Chapter 1 – What is Science and Why Is It Important?

Learning Objectives

Welcome to Chapter 1.  At the end of this chapter you will be able to:

  • Define how science is a valid endeavor that is constantly evolving to change and improve
  • Recognize the origins of the national parks system and its dilemma surrounding enjoyment and conservation.
  • Identify geologists as people who practice their science in four key areas.
  • Describe atoms and their essential parts.
  • Explain what Earth System Science is and define its importance to the future of our planet.
  • Identify the 8 elements that make up the majority of Earth’s crust
  • Differentiate between basaltic and granitic rocks.

Did you complete the Course Orientation?

… when people thought the Earth was flat, they were wrong. When people thought the Earth was spherical they were wrong. But if you think that thinking the Earth is spherical is just as wrong as thinking the Earth is flat, then your view is wronger than both of them put together.
–Isaac Asimov,The Relativity of Wrong, Kensington Books, New York, 1996, p 226. (Note that the Earth bulges a little around the equator in response to the planet’s rotation, but the Earth is still much closer to being spherical than to being flat!)


Before delving too much into the world of geology (broadly, the study of the Earth), this first unit will focus on a larger question that is a more fundamental issue for most people; namely, what is science? Why pay for it? Why do it? Why trust it? Why learn it? Why bother?

Unit 1, SCIENCE!!, will introduce you to this issue, and help you develop the perspectives to answer these questions. This unit will also introduce you, very briefly, to the field of geology, giving you an overview of what it’s about, why it’s important, and how it benefits people. And finally, Unit 1 is our entry point to the magnificent environmental legacy that is our National Parks—a system of parks and monuments that lets us enjoy today, and preserve for the future, so many of our society’s geological, biological, cultural, and historical records and artifacts.

“Science is the most successful way humans have developed to learn how things work, and to use that knowledge to do and predict things”.


Science is not a magic bullet to ultimate truth; science is humans keeping track of what works and what doesn’t, and trying not to fool themselves in the process. The “scientific method” is just common sense, dressed up with fancy words and expensive machines. Science doesn’t tell us what we should do or why we’re here, but it makes us a lot healthier and more comfortable while we try to figure out those really big issues.


Photo of Mount Rushmore
Mount Rushmore Credit: R.B. Alley

Your Geology of National Parks instructional team is made of people who love Science, Geology, and National Parks. We hope you do too, and if not, we’ll try to show you why we do. These “big-picture” questions are probably more important than anything else covered in this class.

We humans have always had a love-hate relationship with our “tools.” Cars are great, but getting run over by one isn’t. Televisions are great, until you really want to have a heart-to-heart discussion with someone who is deeply engrossed in a playoff game. Science collects the wisdom of the world’s peoples, their experiences and insights, and then tests that wisdom repeatedly, revising and improving, to help us learn to do things we want. This may be humanity’s greatest tool… but that also means that occasionally someone may not like it.

Sometimes, a person becomes unhappy when their idea loses to a better one. In the early 1600s, when Galileo advocated the idea that the Earth orbits the sun, Pope Urban VIII saw conflict with certain verses in the Bible (e.g., Psalm 93, “The world will surely stand in place, never to be moved”, or Psalm 104, “You fixed the earth on its foundation, never to be moved”; both quoted here from the New American Bible, although Urban VIII would have read them in Latin.) Some religious authorities of the time did not see any necessary conflict between these verses and Galileo’s ideas, and the Pope initially had been at least somewhat open to Galileo’s ideas. But, the Pope eventually turned Galileo over to the Inquisition over this supposed heresy, and the Inquisition forced Galileo to recant, sentenced him to house arrest, and banned his book and future publications. (It is an interesting question whether the problem was really Galileo’s sun-centered view, or whether the Pope got mad because Galileo’s book featured a dialogue with the Pope’s favored views spoken by the “loser.”)

The papacy subsequently decided that the reality of the Earth orbiting the sun did not undermine scripture, and astronomers could do their job while the religious leaders did theirs. Indeed, rather interesting scientific discussions have been hosted by subsequent popes.

It remains that sometimes conflict arises between some members of some religious or other groups and some aspects of science. In 2005, for example, the state school board in Kansas changed their definition of science, apparently to enable teaching in science classes of ideas that repeatedly have been rejected as being nonscientific by courts and scientific organizations. After another election that changed membership, in 2007, the board restored to their definition that science is a search for natural explanations for what we observe in the world around us. We will have a chance to discuss these ideas later in the course, because Kansas and other states have continued to fight over the issues.

So, let’s look a little more carefully at what science is, and isn’t.

Why Science?

The reason for science is clear—tightly coupled to engineering and technology, science really works. The products of scientists and engineers are tested in the real world every day. Oil companies hire new geologists, geophysicists, and petroleum engineers when the old ones retire because those scientists and engineers really do find oil and make money for the oil companies. Congress funds biomedical research because it keeps lengthening our lives and curing diseases. You read this on a computer, designed using the principles of quantum mechanics, and using the remarkable discoveries of materials scientists and engineers.

High school teachers like to expound on the scientific method. Scientists do have a method of sorts, and it helps them achieve their results. But lots of people—astrologers, palm readers, telephone “psychics”—have methods that don’t get funded by industry and Congress. The typical industrial officer could not possibly care less how a scientist achieves a result, but only that the result is achieved.

Across campus, scientists are sometimes viewed as just another group for the sociologists to study. Scientists have their own tribes, rituals, and other social interactions. Scientists seek fame and fortune, lie, steal, and violate their rituals in much the same way that other humans do. The extremists in sociology have gone so far as to argue that science is only a social construct, one of many possible ones. This, however, is the kind of intellectual exercise that gets academics in trouble with the real world. Anyone with a little common sense knows that it is possible to have a cruise missile deliver a small exploding device to a selected building in another continent using some clever applications of Newtonian physics, and that no other human social construct can make a similar claim. Mere social constructs do not design new antibiotics that save millions of lives, either.

Science differs from other human endeavors in that its disputes are appealed to nature. In art, you cannot judge whether Picasso or Rembrandt was a “better” painter. You can study the brush work, perspective, social context, or whatever, and learn a tremendous amount about art from the discussion, but you cannot reach an objective decision on who is better. But if asked whether Aristotle’s or Newton’s physics work better, we can answer the question.

This is where the scientific method comes in. We study Aristotle’s ideas and Newton’s ideas until we figure out some way that they differ. This allows us to propose an experiment: if we do A, Aristotle expects B to happen, and Newton expects C. Then, we do A, and see what happens. If it comes out C, Aristotle is wrong. In reality, one test is never definitive—the fans of Aristotle might claim that the experiments were rigged, or the experimenters didn’t really understand Aristotle’s ideas and so did the wrong test. But after many tests, the answer becomes obvious. Science has then progressed—we’ve gotten rid of something that was wrong.

Science remains an exercise in uncertainty. If Newton “beats” Aristotle, that means Aristotle is wrong, but it doesn’t mean that Newton is right—maybe he’s just lucky, or pretty close, but not quite right. As it turns out, Newton’s ideas fail for things that are really small, really large, or moving really fast, and we have to turn to quantum mechanics and relativity. (But all that fancy physics reduces almost exactly to Newton’s description for things of size and speed that we usually deal with—bigger than atoms, smaller than galaxies, and much slower than the speed of light—so, Newton was and is useful.) Science thus cannot give the ultimate answers to anything, because we’re never sure whether we’re right, close, or lucky. We can only say that, if we act as if the scientific results are true, we succeed (in curing diseases, finding oil, etc.).

Science is an expensive way of learning about the world. Suppose you’re a farmer and you’re trying to feed yourself. You try an idea (say, burying fish heads with your corn seeds, or planting during the dark of the moon), and the corn grows well. So you do that every year. If it works, great. If it doesn’t work but doesn’t hurt, no big problem. If it actually makes things worse, well, you might starve, but not many other people are bothered.

Now, suppose you’re a modern farmer trying to feed 100 people. If you try something that actually makes things worse, many people may starve, and some of them may get really mad at you before they do. So, you start asking whether the fish-head works, and whether two fish-heads would work better, or whether other parts of the fish would be better, and so on. One test doesn’t do it—crops grow well most of the time, so most things you test (such as planting in the dark of the moon) will seem to work even if they really don’t help.

The modern solution is to have a scientist helping the farmer, trying things carefully, and trying them many, many times, figuring out which ones really work better, and communicating those results to others who are interested. All that testing takes a lot of effort, but it is cheaper in the long run for important things. Rather than 100 people each trying to feed themselves, and some failing and starving, we have a scientist, a farmer, a tractor manufacturer, a trucker and a grocer feed all hundred, freeing 95 to do something else. (Enjoy! You probably don’t have to spend the summer hoeing corn to keep from starving over the winter.) So, although science is expensive, for important things it is cheaper than ignorance. For unimportant things, living with a little more uncertainty may be easier.

Science has been wildly successful on simple questions: If I drop a rock, how fast will it fall? If I put a lot of a certain isotope of uranium in a small area, what will happen? If I use steel beams this big, in this pattern, how heavy a truck can drive over the bridge without breaking it? Most of physics, much of chemistry, and some of medicine fall in this “simple question” part of the world.

Science is gaining ground on some harder questions. Predicting weather or earthquakes, understanding and curing cancer, understanding and managing ecosystems and biodiversity—these are more complex, involve more interactions, and may have limits on predictability (chaos), but real, useful progress is being made. The research frontiers lie in these complex systems. Much of geology lies in complex systems, and we are in the midst of some great advances in geology.

Science has a ways to go on really hard questions, such as predicting how various actions will impact the working of society and the health and happiness of people. And science cannot address many questions—“How should society work?” is a value judgment, not a question of reality, and is not part of science.

Science is restricted to the search for natural explanations of the world around us. This does not mean that science opposes religion, or claims that there is no God. (Some scientists may do such things, but many other scientists don’t.) Quite simply, no experimenter knows how to guarantee the cooperation of an omnipotent deity. A miracle, by definition, cannot be repeated reliably by anyone in any lab anywhere in the world, and so must fall outside of science.

In short, science is a human social activity, but differs from other human social activities in that the ideas of science must be tested against reality. Science enjoys a special place in society because science is so successful. Science shows which ideas are wrong, and also identifies ideas that scientists cannot disprove. If we act as if these not-yet-disproven ideas are true, we are successful in doing things. These not-yet-disproven ideas remain conditional, because we might find better ideas in the future. Science keeps track of what works and what doesn’t, to save future workers trouble. Science is a meritocracy—good ideas tend to rise to the top, no matter who originated those ideas. (This may take a while, because scientists are human with human failings, but the triumph of merit is more likely and faster in science than in most human activities.) Science tests the structure of knowledge continually—a good scientist does not tiptoe around the tower of knowledge put up by earlier scientists, but tries to tear that tower down. Only those ideas sturdy enough to survive such attacks are saved, so the scientific edifice is exceptionally sturdy.

Why National Parks?

Societies have tried many different ways to deal with private versus group ownership. Private ownership often raises ethical questions—did you really come by that piece of land fairly? Can you claim for your king some land that was already occupied by other peoples? Do other species have land rights? Public ownership often raises the “tragedy of the commons”—if I can sneak a few more of my sheep onto the public green, I’ll gain in the short term, even if, in the long term, we all lose because the extra sheep kill the grass.

A big waterfall spills into a canyon.
Lower Falls, Grand Canyon of the Yellowstone River, Yellowstone National Park Credit: R.B. Alley

The US tradition has focused on private ownership, but we’ve also recognized the benefits of public ownership. The idea of a National Park—taking the really choice pieces of the country and placing them under public control—is a US idea, developed by the Washburn expedition to Yellowstone in 1870 and eventually enacted by Congress in 1872.

Since then, the idea of national parks has spread across the nation and worldwide. This is surely one of the great ideas of the modern world, to save key scenic environments in the public domain.

However, the national parks of the United States, and the world, face a grave dilemma. The act establishing Yellowstone and the concept of national parks specified “conservation… unimpaired for…future generations” and “to provide for the enjoyment” of the parks. Saving a wild region for the future while having it enjoyed by millions of visitors each year is perhaps the largest of many difficulties facing the parks today.

Elk eating grass.
Lower Falls, Grand Canyon of the Yellowstone River, Yellowstone National Park Credit: R.B. Alley

Most of the national parks were founded to preserve geologic features—the geysers of Yellowstone, Crater Lake, the Grand Canyon, the Badlands, etc. Many national parks were founded when they were, biologically, small pieces of a vast, unbroken range of similar habitats. Today, the parks are often becoming islands of natural environment in a sea of human-controlled and human-altered land. Thus, much focus on the parks today involves biodiversity. We will revisit the questions of biodiversity and island biogeography later. (Yes, this is a geology course, but some things are too important to pass up just because they belong in a different department.)

What is Geology?

Geology, broadly, is the study of the Earth. Geologists and friends—geophysicists, geochemists, geobiologists—study the rocks that make up the Earth, the history of the Earth as recorded in those rocks, and the processes that change those rocks. This includes oil and ores, landslides and volcanoes, dinosaurs and meteorites, and much more. Most geologists are involved in one of four areas: i) finding valuable things in the Earth (gold and silver, diamonds, oil, building stone, sand and gravel, clean water, etc.); ii) warning of geological hazards (volcanic explosions, earthquakes, landslides, groundwater pollution, etc.); iii) building an operators’ manual for the Earth (Earth System Science); and iv) informing/entertaining (What killed the dinosaurs? How has the Earth changed over time?).

Historically, most geologists have worked at finding valuable things. These geologists have been truly successful, too successful for their own good, in fact. Some of the things we extract from the ground are very cheap today (after you subtract off inflation and taxes), so there have been fewer jobs for geologists with mining companies than in years gone by. Oil prices have gone up recently, and oil companies have started a hiring boom (talk with any of us in case you’re interested in a career move). The US used to spend a lot more money on cleaning up groundwater pollution than we have recently, but it turns out that an immense amount of that money was spent on lawyers arguing about paying for cleanup rather than on scientists and engineers cleaning up. A lot of geologists are not happy with this situation and hope that finding and restoring clean water will be more vigorously pursued in the future.

Warning of geological hazards is also a growing field. As more and more humans build houses on floodplains, debris-flow deposits, and other indicators of past disaster, these people become more dependent on someone to tell them if and when the trouble will return. Many geologists favor a different approach—find out where the dangers are, and then don’t build in those places—but real estate developers often don’t listen. (In the spring of 2012, a bill was introduced to the North Carolina legislature—although not passed in its original form—to make it illegal to use the best science to tell coastal people the regions that might be attacked by the sea. This echoed efforts a century before by developers in San Francisco to discredit scientists who correctly argued that the earthquake that had just devastated the city meant that additional earthquakes were possible.)

The disaster of Hurricane Katrina in New Orleans and surroundings in 2005 really showed the dangers of building in harm’s way. With over 1800 dead, and over $100 billion in damages (that is $300 for every person in the US!), Hurricane Katrina definitely caught the attention of many people. Interestingly, geologists had known of the impending disaster, and warned of it, for decades, as the city slowly sank beneath river-level and sea-level. Thousands of Geosciences 10 students had studied this issue in the years before the storm struck (and you’ll get to look into the issue soon).

The operators’ manual for Earth is a new idea. It may be the most important thing geologists can do for the future of humans. We humans are everywhere today—living on every continent, tilling more and more of the land, claiming as our own more and more of the productivity of the planet. We have changed the forests, changed the soils, changed the atmosphere, changed the waters—nowhere on Earth remains free of our imprint. Credible estimates indicate that we and our close friends—cows and corn and chickens and house-cats and Chihuahuas—are using roughly half of everything made available by the planet. We are managing to support roughly 5 billion people pretty well (out of the 7-plus billion of us here), with population projected to reach 9 or 10 billion in a few decades, so we are planning on doubling the number of people we support well.

Given that we are doing this, and we will continue to do so, many thinkers believe that it would be wise to have a better idea of how all of this works and what we are doing. You would not try to repair a fine watch without knowing how it works—take a few pieces out and you may never get it running well again. We are doing precisely that to the planet, changing a lot of things we don’t understand. Earth System Science is the attempt to understand the planet, its water, air, ice, rock and life, well enough to learn the consequences of our actions so that we can make wise decisions. Earth System Science is in its infancy, and we do not even know whether we will ultimately succeed, but many of us believe that it is an incredibly important effort.

And, there is always education and entertainment. Some people really like to know things, and geologists have some of the most interesting stories to tell. Perhaps you will find some of the stories here to be interesting.

A Brief Overview of Geology

This text will try to show you not only what geologists learn, but how we learn it. For the first few chapters, however, we ask you to take our word for some things. You will see statements such as “The Earth is 4.6 billion years old.” Before we’re done, you will also see where that number comes from, how good it is and much more about it. But we can’t do everything at once.

Anyway, we believe that the universe started in a “Big Bang” about 14 billion years ago. The Earth is “only” about 4.6 billion years old. We live in a second-generation solar system, because the planets and the sun contain abundant chemicals such as iron that were first formed during the death of older stars. So, there were some stars, and they exploded and generated gases and dust, and something (another nearby star exploding?) caused that gas and dust cloud to be compressed a little. Once the dust and gas started falling together, gravity took over. Eventually, most of the mass went to form the sun, which was squeezed enough under gravity that the sun’s hydrogen began fusing to form helium, in the process releasing energy—sunlight! Some of the gas and dust collected into planets.

Assembly of the Earth involved falling together of lots of big and little chunks. The largest chunk was probably about the size of Mars. It hit the Earth after most of the assembly was finished and blasted enough material off the Earth to make the moon. (Note that there is still a little rumbling in the scientific literature about this Mars-sized moon-forming collision, so stay tuned…)

The falling-together of pieces makes heat. That heat partially or completely melted the planet. The melting allowed the planet to differentiate, or become layered. The denser material sank to make a core, mostly of iron with some nickel and a few other elements. The lowest-density material rose to the top to form a silicate scum, or crust, floating on a vast mantle of denser silicate (see the sidebar on chemistry). The Earth is hottest in the middle, coldest on the outside. Heat favors melting, but higher pressure tends to make most liquids turn solid. These two effects compete in the Earth, so you find both solid and liquid down there. Going down in the Earth, the crust and the upper part of the mantle are solid (together forming the lithosphere) except in special places where volcanoes occur; the deeper part of the mantle is solid but soft, and has a zone about 100 km (60 miles) down in which a little melting occurs. The soft zone in the mantle is the asthenosphere–we won’t learn a huge number of new words in this class, but we do get a few great ones! The core has two layers, a solid inner core and a liquid outer core.

Some of the Earth’s heat is left over from when the planet formed, and a lot comes from the decay of naturally radioactive materials in the Earth. As the early heat has escaped and the radioactive materials have decayed, the Earth has slowly been cooling off, but plenty of heat remains to drive geologic processes. The Earth has developed an atmosphere, oceans, and life, and a rich sedimentary history of how those developed. The atmosphere and oceans spend their time wearing down mountains, but the heat of the Earth keeps driving processes that build mountains up, so there is a near-balance. And all of this should become clear as we tour the national parks.

Sidebar: A Very Brief Chemistry Lesson

Most students reaching the university have taken a chemistry course somewhere along the way, but a few of you haven’t. Here is a BRIEF summary of chemistry, as a refresher for those who have had a chemistry course and as a teaser for those who have not. We do not use a lot of chemistry in this course, but it comes up often enough that you may find a summary to be helpful.

If we pick up anything around us (water, chewing gum, rocks, whatever) and try to divide it into smaller and smaller pieces, we will find that it changes as it is divided. A tree becomes a log as soon as we cut it down. If we dry the log before burning it, we find that it contained lots of water, plus other things that are not water. If we then use fire to break the log into smaller pieces, we find that we can do so, while releasing energy. Using tools and energy levels that are easily available to us, we will find that we can continue dividing something until we get to elements, but that we cannot divide the elements.

The “unit” of an element is called an atom. There are 93 naturally occurring elements, plus others that humans have produced. If we use even higher energies, such as those achieved in nuclear accelerators, we find that we can take atoms apart.

Each atom proves to have a dense nucleus, surrounded by one or more levels where electrons are found. It may prove helpful to think of electrons circling a nucleus the way planets orbit the sun, although this simplified model doesn’t capture all the features of an atom.

The nucleus contains smaller particles called protons and neutrons. Protons have a characteristic that we call positive charge, electrons have an equal-but-opposite negative charge, and neutrons are uncharged or neutral. A neutral atom of an element contains some number of protons and the same number of electrons, with their positive and negative charges just balancing each other.

The type of atom, or element, is determined by the number of protons; add one proton to a nitrogen atom, for example, and it becomes an oxygen atom. (Breathing nitrogen without oxygen would cause you to die quickly; they are different!) The positively charged protons packed tightly in a nucleus tend to repel each other, but the neutrons act to stabilize the nucleus.

Some elements come in different “flavors,” called isotopes, which have different numbers of neutrons and so different weights. Slight differences in the behavior of isotopes allow us to use them to learn much about certain processes on Earth, as we’ll see later. All atoms of an isotope are identical, and all atoms of an element are nearly identical.

Chemistry includes all of those processes by which plants grow, we grow, wood burns in a fireplace, etc. Chemistry involves changes in how electrons are associated with atoms. An atom may give one or more electrons to another, and then the two will stick together (be bonded) by static electricity, the attraction of the positive charge of the electron-loser for the negative charge of the electron-gainer. An atom that gains or loses one or more electrons is then called an ion. Atoms may also share electrons, forming even stronger bonds and making larger things called molecules.

Most Earth materials are made of arrays of ions, although some are made of arrays of molecules. The ions or molecules usually form regular, repeating patterns. For example, in table salt, a lot of sodium atoms have given one electron each to a lot of chlorine atoms, making sodium and chloride ions. Then these stick together. One finds a line of sodium, chloride, sodium, chloride, sodium, chloride, and so on, and a line next to it of chloride, sodium, chloride, sodium, …, and above each sodium there is a chloride, and above each chloride a sodium, in a cubic array. A grain of salt from your salt shaker will be a few million sodiums and chlorides long, and a few million high, and a few million deep.

The properties of the grain of salt—how it tastes, and dissolves, and breaks, and looks, etc.—are determined by the chemicals in it and how they are arranged. We call such an ordered, repeating, “erector-set” construction a mineral. Almost all of the materials in the Earth are minerals. Liquid water is not a mineral because the water molecules are free to move relative to each other, but liquid water becomes a mineral when freezing makes ice.

When the Earth formed, we received a few elements in abundance, and only traces of the other naturally occurring elements. More than half of the crust and mantle is composed of two elements–oxygen and silicon. Most minerals and rocks thus are based on oxygen and silicon, and we call these rocks silicates. In silicates, the silicon and oxygen stick together electrically, with each little silicon surrounded by four oxygens. Silicon, oxygen, and six others–aluminum, iron, calcium, sodium, potassium and magnesium–total more than 98% of the crust and mantle. Geology students used to be required to memorize the common elements, and their abundance, in order; for our purposes here, know that only a few are common, and we’ll come back to them later.

The silicon-oxygen groups form minerals either by sticking to each other by sharing oxygens, or by sticking to iron, magnesium, or other ions. Minerals that contain a lot of iron and magnesium are said to be low in silica, even though they may still contain more silicon and oxygen than iron or magnesium. In general, minerals high in silica are light-colored, low-density, have a low melting point, often contain a little water, and occur mostly in continents; minerals that are lower in silica usually are dark-colored, high-density, melt at high temperature, and occur on the sea floor or in the mantle more often than in continents. You may hear “basaltic” used for low-silica, because basalt is the commonest low-silica rock at the Earth’s surface; similarly, “granitic” means high-silica because granite is a common high-silica rock.

This Course

We will take a tour of geologic ideas. Some of the best geological features of the world are enshrined in the US (and other!) national parks. We will use national parks as illustrations, delving into park history and culture when we can, but concentrating on those things that illustrate how the Earth works.

View down into a valley at sunset.
Yosemite Valley, California Credit: R.B. Alley

Optional Enrichment Article

Babies, Big Ben, and the Age of the Earth

In this course, we will deal with a number of ideas—the age of the Earth, the occurrence of evolution, the prospect of global warming, and others—about which there are heated public debates in the US. These debates have persisted in the US, and in some other places, long after scientists reached consensus and moved on, using the science to help people. These debates have persisted here long after most people in many other countries accepted the scientific results, and began helping the scientists use the information to help people. Why is this? Are scientists and people in some other countries just stupid, ignoring common sense? Are many regular people in the US just stupid? Are US politicians cynically exploiting subjects for personal gain? You will get many different answers to these questions from different people!

Here, we’d like to give you something to think about. The discussion here in no way proves that scientists are right about the age of the Earth, or evolution, or global warming—we’ll discuss the evidence about these later in the course. But, the discussion here may help you to think about thinking about these issues, and to examine your own ideas on the topics. So…

Have you ever visited an old European city and tried to drive through the downtown? Or have you watched from the sidewalk, or in a movie, while others tried to drive the winding streets of Rome or London? People who have done so quickly form opinions about the experience, and those opinions are very seldom, “Wow, what an efficiently designed road system, ideal for moving traffic.” Far more common is “Wow, what a mess!” And yet, although almost everyone knows that the roads are a mess in the downtowns of major old cities, those roads are still there. Why?

The answer is fairly simple. The roads were built when the city was tiny, centuries or even millennia ago, to serve that proto-city. Then, as the city grew, it grew around those roads. Buildings went up, and museums and castles and theaters and sewers and all the other stuff of a city. Would you move Big Ben, or tear down the Louvre and start over, to straighten out a winding road? When faced with that choice, people usually keep the old roads. Careful checking will show you that people actually have put a lot of effort into improving the roads over time, moving things, tunneling under or bridging over, adding subways to take off some of the strain, patching and fixing and repairing, spending billions of dollars (or Euros, or pounds, or whatever), but always starting from the existing system rather than starting over.

There is a useful analogy here in considering how humans learn things, and in particular how we learn science. I (this is Dr. Alley writing) have had the joy of watching closely as our two daughters grew from babies to toddlers (and on to remarkable young women), and there is a good chance that you have either closely observed growing babies, or will. Scientists watch babies, too, and are learning a lot about learning.

By the time a baby is a year old, he or she knows an amazing amount about the world. The baby knows that some things are inanimate and others animate—rattles don’t walk away, but parents do. Many things are predictable for a baby—a rattle released in midair always falls down, not up, unless grabbed by a mother or father or other living thing. A rattle placed properly on the railing of a crib will stay there.

In gaining this knowledge, the baby is putting down “roads” in the brain, wiring in information that later will be called “common sense”. When artificial-intelligence researchers have tried to get computers to do human jobs, perhaps the biggest difficulty has been that the computers lack this “common sense”—teaching the computer all the things that a baby learns proves to be quite difficult, because the baby learns so much.

Notice, however, that this “common sense” is often not really correct. For example, babies do not start off with a modern view of the shape of the Earth and the physics of gravity. Whatever a baby does think, a “round, round world”, with people and rattles pulled toward the center by the warping of space-time by mass that causes gravity, is not in the original common-sense picture.

Careful studies show that, when children are finally told about gravity on the spherical Earth, they initially resist the idea. They may deny it, or they may try to modify it to fit with their “common sense”. (If asked to draw the world, they may add a flat spot or divot just where they live in an otherwise spherical Earth, or they may draw people living inside a sphere.) Often, it takes until age nine or so before children really say that they accept the idea that they are held to a spherical Earth by gravity, and they draw pictures properly illustrating the idea.

Furthermore, studies find that children show this sort of resistance to most or all new ideas that conflict with the “naïve physics” or “naïve psychology” formed in the cradle. Like a city preserving its old roads, a child preserves the initial ideas—perhaps adding or patching, building new paths in the “suburbs” of the mind or building “subways” that take the new idea around the old one, but getting rid of the old idea only when absolutely necessary.

Now, almost all children eventually come to accept the spherical Earth. (There actually are a few people out there who still argue against the spherical Earth, just not very many.) But, typically all of the authority figures in a child’s life agree in telling the child that the Earth is spherical—teachers, parents, preachers, TV, books, and more—with almost no disagreement. (And yes, even young children have a ranking of reliability of information sources, picking which “authority figures” to believe more.) Yet with all of the authority figures agreeing, years may still be needed to convince a child to replace the old “road” in the brain with a new one (and that old road might even still be in there somewhere).

What about, say, the age of the Earth? The scientific evidence indicates that the Earth formed about 4.6 billion years ago. But 4.6 billion years is not “common sense” to most people—we don’t imagine such large numbers very well. If you ask a very young child how old the Earth is, you are almost guaranteed to get an answer that is not “4.6 billion years”.

In many parts of the world, all of the authority figures in a child’s life agree in telling a child that the Earth actually is 4.6 billion years old—teachers and parents and preachers and politicians and more—and almost all children in those places eventually come to believe that the Earth is 4.6 billion years old. But in some places, including the USA, many authority figures do not agree on this. Some preachers, some parents, some politicians, and even a few teachers express doubt about this scientific idea, and some may be actively hostile to it, claiming a very different answer. When faced with a scientific idea that runs against the “common sense” developed at a young age, and with a split opinion among authority figures, a typical child will keep the old “road” through the “city” of their mind. And that child is likely to grow up into a parent, or preacher, or politician who disagrees with the science.

As noted above, this does not in any way prove that science is right and young-Earth politicians are wrong, or that young-Earth politicians are right and scientists are wrong. We’ll address those questions later, after looking at how the Earth works. But, lots of evidence (and common sense!) shows that people do arrive at ideas much as described here, and you can go watch babies, visit other places, and convince yourself. (You might also look at the article listed at the end of this text for a little more information; some of the ideas and examples given here were taken from that article, which provides additional insights.) So, when you visit Paris or Madrid, please safely enjoy walking the narrow, winding streets. Then, on the plane home, ask yourself what the “roads” look like in the mind of the person in the seat next to yours—or in your seat.


Childhood Origins of Adult Resistance to Science
Paul Bloom and Deena Skolnick Weisberg
Science, 2007, v. 316, p. 996-997

Key Takeaways for What is Science


  • is a human activity—it isn’t Truth, but it works;
  • is the best way we have to answer many questions (How does something work? How can we use that information to cure disease or find clean water or otherwise help us?);
  • cannot answer many questions (What should we do? Why are we here?).

Scientific Method:

  • Get a new idea (hypothesis) from somewhere (genius?).
  • See if new idea beats old idea in predicting what will happen (experiment).
  • If yes (after many tests), use the new idea; if no, still use old one.
  • Repeat—there’s always more to learn.
  • Ideas that work better may be True, Close, or Lucky, so science never sure.
  • Science can prove ideas wrong, but cannot prove them correct.

Why National Parks?

  • US idea, Yellowstone first (1870).
  • Problem: parks for “conservation unimpaired for future generations” but “enjoyment” for this generation.
  • Doing both is not easy.

Why Geology?

  • Find valuable things (oil, water, gems).
  • Avoid hazards (earthquakes, volcanoes, landslides).
  • Learn how Earth works to keep it and us happy and healthy.

Some Geological Background

  • Earth 4.6 billion years old, pieces from space fell together under gravity.
  • Heated as it formed (natural radioactivity, and the heat from stopping those falling pieces—think of hot-brake smell after stopping a truck on a steep hill).
  • Heating melted Earth and allowed it to separate into layers (think of car-bottom clump on a snowy day—ice and rocks and dead-squirrel parts all lumped together, but separate when they melt in the garage).
  • Layers are: iron-rich core, iron-silica mantle, more-silica/less-iron crust (refer to Chemistry Sidebar in the text if this seems unfamiliar).



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The Geology of North American National Parks Copyright © 2022 by Dr. Richard Alley, Evan Pugh, and Sridhar Anandakrishnan is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

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