Friday, July 2, 2004

In lighter news (yuk yuk yuk)

Speed of light may have changed recently

(Exclusive from New Scientist Print Edition, Eugenie Samuel Reich, 19:00 30 June 04)

The speed of light, one of the most sacrosanct of the universal physical constants, may have been lower as recently as two billion years ago - and not in some far corner of the universe, but right here on Earth. . . .

A varying speed of light contradicts Einstein's theory of relativity, and would undermine much of traditional physics. . . .

Call in Robert Sungenis! Geocentrism Alert!

But some physicists believe it would elegantly explain puzzling cosmological phenomena such as the nearly uniform temperature of the universe. It might also support string theories that predict extra spatial dimensions.

The threat to the idea of an invariable speed of light comes from measurements of another parameter called the fine structure constant, or alpha, which dictates the strength of the electromagnetic force. The speed of light is inversely proportional to alpha, and though alpha also depends on two other constants (see graphic), many physicists tend to interpret a change in alpha as a change in the speed of light. It is a valid simplification, says Victor Flambaum of the University of New South Wales in Sydney.

It was Flambaum, along with John Webb and colleagues, who first seriously challenged alpha's status as a constant in 1998. Then, after exhaustively analysing how the light from distant quasars was absorbed by intervening gas clouds, they claimed in 2001 that alpha had increased by a few parts in 105 in the past 12 billion years. . . .

Throughout the debate, physicists who argued against any change in alpha have had one set of data to fall back on. It comes from the world's only known natural nuclear reactor, found at Oklo in Gabon, West Africa.

The Oklo reactor started up nearly two billion years ago when groundwater filtered through crevices in the rocks and mixed with uranium ore to trigger a fission reaction that was sustained for hundreds of thousands of years.

Several studies . . . have concluded that nuclear reactions then were much the same as they are today, which implies alpha was the same too. That is because alpha directly influences the ratio of these isotopes. . . . [S]ince the rate of neutron capture depends on the value of alpha, the ratio of the two samarium isotopes in samples collected from Oklo can be used to calculate alpha. . . .

Alpha, it seems, has decreased by more than 4.5 parts in 10^8 since Oklo was live (Physical Review D, vol 69, p121701). That translates into a very small increase in the speed of light (assuming no change in the other constants that alpha depends on), but Lamoreaux's new analysis is so precise that he can rule out the possibility of zero change in the speed of light. "It's pretty exciting," he says. . . .

The analysis might be sound, and the assumptions reasonable, but some physicists are reluctant to accept the conclusions. "I can't see a particular mistake," says Flambaum. "However, the claim is so revolutionary there should be many independent confirmations." . . .

Some physicists would happily accept a variable alpha. For example, if it had been lower in the past, meaning a higher speed of light, it would solve the "horizon problem".

Cosmologists have struggled to explain why far-flung regions of the universe are at roughly the same temperature. It implies that these regions were once close enough to exchange energy and even out the temperature, yet current models of the early universe prevent this from happening, unless they assume an ultra-fast expansion right after the big bang. However, a higher speed of light early in the history of the universe would allow energy to pass between these areas in the form of light.

Variable "constants"

That right there is why physics is the most head-cracking science around. It’s the new Pythagoreanism: is it mysticism or math?

would also open the door to theories that used to be off limits, such as those which break the laws of conservation of energy.

Which would in turn open interesting avenues for the feasibility of miracles, in a not-so-closed total energy system as our Newtonian heritage inclines us toward.

And it would be a boost to versions of string theory in which extra dimensions change the constants of nature at some places in space-time. . . .

Another unknown is whether other physical constants might have varied along with, or instead of, alpha. Samarium-149's ability to capture a neutron also depends on another constant, alpha(s), which governs the strength of the strong nuclear attraction between the nucleus and the neutron.

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