Authors: Robert M. Hazen
This is a wonderful vision, but like all scientific ideas it had to be tested. The most dramatic test of Newton’s vision of the universe was made by his fellow Englishman Edmond Halley (1656–1742). Using Newton’s laws and historical records, Halley was able to work out the orbit of the comet that now bears his name and to predict its reappearance in the sky. When the comet was “recovered” on Christmas Day, 1758, the event powerfully underscored the idea of the clockwork universe. Not only could Newton’s scheme explain things that were already known, it could make reliable predictions about events that had yet to occur.
Today, with the advent of quantum mechanics and the field of complex chaotic systems, scientists’ ideas about the clockwork universe have changed. The universe is still, in the modern view, governed by simple laws, but these laws do not always allow us to make the kind of straightforward predictions about the future that Newton envisioned. Nevertheless, much of the Newtonian mind-set survives in modern science.
Newton’s development of the clockwork universe was the first, classic example of the scientific method in use. The method depends on a constant interplay of observation and theory; observations lead to new theories, which guide more experiments, which help to modify the existing theories.
In Newton’s case, some of the observations and experiments were recorded by Galileo, others by Kepler. In each case, the cycle of observation, theory, test-against-new-observations was repeated until the investigators achieved a complete understanding of the phenomenon being studied. Newton, as we pointed out, incorporated these understandings into his sweeping theory of motion, and then his new theory was used to make many predictions like the projected reappearance of Halley’s comet. Only after many such tests was the theory accepted by scientists.
The scientific method does not require researchers to be unbiased observers of nature. Scientists almost always have a theory in mind when they perform an experiment. But the method does require that scientists be willing to change their views about nature when the data demand it.
Newton provided a model for the development of modern science in many ways. He was the first to use the scientific method, and he was the first to show that scientific theories can develop by incorporation rather than revolution.
When Kepler published his laws of planetary motion, he swept aside the old ideas about the solar system. This was a revolutionary change—the old notions were seen to be wrong and were abandoned. When Newton published his work, however, he showed that all of Kepler’s laws could be derived from universal gravitation and the laws of motion. His work, then, incorporates
Kepler’s and expands upon it, but does not invalidate it. In the same way, Newton was able to derive Galileo’s conclusions, in corporating them into the same theoretical framework that ac commodated the description of the planets. This has proved to be a common occurrence in science. When Albert Einstein produced the theory of general relativity, our current best theory of gravitation, it incorporated Newton, Kepler, and Galileo, and when some future theoretical physicist produces the final unified field theory, it will likely incorporate Einstein.
Despite what you read in sensationalistic headlines, true revolutions are rare in mature sciences.
The universe seems far too complex to comprehend all at once, so the classic scientific approach is to examine well-defined pieces of our surroundings, one at a time. The universe can be divided into an infinite number of “systems,” which are nothing more than parcels of matter and energy Each parcel, which can contain almost anything from a single spinning subatomic particle to an entire galaxy, is fair game for scientific study. Astronomers probe stars and the solar system. Chemists investigate systems containing carefully selected groups of atoms. Geologists study minerals or mountain ranges. Biologists examine complex systems called cells or ants or forests. Each system can be something you hold in your hand, like a rock, or it can be an integral part of something else, like your body’s nervous system.
The scientific enterprise consists of thousands of specialized subdisciplines—the chemistry of fluorine, the turtles of Malaysia, the properties of young massive stars, the evolution of the AIDS
virus, lasers, quarks, diamonds, slime mold—each with its own practitioners and jargon. These varied specialties differ primarily in the size and contents of the system under study. All systems, be they stars, bugs, or atoms, are governed by the same set of natural laws, but they are studied and described in very different ways.
Hundreds of thousands of Americans make their livings as scientists. Most of these women and men can be described with one of four broad labels: physicist, chemist, geologist, or biologist. Science is a seamless web of knowledge, but people like to create their niches. So each of the four main science branches (not to mention the hundreds of highly specialized “twigs”) has developed its own distinctive style and organization.
Physicists study matter and energy, forces and motions—the concepts central to all science. Physicists take pleasure in pointing out that theirs is the most fundamental science, because all other fields, from chemistry to cosmology, mineralogy to molecular biology, depend on a few basic physical principles. Physicists are the generalists among scientists, and fields as far apart as molecular biology and field ecology have benefited from an influx of physicists over the years. Nevertheless, parts of physics have turned into the most abstract of the sciences. Physics conventions are replete with discussions of ten-dimensional space, quarks, and unified field theories. For some reason many physicists, particularly those in universities, seem to enjoy appearing sloppy and disheveled—always the ones without ties at faculty meetings. If you want to make a physicist happy, tell him you thought he was the plumber.
The American Institute of Physics, based in the Washington, DC area, represents about 100,000 physical scientists, including astronomers, crystallographers, and geophysicists, who are members of ten affiliated societies. The largest of these groups, the
American Physical Society, boasts almost 50,000 hard-core phyicists on its membership rolls. These societies sponsor professional meetings, lobby for physics research and education, and publish prestigious research journals such as
The Physical Review
Chemists are pragmatists, studying atoms in combinations to discover new and useful chemicals. Most chemists, even those in academia, maintain close ties to industry; science and its applications are seldom far apart. Chemists hold more patents than any other kind of scientist, and they are frequently observed wearing business suits.
The American Chemical Society, headquartered in the nation’s capital, represents both research chemists and chemical engineers. This blend of science and industry, unique among the major science societies, gives the ACS more than 160,000 members, making it the largest U.S. science society (surpassing even the interdisciplinary American Association for the Advancement of Science in total membership). The American Chemical Society sponsors meetings, supports chemical education, and publishes numerous books and journals, including the weekly
Chemical and Engineering News
. As a lobbying organization, the ACS must walk a fine line between environmentalists and major chemical corporations, both of whom are represented among the membership.
Geologists are a different breed. They frequently lecture in worn jeans and sturdy boots, seemingly ready to hike miles in the wilderness carrying rocks on their backs. Geology attracts men and women who love the outdoors and like to get their hands dirty. In practice, not all geology is rugged. The earth sciences employ much of the sophisticated lab hardware of chemistry and physics to decipher the nature and origin of rocks and minerals, oceans and atmospheres.
Most American earth scientists belong to the Washington-based American Geophysical Union, whose 50,000 members encompass a broad range of research, from planetary geology and physics to meteorology and oceanography. The Geological Society of America, headquartered in scenic Boulder, Colorado, represents more than 20,000 experimental and field geologists. Both societies are active in international projects because the earth sciences are global in scope and require global cooperation.
Biologists study life, the most complex systems of all. There are so many levels at which to study living things—molecules, cells, organisms, ecosystems—that biologists are a rather fragmented group. The concerns of zoologists working at zoos are quite different from those of industrial genetic engineers or hospital medical researchers. Consequently, there is no central American biological society, nor is there a strong lobbying presence in Washington, D.C.
Most funding for American scientific research comes from the federal government (your tax dollars at work). In 2007, the total U.S. research and development budget was about $130 billion. Most research outside the defense sector is devoted to human health, so the National Institutes of Health receive the largest piece of the research pie—nearly $30 billion. The National Science Foundation, with an annual budget of about $5 billion, supports research and education in all areas of science. Other agencies, including the Department of Energy, the Environmental Protection Agency, and the National Aeronautics and Space Administration, fund research and science education in their own particular areas of interest, while Congress diverts additional money (the notorious earmarks) for special projects.
Most individual scientists support their labs by submitting grant proposals with an outline of the planned research and a statement about why the work is important to the appropriate
federal agency. The funding agency asks panels of independent scientists to rank proposals in order of importance and funds as many as it can. Depending on the field, a proposal has anywhere from about a 10 to 30 percent chance of being successful. Without this support from federal grants, which buys experimental equipment and computer time, pays the salaries of researchers, and supports advanced graduate students, much of the scientific research in the United States would come to a halt.
Newton’s laws of motion and gravity were published more than 300 years ago and his so-called classical mechanics is now a well-established part of any freshman physics course. But although the regularity and predictability of the universe has become an ingrained assumption of our science, recent studies of complex systems like your heart and the weather are making scientists rethink the meaning of predictability. The dynamic field that studies such complex systems goes by the name of chaos or “complexity theory.”
Many day-to-day systems are predictable in the conventional sense. Automobiles, tennis balls, and grandfather clocks act pretty much the way we expect them to. If you drop a tennis ball from waist-high, it hits the ground at one speed; drop it from a little higher up, it hits the ground at a slightly higher speed. A falling tennis ball is a conventional Newtonian system.
There are, however, systems in nature that don’t display this sort of pleasing regularity. Open the tap on your faucet and you get a small, slow stream. Open it a bit more and you are apt to get a rushing, turbulent flow. In the jargon of physics, the behavior of
tap water is extremely sensitive to the initial conditions. A system with this property is said to be chaotic; turbulent streams, growing snowflakes, your heart rhythms, and many other systems are chaotic.
The point about complex chaotic systems is that you can never measure the initial conditions of a system accurately enough to allow you to predict its behavior for all future time. Although your predictions and the real system may be close to each other for a while, eventually they will diverge. The inevitable errors inherent in any measurement, coupled with the extreme sensitivity of chaotic systems to initial conditions, means that for all practical purposes they are unpredictable (although they are perfectly predictable if the initial conditions are specified with mathematical precision).
The weather provides the most familiar example of a chaotic system. Meteorologists make thousands upon thousands of measurements of wind speed, air temperature, and barometric pressure in their efforts to predict the weather. They do pretty well with 24-and 48-hour forecasts, and sometimes they even get the seven-day predictions right. But no matter how fancy the measurements and the computer simulations, there is no way to predict what the weather will be a year from now. The chaotic nature of atmospheric motion is sometimes dramatized as the “butterfly effect,” which says that in a chaotic system an effect as small as a butterfly’s flapping its wings in Singapore may eventually make it rain in Texas.
Today the existence of chaotic systems is accepted by scientists, who now ask which systems are chaotic, how they behave, and how our newly won knowledge of that behavior can be utilized. Can we, for example, produce accurate monthly forecasts of the weather or the stock market?
FICIONADOS THINK THE OLD
wooden roller coasters are still the best. If you’ve ever ridden one, you’re not likely to forget the experience. The adventure begins calmly enough, as you lean back in your cushioned seat enjoying the gradual climb to the ride’s highest point. The steady clack-clack-clack of straining gears belies the wildness to follow. In the best of roller coaster tradition the car comes almost to a stop, poised at the brink, before gravity takes over. Then comes the plunge.
Faster and faster you go, 100 feet of free fall before the car hits bottom and zooms to the next height, only slightly shorter than the first. For a second time you almost come to a stop, and then another precipitous drop. Now the speeding ride takes off for a series of twists and turns, flinging you around tight loops and over violent bumps leading to one last mighty hill. The journey lasts only a couple of minutes, but you emerge, wobbly-legged, with a high that can last for hours.