Conjurers of conjecture

May 12, 1995

Peter Holland condemns the mystification of science by the popularisers. Physicists are claiming quantum mechanics is incomprehensible and science can chart a path to God. But quantum physics does not support these ideas and their promotion may be fostering mysticism.

Einstein once said: "The most incomprehensible thing about the world is that it is comprehensible." Certainly most physicists feel they are rationalists espousing a healthy scorn for muddle-headed mysticism. More than any other discipline, physics has sought to confront simple faith with a knowable, lawful universe that exists and evolves independently of our volition. Yet bizarrely, recent popularisations of science have been saturated with tales of a physical universe so weird it defies comprehension.

These accounts invoke the theories of fundamental physics developed in the early years of this century, particularly those of quantum mechanics. John Gribbin, a science writer, frequently quotes the American physicist Richard Feynman: "Nobody understands quantum mechanics." The theme is that the weirdness - that is, the incomprehensibility - is an intrinsic facet of nature that humans can never transcend, however resourceful we may be.

Some writers such as Stephen Hawking go further to suggest that modern science provides a niche for God, even a necessary one; science can chart a surer path to the Creator than devotional methods. Paul Davies believes God provides an appropriate mode of discourse in discussing the issue of whether purpose has a place in the scientific view of the Universe. Seasoned observers have been wondering when sex, that other great preoccupation of contemporary shoegazing culture, would be summoned in the rush to flaunt science's street-cred.

Too late, it has already happened. A recent book by Frank Tipler promising immortality for true believers in the laws of physics guarantees heavenly future sex. How long before we get a book that combines the entire set of publishers' buzzwords - the Quantum Sex God?

Significantly it is not just clerics or west coast freaks who are making these claims - they emanate from generally atheistic, and even renowned, physicists. Science is being invoked by scientists to promote what looks like a mystical view of the world. Is an inexplicable, God-fearing universe really a consequence of established science?

To understand the origin of these claims we have to appreciate the difficulties faced by the quantum pioneers, such as Bohr, Heisenberg and Schrodinger, in grasping the meaning of their emergent theory. By the 1920s they had achieved a brilliantly successful mathematical theory to describe the interaction of atoms and light, and had realised that the new physics could not be squeezed into the conceptual straitjacket of 19th-century science. But they could not see how to apply their theory to other aspects of nature, developing new concepts which were intuitively clear. They came to believe that nature itself exhibits an essential ambiguity that resists rational explanation. What emerged as the orthodox interpretation of quantum mechanics is an emasculated rendition of the old physics, which only partially captures the subtlety of atomic phenomena.

This partly explains why popular books are able to invoke quantum physics to justify semi-mystical theories. They represent the public face of professional confusion. And it also explains why the more extravagant claims are rarely contested. Physicists do not know the limits of permissible extrapolation of the quantum theory. Nuclear, atomic, molecular and optical quantum physics is well established. It is not yet known what applications beyond that, to the material Universe or to the problem of consciousness, for example, are meaningful.

Part of the legacy of the quantum establishment has been a culture of intolerance towards efforts at creating imaginative new concepts. Nevertheless, a minority of physicists (including Einstein) persisted. Eventually in the 1950s the American, David Bohm, succeeded in finding the elusive rational alternative, building on earlier ideas of Louis de Broglie, one of the originators of quantum mechanics. For complex historical reasons this work is little known to scientists outside the foundations of quantum mechanics and even now most textbooks and popularisations ignore it. Yet Bohm's theory shows that "quantum strangeness" in the sense of inexplicability is an artefact of an inappropriate language, not a property of the world.

One particular experiment is most often used to illustrate the alleged "quantum weirdness". A set of particles are fired one after another at a board containing two nearby holes. Each particle then hits a screen located beyond the board where a tiny spot of light permanently records its arrival. Imagine what happens if the particles are marbles. Each marble passes through one or the other hole and the cumulative pattern of light spots on the screen will consist of two bright regions of similar intensity separated by a dark region.This is just the sum of the patterns obtained if only one or the other hole were open.

Now scale down the dimensions of the device about a million times and substitute electrons for marbles. If either one or the other hole is open (but not both) we get results similar to the marble case. After the passage of many electrons, a single region will be illuminated on the screen ahead of the corresponding hole. But our intuition from experience with marbles lets us down if we think that we will obtain just two bright regions when both holes are open. Instead, the cumulative pattern is now a band comprising several bright regions of different intensity alternating with dark regions. This is reminiscent of the pattern obtained when light is passed through a similar two-hole system.

Conventionally this is presented as showing that when an electron passes through one hole it knows whether the other hole is open or closed. Otherwise it would just contribute to the sort of pattern obtained with marbles.

An electron appears to negotiate both holes and yet ends up at a single point on the screen. This is the ambiguity that is claimed to be inherent in nature. Feynman referred to this as "the heart of the mystery" of quantum mechanics.

Bohm's approach dissolves the ambiguity. Each electron passes through one or the other hole and proceeds to the screen where it arrives at a point. But, unlike the marble, the electron is subject to a new type of force during its passage from hole to screen. Because the force carries information about both holes, it can bend the electron's path so it lands at a point which is inaccessible when only one hole is open. Moreover this quantum force is generally negligible at the scale of marbles so the same set of ideas includes that case as well. So there is a way round the paradox - it might lie beyond daily experience but the quantum world is nevertheless explicable.

Popular accounts often go on to consider what would happen if the electronic ambiguity of the orthodox view was amplified to the human scale. Typically this is illustrated by Schrodinger's cat. The idea is that quantum mechanics allows macroscopic things, such as cats, to exist in states that would be impossible according to our usual experience. This is an analogue of the electron being simultaneously spread over two holes.

Schrodinger's example is of a cat that is somehow simultaneously alive and dead. But we expect that this is not possible in our world, so the conclusion is drawn that the act of looking at the cat transforms it from dead-and-alive to dead-or-alive. The gee-whiz school aims to educe the reaction "Wow, the world really is weird!" but fails to impart insight. In Bohm's theory macroscopic objects may indeed be put into states we would not normally encounter, independently of whether we are around to observe them. Having an imaginative model helps us to understand this novel feature and dispels claims of incomprehensibility. It also helps us see why such states of matter are never encountered in ordinary experience.

One confronts this emergent genre of science writing with reluctance, for the opposite position of denying any value to speculation would be equally disastrous. But it is necessary to distinguish between radical speculative work that leads to imaginative new insights, which is after all integral to science, and sensationalism. There is a huge gulf between the speculations justified by the actual work of theoretical physicists and those presented to the public. Popularisers are not neutral ciphers who simply relay scientific truth as a benign public service.

There is money in mystery. But mystery leads to obfuscation and that does nothing to enhance the public's appreciation of science. Science still represents a noble tradition of anti-clerical subversion but society infects all its products. What a historical irony that the arch-rationalists end up bearing a new-ageist banner. The mystification of science must worry physicists and elicit a response. At least Einstein got it the right way round.

Peter Holland is professor in the foundations of physical sciences, School of Interdisciplinary Sciences, University of the West of England. His book about Bohm's theory, The Quantum Theory of Motion, is published by Cambridge University Press.

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