Thrilling insights and awesome power. These are the fruits of science. Here I examine the nature and progress of humanity’s most successful enterprise, scientific inquiry, and hazard some guesses about its future.
To science we owe most of our comforts, our leisure, our health and longevity, our ability to mold the environment, to communicate instantly, and to move swiftly over the Earth. To science we also owe our ability to wipe out populations with devices of mass destruction and to numb populations with devices of mass communication. What are the features that set science apart from other human activity? What are the reasons for its remarkable growth? What does the future hold for scientific progress? I can give at best partial answers to these questions, but one thing seems clear: Future scientific understanding can be no better legislated and controlled than can any other creative activity of humankind.
What might be called the defining feature of science is its quantitative character. By “quantitative” I mean not merely numerical, but mathematical in a general sense—subject to rules of logic and order, and reproducible. A heckler could find some examples of non-quantitative science and of quantitative non-science, but in the main it is this quantitative aspect that distinguishes science from other avenues of search for understanding. Because of this feature, science gives to humankind the power to predict and to control, not merely the power to describe.
Paradoxically, it is the modest goals of science that are most responsible for its mushrooming growth. It is commonplace to refer to the vast scope and generality of natural laws, which are indeed magnificent and impressive. Yet it has to be borne in mind—and the scientist is perhaps particularly conscious of this fact—that of all the important questions that thinkers have posed to themselves in recorded history, science has so far provided answers only to the easiest ones. Science encompasses a limited range of human experience, yet with no other range of experience has human endeavor been so successful.
Besides the self-imposed limitation to “easy” questions, another key to understanding the progress of science is the generality of application that springs from an economically few fundamentals. This “amplification factor” (or “leverage” as it may be called in the business world) could as well be called a quality of nature as a property of science. Scientists have found themselves able not only to describe nature quantitatively, but to do so with relatively few basic ideas and relationships. From each of the few important theories and laws in physics flows a wealth of application. The blossoming of a whole area of technology in a few years’ time can spring from the discovery of a single fundamental fact. What is just one significant advance in science may appear as an incredible rapid-fire series of advances because of the latent power of each forward step.
Has the growth of science actually been “explosive”? It is commonly said to be so. In the long view of human history it certainly seems explosive. In the last hundred years both the accumulation of scientific facts and the growth of technology merit the adjective “explosive.” But the pace of scientific progress can be overemphasized. It is important to distinguish between merely rapid growth and accelerating growth. The expansion of the world’s population, at least until the twentieth century, is an example of accelerating growth. For most of human history, the population growth in every century has been greater than in the preceding century. There has indeed been a population “explosion.” Without question, the most evident aspects of science—its catalogue of facts and its application for practical goals—have also shown accelerated growth. So have the number of scientific workers and the amount of money spent on science. Nevertheless, there is little evidence in recent history for an accelerated growth of fundamental understanding of nature. It is more accurate to think of science as having undergone a metamorphosis in the seventeenth century that has led to its continual steady (and rapid) growth since then, rather than to think of an ever accelerating pace of progress.
The true landmarks of scientific progress are the occasional revolutions in our view of the workings of nature, and the enlargements of our horizons in the physical world. Such key points of progress in the twentieth century were the new view of space, time, and gravitation initiated by the theory of relativity; the elucidation of atomic structure through the theory of quantum mechanics; the discovery of the subatomic world of transitory particles; the elevation of principles of invariance to a primary position among the laws of nature; and the discovery of the molecular structure of the basic units of living matter. This last advance represents the union of physical science and biological science at the submicroscopic level. Looking back to the nineteenth century, one finds that revolutions of scientific thought occurred nearly as frequently as in the twentieth century. In the nineteenth century the theory of electromagnetism revealed the nature of light and the unity of electricity and magnetism; the kinetic theory of matter, besides explaining the nature of heat and temperature, revealed the turmoil of random molecular motion underlying our apparently solid material world; the theory of thermodynamics brought scientific precision to the concepts of order and disorder and provided a basis for understanding why we experience only a one-way flow of time; the analysis of all matter into a small number of elements and the orderly arrangement of these elements into the periodic table brought a new simplicity to the view of the physical world; the universal scope of the law of conservation of energy brought hope (and some overoptimism) for the construction of a single overriding theory of natural phenomena; the theory of natural selection revolutionized mankind’s view of human history; the discovery of laws of genetics showed the existence of quantitative simplicity in the living world as well as in the inanimate world.
It is, of course, impossible to measure exactly the relative importance of different advances in science or to arrive at any unique list of “truly fundamental” advances. The purpose of the brief catalogue of scientific progress above is to emphasize two facts about modern science. First, the technological marvels of the present day and the ever greater human resources poured into scientific research should not be confused with true progress in understanding the design of nature. My list is notably deficient in inventions (radio, television, GPS, and the Internet) or technical feats (space flight) or in reference to mere accumulation of data. Second, the rate of generation of fundamental ideas in science has shown no marked trend of acceleration, at least over the past 200 years. Progress in recent centuries has been rich, but not noticeably any richer at the present time than 100 years ago or 200 years ago. It seems that any important new idea requires some time to be thoroughly assimilated and appreciated before it can serve as the basis of further advance. Perhaps the instant communication and high-speed travel of the present era serve to stimulate scientific progress through cross-fertilization of ideas. However, it is clear—and it is important to keep in mind—that the pace of fundamental scientific progress is by no means comparable either to the rate of technological development or to the input of human effort.
Can history teach us the best way to push forward the frontiers of understanding in science? Probably very little. In discussing the future of science, scientists agree only that the future is unpredictable. Past progress has revealed no single scientific method. Idealized versions of scientific induction or of the sequence of experimental and theoretical steps in the evolution of a theory have borne little resemblance to actual progress so far. But two of the aspects of past scientific progress stand out as features likely to persist. (1) Theory and experiment have both been necessary. On the one hand, the mere accumulation of data has been barren without the insight provided by hypothesis and theory. On the other hand, flights of fancy untempered by experiment have not been fruitful. (2) All of the great advances have been but small forward steps in the overall view, resting heavily on what has gone before. In discussing an important advance in science, there is a natural human tendency to emphasize its novelty or the creative genius that it reflects. The less heralded developments that preceded and made possible the giant stride tend to be forgotten.
The modern world abounds in scientific cranks (for some reason, usually men), who ignore one or the other of these paramount aspects of science, seeking radical new departures in science without reference to experiment, or without reference to the past stream of scientific thought. Notwithstanding the oft-repeated charge by the cranks that the “high priests of science” have closed minds, most scientists try to keep an open mind about the possible direction from which future progress might come. Anyone with an idea in science can get a hearing. However, past history makes it seem likely that the fruitful ideas will be generated by people who build upon their own deep comprehension of past achievement, not by people who attempt the great leap from no firm foundation.
It is easy to predict one near-certainty about the future, that scientific progress will continue. This sounds like an obvious statement, yet there have been times in the past when both mathematicians and physicists thought that their fields were drying up. In contemporary science, complacency about the state of our understanding is completely absent. Every practicing scientist is painfully aware of his or her areas of ignorance at the frontiers of science. Although a future unrolling of scientific progress accompanying ever deeper understanding of nature is easy enough to foresee, it is more fascinating to consider how future science might differ from past science. Is science getting more difficult to comprehend, and may progress therefore be slowed or stopped? Will the scope of science increase to make it encompass a larger fraction of human experience?
Fundamental science is undoubtedly becoming more difficult. The new concepts are further removed from everyday experience and are less easy to visualize. The world of our senses changes very little. The world of the fundamental theories of nature has been changing rapidly. Albert Einstein and Leopold Infeld1 expressed this trend in these words: “The simpler and more fundamental our assumptions become, the more intricate is our mathematical tool of reasoning; the way from theory to observation becomes longer, more subtle, and more complicated.” A warning is sounded for the future. Will the progress of science be slowed by the ever longer route which scientists must follow from the world of their senses to the elementary world of nature’s design? So far, we humans have shown ourselves adept at learning to think in terms foreign to our direct sense experience. We believe in the annihilation and creation of matter, the wave nature of particles, the relativity of time, the quantum of energy, and the curvature of spacetime. How far this adaptability will carry us no one can predict.
About the future scope of science there can be little doubt. The range of experience encompassed by science has increased gradually, and a further enlargement of what comprises science is almost certain. Although the expansion of biology and the incorporation into science of parts of psychology will have the greatest impact on mankind, growth has occurred and will continue within physical science itself. A few centuries ago, the question, Why does the Sun give out light? had no answer outside of religion. Not much more than a hundred years ago, the question, Why is energy conserved? belonged to philosophy. Both questions are now answered within the framework of physics. Other scientific-sounding questions are easy to pose that in fact lie outside of science today but may be incorporated in the future: Is the universe boundless? Is our universe one among many? What was going on fifty billion years ago? What is the true nature of time? What is the ultimate source of the matter in the universe?
In the realm of biology, consider disease, which has moved from anger of the gods to a very scientific matter of genes and germs and viruses. What the future undoubtedly holds is scientific understanding of some patterns of human behavior. The past problems raised by science have been mainly technological—industrial automation, and implements of war. The future problems are likely to be more directly concerned with human behavior or with non-human replication of human behavior. They are sure to be even more vexing. It is probably wiser to prepare for an expanding scope of scientific understanding—which means the power to predict and control—than to cry out for the bliss of past ignorance. Fortunately the human being is a mechanism of fantastic complexity. It is unlikely that science will ever impinge on the pleasurable uncertainties that characterize some human relations.
Upon the principles of physics rests the whole of science—biological as well as physical—whose growth provides ever deepening understanding and therefore ever broadening responsibility, and ever increasing opportunity for betterment of the human condition.
1 The Evolution of Physics (New York: Simon and Schuster, 1950).