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| Cosmology and Mutability
Dear Colleagues,
Science & Ultimate Reality
As I wrote a few days ago, I once asked John Wheeler what he regarded as his greatest contribution to science. After a few moments reflection he announced, "Mutability!" Wheeler was impressed by the awesome and inexorable power of gravitational collapse, a phenomenon of such all-encompassing ferocity that it seemed to spell the obliteration of spacetime itself. What, then, might we make of physical laws, formulated as they are within the framework of space and time? Would these laws go into the melting pot too? Wheeler envisioned the cherished laws of physics being transcended one by one as the death-knell of spacetime was tolled. There would be no ultimate, absolute, inviolable, supra-universal laws underpinning physical reality. Instead, only chaos - or "higgledy-piggledy" - from which lawlike regularities might emerge under less violent conditions.
Echoes of this philosophy found favor among cosmologists, who like to think of the hot big bang origin of the universe as an event of limitless violence and fuzzy lawlessness. From this primeval blandness, familiar physics "freezes out" in a succession of phase transitions and symmetry breaks as the universe expands and cools. Taken to its extreme, this point of view implies that the so-called laws of physics we know and love are but random relics of the cosmic birth, frozen haphazardly into our region of space, and not god-given rules on how to run a cosmos.
History has shown that regularities formerly regarded as absolute laws of nature turn out to be the result of special circumstances. For example, the law of conservation of matter is transcended once high enough energies are reached to permit particle creation. Conservation of baryon number would fail for a black hole and most likely fail in the super-hot furnace of the very early universe too. But extreme violence is only one way that laws might be relegated to by-laws. Another is extreme duration. What appears to be fixed might actually vary slightly over immense periods of time. A possible candidate is the so-called fine-structure constant of atomic physics, a universal quantity obtained by combining the speed of light, Planck's constant and the fundamental unit of electric charge. The idea that this number, known to physicists as "alpha," might change over cosmological time is an old idea, but only recently has there been half-way credible observational evidence for it. John Barrow is a theoretical physicist and astronomer at Cambridge University, and has been closely involved in the work on the spectral lines of distant quasars that display tantalizing hints of a varying alpha. His paper is summarized below.
Paul Davies
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Title: Cosmology and Mutability
Author: John D. Barrow
Summary:
This chapter will provide a discussion of what are the unchanging attributes of the Universe. We will discuss the identity and character of the traditional constants of Nature and discuss the evidence for their constancy in space and time. This discussion will draw on recent observational and experimental investigations of the constancy of the fine structure constant, particle mass ratios and the gravitation 'constant' of Newton, and introduce the modern theoretical motivations for considering the variations of constants. We will also consider the narrow ranges of values that many constants are seemingly permitted to take in a Universe similar to ours if complexity is to be possible. The role of extra dimensions of space and time will also be described together with future prospects for understanding the status of the constants of Nature.
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This essay was part of the Science and Ultimate Reality Symposium in honor of John Archibald Wheeler in Princeton, NJ, March 2002.
Published 2002.03.20
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