses you might like to read The Ubiquitous Atom by Grace and Larry Spruch. Radiation is emitted from the dirt below us, the bricks around us, and from the stars above us. Every day our bodies absorb a small amount of radiation.
Next, we define the term "half-life" so that we can then go on to understand the radioactive dating technique. Imagine that you shake a bag of one thousand coins and then pour the coins onto the ground. Next, pick up the coins that show "heads" and place them back into the bag while taking away those showing "tails." Pretty close to half the coins will be heads and half will be tails so that the bag will now contain about five hundred coins–that is, the bag has lost half its original contents. (By the way, five years after finishing a course at school, I have forgotten about half of the material covered. After five more years, I have forgotten half of what remained, leaving one-quarter of the original amount.) Shake the bag again and then dump the coins onto the ground once more. Again, half the remaining coins will be heads, and half will be tails. If you pick up the heads, you will find about 250. We see that about half the contents of the bag are lost after each shake. Initially the bag had 1,000 coins. After shaking and removing "tails" the bag contained 500, then 250, then 125, 63, 32, 16, 8, 4, 2, 1, and finally zero coins. (See Student Study Guide for Energy for a Technological Society by Joseph Priest, page 89.)
In the same way it has been measured that half the radioactive atoms of an unstable material will emit radiation during each half life. This changes the unstable atoms into a stable non-radioactive form. For example, if you have 10 kilograms (22 pounds) of a radioactive material then half of it will change into another chemical during a period of time equal to its “half life.” The half life of each type of radioactive atom has been measured. The half life of an atom never changes. Radiation is a natural process. Just as a hammer will always fall whenever it is pushed off a table, during each half-life, half the nuclei in a radioactive material will become more-stable by radiating either light waves, electrons, or helium nuclei.
Different radioactive chemicals have different half lives; this makes them suitable for determining different sizes of time spans. For example, one can measure how much time has elapsed since a rock had last been in a molten state. This shows that the molten Earth solidified about 4.5 billion years ago. This technique can also be used to measure the age of a given volcanic eruption.
It was mentioned above there can be a small range of numbers of neutrons within a nucleus. For example, we saw that carbon atoms always have six protons but six, seven, or eight neutrons for a total of twelve, thirteen, or fourteen neutrons and protons. The percentages of each type (each type is called an isotope) of carbon have been measured. If you start with 1,000 atoms of radioactive carbon-14, you will find that after 5700 years have elapsed , which is its half-life, only 500 of these carbon-14 atoms will be remaining; the other half of them will have emitted radiation and turned into a more-stable atom. After another 5700 years elapse, only one-fourth of the original carbon-14 atoms remain.
When the Earth formed it contained a certain amount of carbon; a small percentage was the radioactive carbon-14 variety. The carbon-14 essentially disappears within about ten half lives, which would be 57,000 years. The Earth is much older than 57,000 years. (We have measured the age of the Earth by counting radiation tracks and by measuring the relative amounts of radioactive uranium and thorium, as described in Chapter 4.) Since the Earth is much older than 57,000 years it means that carbon-14 is continually being produced, otherwise it would all be gone.
Scientists have found that energetic neutrons from the Sun and the other stars collide with nitrogen nuclei in the Earth's atmosphere and create carbon-14. This collision rate will certainly be variable but not drastically so. Little variation is likely to have occurred in the last 50,000 years because the Sun's lifetime is much longer than that. Some carbon-14 combines with oxygen to form a carbon-dioxide molecule. Living things absorb this as they breathe. Every living creature contains carbon, and all living creatures have identical relative mixtures of the non-radioactive carbon-12 and the radioactive carbon-14 varieties. After death, the relative proportion of carbon-14 steadily decreases in time. Every 5700 years after death, half the remaining carbon-14 will have undergone radioactive decay. A measurement of the relative proportions of carbon-12 and carbon-14 atoms makes it possible to determine how many carbon-14 half-lives have occurred since the object died. This is the radioactive dating technique. The greater the number of years since the death of the creature, the longer its carbon-14 has been radiating away.
We see how it can be said that millions of seemingly unrelated phenomena are just different aspects of a small number of more-fundamental phenomena. We saw how all motion can be described by a single equation, that heat is nothing but the energy of motion, and that there are many manifestations of electromagnetism.
We have also seen something of the scientific process and its accumulation of knowledge and techniques through the centuries. We see that with each generation of us humans, we add to our collective knowledge of nature. It is certain that we will continue to build additional knowledge forever. Knowledge is an important part of our civilization. We often look back at the knowledge of previous generations as we discuss the building blocks of our own knowledge. Today's knowledge forms the foundation for that of tomorrow.
The topics of this chapter provide a basis for the descriptions, in the next few chapters, of the gravitational formation of the Earth and of the electrical formation of the molecules of life. The technique of radioactive dating will appear many times in the coming chapters. The following six chapters present our understanding of the nature of a human. This knowledge has been gained through the application of the scientific process. For more information about physics, visit http://textbookrevolution.org/Textbooks/Physics.html.
We saw that some persons do science just for the pleasure of satisfying their own human curiosity; others hope to contribute to the well-being of every person on the planet–for centuries to come. The mathematics and science of the Renaissance and Enlightenment were done more for pleasure than profit. For example, nobody asked Mr. Bessel how much money he could make from his new function, and he did not demand royalties for its use. (Bessel's function appears in the mathematical solution to any system that has the shape of a cylinder or a sphere.) There are scientists who enjoy the attempt to understand the rainbow–even though they will not obtain any financial profit from this. (Each time you see a rainbow, please send some money to my friend James Clerk Maxwell.) Some of us humans enjoy music, cooking, or just eating; others follow sports or climb mountains–because "they are there"–and yet others simply want to understand the world. These are things that humans do. If you are not amused by studying the world then you might still be amused to know that there are people who are amused by studying the world.
Questions
1. List the motions of some objects. These motions can be described by Newton's equation.
2. How many electric and magnetic machines do you use every day?
3. Describe a phenomenon that involves light.
4. Describe a phenomenon that involves heat.
5. Describe a use of nuclear radiation.
6. List some future machines that will result from today's science.
7. What is the proper mispronunciation of "helium nucleus."
8. Describe a heat machine that you used today.
9. For the list of phenomena in question 41 part iii of Chapter 1, classify each phenomenon as motion, heat, or electromagnetism.
10. Measure the period of a pendulum.
11. What was the role of business and government in the scientific progress described in this chapter?
12. Why did it require a couple of centuries of research efforts to understand electromagnetism? How long have we been studying atomic, nuclear, and gravitational phenomena?
13. Should we patent both machines and scientific principles?
14. How have today's science and technology depended on that of past centuries?
15. What portion of the world's population is involved in research in science and technology? How has this portion changed through the centuries?
16. Why do some machines behave in a way that wasn't expected?
17. What is the purpose of knowledge? What is the purpose of machinery? Why do humans pursue these fields?
18. How do science and technology affect our social and cultural ways? Our health has certainly been improved by this research, have our social and cultural ways been "improved?" What portion of our happiness is due to the machines we use or the knowledge we hold? Compare the effects of science and technology on the happiness and the social interactions of people living in Ancient Egypt, an industrialized nation today, the Medieval world, and as gatherer-hunters in today's Brazilian jungle or in ancient America. When and where did we first learn to make newspapers, dishware, pajamas, cigars, wheat bread, and maple syrup?
Suggestions for further reading
A History of Scientific Ideas by Charles Singer, 1959, Barnes and Noble Books New York.
The History of Physics, by Isaac Asimov, 1966, Walker and Co, New York.
Science, Its History and Development Among the World's Cultures, Colin A. Ronan, 1982, Facts on File Publications, New York.
Understanding Physics, Isaac Asimov, 1966 and 1993, Barnes and Noble Books.
Electrostatics, Scientific American March 1972.
The Ubiquitous Atom, Grace and Larry Spruch, 1974, Charles Scribner's Sons, New York.
For descriptions of lots of everyday phenomena see The Flying Circus of Physics With Answers, Jearl Walker, 1977, John Wiley & Sons, New York.
Madame Curie, by Eve Curie, 1937, Pocket Books Inc, New York.
From Quarks to the Cosmos, Tools for Discovery, by Leon M Lederman and David N Schramm, 1995, Scientific American Library. Pbk ISBN 0716760126.
How and when the Universe began
What was the Big Bang and what measurements led scientists to think it had occurred? How and when did stars and planets form? How and when did atoms form, including those that are inside our bodies at this very moment? What is a supernova? You’ll find answers to questions like these in The Origin and Evolution of the Universe, Edited by Ben Zuckerman and Matthew A. Malkan, which was the source for some of the following sections.
The size of the universe is almost unimaginably large. The distance from the Earth to the Sun is about one hundred million miles. Driving at one hundred miles per hour (160 km per hour), it would take about three thousand years to travel that distance. The closest stars are twenty-five million times farther than that. The radius of the universe is about fifty billion trillion miles. The increase in scale from your height to the width of the universe is much greater than the increase in scale from an atom to a person. You are a one hundred million times larger than an atom and one hundred billion times larger than a proton, but the universe is thirty million million times larger than you. You can zoom from above the Milky Way galaxy down to a planet, then a plant, then its cells, then its molecules, and then its nuclear particles by visiting the website http://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10/index.html
When you look at the night sky, you see zillions of stars. For some centuries now, there have been thousands of astronomers who have spent their lifetimes measuring such things as the position, speed, temperature, and chemical composition of millions of these stars. (Each of these things is determined by measuring the light received from each star, as described below). Since we can see so many stars, we can appreciate the magnitude of the job the astronomers have been tackling. They have accumulated a base of millions of measured facts that enable them to understand much of the origin, development, and end of stars.
The stars of the universe are currently seen to be spreading apart from each other. This also means that they had been closer together in the past. In fact, the only way for them to be moving apart today is for them to have been close enough together in the past to have been propelled apart. This observation and its related deduction led to the development of the Big Bang picture of the origin of the universe. The Big Bang is not a theory "out of nowhere" awaiting a confirming observation but is the name given to the observations plus deductions that have already occurred.
To help understand this process, this chapter first contains a description of the extreme heating of a block. This is followed by a discussion of the methods used to measure the position, speed, temperature, and chemical composition of stars and galaxies. We next discuss the gravitational force of a spherical mass so that we can understand how stars and planets–including the Earth–form out of debris-filled regions of space containing unconnected pieces of material. The origin of atoms, including the atoms within our own bodies, is also described in this chapter. We'll see that when the universe first formed there weren't any atoms because it was too hot for them to exist. They began to occur only after the material of the universe had cooled a bit.
Extreme heating of a block of material is the reverse of the outwardly expanding and cooling universe
To begin with, we want to think about what happens when a block of material is heated: a lump of metal is most easily pictured. As described in the previous chapter, measurements show that the atoms of the metal jiggle increasingly rapidly as the block is heated. The heated block will first glow red and, with continued heating, will glow white and then blue (the temperature of a star is determined by analyzing its color in this way). The emitted light is increasingly energetic, from red to blue. The white color results when red, green, and blue are being emitted at the same time. You can measure the temperature at which this block melts into a liquid, and after further heating, the temperature at which it vaporizes into a gas of atoms. Continue heating an atom and its nucleus will separate into its constituent protons and neutrons. With further heating, these will separate into their constituent elementary particles and light. The temperatures and energies at which these events occur have already been measured.
The reverse process also occurs. Take the same collection of energetic light and elementary particles and continue cooling until they gather into nuclei, then gaseous atoms, and then finally form into a solid block. The heating and cooling of this block are important to our discussion of the evolution of the universe. Instead of a small block of metal, we consider the matter contained within the entire universe at the moment that it comprised a single, compact blob. At first this blob was too hot for matter to exist in any form, even elementary particles could not exist; only light existed and it had energies much greater than even that of x-rays. As the blob expanded outward and cooled, its physical state went through the same sequence as did the cooling block just considered.
Measuring the distance, speed, and chemical composition of stars
Astronomers determine the chemical composition of distant stars and galaxies by looking carefully at the colors of light received from these objects. Each chemical has been found to emit its own unique set of colors of light. For example, neon emits a red color while mercury emits a purple color. The color-spectrums of many thousands of chemicals have already been measured and tabulated. The set of colors comprising the light received from a particular star is measured by passing the light through a prism to separate it such that each color becomes completely distinguished. The chemical composition of that star is then determined by comparing its light-spectrum with the previously measured color-spectrums of various chemicals.
Astronomers measure the distance to a nearby star by comparing its position from two different viewpoints along the Earth's one-year orbit about the Sun. During one month of the year, say January, the angle between our Sun and that star is measured. Six months later, in July, the Earth has moved to the opposite side of the Sun and the angle is again measured. Distant stars will have a larger angle than do nearby stars but their apparent position will shift by a smaller amount. Trigonometry is used to calculate the star's distance knowing the measured angles and the size of the Earth's orbit about the Sun. However, this approach allows distances to be accurately measured only for the closer stars. David Nash has made an animation of the annually shifting positions of nearby stars against the background of more distant stars. To view it select Parallax Demo at www.astronexus.com/3duniv/anim.php.
The approach used to measure the distance to more distant stars involves a comparison of their actual and apparent brightness. You may have noticed that a truly bright lightbulb, such as a car or a street light, appears to be dimmer when you look at it from a distance. It has been found that the apparent brightness of a lightbulb decreases as the square of its distance from you. There is a type of star for which its true brightness is known (they are called Cepheid stars) so that a measurement of its apparent brightness indicates how far the star is from the Earth. (You may have seen photographers using little machines that measure brightness.)
Astronomers measure the speed of a star by measuring the Doppler shift in the light received from that star. We have all experienced the way in which the sound of a train or car-horn changes it passes you. The sound of the horn changes from high to low pitch as the train or car moves first toward you and then away from you. This is the Doppler shift and it happens to both sound waves and light waves. You can graphically see how wavelengths change with relative motion at www.astro.uiuc.edu/projects/data/Doppler/index.html.
The color of light is determined by its frequency, that is, by how many waves per second arrive at your eyeball. When you look at red light, fewer waves per second are passing your eye than occurs when looking at green light; blue light contains more waves per second than does green light. Imagine you are standing still while looking at a green light. The light appears green because 5,500 million-million waves per second are moving past you. The distance between successive wave crests is 550 billionths of a meter. Now imagine the same green light is being emitted from a lightbulb placed on the train. Since it is moving toward you, more waves per second will arrive at your eyeball and this makes you think the light is more blueish. In the same way, as the train's light (and sound) moves away from you, fewer waves per second will reach your eyes and the light will appear more reddish. This "Doppler effect" is also used to measure the speed of the wind and rain to produce weather reports. Police radar uses the Doppler effect to measure automobile speeds. (Just yesterday, the speed of my car was measured this way.)
Gravitational formation of stars and planets
We want to understand how planets and stars form into spherically shaped objects due to the mutually attractive force of gravity among their material pieces. For example, I am standing at a particular spot on the surface of the Earth. There is a gravitational attraction between my mass and the mass of each piece of matter throughout the Earth, including the pieces that make up the Earth's core, the pieces that make up China and Africa, and the pieces right under my feet. The total force of gravity between me and the entire Earth comes from adding together each of these attractions. It turns out that calculus shows that you get the same total force when you replace the spread-out Earth with a single point-sized mass. This single mass is located at the center of the Earth and has the same mass as the entire Earth.
............
. Greg .
. ............ .
. . .
. . .
. . .
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. John . Greg is pulled downward . Jeff .
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To see how this can be true, imagine two persons–John and Jeff–pulling equally hard on ropes tied to Greg. Both John and Jeff are two steps in front of Greg but John is three steps to the left, while Jeff is three steps to the right. We can believe that Greg will move downward, in the direction shown, because portions of John and Jeff’s pull cancel each other. If we add two more equally-strong pullers, Kari and Bryan, right next to John and Jeff, the net or equivalent pull will still be in the same downward direction as before.
Imagine now that John and Jeff are replaced with two equally sized portions of Earth which are below its surface. Greg is still being pulled equally hard by two symmetrically paired pulls, which are coming from pieces of the Earth. For example, the attraction between Greg and a piece of the Earth that is to his right but twenty miles down into the Earth can be combined to the attractive pull from a piece that is to his left and down twenty miles. If we think of these two pieces to his right and to his left, it is like a pair of ropes pulling him equally to the right and to the left but also downward. These right and left pulls cancel each other's effect. Greg is pulled equally by each so he will not move toward either; instead, he moves along the center line between those two pulls. The two sideway pulls add up to a single "gravity rope" pulling him straight toward the Earth's center.
We can divide the entire material of the Earth into similarly paired blocks to see that they all add up to a single pull toward the Earth's center. In the same way there are pieces right under his feet that can be compared with far away pieces that are near the opposite surface. The nearby point pulls more strongly than does the far-away point. The far-away and nearby pulls add up to a single "puller" placed right at the center. This fact was first worked out by Isaac Newton in 1685. (Whenever one of us humans figures out a new fact, it is recorded and made available to everyone, used again and again, and never unlearned or forgotten.)
We feel our own weight because that is how strongly all of the pieces of the Earth are pulling on the matter of our own body. If you stand on a scale and weigh yourself but then have somebody pull down on your feet, the scale will read as if your weight has suddenly increased. When you stand on the scale, the Earth is pulling on your feet with the force indicated by the meter. It is an attractive force between each piece of your body and each piece of the Earth. The more pieces you have the larger will be the force and the higher the scale reading.
The point of this discussion is that each piece of the Earth thinks it is simply being attracted toward that single central point of the Earth's sphere. The gravitational force between you and the entire volume of the Earth is identical to the gravitational force between you and a point mass, whose mass equals that of the entire Earth, placed at the position of the center of the Earth. This gravitational force actually pulls each of us toward the center of the Earth; that’s why we don’t fall off . In the same way each piece of a star feels an attraction toward the star's center. And in interstellar space, a dispersed amount of gaseous debris can become gathered together through a mutual attraction toward its center and result in the formation of a spherical star. A planet also forms in this way. Another example is that all of the mass of the universe is gravitationally attracted toward its center, and this attraction slows the rate of expansion of the universe.
Astronomers have measured the motion of many galaxies. The distances and speeds of these galaxies have been determined in the manner discussed above. We observe that, right now, all of the galaxies are moving away from each other such that the universe is seen to be expanding. The galaxies are moving away from each other in the same manner that raisins spread apart within a baking and expanding loaf of raisin bread. Another analogy is that the galaxies are moving away from each other in the same manner as do small pieces of paper glued to the surface of a balloon that is expanding as it is being blown up.
It is natural to extrapolate backwards in time and conclude that in the past, the galaxies had been closer together. Even further back in time, all the galaxies had to be clumped together in one blob. Gravity doesn't push objects away from each other; it only pulls them together. The only way for the galaxies to have been propelled apart is by having been close enough together in the past for a non gravitational force to have been involved. Measurements and calculations show that about somewhere between twelve and fourteen billion years ago the universe began to expand from a single, very hot, compact blob. This was the "Big Bang." A video clip of the Big Bang can be seen at www.tufts.edu/as/wright_center/cosmic_evolution/docs/fr_1/fr_1_mov.html on the Tufts University website. An animation is available at http://resources.schoolscience.co.uk/PPARC/bang/bang.htm. See also, http://chandra.harvard.edu/resources/animations/bigbang.mov.
This initial blob included all of the energy and matter of the universe, including the future contents of our bodies, and even space itself. Space itself is included because it has been found that the presence of mass bends the structure of space with the result that the mass then has to move along within the bent space. To visualize bent space, consider a horizontally stretched sheet of cloth with a heavy ball placed on its surface. That heavy ball bends the surface of the sheet in the same way that mass bends the space in which it travels. For a video clip, watch A New Picture of Gravity at www.pbs.org/wgbh/nova/elegant/program_d_t.html. When all of the mass of the entire universe was clumped into one small region just before the Big Bang occurred, space itself was also contained within that same region. Newly discovered Dark Matter may also be curving spacetime, as shown at http://chandra.harvard.edu/photo/2002/igm/Rivers.mov. This aspect of space is described by Einstein's General Relativity equations that he published in 1915. This interaction of space and mass has been measured in many ways–for example, by measuring the trajectory of light waves traveling past the massive Sun. This means that the galaxies aren't moving out into empty space that has been sitting there waiting for their arrival, but that the galaxies and space are both expanding outwards together. This means that not only is the matter of the universe expanding outward from the Big Bang but that space too is expanding outward. The matter of the universe is not expanding into previously-existing, empty space that has no edge. Our universe is comprised of both space and matter. The edge of our universe is expanding outward as space and matter move there.
It is to be stressed that the observations came first, and that the Big Bang scenario was later developed to explain the observations. The observed expansion of the universe has lead to the description called the "Big Bang." It is not the case that the observed expansion of the universe came as later evidence to support the earlier "theory of the Big Bang."
Each group of us humans have used our imagination to guess the nature of stars and the manner in which the universe began. It is fun to hear of the cosmological explanations of various cultural groups of us humans. Luckily, we have recently been able to make more concrete measurements of these processes. We have found that the actual workings of nature are more interesting and unbelievable than the explanations our imaginations have produced.
The gravitational attraction of all of the matter of the universe is pulling all of the matter inward as described above. It is not known yet whether there is enough mass to pull the matter back into a centrally located clump. It may be that the contents of the universe repeatedly come together into a compressed compact region that then expands again in another Big Bang. This cycle could repeat over and over. Alternatively, it may be that an uncountable number of Big Bangs occur within the material of earlier Big Bangs like many bubbles expanding from the surface of many other bubbles forming a foam of bubbles. Absolutely unique events are rare in nature; if one occurs–including a Big Bang or the development of life–than there are likely to be many more. Much research is occurring right now, trying to figure out the basic nature of the Universe. You might like to join in the effort. Most every question pales in comparison with that of the origin and fundamental nature of the universe.
How and when atoms first formed
Give a physicist pictures of things like cows, dogs, toasters, lemons, boats, and shirts, and then ask her to classify these items. She will categorize them by such physical properties as electrical resistance, thermal conductivity, and nuclear structure. If you show a person to a physicist then she will want to know about its atomic structure. The following paragraphs contain a description of the formation of the atoms and molecules of our own bodies.
Initially, the material of the Big Bang was too hot for atoms or even nuclei to exist. Our bodies consist mainly of atoms like hydrogen, carbon, oxygen, and iron and such. At the initial instant of the Big Bang, none of these atoms yet existed in the universe because its temperature was too high. Instead of containing particles, the early universe was flooded only with energetic light. The remnants of this light are still visible today as the background cosmic radiation that has cooled to a temperature of -270 Celsius (-460 Fahrenheit) degrees. This background radiation was first observed by Arno Penzias and Robert Wilson, for which they received the 1978 Nobel Prize in physics (Wilson’s Nobel prize acceptance lecture can be read at http://nobelprize.org/physics/laureates/1978/wilson-lecture.html. As the universe expanded and cooled, elementary particles were able to form.
When physicists use particle accelerators to measure the properties of high energy, elementary particles, they are also measuring the properties of the early, energetic universe. These particle accelerators reproduce the energy that pieces of the universe had right after the very first instant–within a tiny faction of a second–of the Big Bang. They cannot quite reproduce the energy of the very instant of the Big Bang. This means that there are no measurements to give us a detailed understanding of that very first instant. Scientists propose mathematical descriptions of that first instant and then propagate their models of the newly formed universe forward in time a few seconds so that the model’s predictions can then be compared with the measured properties of the later universe.
The material of the Big Bang continued to expand and cool, allowing the elementary particles to gather into neutrons and protons. When its temperature became low enough, the simplest atoms could form. Scientists have already measured the temperature at which each type of atom forms. The universe then consisted of the simplest chemical elements, including only hydrogen, helium, and tiny amounts of Lithium (which is used as a medication), and Beryllium. Stars consist mostly of hydrogen. Until there was hydrogen, there were no stars. We will see that the heavier elements are formed by stellar fusion and in supernova explosions.
Star formation and stellar fusion
Stars form as clumps of hydrogen gas gravitationally coalesce. Computer experiments involving the gravitational attraction of 10,000 mass points have shown that a slight clump in the hydrogen gas will coalesce into a star in 10,000 to 100,000 years. These clumps are often accompanied by a surrounding disk of material that will similarly coalesce into planet-sized clumps. For a two-minute animation of the gravitational accumulation visit http://wapi.isu.edu/Geo_Pgt/Mod02_SolarSys/images/nebula.GIF. Star formation is now occurring inside the gaseous clouds of the Eagle Nebula, see http://antwrp.gsfc.nasa.gov/apod/ap970119.html, and in the fuzzy spot you may have seen in the constellation of Orion. Visit the Tufts University website at www.tufts.edu/as/wright_center/cosmic_evolution/docs/fr_1/fr_1_mov.html for an animated video clip of the formation of our solar system. By the way, you can travel through the Orion Nebula by downloading C. Robert O'Dell’s mpeg movie from the website www.batse.msfc.nasa.gov/colloquia/abstracts_spring05/crodell.html.
The weight of the central clump of a newly forming star will continue to increase as its gravitational pull brings in additional mass. The inward, gravitational pull of the star material causes the size of the clump to shrink. The centrally directed compression of an initially forming star (the same thing happens for smaller clumps that form planets) continually increases the central material's density, pressure, and temperature. The huge weight of the outer material of a star crushes its central material. Most of the star's mass consists of hydrogen atoms. When the star's weight becomes great enough that pairs of hydrogen nuclei are crushed together to form a helium nucleus, a great amount of previously-stored nuclear energy is emitted in the form of light and particles: this process is called "fusion." We see this energy as the sunlight that heats our planet. When a newly formed star first begins to shine, its outwardly moving light blows away the remainders of the dust cloud from which the star formed.
The star's fusion process releases energy in the form of light and elementary particles. This results in an outward pressure that works to slow the inward collapse caused by the gravitational pressure. The fusion process continues to intensify until its outward pressure exactly balances the inward gravitational pressure. At the moment this occurs, the outward pressure is actually holding up the entire weight of the star and the radius of the just-formed star stops changing.
A stellar-candidate clump will not be able to fuse hydrogen if it does not contain enough mass to supply the crushing weight needed to initiate fusion. A clump will never emit light if its mass is less than 8% of the mass of our Sun. Jupiter is an example of this; its weight is too small for fusion to occur. If a candidate clump's mass is one hundred times larger than that of our Sun, it will be too unstable to form a star.
The energy released by this fusion process is humongous. Fusing the 30 grams (0.07 pounds) of deuterium found in one cubic meter of water releases the same amount of energy as that obtained by burning 240 tons of coal. The total energy contained in the ocean's deuterium amounts to 3 x 1031 Joules and would provide us with energy for the next ten trillion years if our civilization continued to use energy at its present rate of ten trillion Joules per second.
Today's average U.S. home uses about one thousand watts of power, which is the same thing as one thousand Joules per second. (Until this century, a cooking fire supplied the only energy that each of us used in our home; our homes today use as much energy as thousands of homes had used a few centuries ago.) With the huge amount of energy that would be available from fusion, the average home would have access to one thousand to one million times our current energy usage. If each family throughout the world began using one million times as much energy as does the average family in the U.S. today, then the energy available from the ocean's deuterium would last for ten million years.
For the last fifty years, scientists and engineers have been trying to build a fusion machine. (For an animation of a fusion machine, visit www.visionlearning.com/library/flash_viewer.php?oid=2747.) The difficulty has been that the machine needs to develop the temperatures and pressure found within stellar interiors. The center of our Sun has a temperature of fifteen million degrees. Within a couple decades–or ten–we might succeed in developing this fusion machine. It will be an important moment in our history when we do succeed. I can imagine that soon after fusion-powered electrical generating plants are successfully engineered we will have access to one megawatt of power in each of our homes; this is one thousand times the power we are currently using. This is enough power to change one chemical element into another by changing the number of protons in its nucleus. Such an energy would greatly improve the quality of life of us humans. It is hard to imagine the full impact of having so much energy available to each of us. For example, how will our daily life change, and how will our outlook on material possessions change, if each of us has a kitchen appliance that changes lead into gold. If you place a little carbon, hydrogen, and oxygen together with a few other chemicals into a container and then apply a few megawatts for a moment, you might be able to make a green chile–or at least a tomato.
Our Sun gets its energy from this hydrogen-fusion process. Every process on the Earth gets its energy by absorbing sunlight (very few of the Earth’s life forms instead obtain energy from deep-ocean volcanoes). Sunlight from solar fusion heats the Earth and supplies the energy to drive the weather and all of the chemical processes that occur inside plant life. About 10% of the sunlight that falls on the Earth is absorbed by plants, mostly algae. As plants absorb sunlight, they convert its light-energy into stored, chemical energy. When we eat these plants, we convert their stored energy into our own heat and motion. We power much of our civilization with the coal and gasoline that comes from the energy stored within plants and animals that died and became buried long ago.
The products of aging stars and supernova explosions form the carbon, oxygen, iron and heavier atoms that are now part of our own bodies
A star will continue to convert its hydrogen into helium until much of the hydrogen is gone. An average star, like our Sun, converts about 700 million tons of hydrogen per second. At this rate the star's material lasts for about ten billion years. This is what is meant by the length of a star's lifetime. Stars with twenty times the mass of our Sun are seen to be able to crush the hydrogen together so strongly that the star exists for only ten million years; it lives a short and very bright life.
As a star begins to run out of hydrogen, its hydrogen fusion process will slow. The outward pressure of the fusion products is then smaller, and the star's radius will again begin to decrease. The star will become more compressed, causing it to become hotter. When the temperature is high enough, the star's helium will begin fusing into heavier atoms. After its helium has all been fused, the star’s radius again shrinks, heating the star’s interior and causing yet heavier elements to fuse into even heavier elements. After such a series of differing elements being fused, old stars come to contain concentric, spherical layers of differing chemicals. (For a picture, see http://wapi.isu.edu/Geo_Pgt/Mod02_SolarSys/images/onionstar.GIF.) This atom-building process continues to result in increasingly heavier atoms until iron is created. The centers of these stars contain a lot of iron. Iron is the heaviest atom built by the fusion process occurring inside stars. Elements heavier than iron do not release energy when fused together; instead, they must absorb energy to be fused. Sufficient energy for this occurs only during supernova explosions.
For smaller stars, like our Sun, the last stage of their lives results in an expansion. The usual lifetime of stars like our Sun is about ten billion years. Since our Sun is currently about five billion years old, it has another five billion years before its life ends in such an expansion. At that time, the radius of our Sun will increase outward beyond the Earth. We will then have to move somewhere else. Try to imagine how we might go about re-establishing the Earth’s life forms on another planet.
For heavier stars the compression process wins, and the star becomes squeezed until its protons and electrons merge to form neutrons plus escaping light. The material of this star, much of which had recently been iron, is then nothing but neutrons. For this reason, it is called a neutron star. The star then has the density of a nucleus. A spoonful of this star would weigh millions of tons. As that final compression begins, the outer layers of these massive stars are ejected in a supernova explosion. It is only within these explosions that the elements heavier than iron are formed. These heavier elements include copper, lead, gold, and uranium, and such. You might visit the NASA websites www.nasa.gov/vision/universe/watchtheskies/grb_supernova.html and http://imagine.gsfc.nasa.gov/docs/science/know_l1/supernovae.html to see animations of supernova explosions.
The center of the Earth is nothing but a large piece of iron formed through stellar fusion. Except for hydrogen and helium, the heavier chemicals now found within the Earth–and within you, too–were created by stellar fusion or during stellar explosions. Supernova explosions eject these chemicals into space. The ejected material forms “dust clouds” in space, some of which later formed into the Sun, Earth, and us. Our Sun is a third generation star, meaning that some of its material has gone through two previous cycles of stellar formation and death.
It is often said that we are made of the material of stars and supernova explosions. We can also claim to have been at the Big Bang because all of the universe was there, including the energy that later became the hydrogen atoms and other chemicals within our bodies. We were sort of there but spread out into many packets of energy. Some of our protons may have been temporarily held in a series of differing atoms within differing stars and dust clouds.
While on the Earth, the atoms of our bodies have gone through similar cycles. The Earth’s carbon atoms have been on the planet since its formation, and they will remain there until the expanding, dying Sun engulfs and disintegrates the Earth. Each carbon atom now sitting inside your body has been within a series of living creatures, air parcels, and rocks during the last 4.5 billion years. It may have been eaten by one animal who in turn was eaten by another who exhaled it. After sitting on the ground for a million years it may have been taken up by a plant only to be eaten by another animal. It is within you only temporarily.
When astronomers observed the spectra of the supernova cataloged as 1987a, they monitored the heavy element synthesis and observed the creation of the neutron star. This supernova converted a huge amount of mass, equal to about one-tenth of the mass of our Sun, directly to energy. This is described by Einstein's famous equation E=mc2, and is about the energy produced in one second by all of the observable universe. (A typical supernova explosion releases as much energy as five trillion trillion atomic bombs.) These are huge numbers. (Visit www.csun.edu/~gsl05670/619%20class%20projects/audio_files/einstein_speaks.mp3 to hear Einstein say his equation.)
The ejected material flies outward into space, dispersing for some thousands of years. These expanding shells of gas can be seen in small hobby-sized telescopes. An example can be seen near the star Vega within in the constellation Lyra. This is the Ring Nebula, which is cataloged as Messier object 57. You can see a picture of it at the NASA website http://antwrp.gsfc.nasa.gov/apod/ap040704.html. About 10,000 years ago its star exploded, sending a spherical shell of material outward. It is about 25,000 trillion miles away and 12 trillion miles in diameter.
Scientists have measured the percentage of each type of atom existing today. About 90% of the matter of the universe is found to consist of hydrogen. Scientists also start with the high-temperature, compressed material of the Big Bang, and then apply the equations for the energies and transition temperatures to calculate the percentage of each kind of atom that would develop from that cooling and expanding blob. They combine these figures with calculations of the amounts of each chemical that would be produced in stars and in supernova explosions. This allows them to start with the material of the Big Bang and then calculate the percentage of each type of atom that should be seen today. Since the results of this calculation matches the measured percentages, we know that we have a fairly complete picture of the way the universe is developing.
The most important atoms of life are those that are also the most commonly occurring. It might be expected that life forms would develop from the most common types of atoms rather than from rare atoms. This argues that most of the universe's life forms, if others exists, are likely to consist of the most common chemicals. In addition, heavy elements are also needed for life. Astronomers observe that older, more metal-rich stars are found toward the centers of galaxies. Life might form on star-orbiting planets but only if those stars last long enough for this to occur. As mentioned above, medium-sized stars last about ten billion years while the brighter and larger stars last only ten million years. This means that the oldest life forms–and civilizations–may be found around the medium-sized stars that are located near the center of the galaxy. It would take a radio signal 50,000 years to reach them from here. For information about NASA’s search for planetary systems outside our own solar system, visit http://planetquest.jpl.nasa.gov/gallery/gallery_index.html.
How long did it take for life to form on the Earth? The oldest geologic deposits of organically enriched carbon-12 sediments are known to have occurred within a few tens of millions of years after the formation of the Earth. The formation of life will occur more quickly on planets that have liquids because chemical mixing-rates are greatly increased within liquids. Heat from the radioactive decay of underground materials may result in liquid water occurring underneath the frozen surfaces of Jupiter’s moons Europa, Callisto, and Ganymede. Recently, the Huygens space probe landed on Saturn’s moon Titan and found liquid methane at a temperature of -290 degrees Fahrenheit (-190 Celsius). For more information about Huygens, visit the European Space Agency website at www.esa.int/SPECIALS/Cassini-Huygens. Will we find life on any of these moons or on other planets?
An exploding star sends its material outward. Debris from several stellar explosions can mix in one region of space and begin to coalesce gravitationally into a new star. This coalescence of debris is the way that our Sun and solar system formed. Computer simulations show that it takes from 100,000 to ten million years for gravity to form the large gaseous planets out of the disk of that proto-star. The rocky planets instead form through the accumulation of dust into larger and larger bodies.
The spectrum of light we receive from our Sun tells us that 99% of its material consists of hydrogen and helium, but the planets of our solar system are composed of a larger proportion of heavier elements. The four gaseous planets–Jupiter, Saturn, Uranus, and Neptune–have been found to contain much less hydrogen and helium than does the Sun. The inner, terrestrial planets are rocky and are composed of little hydrogen and helium.
Our solar system also consists of the asteroid belt, which is located between the Earth and Mars, and comets that move in large orbits around the Sun. The comets are remnants of the initial material that formed into our solar system. Scientists measure the chemical composition of comets to determine the chemical composition of the early solar system. This means that comets are like little “chemical time-packets” in that they are a record of the past. An iron meteorite is a remnant of the interior of a star.
The point of this chapter has been that the measurements of the positions and speeds of stars reveal that the universe –that is, its space and matter–is expanding outward. The material of the universe does not produce outwardly-directed expansive forces unless the material is contained within a tiny volume. The observed, ongoing expansion of the universe would not be occurring today if it hadn't been the case that the initial universe used to be contained within a volume that was small enough to allow the expansive forces to have been generated. This tells us that the universe has been expanding from an initial, central clump. This observation has been stated as the "Big Bang" scenario. Visit www.pbs.org/wgbh/nova/origins for a video series concerning the sequence of events from the Big Bang to biochemistry.
There are one-hundred types of atoms; each forms a portion of all of the matter of the universe. These portions have been measured and found to agree with the portions expected from mathematical models of the expanding and cooling material of the Big Bang. This agreement shows that we understand the overall process of the creation and expansion of the universe. If the two did not agree then we would know that our model of the universe was still missing pieces of the actual process.
Another point here is that our bodies consist of chemicals that did not exist at the moment of the Big Bang; instead, these chemicals were formed later within stars and supernova explosions. We have found that we are tiny, tiny constituents of the universe. Even the Earth and the Sun are found to be minuscule objects when compared with the entire universe. Our Sun is just one of the zillions of stars. The processes in which stars form, age, and die are well understood because millions of stars have been observed and studied.
Questions
1. How much has the Sun changed during your lifetime?
2. How much have the shapes of the constellation figures changed during your lifetime?
3. Is there life outside the Earth right now?
4. Will humans build cities on other planets?
5. Can you tell that the temperature of your camp fire is increasing as it first gets going? How does its color change? How is this color and temperature sequence related to a star's color and temperature?
6. Can you use trigonometry to determine your distance from a tree or a building of known height?
7. Find two trees separated by about one-hundred footsteps. Walk from the first tree toward the other and then go ten steps beyond the second tree. Now turn right by 90 degrees and as you walk ten more steps, make a note of the change in angle between your direction of motion and the positions of the two trees. The closer tree appears to move relative to the more-distant tree. This is called parallax and is the way astronomers measure the distance to nearby stars. Instead of moving ten steps, the Earth moves a distance equivalent to the diameter of its orbit as it circles halfway around the Sun.
8. Describe a machine that uses gravity.
9. When will we harness fusion power? If you had available for your own use as much energy as is currently used by all the people of the entire planet, what would you do with it? How would your life be different?
10. What does it mean that you have breathed the same oxygen atom that Julius Caesar had earlier breathed? During your lifetime, what percentage of the Earth's atmosphere will you have breathed? Are the oxygen atoms of our atmosphere disappearing? Are new ones appearing? Were any of the carbon atoms in your body today part of Caesar’s body in the past?
11. Did the copper atoms within everyone's body come from the same star or from many different stars?
12. The average atom in your body remains there for just a couple of years before being replaced by another. How can we still be the same person if each of our atoms are being replaced?
13. Will all of the stars eventually burn out? What happens then? You might like to read Heat death and the Phoenix: entropy, order, and the future of man, Norman H. Dolloff, 1975, Exposition Press, Hicksville, NY
14. Has there been a series of Big Bangs and Big Crushes within our universe? Some astronomers use the term Big Gnab for a Big Crush because it is the reverse process of a Big Bang.
Primary source for the chapter
The Origin and Evolution of the Universe, Edited by Ben Zuckerman and Matthew A. Malkan, 1996, Jones and Bartlett Publishers Sudbury, Mass.
Suggestions for further reading
The Moment of Creation by James S. Trefil, 1983, Charles Scribner's Sons New York.
The latest details concerning the Big Bang, and its first instant, are described in the following two books.
The Whole Shebang, A State-of-the-Universe Report, Timothy Ferris, 1998, Touchstone Books, Simon & Schuster, New York.
The Inflationary Universe by Alan H Guth, 1997, Addison-Wesley Publishing Company, New York.
Universe in Focus by Stuart Clark, 1997, Barnes and Noble Books, New York.
The Planetary System, David Morrison and Tobias Owen, 2003, Addison-Wesley Publishing Company, New York.
Ancient Astronomers, Anthony F. Aveni, 1993, St Remi Press and Smithsonian Institution, edited by Jeremy Sabloff.
How and when the Earth began, and the effects of its moving continents on life
In this chapter we look at the initial formation of the Earth and then describe some evidence for its moving, tectonic plates and for its fluctuating climate. The main points of this chapter are that the global position of each continent slowly changes through time, that the climate of each continent changes as they move about in latitude and longitude, and that this in turn causes changes in the plant and animal species of each region of the Earth. You might to visit http://svs.gsfc.nasa.gov/search/Keywords/Rotating.html to see NASA’s animation of the rotating Earth. Visit www.solarviews.com/cap/earth/vearth4.htm for an Earth topography animation. For additional Earth-science information, visit http://textbookrevolution.org/Textbooks/EarthSciences.html.
The primary source for this chapter is A Short History of Planet Earth, Mountains, Mammals, Fire, and Ice by J. D. Macdougall. I have included the portions of his book that present the measured facts concerning the age of the Earth, the interior of the Earth, continental drift, changing sea levels through time, glacial advances and retreats, and the temperatures of past ages. These items are directly involved in changes in climate and in plant and animal types. You should read his entire book because it contains many other interesting topics.
Initial formation of the Earth
The previous chapter contained a description of the gravitational process by which a new solar system is formed out of the debris of older stars. In our Solar System, debris gravitated into one large central Sun and also into several smaller planets; near these planets, even smaller clumps formed into moons. The Earth accumulated out of a portion of this clump of dust, gas, and debris in a process that required about ten thousand years to be completed. When the Earth's size became large enough, the weight of its outer material crushed and heated its inner material, causing that material to melt. There is no video tape of the formation of our Earth (unless a family from Andromeda happened to take a few photos while on a long vacation); this gravitational-accumulation scenario is instead observed as a computer experiment where trajectories are calculated for tens of thousands of dust- and rock-sized particles that initially comprise an interstellar dust cloud. One on-line video is available at http://jrscience.wcp.muohio.edu/movies/solarsystemformation.mov and another at http://hubblesite.org/newscenter/newsdesk/archive/releases/2004/33/video/b. You might like to visit http://yso.mtk.nao.ac.jp/~kokubo/moon/kit/movie.html to view a movie showing the formation of the moon through the collision of the Earth and a Mars-sized mass.
Within the molten portion of the Earth, the heaviest materials sank to the center to form the core while the lightest materials floated to the top to form the continents. For example, iron is heavier than many of the Earth's minerals so it sank toward the Earth's center. Iron also has a higher melting point so that it remains in solid form for a longer amount of time compared with many of those other chemicals. It has been calculated that a half-mile (one km) sphere of iron would take about one million years to sink through the molten Earth to its center. Such calculations are possible because scientists have measured the time it takes lumps of various materials to fall through various liquids–for example, the time for a pearl to fall through a bottle of hair remover or the time for a bucket of oil to leak through a hole, which is the way the viscosity of car oil is measured. This fall-time depends on the densities of the lump and of the liquid and on the viscosity of the liquid. These properties have been measured for thousands of chemicals. Remember that the Earth's heaviest elements came from stellar interiors and supernova explosions, and that the Earth's iron core is a remnant of the last fusion-stage of a star that later exploded. (This means there might be city-sized chunks of iron floating around the galaxy.) In just tens of millions of years, the materials of the early Earth had separated into layers of differing densities. In general, the heavier chemicals had moved toward the Earth's center while the lighter chemicals moved toward its surface to form a crust. The material of the continents consists of the lightest chemicals. The other rocky planets and moons have crusts also but no continents. The lack of continents on other planets indicates a lack of such easily accessible minerals because these minerals will not have already risen to the surface.
The Earth's crust first solidified about 4.5 billion years ago (for comparison, 4.5 billion seconds are about one hundred years). This fact has been determined in a several ways. For example, when a piece of liquid emits radiation there is no permanent effect on the surrounding liquid but a measurable track remains visible when this happens inside a solid material. In the same way that running your finger through cake batter does not leave any permanent effect while running your finger through a baked cake does leave a visible result. When a liquid material cools and solidifies it can then begin to accumulate radiation tracks. A higher number of tracks indicate that it has been in solid form for a longer period of time. The 4.5 billion-year-old age of the Earth can be determined by counting either uranium or thorium decay tracks in lead rocks.
Still today, the center of the Earth's core is hot enough that its iron would normally be a molten liquid. The huge pressure caused by the weight of the material above the core causes it to instead remain in solid form. We have laboratory machines that can generate these great pressures, and this allows us to make measurements of the properties of materials that are being subjected to such high pressures. This solid core has a radius of 750 miles or 1,200 kilometers, which is about the width of Texas, and is mostly iron. It is actually spinning relative to the Earth’s surface. It is surrounded by a molten layer of iron that is 1,400 miles (2,200 km) thick, which is about the same as the distance across the Atlantic from Reykjavik, Iceland to Bonn, Germany. In turn, this is surrounded by yet another layer, called the mantle, that is 1,800 miles (2,900 km) thick. Surrounding the mantle is the crust that is three or four miles (5.5 km) thick underneath the oceans but it is 18-25 miles (35 km) thick underneath the continents. The mantle contains more of the heavier chemicals, like iron and magnesium, and less of the lighter chemicals than does the crust. The continents form the Earth's outermost layer. You can see a picture of these layers at http://pubs.usgs.gov/publications/text/inside.html, which is part of the U.S. Geological Survey website.
These layer sizes and their densities are deduced by measuring the time it takes earthquake waves to pass through the Earth along various paths. To understand the details of just how a wave passes through matter, consider a solid block of a certain chemical, like iron. Each atom within the block is held in place by the electrical forces of its neighboring atoms, making each adjacent pair of atoms behave as if they are held together with a spring. (The positions of these atoms can be measured in many ways–for example, with a scanning-tunneling microscope, for example see http://www.nrel.gov/pv/measurements/ on the National Renewable Energy Laboratory website.) When one side of the block is pressed inwards, its "springs" will be compressed. These springs will rebound outward when that external pressure is removed, and this results in a wave motion that spreads throughout the iron. It turns out that a forced disturbance causes one wave to move inwards and outwards along the direction of the applied force, and a second, more slowly moving wave that wiggles perpendicularly to that first wave. (See www.kettering.edu/~drussell/Demos/waves/wavemotion.html for animations of these so-called longitudinal and transverse waves.) These speeds of these two types of waves have been measured for many materials and are determined by the density of the material and the strengths of the interatomic forces, which determine the "stiffness” of the springs. Waves move faster along strong springs then weak ones, just as waves move faster along a string held tightly–rather than loosely–between two hands. If you compress and release a liquid you will not get the perpendicular waves because you can't really wiggle a piece of liquid sideways, you can only compress it. To finally relate this discussion of waves to our description of the Earth's interior, it occurs that when an earthquake wave passes though a liquid, only the parallel waves continue onward while the perpendicular waves disappear. The USGS website http://pubs.usgs.gov/gip/interior has additional information about this. For the video Earthquake animation: Northridge showing the complicated earthquake process, visit http://solidearth.jpl.nasa.gov/rp.html.
An earthquake occurs when a piece of the solid Earth suddenly shifts. This sudden movement generates both perpendicular and parallel waves that travel outward from the point of origin. Geologists use seismometers to measure the magnitude of the earthquake waves and also their arrival times at many points around the globe. The distance between each receiving seismometer and the wave's point of origin tells geologists about the speed of the wave as it traveled through the Earth to arrive at those seismometers. Since wave speeds are affected by the density and the type of material that they pass through, geologists are able to deduce what sorts of materials occur within the Earth. Visit www.nchc.org.tw/english/vr_result_franctal1.php for an earthquake wave movie and accompanying music that is also art.
Geologists know that the Earth's middle layer is liquid because perpendicular waves do not pass through this region. Imagine an earthquake occurring at a point on the surface of the Earth. Waves move outward from the site of the earthquake in all directions. Some waves head straight to the opposite side of the Earth, others move toward the nearby horizon, and yet others travel at a forty-five-degree angle into the Earth to emerge at the more-distant surface. A perpendicularly wiggling wave which tries to move straight through the Earth toward its opposite side will be blocked by the liquid region described above. Other perpendicularly wiggling waves, which travel along on a line just below the Earth's surface, can emerge at the nearby surface and be detected by a seismometer. Those waves moving downward along a forty-five-degree angle might pass all the way through the Earth while those moving downward at sixty-degree-angles do not. The angles of those which do pass through the Earth serve to locate the Earth's molten region.
The interior of the Earth includes radioactive elements. As mentioned above, when a radioactive atom decays, its emits energetic particles in the form of a helium nucleus, electron, or light. Inside the Earth, these can travel but a short distance before being absorbed by surrounding material. The surrounding material is heated when it absorbs those energetic particles. Through the last four billion years, such radiation has continually heated the Earth’s interior. If there were no radiational heating, the Earth would cool off in just fifty million years. The interior of the Earth is the source of much of the background radiation that our bodies absorb everyday.
Moving tectonic plates and the factors that affect climate
We see that the interior of the Earth consists of several concentric, spherical shells. We live on the outermost shell. But the surface of the Earth is not formed of one solid piece of material that moves as a whole; instead, it is broken up into ten large and many small pieces in the manner of adjoining jigsaw pieces, which geologists call "tectonic plates." Below the Earth's crust, some hotter sections of the mantle are moving upwards while adjacent sections are cooler and moving downwards. This convective movement of mantle pushes the plates around the surface of the Earth.
We are all familiar with the Earth’s continents, including Africa and Australia and such. Due to their lower weight, the continents ride along on top of the heavier, crustal material–in the same way that bread would float on oatmeal. The molten material of the mantle slowly churns around with hotter sections moving upward and adjacent, cooler sections moving downward. The motions of the mantel push the continents around the surface of the Earth. To see an animation of the continents moving around the planet through the last 225 million years, and to also see a picture of where the continents might be 250 million years from now, you might like to visit the NASA website at http://liftoff.msfc.nasa.gov/news/2000/news-collision.asp. The arrangement of oceans and mountains as they appeared in the U.S. some 80 and 300 million years ago can be seen by visiting the United States Geological Survey (USGS) website http://pubs.usgs.gov/gip/continents. Animated globes showing continental positions and features can be seen at www.scotese.com.You can view on-line books describing the Earth’s interior, geologic time, moving continents, ice ages, glaciers, dinosaurs, volcanoes, and fossils by visiting http://pubs.usgs.gov/products/books/gip.html. The BBC website has an animation called Welcome to Britain’s Rocky Past, From the Big Bang to the Present that includes the continental movements through the last 500 million years, see www.bbc.co.uk/education/rocks/flash/indexfull.html.
Each continent rides on top of one or more of the moving plates. Sometimes a continent is sitting on top of two adjacent plates that begin to move apart due to an upwelling of mantel material, as seen in the animation Plate Tectonics II at www.mhhe.com/biosci/genbio/tlw3/eBridge/Chp20/20_keypoints.mhtml. This causes that continent to become torn or split into two pieces which then begin to move away from each other. This is called a continental rift. About a billion years ago, a rift began to develop around the Great Lakes region of the U.S., but then stopped. The Rio Grande, Red Sea, and East African rifts are more recent developments.
In your kitchen you can see little "continents" moving, splitting, and colliding by placing two small separate drops of liquid oil on top of a pan of water and then slowly heating the pan on a stove. You'll see that some regions of the water will be rising while others are sinking. You might also place a line of pepper on top of the oil and then watch the pepper-line become split and dragged around the surface.
When a continent is split and its pieces begin to diverge, an ocean may develop between those former pieces. For example, about two hundred million years ago, the South American and African continents were not separated by an ocean but were adjacent to each other; still today, the shapes of their coastlines are similar. The plates move so slowly that it has taken about two hundred million years for the Atlantic ocean to widen by 2,500 miles (4,000 km). These two continents will eventually be pushed far enough apart that they will collide with other continents. The positions and widths of the oceans have continually changed through time.
Along the entire centerline of many oceans, the original rifts continue to grow into humongous, underwater mountain chains larger than the Himalayas and longer than the Andean-Rocky-Mountain system. The mid-oceanic ridge averages 4,500 meters (13,500 feet) above the sea floor and 2,000 kilometers (3,200 miles) in width. The entire ridge system is 50,000 kilometers (30,000 miles) in length and is the largest feature on the Earth; yet it is all underwater. You can see map of the mid-oceanic ridge system at the USGS website at http://pubs.usgs.gov/publications/text/developing.html and an animation of sea-floor spreading at the University of University of Ohio website at http://jrscience.wcp.muohio.edu/movies/sea-floor-spreading.mov. See also the animation at www.visionlearning.com/library/flash_viewer.php?oid=1683.
As one plate moves, it might scrape past an adjacent plate with a stick-slip motion or it might instead directly collide with its neighboring plate. During a collision, one of the plates is driven underneath (it is said to be subducting) while the other is pushed up and over. Through several million years, such a collision often pushes up a section of Earth into a new mountain range. It then takes another fifty million years for the erosive effects of the wind, ice, and rain to wear down that mountain range. There have been many such cycles of mountain formation and erosion throughout the Earth’s 4.5-billion-year history. New mountains are rugged, tall, and steep, like the Sierra Nevada, Andean, European Alps, and Himalayan ranges, while old mountains have been worn down in size, like the Australian Alps and the Appalachians. You might like to visit the University of Leeds website at http://earth.leeds.ac.uk/dynamicearth/himalayas/india/animation.htm to view an animation of the Himalayan-producing collision of India with Asia. For more information about the Appalachians, visit http://pubs.usgs.gov/gip/birth. The Appalachians were pushed up a few hundred million years ago when Europe, America, and Africa collided.
The moving, rising, and subducting plates cause earthquakes in several ways. For example, cool brittle subducting oceanic plates can fracture. Sometimes solid minerals from the crust can be carried down to a great enough depth that they suddenly melt and cause a movement due to their decreased rigidity. Subducted minerals can also suddenly become mixed with water that lowers their melting point, resulting in an earthquake. Laboratory measurements of rocks subjected to large pressures have shown that the decrease in melting point occurs at the pressures that are found at a 150-kilometer depth within the Earth. For more information, visit http://pubs.usgs.gov/gip/earthq1.
The tectonic plates move at the speed of about one inch (2.5 cm) per year, which is about the same speed at which your fingernails grow. This slow speed is hard to see with your eyes but is easy to measure with ground-based devices that bounce laser light off satellites orbiting the Earth. At this speed, every fifty million years or so, a continent can move to a very different location on the planet. Sometimes a particular continent may get carried from an equatorial position to a more polar position, causing its climate to change.
Through the last 4.5 billion years, most every continental region has spent time submerged under oceans and uplifted into mountains and has experienced climate ranging from glacial to desert to rain forest. Plate tectonics slowly changes a regions location, with the result that every few million years, the regions climate will have changed. In turn, these slow changes in climate result in slow changes in the successive generations of plants and animals living on each continent. Tectonic plate movements have a slow effect on climate and species, but the weather changes by the day and the season.
Energy from the Sun drives the daily weather and the seasonal climate of the Earth (You might like to view NASA’s Pulse of the Planet at either http://svs.gsfc.nasa.gov/vis/a000000/a002300/a002395/index.html or http://svs.gsfc.nasa.gov/search/Keywords/SIGGRAPH.html for music-accompanied plots of the dynamic Earth.) Energy from the Sun drives also feeds all of the life on Earth as plants use its energy to make organic molecules. The Earth's outer atmosphere, above the clouds and weather, receives about fourteen hundred watts per square meter from this sunlight for a total of twenty million-billion watts. This is equivalent to 200 million-million, 100-watt light-bulbs and is 20,000 times as much power as the ten trillion watts used by our entire civilization of six billion persons–or 100,000 times the power used by the people of the United States. (For further comparison, a single hurricane generates ten times the power used by the United States while a one-megaton nuclear bomb would supply only one-ten-thousandth of the U.S. needs.) How much power is one hundred watts? It is the power needed to lift fifty kilograms up a distance of two meters every second–or in English units, one hundred pounds being lifted six feet every second. The operation of your body requires about one hundred watts of power. This power is also obtained from the sun, no matter if you eat plants directly or if you eat animals that have eaten plants.
To see the cause of the seasons, imagine the Sun and the Earth as two spheres placed on a table, each with a line painted around its center or equator. The Earth is placed to the right of the Sun. The center line of the Sun is parallel to the table top but the Earth must be tilted so that its center line points upward by twenty-three degrees from the horizontal table top. The Earth's axis remains tilted this way as it orbits the Sun. Light coming from the Sun always shines more directly onto the equatorial region but glances along the polar regions. One pole is tilted toward the Sun but the other is tilted away from it. This makes the regions near the equator warmer than the polar regions. Six months later, the Earth has traveled halfway around the Sun. In terms of our table-top model, we would slide the Earth around the Sun, being careful not to change the orientation of the Earth's center line, until it is on the left side of the Sun. The pole which had been tilted toward the Sun is now tilted away from it. This means that each pole drastically cools for a few months of each year while it is receiving no sunlight. The north pole receives no sunlight at all around January, while the south pole is in the dark around June. Visit www.astro.uiuc.edu/projects/data/Seasons/seasons.html to view an animation of the orbital-caused seasons.
As air circulates around the planet, it cools whenever it moves into a sunless, polar region and heats while in daylight, especially whenever it travels near the equator. The same thing happens to ocean water as it travels around the planet, moving between equatorial and polar regions. Water circulates around the world’s oceans following paths largely determined by the current positions of the continents. Circulation patterns change as the positions of the continents change. When ocean currents flow from the equator toward the poles, they carry heat that warms the poles (air movements have a smaller role in moving heat from the equator toward the poles). The ability of ocean currents to move equatorial heat pole-ward changes as the location and shape of the continents change through time. A plot of global ocean currents is shown at the NASA website http://vathena.arc.nasa.gov/curric/oceans/drifters/topo_arr.gif, which can also be reached by clicking on the map shown at http://vathena.arc.nasa.gov/curric/oceans/drifters/ocecur.html. A 3-D movie clip showing warm water moving away from the equator, cooling at the north pole, and returning to the equator as cold water, can be seen at http://svs.gsfc.nasa.gov/search/Keyword/OceanCirculation.html. For other satellite images of the oceans, you might visit http://topex-www.jpl.nasa.gov/science/jason1-quick-look.
Climate changes as temperatures and the distribution of rainfall changes. The annual amount of rainfall in a region is sometimes altered because the incoming air currents shift from passing over land or mountains to instead passing over oceanic areas. As mountains are built through a several-million-year time-span, the surrounding region’s climate changes. One such climate change is of special importance in our own biological history: A continental rift developed in Africa about fifteen million years ago, resulting in the formation of a new mountain range that changed the area's rainfall patterns. As Eastern Africa become drier than Western Africa, the ensuing changes in its plant and animal life led to a type of ape that walked upright. It also occurs that as mountains are worn away through a fifty-million-year time-span, the regional climate again changes.
The Earth’s climate is also affected by the number of volcanoes around the world that are active at the same time. In the year 1815, a large volcano threw a lot of dust into the atmosphere that in turn blocked enough sunlight to cancel that year's summer. Larger volcanoes can cause several summers to be skipped and trigger a glacial advance, as has occurred in the past. In the Philippines in 1991, the volcanic eruption of Mt. Pinatuba released dust that blocked enough sunlight to cool the Earth's air by 0.5 centigrade degree (one degree Fahrenheit), see http://svs.gsfc.nasa.gov/search/Keywords/Mt.Pinatubo.html. For an explanatory animation of a volcano, visit www.sci.sdsu.edu/volcano/volcano.mov. A very large volcanic eruption that occurred 71,000 years ago may have caused a six-year-long winter and triggered a 1,000-year-long ice age, as described at www.ngdc.noaa.gov/paleo/ctl/clihis100k.html.
The Earth’s climate is first of all driven by the Sun. Variations in the energy output of the Sun have been directly measurable for only the last twenty years. Satellites have found a 0.1% change. The Sun's magnetic activity varies with an eleven-year cycle and also a 100,000-year cycle. Mukul Sharma found the longer cycle when studying changes in the amount of radioactive beryllium-10, which has a 1.5-million-year half-life, produced on the Earth by cosmic rays. This amount depends both on the magnitude of the Earth’s magnetic field and on the magnetic activity of the Sun.
Several astronomical factors affect the Earth's climate. The 23-degree tilt of the Earth relative to its orbital plane results in the yearly seasonal changes with which we are all familiar. But the tilt of the Earth varies between 21.5 and 24.5 degrees on a 41,000-year cycle. The elliptical orbit of the Earth around the Sun slowly alternates between being more circular and less circular, and this 100,000-year cycle changes the distance of Earth's closest approach to the Sun and so changes the maximum amount of received sunlight. All these cycles are simultaneously occurring. Sometimes their effects cancel, sometimes they combine into a heating trend, and sometimes the combine into a cooling trend. The Earth’s temperature necessarily follows the net effect, but these astronomical variations alter only slightly the amount of received sunlight. Asteroid and comet collisions can instantly and drastically alter the Earth's climate.
When asteroids having a diameter of one kilometer (0.6 mile) or more collide with the Earth, the collision might throw enough dust into the air to cause darkness for over a year. In addition, several years would elapse before the dust would settle back to the ground and stop blocking sunlight. The darkness and cold would cause the death of many plants and in turn, result in the death of the animals that eat the plants–and in the animals that eat these animals. Such a sequence of events might lead to the extinction of a large portion of the species of life on the Earth. In fact, there have been five such extinctions where 50% to 90% of the Earth's species have suddenly disappeared. (Visit http://www.arkive.org for lists and video of today’s endangered species. Visit www.unesco.org/culture/worldreport/html_eng/stat2/table30.pdf for an international comparison of numbers of endangered species.) These extinctions may be due to asteroid or comet collisions, or they may be due to rapid changes in climate. A large crater off the Mayan peninsula is a record of a collision that might have caused the extinction of the dinosaurs. Visit http://sherpa.sandia.gov/planet-impact/asteroid/movies/aster_vr2.qt for an animation of a meteor hitting the ocean near New York City. For an animation of the propagating tsunami from a meteor impact, visit http://es.ucsc.edu/%7Eward/eltanin_small.mov. For an animation of the kt-impact, visit www.tufts.edu/as/wright_center/cosmic_evolution/docs/fr_1/fr_1_mov.html. Throughout the surface of the Earth, a buried layer of iridium (a component of comets) has been found that dates to the time of the disappearance of the dinosaurs. Scientists estimate that the energy from this collision was about 10,000 times larger than the energy from all of the world's nuclear weapons. About once per year, a much smaller but still massive 20,000-ton asteroid burns up in the atmosphere. In the year 1908 an extensive forest area of Siberia was damaged by an explosion of unknown origin, speculations concerning its cause range from antimatter to asteroid impacts.
Individual species also come and go through time, typically lasting a few million years. A single species will become extinct whenever the climate changes too rapidly or too drastically or if its food sources, predators, or competitors change too rapidly. There might be competition for food by other species that are better suited to the current environment. Changes in plants and animals–that is, evolution–is driven by these changes. The climate changes less in the oceans than on the land so that there has been less change in ocean life. Ocean life changes slowly as food finds new ways of avoiding predators and as predators find new ways of finding food.
Scientists have gathered millions of facts enabling them to piece together the picture of past continental positions and the past location and period-of-existence of the plant and animal species on those continents. Working region by region, this has been a large task. Evidence for the past positions of the Earth's plates has been gathered in many ways and by many scientists. The first clue that the continents were moving around the planet's surface came from the simple observation that the coasts of Africa and South America have similar shapes. If one could push them back toward each other, they would fit together like two jigsaw-puzzle pieces. We have seen that geological layers and their fossils can be dated using relative and radiological means. In another approach, geologists and paleontologists have run around the planet noting each region's geologic formations and its species of fossilized plants and animals. As a continental tear or rift develops, it begins to spread apart the area's previously unbroken geological formations and to separate the area's plant and animal species. The rift continues to separate the two areas for millions of years so that scientists today see them separated by a large distance. The similarity of the geological formations and the fossilized plant and animal species on both sides of the rift indicates that the two regions used to be connected. As two continents move away from each other, an ocean often grows in between them.
A mid-oceanic ridge is built as molten rock emerges from the mantle. The recently emerged rock is continually pushed away from the ridge by yet-newer material emerging behind it. This creates new ocean floor and pushes originally-adjacent continents apart, widening the ocean, while the ridge stays in place and grows. The pushing goes on for one or two hundred million years until another tectonic collision occurs.
The histories of the ridges are deduced from measurements of their magnetism. To see this, consider that the atoms of the emerging, molten rock act like little magnets. As this rock cools, its atomic magnets will line up with the current direction of the Earth's magnetic north pole. But it has been found that the Earth's magnetic field occasionally flips its orientation; In fact, the dates have already been determined in which 170 of these reversals took place through the last 75 million years. The result is that the atomic magnets within newly-emerged rock will point in the opposite direction compared to rock that had emerged when the Earth’s magnetic field pointed in the opposite direction. The atomic-magnet orientation of the emerged rock alternates many times as one moves outward from the rift's location. Paleomagnetic data is available from the National Geophysical Data Center at www.ngdc.noaa.gov/seg/geomag/paleo.shtml, and a figure showing a series of reversals as the plates diverge can be seen at http://pubs.usgs.gov/publications/text/developing.html.
The histories of mid-oceanic ridges are also deduced from measurements of their density because heavier basaltic rocks erupt where crust is pulled apart. Mantle basalt has a higher iron content and a higher density than crustal material (we have seen that the proportion of iron increases toward the Earth’s center). Measurements of a region's density detect this difference in materials. The heavier basaltic ocean floor upwells along mid-oceanic ridges and then moves slowly toward the continents. After a 100-million-year journey, this heavier basaltic rock subducts underneath the lighter continents that keep floating above this material. Deep sea trenches may form along the line where oceanic crust is forced back down into the mantle. For example, the Mariana trench in the Pacific Ocean is more than 11,000 meters (33,000 feet) deep. The continents are 4.5 billion years old, but the ocean floors are never more than about 200 million years old because they are continually opened and submerged. By the way, ocean floors are more often rocky, not sandy, except near the shore.
The past positions of continental shorelines can be deduced from the horizontal movement of beaches, whose sand forms as a strip of quartz ground up by crashing waves. Near a shoreline there is coarse-grained sand, while a little way offshore there is sand and sandstone. Mud and shell is found farther out. Farthest from shore is a line of limestone, which consists of calcium carbonate accumulated from seashell skeletons. As sea levels rise and fall, this series moves horizontally as it follows the juncture of land and sea. Offshore sediment accumulates at the rate of one centimeter (one-half inch) every five to fifty thousand years. Some information about the coastal geology of the Southeastern U.S. seashore can be found at the NOAA website at http://www3.csc.noaa.gov/beachnourishment/html/geo/geo.htm.
The total amount of water on the Earth has changed little through time. It is mainly found in the oceans or locked up in glacial ice, only 3% is held within rivers. But scientists have found that the sea level rises and falls through time as the volume of the Earth’s glaciers change due to global temperature changes. (The height of the sea is also affected by the volume of the oceanic ridges.) As glaciers appear, grow in time, and then melt and disappear, the Earth's ocean level rises and falls. Whenever there are large glaciers then there will be less water in the oceans. As glaciers have advanced and retreated, the ocean levels have been found to raise and lower by a 300-yard (300 meter) vertical distance. It has risen by 120 meters (120 yards) in the last 20,000 years. When the glaciers melt, a lot of water is temporarily held in many lakes. These lakes occasionally burst free, releasing huge torrents that create instant canyons. About 8,000 years ago, a single Canadian lake-burst released enough water to raise the level of the ocean by 20 to 40 cm (4 to 8 inches).
In the last two million years there have been about twenty cycles of glacial advance and retreat. These cycles have roughly followed a 100,000-year period and may be related to the 100,000-year cycle in the Sun’s magnetic activity. Within this more-lengthy period occurs shorter cycles of glaciation. In Northern Europe, some of these have been dated to 75, 65, 59, 40-29, 19-13, and 11-7.5 thousand years ago. Some relatively recent, large temperature changes occurred about 14,000, 11,500 and 7,600 years ago. Smaller and more recent changes include a warmer period during the years 900 to 1200 ad and a cooler period from 1450 to 1850, during which time Holland's canals and London's Thames river would freeze–the last time was in 1814. In the sixteenth century, Spanish Conquistadores encountered snow in Mississippi.
During a glacial maximum or “ice age,” summer temperatures are ten to twenty degrees Fahrenheit (five to ten degrees Celsius) colder than they are now. Four of the ice ages that occurred in the last one million years–the Nebraskan, Kansan, Illinoian, and Wisconsinan–were named for the most southerly advance of year-round ice. Sometimes the northern, year-round glacial region extends down to Britain and Kansas, while at other times there is no region of year-round ice anywhere on the planet. Since there is less year-round ice today, we are living in a relatively mild phase of an ice age. You can see the glacial retreat during from 18,000 to 8,000 years ago in the Midwestern U.S. by visiting www.museum.state.il.us/exhibits/larson/content.html or www.museum.state.il.us/exhibits/ice_age/laurentide_deglaciation.html for the North America retreat. For an overview and movies, see http://jesse.usra.edu/articles/iceagemodule/iceagemodule-paper.html.
The last glacial advance began 130,000 years ago, peaked 20,000 years ago when one-third of the Earth's land was covered by ice, and has been in a steady decline since that time. This glacial extreme created a land bridge between North America and Asia and allowed many groups of us humans to migrate from Asia into the Americas. As the glacier retreated, the land bridge became submerged under the ocean. This process can be seen in the video Postglacial Flooding of the Bering Land Bridge: A Geospatial Animation made by the Institute of Arctic and Alpine Research at the University of Colorado. This video is available at their website
http://instaar.colorado.edu/QGISL/bering_land_bridge. The institute also shows a plot of sea level changes through the last 20,000 years at http://instaar.colorado.edu.QGISL/bering_land_bridge/blb_overview.html. Rising ocean levels submerge flat islands and cause higher, coastal land to be stranded out at sea, as was the case for Britain. Visit www.pastperfect.info/sites/lowhauxley/climate/coastalclip_c.html to see the ocean rise from ten to five thousand years ago, stranding Britain out to sea. In the distant future, the ocean level will again fall and Britain will rejoin the continent. The sea level changes with the Earth’s temperature.
The age of the glacial advances and retreats are determined in many ways. For one, as a glacier retreats it exposes underlying rock to cosmic radiation. The radiation builds up through time and can be measured to deduce how much time has passed since the glacier retreated. Coral reefs always remain near the surface of the ocean, growing upwards and downwards as the level of the ocean changes; a history of their height reveals ocean levels and hence glacial volumes through time. Ocean levels and glacial volumes also give information about past temperatures, as do past longitudinal distributions of warm- and cold-water plankton.
Geologists and paleontologists have pieced together a history of the Earth's past temperatures in many ways. Information is obtained from the types of plants and animals that are found in geologic layers because the temperature range of each species is known. Insects are especially useful in this way because each species lives in a particularly limited temperature range. If a ten-million-year-old geological layer contains seeds from palm trees rather than pine trees, then we know something of that region's past climate. It is known that in tropical regions, with high temperatures and high rainfall amounts, leaves are broad instead of narrow and have smooth instead of jagged edges. The ratio of broad-to-narrow and smooth-to-jagged-edged leaves indicates past temperatures.
Many websites contain information about the flora and fauna of past geological epochs. Jonathan Adams has constructed maps of the vegetation found in each of the Earth’s continents at the time of the last glacial maximum 18,000 years ago, see www.esd.ornl.gov/projects/qen/adams1.html. He also shows plots of vegetation cover ranging from 150,000 to 500 years ago. The National Climate Data Center (NCDC) of the National Oceanic and Atmospheric Administration (NOAA) maintains the World Data Center for Paleoclimatology at www.ncdc.noaa.gov/paleo/data.html. This website has information about climate and plants, mammals, and insects of past ages obtained from corals, glacial ice cores, and pollen samples. The current land cover of the U.S. can be seen at http://geography.usgs.gov/www/products/geoface.html. See http://windowsonmaine.library.umaine.edu/fullrecord.aspx?objectId=7-191, for written records of New England during the years 1623 to 1900.
The annual layering of snow, dust, and pollen tells us much about past temperatures and climate. Pollen is released each spring; some of it forms annual layers on lake bottoms, giving yearly records of the species present at the time each annual layer was formed. The ratio of fern spores to pollen grains indicates the mix of species that had been present. Annual pollen layers are also found just offshore along seacoasts. (We'll see in Chapter 12 that this fact was used to determine the changes in rainfall occurring at the time that a group of us humans first began to become full-time farmers in ancient Mesopotamia.) Through time, the accumulated weight of the dust and organic material that has settled onto lake bottoms begins squeezing the earlier, lower layers into so-called sedimentary rocks. We know that the Earth's oceans are at least 3.8 billion years-old because the oldest known sedimentary rocks were formed that long ago. Snowfalls are similarly layered annually on top of glaciers, giving information about winter-to-summer temperature and precipitation changes. The chemicals found in trapped glacial-air also gives a record of past atmospheric contents. For an example of what can be learned about fauna and climate from lake-bottom layering, see the USGS website at http://pubs.usgs.gov/fs/fs-0059-99. It. contains a report of the mineral contents of the annual layers of Elk Lake in Minnesota. This lake bed provides a 10,400-year record of terrestrial vegetation, windiness, and moisture levels that shows how this now-forested region experienced dry, warm, windy, dusty, sagebrush covered prairie conditions during the time span from 8,000 to 4,000 years ago. You can see a number of ways in which past temperatures are deduced by visiting www.ncdc.noaa.gov/paleo/proxies.html.
Limestone is composed of dead sea-shells that in turn consist of dissolved seawater components, including oxygen. The percentages of oxygen isotopes in limestone indicate past ocean temperatures. Oxygen always contains 16 protons but it can have 16, 17, or 18 neutrons. Oxygen having 16 neutrons weighs less and so evaporates more readily than do the two heavier types. The ratio of oxygen-18 to oxygen-16 decreases 0.02% for each centigrade-degree increase in water temperature. This is used to find how past water temperatures changed with ocean depth and how past temperatures changed with latitude from the equator to the poles.
There are a large number of factors affecting the amount of glaciation on the Earth's surface. The USGS website has information on the extent of glaciation at http://pubs.er.usgs.gov/pubs/fs/fs13399. Mile-thick glaciers cannot accumulate on the ocean surface but can build on mountain tops. As the number of mountain ranges on the Earth varies through time, the total volume of water held in mountain glaciers also varies through time. Continental glaciers can occur whenever a continent is located at a pole during a time of both cool temperature and high precipitation at polar latitudes; glacial buildup most rapidly occurs in the presence of warm equatorial oceans with pole-ward currents. The continental positions, shapes, and groupings also determine if sea currents can carry warm water from the equators toward the poles. The amount of sunlight that reaches the ground to be absorbed by the Earth’s surface depends on how much is reflected back into space. The reflected portion of solar energy depends on the distribution of land and sea by latitude, the percentage of ice-covered and cloud-covered land, the nature of the land surface (seas absorb sunlight while ice and desert reflect it), and the composition of volcanic dust held in the atmosphere. Through the last few centuries of industrialization, we humans have been altering the chemical composition of the atmosphere sufficiently to change its absorptive and reflective properties. Many man-made chemicals, from carbon-dioxide to soot, are contributing to global warming. A presentation of the factors in global warming, including a plot of “Atmospheric Carbon Dioxide Concentrations From Ice Cores 1734 - 1983," is given at www.fsl.noaa.gov/visitors/education/climgraph.The NASA/Goddard Space Flight Center, the SeaWiFs Project and ORBIMAGE, and the Scientific Visualization Studio have created the video SeaWiFS: NASA Carbon Cycle Initiative showing the seasonal changes in global atmospheric carbon-dioxide levels along with changes through the last fifty years and the last one thousand years. To view the clip online, visit http://nix.larc.nasa.gov/info and search for SeaWiFS: NASA Carbon Cycle Initiative. Visit www.pnl.gov/atmos_sciences/snowmovie.html to see a comparison of snow-accumulation with and without a doubling of the atmospheric carbon-dioxide level.
The glaciation found today in the northern and southern poles developed through two different continental movements: the separation of the Antarctic continent and the joining of North and South America. About thirty-six million years ago, the continents of South America and Australia separated from the Antarctic continent, which then drifted toward the southern pole. In addition, a circumpolar oceanic current developed that allows little equator-to-pole heat movement, see http://topex.ucsd.edu/marine_topo/video/acc.mov. The polar location of the Antarctic continent and the circumpolar oceanic current both enabled the southern ice cap to develop. The glacier of Antarctica averages 6,500-feet in thickness (2,000 meters) and account for 90% of all glacial volume. Greenland’s glacier accounts for another 9% of the total volume and mountain-top glaciers account for the remainder. The amount of water held in these glacial regions can be found at http://ga.water.usgs.gov/edu/watercycleice.html. (For a 3-D view of the Martian polar ice cap, see http://ltpwww.gsfc.nasa.gov/tharsis/agu_f98.html.) Mile-thick glaciers can not form on top of the ocean surface. The sea-ice found at the North Pole of the Earth is only three meters (ten feet) thick. During the summer, it becomes 30-centimeters (one-foot) thinner. The sea-ice at the southern pole is only half that thick because it spreads more easily across the wide-open ocean. For more information, visit the NASA websites at http://rst.gsfc.nasa.gov/Sect14/Sect14_14.html and http://svs.gsfc.nasa.gov/stories/arctic. The NOAA website at www.gfdl.noaa.gov/~kd/KDwebpages/NHice.html has an animation of the changes in sea-ice thickness through the last fifty years. Many other animations are found at http://icesat.gsfc.nasa.gov/animations.html. You might also like to check the webcams placed at the north pole, see www.arctic.noaa.gov/gallery_np.html, and the south pole, see www.cmdl.noaa.gov/obop/spo/livecamera.html. The amount of sea-ice occurring at the north pole was indirectly enhanced by the joining of the North and South American continents, which happened about three million years ago, see http://piru.alexandria.ucsb.edu/collections/atwater/emvc/emvc0001.mov. When these two joined, they blocked an east-west flowing ocean current. The gulf stream that developed in its place carries moisture-laden air that increases precipitation near the north pole.
For most of the Earth's history, the average year-round temperature throughout the planet was about 70 degrees Fahrenheit (20 degrees centigrade). There were no areas of year-round ice because wintertime temperatures were not much less than summertime temperatures. In fact, with no polar continents it didn't often get cold enough to snow even during the winter–as occurs today. Under those conditions, each region of the Earth received similar amounts of rainfall so that there were no extensive desert areas. Today, the deserts of the Earth cover about 20% of the surface area and reduce the amount of available farm land. During much of the past, the lack of desert regions meant that a larger portion of the Earth's surface could have been farmed (except that no humans were yet there to do the farming). Today’s year-round temperature is not so comfortable because we are in the middle of an ice age. We might be stuck with this cold weather, with regions of glaciers and deserts, for as long as Antarctica is parked over the south pole and for as long as there is decreased heat flow from the equator to the poles.
We see that there are a large number of variables affecting the Earth’s climate and temperature and that all these variables are simultaneously occurring. Each variable is at some time trying to cool the Earth while at other times it is trying to warm the Earth. If enough of the variables are in a warming phase then the Earth's temperature will increase, otherwise it will decrease; sometimes a temporary balance exists. About ten astronomical cycles are simultaneously contributing to the heating and cooling of the Earth. The two main factors are the heat output of the sun and the heat-holding properties of the Earth’s atmosphere, which raises the Earth’s surface temperature by fifty degrees Fahrenheit (twenty-degrees Celcius) as explained at http://www.meteor.iastate.edu/gccourse/alumni/chem/evol/text.html . In addition, the reflective and absorptive properties of land, sea, and sky change as continents drift from equatorial to polar locations, as ocean currents allow or do not allow heat movement from the equator toward the poles, as the amount of cloud cover and the proportions of desert- and ice-covered land changes, as the number of dust-emitting volcanoes changes, as the chemical composition of the atmosphere changes and as manmade chemicals are added to the atmosphere. See http://yosemite.epa.gov/oar/globalwarming.nsf/content/ResourceCenterPublicationsGHGEmissions.html for an inventory of greenhouse gas emissions and sinks. For information about worldwide carbon dioxide emission, visit www.eia.doe.gov/emeu/international/gas.html#IntlCarbon.
We don’t want to make a too-hasty conclusion about manmade global warming, but at the same time there is no reason to gamble needlessly with the Earth's ecological balance. Recent and cautionary data obtained from glacial drilling experiments show that a global transition from cooling to warming can occur in a time-span of just a few decades. Our environmental impact could go as far as to cause a massive extinction of species. Will the next generation of citizens decide to end pollution by requiring that each factory, home, and car emit nothing at all into the environment? Scientists and engineers would be thrilled to tackle the problem of designing factories, cars, and homes this way. Are factory owners willing to add to the original cost of building a plant and are consumers willing to pay more for products, or should we just spoil our own environment? Zero-emission designs mean that each factory will collects its waste products for use by other industries and that cars will have both a fuel tank and a waste tank. Can you design a tank that collects the exhausts of an automobile engine, and can these exhausts be exchanged at the gas station for further processing? By the way, our car engines consume about fifteen pounds of atmospheric oxygen to burn each pound of gasoline. The combustion products consist of water, carbon dioxide, nitrogen and nitrogen oxides. The atmosphere consists mostly of nitrogen (78%), oxygen (21%), and small amounts of argon, carbon-dioxide, and other gases (1%).
After talking about the effects of us humans on our own environment, let’s talk about the direct effects of our environment on our appearance. We do this by taking a brief digression on physics to help explain the size, shape, and color of objects which are the most effective at removing excessive heat or cold. A warm object cools by releasing heat through its surface. An object retains warmth if it has lots of volume but little surface area. For this reason, the size and shape of humans varies with climate. At the warm, sunny equator we are tall and thin so that we are more easily cooled. In polar areas, we retain more heat by being shorter and rounder so that we have more volume and less surface area. We humans are also found to have darker colored skin when living near the equator and lighter colored skin when living near the poles. Dark skin helps reflect sunlight–especially ultraviolet light–while light skin absorbs more sunlight. Light skin also avoids the rickets caused by a lack of sunlight–as occurs in northern, cloud-filled latitudes. The color of our skin shows our relationship to the Earth and its latitudes. One anthropologist made a globe of the Earth with each region colored like that of local human skin. Humans are also about 10 percent smaller in height and size whenever we live in year-round highly-humid locations because the decreased sweat evaporation makes a larger volume harder to cool.
Liquids and gasses in the development of life on Earth
Chemical reactions occur more rapidly in a liquid medium than they do when lying on the ground. An energetic environment, as existed in the early periods of the Earth's formation, also enables chemical reactions to occur more quickly. Still, organic compounds have been detected in Halley’s comet, in meteorites, and in interstellar space. Life occurs as organic molecules combine into larger units. Since chemical reactions occur more rapidly in an energetic, liquid environment, the Earth's life began in the ocean. Microbial, pre-life forms, consisting of large numbers of molecules but no cellular structure, are likely to have developed in the Earth's water within some tens of millions of years after its formation. (About four billion years were needed for microbial life to develop into multicellular forms that were large enough to leave easily-found fossil remains.) Since the Earth’s life developed in water, life might also develop on other liquid-covered planets and moons. Water has been found to exist in limited amounts on Mars and on the Moon. If water existed for a few tens of millions of years in an energetic and chemically-rich environment on Mars, then it is possible that microscopic life developed there, too. We already have spacecraft looking for signs of life on Mars and on Saturn’s moon Titan. You might visit the NASA website at http://observe.arc.nasa.gov/nasa/gallery/movie/Solar_System/solar_1.html. It includes a movie of Titan and some images of possible Martian microscopic fossils on a meteorite that originated from Mars but was found in Antarctica. We will soon make expeditions to find out whether microbial life has existed on Jupiter's moon Europa, which might have liquid underneath a frozen surface. Visit
http://jrscience.wcp.muohio.edu/movies/veuropa1.mov to see a video of rotating Europa. For a zooming closeup of its surface, see http://jrscience.wcp.muohio.edu/movies/europa.chaos.19.1.5.mov.
There was little atmospheric oxygen for the first half of the Earth’s history. Four billion years ago, the Earth's atmosphere was mostly carbon-dioxide (the stuff in soda drinks). As plant life occurred, it began converting carbon-dioxide into oxygen, which then accumulated in the atmosphere. Oxygen breathing reactions are more energetic and can power multicellular life forms. The Earth's life forms began to take advantage of oxygen soon after it had become consistently available.
The build up of oxygen is determined from the appearance and disappearance of certain chemical minerals. For example, the two minerals Pyrite and Uranite rapidly convert into other chemical forms when they encounter oxygen. These two minerals stopped occurring about two billion years ago, indicating that oxygen began occurring at that time. The relative amounts of two states of iron, which we'll call iron-2 and iron-3, also provide information about the appearance of atmospheric oxygen because the iron-2 form oxidizes into the iron-3 variety. It is found that iron beds older than two billion years contain more iron-2, while newer beds contain more iron-3. More evidence of increasing atmospheric oxygen is given by the fact that no red oxidized sandstone beds occur before about two billion years ago.
The Earth formed through the gravitational accumulation of the debris that was already in the area. We have seen some evidence for the Earth's moving, tectonic plates and for its fluctuating climate. The main point of this chapter is that the global position of each continent slowly changes through time and that their climate changes as they move from one region to another, or as they block and unblock heat-moving, north-south ocean currents. In turn, this causes changes in each region's plant and animal species.
Now that we have described the Earth's origin and the reasons for its changes in climate, we will next describe its life forms and see how they change as climate changes. The next chapter begins with a description of the physical nature of the molecules of life and ends with a summary of the sequence of animal types that have occurred on the Earth.
Questions
1. The news often discusses global warming. Measurements show that in the last century, the Earth’s temperature has increased by one degree centigrade (two degrees Fahrenheit). What should we measure in order to determine if humans are causing this to occur?
2. What causes ice ages and warm periods? How long do they last? How quickly does an ice age develop or end? How much warmer or cooler is the temperature during these periods than it is today?
3. Can we predict earthquakes?
4. How would the Earth's distribution of plants and animals be different if the continents never moved? Suppose the continents moved completely around the Earth seven times per year while moving in figure-eight patterns. Describe your region's annual temperature changes. How would this affect the type of trees and animals in your region? What if the continents circled the Earth once every one-hundred years?
5. Write down the equations for relativistic plate tectonics. (These would be useful if the continents circled the Earth seven times per second.)
6. How would life be different if we had two-hour days instead of 24-hour days? We never see the backside of the Moon because it always presents the same face toward the Earth. From the surface of the Moon, this means that one side always faces the Earth while the other side always faces outward into space. If the Earth spun about its axis only once during the time needed to make one orbit around the Sun–that is, if each day lasted a year–how would life vary from one side to the other and along the light-dark boundary? How would the Earth's distribution of plants and animals be different if one side of the Earth always pointed toward the Sun throughout the year? What if the Earth then flipped its orientation every 50 (or 500 or 5,000) years so that the opposite pole faced the Sun? If the region of the border between light and dark didn't move as the flips occurred, this region would provide the most stable home. A portion of the observed stars systems have more than one Sun so that days and nights occur in more complicated intervals on its planets than happens on the Earth. How would this change the Earth's life? The output of many stars varies by a factor of two through periods of several months. If our Sun was such a variable star, how would that affect life on Earth? By the way, the planet Mercury has but three days every two years and a sufficient difference between closest and farthest orbital distances that, from the surface of Mercury, the Sun’s apparent size grows and shrinks through the year.
7. Do you believe the rumor that the dinosaurs were wiped out by alien sports hunters using iridium bullets? Do alien zoos still contain any of the Earth's dinosaurs? Do aliens have movies of the dinosaurs? Will we be able to clone dinosaurs? Would a pair of cloned dinosaurs know how to behave if they had no parents to teach them how to be dinosaurs? Were dinosaurs raised by their parents? Are today's reptiles raised by their parents?
8. How will our civilization change when the next glacial advance or retreat occurs? And the next?
9. List some physical, chemical, geological and astronomical things that can affect the rate of appearance of new species.
10. What sort of plants and animals existed in your area one million years ago? 50? 500? 1,000?
11. Each sudden extinction of most of the Earth's species has been followed by an increase in the variations of the remaining species. If we humans are currently causing such an extinction, what sort of species will replace those that will become extinct? How will we live if it occurs that we are the only remaining species?
12. If each species is well-matched to just one climate, what is the climatic range of our crops? How quickly can this be changed?
13. What has enabled us humans to live in each of the Earth's climatic regions?
Primary source for the chapter
A Short History of Planet Earth, Mountains, Mammals, Fire, and Ice by J. D. Macdougall, 1996, John Wiley and Sons New York.
Suggestions for further reading
Geologic Time Don L. Eicher second edition, 1976, Prentice-Hall Inc Engelwood Cliffs, New Jersey.
Paleoclimate and Evolution with Emphasis on Human Origins, Elisabeth S. Vrba et. al., 1995, Yale University Press, New Haven.
Why the Earth Quakes, The Story of Earthquakes and Volcanoes, Matthys Levy & Mario Salvadori, 1995, W W Norton & Co, New York.
The nature of a human
The nature of the molecules of life, and the sequence of plants and animals that have developed on the Earth
In the first part of this chapter we will see how the electrical force holds together combinations of atoms and that the molecules of life consist of large numbers of these naturally occurring combinations. (Molecules are combinations of two or more atoms bound together.) This means that the fundamental basis of life is nothing but the electrical interactions of atoms. (This interaction was described in Chapter 2.) The second half of this chapter contains a summary of the sequence of animal types, from bacteria to mammals, that have developed on the earth.
We will see that a certain molecule, called DNA, consists of a pair of parallel strings of atoms. These paired strings are bound together such that each is a sort of mirror image of the other. When the pair becomes split apart, each of the two strings will gather components from the surrounding chemical mix to rebuild its missing mirror-image half. The result of this splitting and rebuilding is that the original pair of strings has been replaced by two pairs of strings. This is a self-duplicating molecule. This molecule also electrically guides the sequences of gathering-up of smaller molecules into larger combinations that grow and operate an individual plant or animal. DNA grows an individual from ingested and absorbed chemicals altered in the right way to produce the chemicals forming various tissues and organs; DNA also chemically directs the operation of an individual through the production of those chemicals needed at any moment. These are the things that DNA does naturally. Change DNA and the resulting individual will change.
It is natural that any change in the resulting organism that makes it better matched to its surrounding environment of climate, predators, and food will also make it more likely to live long enough to produce additional generations. Any organism poorly matched to its surrounding environment will not as likely be around long enough to produce an additional generation. Keep in mind that when two different species seek the same food and share the same environment, the species having just a 1% better match to the environment will increase in number sufficiently faster to swamp the other within a couple dozen generations. The surrounding environment selects those individuals possessing the best-matched characteristics and unselects those that are unmatched. An individual is “selected” simply by being well enough matched to its environment to live long enough to produce offspring. As the environment of climate, predators, and food changes, so too will the DNA that best matches that environment. A range in DNA always exists in the current members of a species. That collection of individuals have a range in characteristics due to a range in their DNA. Just as the height of people follows a bell-shaped distribution, so too will their abilities to handle cold, digest peanuts, and so on. (For more about bell-shaped curves, visit www.upscale.utoronto.ca/PVB/Harrison/ErrorAnalysis/BellShaped.html or http://math.elon.edu/statistics112/norm_dist.html.) A species is more likely to survive a change in its environment if its individuals possess a sufficient range in characteristics that some individuals are already suited for that changed environment; they already possess DNA better-matching the changed environment. As the environment changes in time, the peak in the bell-shaped curve of an important characteristic shifts. The sequence of changes in the individuals of a species is described as evolution and it occurs through natural selection by the environment of climate, predators, and food. Changes occur through the generations. Generations last but a few minutes in bacteria and a few days in insects. Visit http://devolab.cse.msu.edu for information about a project in which digital organisms evolve at the speed exercised by computer software.
This following description of the origin of the molecules of life is a summary of The Realm of Molecules, by Raymond Daudel. The primary source for the description of the chemistry of our bodies is The Chemistry of Life by Martin Olomucki. The outline of the sequence of the species of life on Earth was taken from Life Through Time, by Harold L Levin. (Technically, two animals are said to be of the same species if the two can mate and produce offspring that in turn are also able to produce offspring of their own.) An on-line, talking glossary (with illustrations) of biological terms has been developed by the Human Genome Project and can be found at www.genome.gov/page.cfm?pageID=10002096.
Electrical binding in atoms is the physical basis of the molecules of life
The electrical interaction is one of the five basic forces found to exist in nature, as described in Chapter 2. We have seen that about one hundred types of atoms occur in nature, including hydrogen, helium, carbon, and oxygen and such and that nearby atoms interact through the electrical force involving their outermost electrons. Living creatures consist of one to one-trillion cells, each of which contains one trillion interacting atoms. The operation of each creature occurs through thousands to millions of chemical reactions, each of which involves the electrical forces among the charges of the mixing atoms. The electrical interaction forms the underlying, physical basis of the multi-atom molecules of biology and life.
In chemical combinations, atoms become mutually bound to each other through either the lending or sharing of outer electrons that occurs between pairs of nearby atoms (see The Sciences, An Integrated Approach, by James Trefil and Robert M. Hazen). As one atoms lends an electron to another, the giving atom is left with a net positive charge while the receiving atom acquires a net negative charge; these two oppositely charged atoms then experience a mutual, electrical attraction in a so-called ionic bond. An electron can also be shared among many atoms within a molecule (covalent bond). Most atoms have only one or two electrons that are shareable, but carbon has four. Since each carbon atom can bond with up to four neighboring atoms, it is able to forms rings, chains, and branching structures not possible for other atoms. The building blocks of living structures consist of these carbon structures. Electrons are shared by many atoms in metals (metallic bond). This relatively free movement of electrons is responsible for the shine and for the rapid heat transfer of metals. In some molecules, a shared electron spends more of its time orbiting one of the partnering atoms. In affect, this causes the side on which it is spending the most time to be more negatively charged than the less-often visited side. These are referred to as polar molecules. Hydrogen can be polarized in this way and become bound to other atoms–especially oxygen and nitrogen–in a relatively weakly bond (hydrogen bond). In Chapter 2 we saw that a block of atoms that contains equal mixtures of positive and negative charge and so is electrically neutral can still be attracted to a nearby, external charge. This so-called van der Walls force can form a weak bond between molecules.
Molecules react with other atoms and molecules, sometimes merging, sometimes breaking apart, and sometimes forming new collections out of the interacting units. The ease with which two approaching molecules can electrically interact depends on their shapes and charge distributions and also on their relative orientations and speeds while near each other. Each type of molecule has a specific shape and consists of a specific combination of atoms and, perhaps, smaller molecules. Biological molecules contain thousands to millions of atoms and have convoluted shapes. Their outer surfaces have numerous bumps, indentations, and projections. Some of these features or regions have an overall positive electrical charge, others have a net negative charge, and yet others are neutral. Two large collections of atoms can become bound either by sharing electrons between adjacent atoms or molecules or through the mutual attraction of oppositely charged regions of their outer surfaces.
To picture a convoluted shape you might imagine gluing soccer balls together. You might first glue twenty soccer balls into a roughly spherical clump. Then form an arch using another thirty soccer balls and attach it onto the first clump such that the arch sweeps out from the left side and rejoins on the right. Then add more arcs, and bridges between arcs. The shape of a molecule can become ever more tangled as its number of atoms increases. They take on strange shapes because some areas of a molecule can have an overall positive electrical charge while other portions of the same molecule have an overall negative charge.
As you attempt to join two molecules into a larger conglomeration, the two pieces are able to fit together only if and where two constituent molecules can share electrons or if they are facing each other such that a negatively charged portion of one attracts a positively charged portion of the other. Often, there is no relative orientation in which the pieces attract each other. You might imagine what would happen if you similarly attempt to join two handfuls of magnets. Depending on their orientations, some might fly away while others join. If two different types of molecules drift past each other while having oppositely charged regions facing one another then these two molecules can join to form a yet larger molecule; two molecules do not merge when like-charged regions face one another because of their mutually repulsive electrical force. Those molecules that can merge, will; in fact, they must. Those that cannot merge will not do so. If many different types of atoms are mixed together then those that can do so will merge with others to form molecules. (Sometimes the presence of a certain chemical, a so-called catalyst, will cause others to interact more rapidly.)
The one hundred types of atoms found in nature can be placed side by side two at a time, three at a time, and so on, into countless sequences of increasing numbers of atoms. But few types of atoms simply placed next to each other will be able to electrically hold on to each other. Of the zillions of possible combinations, most do not produce an electrically stable molecule and so do not occur in nature. (In the last century or two, chemists have found many rules that help to predict which combinations can form stable molecules.) Any combination that is stable will occur whenever its components are mixed together.
Out of the one hundred types of atoms, we have seen that carbon atoms are the most suited to be joined together into rings and long chains containing hundreds or thousands of atoms. Much of biology involves the organic chemistry of carbon. For example, proteins are large molecules formed by combining several types of atoms and lots of carbon rings. The largest biological molecules contain billions of atoms. Often, these organic structures are more stable than many of the inorganic molecules because they are not as easily torn apart. Organic chemicals have been found in space and even on Halley's comet. All of the Earth's life-forms consist of these organic compounds.
Four families of organic compounds form the building blocks of life: twenty amino acids, carbohydrates such as sugar and glucose, lipids or fatty acids that do not dissolve in water and so form cell walls (see www.life.uiuc.edu/crofts/bioph354/membrane_phase.html) and store energy within fat, and the five nucleotides that comprise DNA and RNA (visit www.sis.nlm.nih.gov/enviro/toxtutor/Tox3/a25.htm for more information about these components). The molecules of each of these four organic compounds consist of about twenty carbon, oxygen, nitrogen, and hydrogen atoms (97.5% of the atoms within our bodies consist of these four elements, while calcium comprises 2%, phosphorus 0.2%, sulfur 0.1%, and all others 0.2%). Though hundreds of amino acids have been synthesized in the lab, only twenty different amino acids appear in living systems. These four types of compounds form the building blocks of larger structures– just as a home is built of individual bricks, doors, and windows (see Trefil and Hazen)–in that our bodies consist of, and operate using these four things. In particular, the twenty amino acids form the proteins used in the operation of our bodies.
Strings of twenty or so amino acids create the simplest proteins containing about four hundred atoms. Many proteins contain hundreds to thousands of amino acids joined into a long chain that folds over and electrically attaches to itself in several places, producing a convoluted, three-dimensional structure. To illustrate this convoluted shape, consider that a rubber band consists of molecules formed into a strip. While it usually forms a ring, we could cut it and lay it flat on a table. This strip could be laid down left to right for a short distance, folded back on itself, and laid down right to left in an adjacent strip. This could be repeated many times to have an s-shaped sheet. We could next place our palm on top of the sheet and rub forward to cause the sheet to clump–as rubber bands do–into a three-dimensional structure. We might take three other rubber bands and repeat this procedure to have four clumped structures of s-shaped sheets of rubber band strips of molecules, and then place the four next to each other, two above the other two. The U.S. National Library of Medicine has a three-dimensional illustration of the similarly-shaped Phenylalanine hydroxylase enzyme at http://ghr.nlm.nih.gov/ghr/picture/ph. The results of a computer model of the protein folding process is shown in the video at http://www-vis.lbl.gov/Vignettes/RAOliva/t209/movies/71150_50.mpg. Each protein has a specific shape, formed from clumped sheets of s-shaped strips of amino acids. Each protein simultaneously has one-, two-, and three-dimensional shapes (they have a fractal dimension). The shape of each protein determines its chemical properties in that it will electrically hold onto those other molecules having a compatible shape.
Some examples of protein include hair, nails, silk spider webs, tendons, and connective tissue but proteins serve many important functions in the body. A hormone is a protein that gives molecular messages to organs. For example, hemoglobin is a protein that transports oxygen from lungs to cells. Proteins determine which chemicals can flow into or out of cells. Proteins play a crucial role functioning as enzymes.
Enzymes are a class of proteins that speed up (catalyze) reactions between specific substances. To see how enzymes work, consider that the shape of a grocery store egg carton is such that it holds a dozen eggs in individual little pockets. Each egg is held close to others. Imagine that the egg carton was able to crack together two neighboring eggs and cook them into a flat oval. Since the shape of the two cooked eggs has changed, the egg carton will no longer hold them in place. The two eggs can now easily slide out of the carton. The carton has not changed but the shape of the two combined eggs have. Enzymes perform a similar function in that they have the right “carton-shape” to hold two smaller molecules together long enough for them to merge into a new molecule that no longer fits in the carton and so moves away. The enzyme has not changed but the shape of the two held together molecules has changed. The enzyme helps along the chemical reaction that merges and changes other molecules. Our bodies vary the number of enzyming proteins to vary the rate of chemical reactions, thus controlling specific functions. In the next section, we will see how DNA controls the production of reaction-controlling proteins (enzymes).
The four so-called nucleotide molecules adenine, thymine, cytosine, and guanine–which we'll call A, T, C and G molecules–have important properties when placed together to form lines of molecules. (The fifth nucleotide is uracil, symbol U, which replaces thymine in the formation of RNA.) When these four types of molecules face each other, their size, shape, and charge distribution enables just certain pairs to be able to hold electrically onto each other. It occurs that A and T molecules will hold electrically onto each other, but they cannot hold onto any C or G molecules; similarly, C and G molecules will hold onto each other but cannot hold onto either A or T molecules.
DNA naturally duplicates itself
DNA is a long string of thousands to millions of the four nucleotides A, T, C, and G. DNA molecules contain billions of atoms and are a few centimeters (an inch) in length but only a few molecules wide, as explained in Our Molecular Nature by David S. Goodsell. The structure of the DNA molecule was determined from x-ray analysis (see The Double Helix edited by Gunther S. Stent). DNA molecules resemble a ladder in that they take the shape of two parallel atom-strings laid side by side but twisted into a helix as the “ladder” moves upwards. The “ladder poles” consist of a sugar phosphate, while the “ladder rungs” consist of either a G-C or an A-T pair. The left and right halves of a ladder rung each consist of one A, T, C, or G molecule. Whenever the left half of a ladder rung consists of an A molecule, the right-side of that rung must have a T molecule, similarly for C and G molecules. The U.S. National Library of Medicine has an illustration of DNA at http://ghr.nlm.nih.gov/ghr/picture/dna. Tufts University has an animated video clip of a DNA molecule at www.tufts.edu/as/wright_center/cosmic_evolution/docs/fr_1/fr_1_mov.html.
The two parallel ladder poles are separable. (The production and presence of a certain chemical causes the ladder to sort of unzip.) As the ladder poles separate, each of the rungs also become divided into two, separating the A-T and C-G pairings. Each ladder pole then has its set of ladder rung halves stick outward into the surrounding chemical soup that includes freely drifting A, T, C, and G molecules. Each of the A-molecules of a ladder rung half can electrically re-attract only another T molecule because that is its "mirror-image," similarly for C and G molecules. In this way, the right side of the ladder can gather up a replacement of its missing left side by electrically attracting another set of mirror-image molecules. The two separated molecule-strings have attracted another set of molecules, one-by-one, out of the surrounding chemical mix within the cell to gather its "mirror-image." The result is that the DNA molecule has reproduced itself (more technically, it has replicated itself). It took a number of groups of twenty carbon atoms before a self-duplicating arrangement formed. Those molecules that naturally duplicate themselves, do; in fact, they must.
The fact that DNA is naturally self-duplicating is demonstrated by placing one DNA molecule into a soup of A, T, C, and G molecules. Heating the soup causes DNA to separate into its two strands. When the soup is then cooled, the two separated strands will each rebuild their mirror image, resulting in two complete DNA molecules. Repeat this cycle of heating and cooling many times. Each time the soup is heated and then cooled the number of DNA molecules will double. After ten such cycles, the amount will have doubled ten times, which is a one thousand fold multiplication. In this way a large amount of DNA can be obtained from a small sample, as is done in scientific studies and in crime labs.
Errors often occur during duplication but they are usually found and removed because they cause a local bulge or kink in the inaccurate copy, as described by Trefil and Hazen. For example, two successive G nucleotides on one ladder pole sometimes attach to a single C nucleotide on the opposite ladder pole. A bulge results just as would occur if, during construction of a ladder, you accidentally nailed two ladder rungs from the left pole to the same spot on the right pole. The resulting bulge is found by an enzyme that wraps itself around DNA and reacts to any bulge simply by cutting away that section of one ladder pole. The next time the DNA is duplicated, the missing section is automatically re-created. Repairs are continually made to correct damage caused by any other source, including ultraviolet light, x-rays, and countless types of eaten or absorbed chemicals.
DNA is also changed or damaged by radiation. Radiation damage to people, or any other animal, occurs when energetic light-waves (gamma radiation) collide with their DNA molecules. These energetic light-waves are stronger than the usual medical x-rays. Damage is also done as electrically charged radiation, which consists either of positively charged helium nuclei (alpha radiation) or negatively charged electrons (beta radiation), pulls electrons away from the atom's of your body. A tiny change in a DNA molecule can have a large affect on the operation of an individual. Around the year 1900, the effects of radiation began to be learned the hard way by the physicists who first studied its properties, as mentioned in Chapter 2. In fact, Marie Curie’s lab book contains radioactive fingerprints. (In 1911, Marie and her husband Pierre won the Nobel prize in chemistry for their research on radioactive atoms. Marie later won the Nobel prize in physics. In 1935, their daughter Irene and her husband Frederic Joliot-Curie won the Nobel prize.)
During the early years of the Earth, 4.5 billion years ago, no DNA molecules existed. From the start, molecules were forming into those larger and larger structures that could naturally form. Once formed, molecules remain intact until they become sufficiently heated or until either broken down or further enlarged through encounters with other chemicals. For the first billion years of the Earth's history, these molecular structures grew in length at an average rate of about one atom per year. (The Tufts University animation at ww.tufts.edu/as/wright_center/cosmic_evolution/docs/fr_1/fr_1_mov.html shows the origins of life on Earth.) My friend Becca Barter says that the difference between living and non-living matter is nothing but a simple divergence of atomic structure. Combinations of carbon and other atoms results in multi-purpose, biological structures that ponder themselves while combinations of non-carbon atoms result only in structures such as rock crystals.
In time, a molecular structure became self-duplicating. Once a self-duplicating molecule had developed from the chemical mix, it would naturally occur that any change making that molecule better able to make duplicates would result in increased numbers of that molecule. Each successive generation in this molecule could give rise to slightly changed copies. Those changes that resulted in less stable duplicates could mean an end to that version of the molecule. Evolution began with the first self-duplicating molecule. Your own DNA, and that of every other species on the earth, is a direct descendent of the first self-duplicating molecule that developed nearly 4.5 billion years ago.
By three billion years ago, DNA and its surrounding pool of A, T, C, and G molecules came to protect itself from chemical bombardment by becoming enveloped within an enclosure. The resulting, so-called cell is the fundamental unit of life in that all living matter–from bacteria to plants and whales–is composed of cells and that every cell arises from previous cells. (This was first proposed by Theodor Schwann in 1839, see Trefil and Hazen). Every living organism consists of cells that contain DNA. The size of a cell usually ranges from 0.01 to 0.1 millimeters (0.004 to 0.04 inches), but in a larger example, a bird egg is also a single cell. Each human contains one billion cells per gram. An entire person contains a few trillion cells. Each cell contains a few trillion atoms (a trillion is a million-million) and its own copy of DNA arranged into twenty-three paired pieces called chromosomes.
Cells were first observed in a microscope by Robert Hook in the year 1663. By 1675, Anton van Leeuwenhock had observed several types of cells and noted that water contains many microscopic, living creatures. (One never forgets the first time one sees amoebas and such in a microscope, the rings of Saturn in a telescope, or lightning bolts emitted from a Tesla coil. These are three of the most impressive sights for the beginning nature lover.) Hundreds of species of microscopic creatures can be seen at the website http://microscope.mbl.edu/baypaul/microscope/general/page_01.htm. The Exploratorium has video clips of amoebas and such at www.exploratorium.com/imaging_station/gallery.php. You might also visit www.microscopyu.com/moviegallery. Visit www.genome.gov/Pages/EducationKit/download.html for an animated time-line of biological discoveries and to download Milestones in Genetics: Timeline from the Human Genome Project website.
In the variety of organisms today, cells exist in about two hundred shapes and sizes, and they have taken on various specialties. For example, nerve cells allow the flow of electrical charge while muscle cells are stretchable. The structure of a cell can be seen at the National Library of Medicine website at www.sis.nlm.nih.gov/enviro/toxtutor/Tox3/a24.htm. Living creatures consist of a hierarchy of components: chemicals form cells that comprise tissues that in turn make organ systems. Organs include the liver, heart, kidneys, and brain and such. For 3-D animations and internal views of organs taken with cameras, see www.medicdirect.co.uk/virtual_body/default.ihtml. The human body consists of eleven organ systems (see www.sis.nlm.nih.gov/enviro/toxtutor/Tox3/a22.htm) including the circulatory, nervous, muscular, skeletal, reproductive (which comes in two varieties), urinary, digestive, respiratory, lymphatic, cardiovascular, and endocrine systems. (To see the beginnings of surgery simulators, which are similar to flight simulators, for use in medical school, visit http://virtual.uta.edu/CD/SYH%20Research/demopage.htm.)
Each organ within our body contains cells organized into four types of tissue: epithelial, connective, nerve, and muscle. These tissues are shown at www.sis.nlm.nih.gov/enviro/toxtutor/Tox3/a23.htm. Epithelial tissue forms the lining around organs and also forms skin. Connective tissue includes ligaments, tendons, cartilage, bone, blood, and the fibers of organ walls. This tissue connects, supports, and protects other tissues. Nerve tissue forms brains, transmits signals to muscles, and senses hot and cold and other exterior conditions. Muscle tissue includes the four varieties that continually move and support bodies, flex when signaled to move particular bones, continually beat hearts, and the smooth variety that contracts on its own to move the internal fluids of bladders, lung bronchi, and the walls of the blood vessels. Blood and nerve signals flowing within every organ. From head to toe and backbone to skin, we have a couple dozen organs, a couple hundred bones, and about five hundred body components, including muscles and cavities and such. The Visible Human Project at www.nlm.nih.gov/research/visible/visible_gallery.html has a video clip showing a succession of slices through a person, from head to toe. There is little difference in cell, tissue, and organ components between us human beings and any other mammal, and even less difference between us and any of our fellow primates. There are increasing numbers of differences between us and reptiles, amphibians, fish, insects, worms, and plants.
DNA naturally builds and operates entire individuals
DNA also contains the chemical-construction maps used to produce the chemicals or proteins needed to operate an individual. Every aspect of the operation of our bodies occurs through a series of chemical reactions. Within each cell, the presence, over-abundance, or under-abundance of any one of a number of specific chemicals, foreign or domestic, will activate the production of a responding or counteracting protein. We maintain internal, chemical equilibrium this way. In the case of a counteraction to a triggering chemical, protein production ceases when the triggering chemical has been actively converted into an ignorable chemical. DNA contains the information needed to produce the proteins in reaction to the triggers. The greater the number of reactions to control and triggers to deal with, the greater the information content of a creature’s DNA.
In reaction to the triggering chemical, a copy of a specific section of DNA is made within the cell nucleus by temporarily unwinding that section. Such a DNA section is called a gene. One gene contains the chemical-construction map needed to produce one specific protein. This is the so-called Central Dogma of biology. The copy of the DNA-segment or gene is called RNA and is transported to another organelle within the cell, the ribosome, where the chemical-construction map will be followed to mass-produce the specified protein that will serve as the enzyme (chemical catalyst) needed to control that triggering chemical and its reaction rate. DNA “says” when that chemical is present, produce this chemical by forming a series of amino acids and joining them together. The entire process is described as the transcription of DNA into RNA followed by the translation of RNA into proteins. You might visit www.genome.gov/Pages/EducationKit/online.htm to view an animation of the process.
Certain diseases are caused by the failure of DNA to produce a specific protein. For example, diabetes occurs when the body does not produce the protein insulin. The newly developing techniques of gene therapy hope to replace specific sections of a patient’s improperly functioning DNA with working copies. This technique has successfully treated severe combined immunodeficiency (SCID). Trefil and Hazen relate that Ashanti de Silva was the first person to have defective genes in blood cells replaced with normal ones.
How does DNA serve as a protein construction map? We saw that DNA consists of strings of A, T, C, and G molecules or nucleotides. How many combinations of A, T, C, and G molecules can be made in a series of two or three of them? Sixteen different pairs of nucleotides can be made from these four nucleotides because there are four ways to choose the first of the pair and four ways to choose the second, so its 4x4=16. Eight of the sixteen possible pairs are GG, GC, GA, GT and CG, CC, CA, CT (these are not ladder rung pairs but successive rung components). Sixty four combinations can be made that consist of a series of three of these nucleotides (notice that 4x4x4=64). Two examples are AGC and AAT. Recall also that the same twenty amino acids–and no more–are present in every living creature and that each specific protein consists of a specific series and number of amino acids joined together in a structure that is simultaneously one-, two-, and three-dimensional. The DNA construction map indicates the sequence of amino acids that are to be joined by coding each as a series of three A, T, C, and G molecules. For example, Olomucki explains that the triplet sequence A-G-C followed by A-A-T will cause a tyrosine and an alanine molecule to be formed out of the surrounding mix of chemicals and then joined together. (Visit http://en.wikipedia.org/wiki/Genetic_code for the complete, 64-element genetic code.) Triplets of A, T, C, and G molecules could code for sixty four amino acids but only twenty occur within the Earth’s life forms. Three of the extra forty-four are used to indicate the ends of genes. The remaining forty-one extras allow for a redundancy that protects against partially damaged triplets. Chemical disruptions, attacks, and damage occurs many times per day.
DNA also contains the chemical-construction map used to produce the sequence of chemicals needed to grow an entire individual–from seed to adult–from its food and from absorbed chemicals. An organism ingests (eats) and absorbs chemicals from its surroundings, breaks them down into simpler molecules, and then recombines them into other chemicals determined by the DNA of the organism. A complete plant or animal develops from the single cell of its seed by producing the sequence of molecules indicated by its DNA code–its "construction and operation map." The chemicals within our food are altered to become the chemicals needed to operate and grow ourselves. Feed milk to your newborn infant and his or her DNA will direct the conversion of the chemicals within milk into the chemicals comprising your baby. Place a seed into the ground and its DNA will reform absorbed chemicals into those chemicals that are a plant.
The flowering rose is a relatively new type of plant (flowers appeared just fifty million years ago). It contains DNA molecules each held together by the electrical forces among its constituent atoms. DNA contains the directs a sequence of reactions that take certain external chemicals and then alter and mix them with internal chemicals to result in those chemicals that are the rose. This chemical series will result when you place the blobs of chemicals of the rose seed into contact with the chemicals of the ground and air. The reactions occur naturally–and are going to occur; indeed, they must. Through its particular series of chemical reactions, a rose will develop from its seed. The chemicals of the seed and of its surroundings, and the chemical directions of the seed's DNA, are going to result in a rose. In the same way that pushing an initial chemical through a container of a second chemical, and the resulting mixture through a set of additional chemicals, always produces the same result. The rose consists of a large number of atoms and molecules and a large number of chemical reactions. The incredibly complicated, molecular nature of the rose increases its beauty tremendously.
To grow an entire individual from a single cell requires that millions of chemicals be produced in the right order. The information needed to produce this sequence of chemicals is contained in the individual's DNA. That information does not spring into being at the moment of an individual’s birth–nor did your own; it originated in the first
