Science Fashions and Scientific Fact
Posted on Thursday, November 13, 2003 @ 19:44:43 GMT by vlad
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Anonymous writes: "If so, I think it would be a terrible mistake [To disregard experimentation] . There would then be little to distinguish the practice of physics from, say, that of painting or printmaking--in which the criteria that distinguish the good from the bad are based largely on opinions of art critics and historians. There is something unique about scientific fact, and that uniqueness has much to do with the often tedious practice of making telling empirical observations. The primary criterion of good science must remain that it has been repeatedly tested by measurements--no matter how difficult they may prove to be--and found to be in excellent accord with them." -Michael Riordan
The following is an extract from a Physics Web opinion piece by Michael Riordan. The full text is in: http://www.physicstoday.org/vol-56/iss-8/p50.html
References are included at end of posting.
Count on experiments
This brief history of the quark discovery illustrates the crucial role that experiments play in making modern physics. It was not theory but experiment that plucked the quark idea from near oblivion. Aided and abetted by theory, experiments made quarks real, transforming them from a wayward hypothesis into concrete objects of experience. Experiments are what ultimately discarded the science fashions of the sixties and turned quarks into hard scientific fact.
As psychologist William James observed in his book Pragmatism, "Truth happens to an idea. It becomes true, is made true, by events" [italics in original].2 He was popularizing the views of his idiosyncratic colleague Charles Sanders Peirce, one of the few philosophers of science with experience doing experiments. For Peirce, the true hallmark of the "real" is the observable consequences that a community of experienced practitioners agrees occur in actual practice.
That hallmark has indeed proved true for quarks, which form the bedrock of the standard model, the dominant paradigm of particle physics. Today we work with quarks almost unthinkingly, taking them for granted in high-energy experimentation. At Fermilab, physicists bash together bags of quarks and antiquarks, hunting for Higgs bosons and other exotica. Quarks have indeed become things.
I find it difficult, however, to imagine how such a rigorous criterion of reality could ever hold true for some of the fanciful ideas and constructs that have emerged in recent years from the minds of many theorists. How can we ever hope to work in everyday practice with such entities as superstrings, parallel universes, wormholes, and phenomena that occurred before the Big Bang?
Some of these ideas may have great mathematical beauty and significant explanatory power, but so did many discarded physics fashions of the 1960s. Superstrings are in fact an outgrowth of one of those earlier ideas, the dual resonance model, which John Schwarz resurrected in the 1980s and applied at the Planck scale. But how can we ever hope to make meaningful measurements at this scale when we have such difficulty building particle colliders to work at the comparatively lowly Higgs scale?
One or more of the extra dimensions required in superstring theories may soon become observable at the energies accessible at Fermilab or CERN's future Large Hadron Collider. Such a phenomenal discovery, if it occurs, would be tantamount to bringing superstrings down to Earth. But for such large extra dimensions ever to become truly real, experiments would have to exclude all other possible explanations of what occurs. That will not be an easy task.
Cultivate skepticism
One of the great strengths of scientific practice is what can be called the "withering skepticism" that is usually applied to theoretical ideas, especially in physics. We subject hypotheses to observational tests and reject those that fail. It is a complicated process, with many ambiguities that arise because theory is almost always used to interpret measurements. Philosophers of science say that measurements are "theory laden," and they are. But good experimenters are irredeemable skeptics who thoroughly enjoy refuting the more speculative ideas of their theoretical colleagues. Through experience, they know how to exclude bias and make valid judgments that withstand the tests of time.3 Hypotheses that run this harrowing gauntlet and survive acquire a certain hardness--or reality--that mere fashions never achieve. This quality is what distinguishes science from the arts.
But many of today's practicing theorists seem to be unconcerned that their hypotheses should eventually confront objective, real-world observations. In a recent colloquium I attended, one young theorist presented a talk on his ideas about what had transpired before the Big Bang. When asked what observable consequences might obtain, he answered that there weren't any, for inflation washes away almost all preexisting features. Young theorists are encouraged in such reasoning by their senior colleagues, some of whom have recently become enamored of the possibility of operating time machines near cosmic strings or wormholes. Even granting the existence of cosmic strings, which is dubious, I have a difficult time imagining how anyone could ever mount an expedition to test those ideas.
I like to call this way of theorizing "Platonic physics," because implicit within it is Plato's famous admonition that the mathematical forms of experience are somehow more real than the fuzzy shadows they cast on the walls of our dingy material caves. And, in reaction to the seemingly insuperable problems of making measurements to test the increasingly abstract theories of today, some people have even begun to suggest that we relax our criteria for establishing scientific fact. Perhaps mathematical beauty, naturalness, or rigidity--that Nature couldn't possibly choose any other alternative--should suffice. Or maybe "computer experiments," as Stephen Wolfram intimated last year in A New Kind of Science, can replace measurements. According to a leading science historian, such a subtle but ultimately sweeping philosophical shift in theory justification may already be underway.
If so, I think it would be a terrible mistake. There would then be little to distinguish the practice of physics from, say, that of painting or printmaking--in which the criteria that distinguish the good from the bad are based largely on opinions of art critics and historians. There is something unique about scientific fact, and that uniqueness has much to do with the often tedious practice of making telling empirical observations. The primary criterion of good science must remain that it has been repeatedly tested by measurements--no matter how difficult they may prove to be--and found to be in excellent accord with them.
Without such a rigorous standard of truth, science will have little defense against the onslaughts of the creationists and postmodernists, for whom it is just one of many ways to grasp the world. How could we ever hope to defend science against such attacks if it were based only on the opinions of its leading practitioners? Mathematics is not enough, no matter how beautiful. Even Einstein, who helped foster this theoretical style, insisted his ideas had to have observable consequences.
The essence of scientific truth rests in the requirement that it should have strong accordance with the natural world that exists outside our minds and beyond human artifice--what Peirce called "the vagaries of me and you." Experimenters must continue ripping away at new ideas to make sure this accordance indeed holds true. Their skepticism plays a role like death in natural selection--only the strongest survive to take their place among what actually lives on.
In this evolutionary metaphor, speculative theorizing plays a crucial role, too, by helping to ensure that science investigates the many philosophical niches where truth might lurk. My one caveat is that hypotheses resulting from such wide-ranging explorations of possible theory space must ultimately lead to testable consequences--a process that may take years, even decades--if science is to advance. Otherwise, theorists are doing metaphysics, not physics.
The Book of Nature
Early in the 17th century, Bacon and Galileo enunciated a new approach to knowledge, based not on the words of Aristotle or the Medieval Scholastics but on reading what they called the "Book of Nature." According to Galileo, "Philosophy is written in this great book, the Universe, which stands continually open to our gaze."4
For nearly four centuries, reading the Book of Nature has been the foundation of an extremely powerful practice that has proved remarkably successful in extending cognition into the diverse corners of experience. It was by reading that book, in fact, that we stumbled upon quarks in the late 1960s. To abandon the practice now would be to risk a return to the chaos of opinion that preceded Bacon and Galileo. As physicists concerned about the future of our discipline, we must do everything we can to continue reading this rich and fascinating book.
References
2. W. James, Pragmatism--A New Name for Some Old Ways of Thinking (1907), in J. J. McDermott, ed., The Writings of William James, Random House, New York (1967), p. 430.
3. See, for example, A. Franklin, Selectivity and Discord: Two Problems of Experiment, U. of Pittsburgh Press, Pittsburgh, Pa. (2002).
4. Quoted in S. Shapin, The Scientific Revolution, U. of Chicago Press, Chicago (1998), p. 69.
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