What is Science from a Physics Perspective?
Paul Craig and Ellen B. Stechel
Motivation: As current members of APS Panel on Public Affairs (POPA), we share POPA's long-standing concern about misunderstandings by the public about science and about what does or does not fall within the domain of science. We felt that a prerequisite to approaching the larger issue would be to clarify what science means to physicists. The following paper evolved from several discussions within POPA. The intended audience for this article is the physics community. The primary motivation is our sense that physicists need an agreed-upon statement to use as a foundation for discussing complex issues in the realm of "science or anti-science." For the most part, the physics community shares, a not often articulated, vision for science. With a clear view as to what science is, it becomes easier to also understand what science is not.
POPA has discussed and critiqued this article, which draws heavily on two carefully crafted reports by the National Academy of Sciences: "Science and Creationism" [NAS:1984] and "The Nature of Physics" [NAS:1972]. Our sense of the POPA discussion is that it would be useful to place this article before the physics community via the Forum on Physics and Society. We will welcome and appreciate any comments (whether pro or con).
The format for this article is a central statement supported by explanatory discussion framed as responses to anticipated questions. The first part defines the scientific method. The second part uses the device of questions and answers to provide clarification and further explanation.
What is Science?
"In broadest terms, scientists seek a systematic organization of knowledge about the universe and its parts. This knowledge is based on explanatory principles whose verifiable consequences can be tested by independent observers. Science encompasses a large body of evidence collected by repeated observations and experiments. Although its goal is to approach true explanations as closely as possible, its investigators claim no final or permanent explanatory truths. Science changes. It evolves. Verifiable facts always take precedence.... " [NAS:1984:8]
The scientific method. "Scientists operate within a system designed for continuous testing, where corrections and new findings are announced in refereed scientific publications. The task of systematizing and extending the understanding of the universe is advanced by eliminating disproved ideas and by formulating new tests of others until one emerges as the most probable explanation for any given observed phenomenon." [NAS 1984:9] [Italics added].
The NAS is careful to emphasize that science does not recognize absolute truth. [See, however, a question below on scientific "laws."]
Hypotheses. "An idea that has not yet been sufficiently tested is called a hypothesis. Different hypotheses are sometimes advanced to explain the same factual evidence. Rigor in the testing of hypotheses is the heart of science" [NAS1984:9]
Falsifiability. "If no verifiable tests can be formulated, the idea is called an ad hoc hypothesis, one that is not fruitful; such hypotheses fail to stimulate research and are unlikely to advance scientific knowledge." [NAS 1984:9]
One refers to the concept that a hypothesis can be proven wrong as falsifiability. A hypothesis is valuable only if it is testable or at least provokes further investigation. It is typically impossible to prove something true; however if there is also no expectation that it can be proven false then it is outside the realm of science.
Theory and accepted theory. "A fruitful hypothesis may develop into a theory after substantial observational or experimental support has accumulated." Scientists eliminate a hypothesis when it fails to produce predicted consequences. When a single hypothesis survives repeated opportunities for disproof and no other competing hypotheses remain viable, then that single hypothesis may become the accepted theory to explain the original observation. [paraphrased from NAS 1984:9]
Reproducibility. A hallmark of accepted science is that several research laboratories have reproduced the observed phenomena.
Prediction. "Scientific theories are also predictive. They allow us to anticipate yet unknown phenomena and thus to focus research on more narrowly defined areas. If the results of testing agree with predictions from a theory, the theory is provisionally corroborated. If not, it is proved false and must be either abandoned or modified to account for the inconsistency." [NAS 1984:9]
Provisional character of theories. "Scientific theories, therefore, are accepted only provisionally. It is always possible that a theory that has withstood previous testing may eventually be disproved. But as theories survive more tests, they are regarded with higher levels of confidence. A theory that has withstood ... many severe tests... is held with a very high degree of confidence ..." [NAS 1984:9]
Scientific "Laws." Higher levels of generalization are formulated into scientific laws. A law identifies a class of regularities in nature from which there has been no known deviation after many observations or trials. It is usually expressed mathematically...Scientific laws tell us the ways but not the whys of nature... We must heed them in formulating new hypotheses and theories." [NAS 1984:9]
Attitudes toward new discoveries "[S]cience accommodates, indeed welcomes, new discoveries: its theories change and its activities broaden as new facts come to light or new potentials are recognized..." [NAS 1984:26]
Science and Religion "Scientists, like many others, are touched with awe at the order and complexity of nature. Religion provides one way for human beings to be comfortable with these marvels. However, the goal of science is to seek naturalistic explanations for phenomena." [NAS 1984:26]
Questions and answers about science
In this part we use questions and answers to further explore the ideas outlined above.
Do scientists believe in an objective reality? Yes. The belief that there is an external reality is the basis for science. Scientists believe that the scientific method offers the best tool or technique yet devised for learning about that external reality. Scientists assume that the universe operates according to invariant rules. The concept of reproducible experiments, a cornerstone of science, is predicated on the idea that the universe operates according to fixed, discoverable, invariant rules. The evidence for the validity of these assumptions is the success of the scientific method at developing effective techniques for manipulating the world.
"Physics... is concerned with questions that cannot be decided by thought alone. Answers have to be sought and ideas tested by experiment. In fact, the questions are often generated by experimental discovery. But there is every reason to believe that the answers, once found, have a permanent and universal validity" NAS:1972:57
"The reality is that many experiments can be and have been repeated by many individuals, with the same outcomes. ....[Scientists] define objective reality as those matters about which the scientific public agrees". [Cromer 1993:145]
What do scientists mean by the word "Law"? "Law" is a technical term in science. The scientific meaning differs substantially from common usage. Moreover, the scientific meaning does not rank a high priority in dictionaries. In one well-known dictionary the scientific meaning shows up as the eleventh definition:
"[Law]: A formulation describing a relationship observed to be invariable between or among phenomena for all cases in which the specified conditions are met: the law of gravity" (AHED 1995).
The specialized use of the word "law" has lead to a great deal of confusion and numerous miscommunications. Scientific "laws" such as conservation of momentum and of mass-energy, and the laws of thermodynamics, are deeply felt convictions of most physicists. The use of the term "law" expresses the idea that it is inconceivable to the physicist that the concept might be violated. There is no option to repeal a scientific law. If pushed, the physicist should, however, admit in principle to the remote possibility of violations. When violations to accepted laws do occur, a generalization or enlargement of the theory becomes necessary.
A well-known example is the discovery and the subsequent theory of quantum physics. Quantum physics accounts for violations to Newtonian mechanics for particles with small mass. Quantum physics did not overthrow Newtonian mechanics. Newton's laws of motion are still laws with limitations on their validity. Similarly, under extreme conditions, Newton's law of universal gravitation yields to the more complete theory of Einstein's general relativity. Nevertheless, Newton's laws describing motion and gravitation are remarkably accurate descriptions of physical phenomena over a wide range of particle masses, velocities and distances.
Some further confusion arises because in some instances scientists have used the word "law" quite loosely as in Hooke's law and Ohm's law. In contrast to Newton's laws, the ranges of validity of Hooke's and Ohm's laws are quite limited. Yet at the same time we still refer to Einstein's theory of special relativity as a theory; certainly it would qualify as law. Similarly we refer to the theory or theories of evolution. Much of Darwin's theory of evolution and natural selection would also qualify as laws.
What is the meaning of "Progress" in science? New "laws" must explain at least as much as the old ones. Science is cumulative, always building on previous knowledge. It is the cumulative character of scientific knowledge that provides the justification for the claim that science is "progressive". The cumulative aspect of science is one of the most important distinctions between science and (for example) art.
Quantum physics provides a good illustration of the concept. As it must, quantum physics predicts everything successfully predicted by its predecessor, classical mechanics. Furthermore, it predicts and explains much more.
What makes one theory good or better than another? New theories in science are objectively better than old ones in the sense that they are able to make new predictions, or they provide more all-encompassing ways of integrating existing knowledge, or they provide simpler more elegant ways of explaining phenomena.
Do scientists make mistakes? Is science self-correcting? Human beings embark in the activities known collectively as "Science." Moreover, humans can and do make mistakes. They do so individually as well as collectively. They make both honest and dishonest mistakes.
Nevertheless, science is self-correcting; "science isn't dependent on the honesty or wisdom of scientists. The scientific enterprise rises above individual shortcomings" [Cromer 1993:165].
"The scientific enterprise is collective... It is never one individual that goes through all the steps in the logico-deductive chain; it is a group of individuals, dividing their labor but continuously and jealously checking each other's contributions... " [Cromer 1993:143]. "Science is the search for a consensus of rational opinion among all competent researchers" [Ziman 1968:10]
It should be noted that "failure" is very much a part of the scientific process. Most failures are never even reported but are part of scientific progress.. Nevertheless, reputations are often made by finding mistakes or holes in the work of others. Since, scientific findings are reported openly in the literature and at conferences this often happens very quickly, sometimes at the peer review stage prior to publication. It is the openness, self-skeptical and critical nature of science and the scientist that helps assure that science is self-correcting. Another frequent "mistake" in science is an interpretation of experimental data reported as observation. When used to "falsify" a hypothesis the scientist may and should question assumptions built into the interpretation of the experiment. This in itself often leads to self-correction and progress.
What is meant by the term "competent" researchers? Who decides which researchers are competent and which are not? This is an unstructured social process. The process apparently works remarkably well. It again depends on the openness in the physics community. Credibility of a researcher develops as one's work is reproducible and consistently advances the current state of knowledge and stimulates further research.
Is science sometimes counterintuitive? Yes. The physics of motion provides a good example of counterintuitive behavior. Studies of student's anticipation of the motion of objects dropped from moving platforms, such as trains, rotating turntables, pitched ball, etc. show that actual behavior is strikingly counterintuitive to many students. New discoveries are often counterintuitive even to the discoverers. Aspects of quantum mechanics and the wave-particle duality remain counterintuitive even to many physicists who use these concepts regularly. However, experience typically causes concepts to become more intuitive. Students trained in physics make the kind of errors described here far less frequently than do untrained students.
Do scientists "understand" how the world works? Theories unify phenomena. Whether they provide "understanding" is a matter of definition. Nobel Laureate Murray Gell-Mann put it this way:
"All of modern physics is governed by that magnificent and thoroughly confusing discipline called quantum mechanics invented more than fifty years ago. It has survived all tests. We suppose it is exactly correct. Nobody understands it, but we all know how to use it and how to apply it ... : and so we have learned to live with the fact nobody can understand it" [quoted in Wolpert 1992:144]
In other words, operationally quantum mechanics is well-understood. It is probably fair to say that many practitioners feel they do understand the wave-particle duality as well as the concept of the non-separability of the system and the act of measurement. They also understand the Heisenberg uncertainty principles. However, understanding what the wave function means and some of the implications tend to challenge intuition.
Will there be an "End to Physics"? "It is possible to think of fundamental physics as eventually becoming complete. There is only one universe to investigate, and physics, unlike mathematics, cannot be indefinitely spun out purely by inventions of the mind... Is there an irreducible base, or design, from which all physics logically follows? The history of modern physics warns that the answer to such a question will not be attained just by thinking about it. .. But without experimental exploration and discovery, new ideas are not generated. Physics will remain an experimental science at least until very much more is known about the fundamental nature of matter" [NAS 1972:80-82]. In short, experimental and theoretical physics is still very vibrant with no apparent decrease in the pace of innovation. At the present time no "end of physics" is in sight.
Why do scientists show so little interest in flying saucers, spoon bending, cold fusion, psi phenomena and the like? The world is very complex, and science is challenging. To be successful a scientist must work in limited areas where progress is feasible. Decisions on which areas are likely to prove fruitful are a matter of style. The Nobel Laureate Richard Feynman told a believer in flying saucers that flying saucers are not impossible, just unlikely. When charged with being unscientific, Feynman said it is scientific to say only what is more likely and what is less likely, and saucers are less likely. Science, he said, proceeds by informed guesses that lead to predictions which are experimentally testable. [told in Wolpert 1992:139]
In areas outside the main stream new claims must bear a far greater-than-normal burden of proof. This requirement allows one to understand why the scientific community accepted high temperature superconductivity, but broadly rejected cold fusion and "psi" phenomena.
In the former case (high temperature superconductivity) the discoverers provided detailed information on what they had done. It was possible to replicate their experiments. Consequently, many researchers did replicate the reported observations. In the latter cases (cold fusion and "psi" phenomena) the information provided was insufficient to allow replication of the process used in observing the so-called phenomena. The main stream scientific community considers the cold fusion and psi observations likely to be wrong. A long history of scientific errors supports this way of thinking. For example: N-rays, polywater, and Bienveniste's "infinite dilution" experiments that claimed to show that water has memory [Wolpert 1992:142].
Does this mean it is possible that cold fusion could be real? Yes. At the present time the preponderance of scientific opinion is that cold fusion is an experimental artifact. However, should someone develop a repeatable procedure for demonstrating the phenomenon of cold fusion, researchers in many laboratories quickly reproduce that procedure, and would become a part of science. Reproducibility is the key, not basic understanding. Many phenomena have remained unexplained for decades. Low temperature superconductivity was first discovered in 1911, but remained unexplained until 1958. Many phenomena in high temperature superconductivity remain unexplained today. However, unlike cold fusion and psi, both phenomena are readily replicated and therefore readily accepted.
Are science and religion incompatible? Science and religion are not necessarily in conflict or incompatible. One may characterize the gulf between science and religion by degrees of faith. To the scientist, every idea is in principle open to question. Religion requires unquestioning faith. To Einstein, "a religious person is devout in the sense that he has no doubt about the significance of those supra-personal objects and goals which neither require nor are capable of rational foundation...Science focuses on the how's and what's in nature. It does not address questions such as why we exist, is there life after death, and is there intelligent design underlying the existence of the universe and of life. The latter questions fall outside the domain of science, but are often addressed in religions.
Could the world have been created in an instant -- or in a day or in seven days? In principle. "... Bertrand Russell has argued that there is no evidence, scientific or otherwise, that can disprove the statement that 'the world was created two days ago'. Our memories, this book, everything around us would be part of that creation. The trees would have many rings to show their apparent age, and old people would have wrinkles to indicate the many years they appear to have lived. The fact that our experience is so real to us does not serve as a logical proof that the world is any older than two days, frustrating as this argument may be.
Russell was, of course, only presenting an argument in which neither he nor anyone truly believes, but it is an argument useful in illustrating the limitations of scientific proof for what is essentially a philosophical notion -- that the earth is (or is not) as old as it appears to be. This also illustrates the concept of falsifiability. Conjecturing that the world was created only two days ago with all the appearance of being around for billions of years is impossible to prove false and therefore is outside the real of science.
In the words of Albert Einstein... 'The truth is by no means given to us; given to us are the data of our consciousness'. " [Kantor, 1989:3]
What is the difference between science and engineering or technology? Science is about advancing the forefront of knowledge, about discovering unifying or simplifying concepts. Science is about framing well posed questions and designing clever experiments to probe nature in order to unlock its carefully guarded secrets. Engineering is about applying knowledge in novel ways to solve specific problems. Much of scientific inquiry is about engineering carefully designed experiments. Often in the process of problem solving scientific discoveries occur. In other words the distinction generally gets blurred. Nevertheless, the essential difference remains.
Science focuses on the search for reproducible laws that govern the workings of nature. Technology seeks to produce devices for some human purpose. Technology often draws upon science, and scientific research makes heavy use of technology. The objectives, however, are entirely different.
How do physicists think about practical applications of science? Science is a specific way to search for underlying truths about the structure of the universe. As such, science is value-neutral. Scientists themselves take diverse views about the applications of science. When they do so, they are not acting as scientists. Accordingly, it is no surprise to find scientists on virtually all sides of debates concerning the applications of scientific knowledge.
What is the ethical obligation of the scientist when the applications of new scientific knowledge become evident? Scientists have often found themselves in difficult ethical terrain when they realized that their search for basic understanding of nature had unforeseen practical applications. Such dilemmas are intrinsic to science. It is rare that a scientist has the prescience to anticipate even a portion of the applications of his/her work.
J. Robert Oppenheimer strikingly expressed this difference:
"The scientist is not responsible for the laws of nature, but it is the scientist's job to find out how these laws operate. ... [I]t is not the scientist's responsibility to determine whether a hydrogen bomb should be used. That responsibility rests with the American people and their chosen representative" [Wolpert 1992:157]
Nevertheless, at the stage when the prospect of particular applications of scientific knowledge come to light, the thoughtful scientist will reflect on the moral and ethical implications of success. He/she may then make a personal decision not to continue the work along lines that would lead to negative consequences. However, often times even when there appears to be potential negative consequences, there are simultaneously positive consequences. Then it may still be very important to continue further investigation. In either case, it is the responsibility of the scientist to help the public and policy makers to understand the possible implications of his/her research.
Is performing science a social process? Yes. "Science is very much a social process. This appears with clarity in perceptions of subjectivity and objectivity... [T]he idea of scientific objectivity has only limited value, for the way in which scientific ideas are generated can be highly subjective, and scientists will defend their views vigorously........ Being objective is crucial in science when it comes to judging whether subjective views are correct or not. One has to be prepared to change one's views in the face of evidence, objective information. It is... an illusion to think that scientists are unemotional in their attachment to their scientific views; they may fail to give them up even in the face of mounting evidence against them. [A major goal of scientists is] finding a common explanation for all the relevant phenomena, and an explanation which other scientists would accept" [Wolpert 1992:18]
How do physicists think about deconstructionist and postmodern analyses of science? Deconstructionism and postmodernism are relatively new areas of sociology. Practitioners of these fields hold to a diverse set of views. One central (extreme) strand is the idea that reality is a human construction. When applied to science, the extreme deconstructionist viewpoint is inconsistent with physicists' view of the world. The fundamental basis for the scientific method is the assumption that there does exist an external reality. Physicists believe that the scientific method provides for the best means yet discovered for learning about this assumed external reality [NAS 1972; Ziman 1996].
To the extent that criticisms of science emerge from extreme perspectives that deny the possibility for the existence of an objective reality there appears to be little possibility for common ground. However, scientists do recognize that this extreme perspective is held by a minority faction of science and technology studies.
Scientists do recognize that they are a part of a social enterprise and that their techniques for exploring reality are subject to human failings. Investigations of the process and the culture of science is a domain where dialogue with postmodern tradition could prove rewarding.
References
AHED. American Heritage Dictionary. (1995 : CD version 4)
Cromer, Alan. Uncommon Sense: The Heretical Nature of Science. New York: Oxford University Press, 1993.
Kantor, Mattis. The Jewish Time Line Encyclopedia, Jason Aronson Inc. .230 Livingston Street, Northvale NJ 07647 (1989:3)
NAS. Science and Creationism: A View from the National Academy of Sciences. National Academy of Sciences Press, 1984.
NAS. Physics in Perspective. Volume I: The Nature of Physics. Physics Survey Committee of the National Research Council, D. Allan Bromley, Chair. Washington DC 1972
Shamos, Morris H. The Myth of Scientific Literacy. New Brunswick: Rutgers University, 1995.
Weinberg, Alvin. "Science and Trans-Science." Minerva: A Review of Science, Learning and Policy X (#2 1972):209-222.
Wolpert, Lewis. "The Unnatural Nature of Science". Faber and Faber, London 1992 pp192
Ziman, John M. Public Knowledge. Cambridge: Cambridge University Press, 1968.
Ziman, John M. Is Science Losing its Objectivity. Nature 382, 751-754, 29 August 1996
Paul Craig is at the Department of Applied Science, University of California, Davis, CA 95616,
ppcraig@ucdavis.edu
Ellen B. Stechel is at the Physical and Chemical Sciences Center, Sandia National Laboratories, Albuquerque, NM 87185-1421, ebstech@sandia.gov