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Is Basic Law of Physics Changing?

Posted on: Friday, 13 May 2005, 15:00 CDT

Legislators change laws from time to time, but Mother Nature's laws are eternal -- or so it has seemed.

Now, though, scientists are debating clues that suggest the laws of physics change over time, threatening to shake up our basic notions of reality.

At stake is one of the fundamental values in physics: the arcane- sounding "fine structure constant," which measures how subatomic particles interact with light and with each other.

Some astrophysicists have proposed that the value of the fine structure constant, a k a "alpha," has changed subtly over billions of years. They base this proposal on their work -- using telescopes like the giant Keck telescope, which sits atop a dormant Hawaiian volcano -- analyzing light from interstellar gas and galaxy- gobbling super-furnaces called quasars on the outskirts of the universe.

If they're right, then our theories of the cosmos might be due for an overhaul. One speculation is that alpha is changing over time because of now-unknown alternate dimensions. As these hidden dimensions change shape, they change the fine structure constant.

But skeptics, citing observations that contradict the claim that alpha is changing, are plentiful -- and even the pro-change claimants are being cautious, partly because there's so much at risk. The notion that the laws of physics are eternal and unchanging is one of the ground-floor assumptions of everyday life -- when you drop a ball, for example, you expect it to fall, not to rise -- and no one wants to abandon that assumption unless they've got compelling reasons.

"We are claiming something extraordinary here," acknowledged astrophysicist Michael Murphy of Cambridge University in England, one of the scientists who reported possible evidence of a change in the fine structure constant at a scientific conference earlier this year. "And the evidence, though strong, is not yet extraordinary enough."

At another science conference, a group of Berkeley, Calif., scientists reported that alpha is not changing, based on their independent analysis of light from galaxies.

Murphy defends his observational technique as more precise than that of critics. As he reported recently, his latest observations have "a precision of 1 in a million. So it's about a factor of 30 better" than the technique deployed by critics, he said.

The critics disagree. They say that their observational technique is relatively simple and, thus, yields pretty unambiguous results, whereas Murphy's technique is an especially complex one that is vulnerable to all kinds of "systematic errors," in scientific lingo.

In short, what's brewing is a dandy little scientific controversy. It's one in which, paradoxically, very much depends on very little -- that is, in which unimaginably slight variations in measurements could alter our understanding of the whole universe.

The idea that nature's laws change over time was proposed in the 1930s by one of the titans in the history of physics, Paul Dirac of England. According to Dirac's large-numbers hypothesis, the force of gravity changed over time. Others modified his thesis to argue that the fine structure constant is, in fact, inconstant.

Twenty-one years after Dirac's death, his theory still hasn't been proved.

"These are very adventurous ideas -- and it's always healthy to challenge the things that 'everybody knows,' " says one of the nation's most distinguished astronomers, Robert Kirshner of Harvard. "I would be very surprised if there are measurable changes in the fine structure constant."

But, referring to the 1990s discovery of dark energy, a mysterious cosmic force that counteracts the force of gravity and causes the universe to expand faster over time, he added, "I was also very surprised that the 'cosmological constant' isn't zero. In any case, the burden of proof is on the person making an extraordinary claim. The rest of us are skeptical, but our minds are open to convincing evidence."

In mid-April, noted physicist-author Lee Smolin of the Perimeter Institute in Waterloo, Ontario, heard Murphy present his latest findings.

It is too soon to tell if the fine structure constant is changing, Smolin said in an e-mail. "It is a very hard measurement, and there are many possible sources of error." At the same time, he wrote, "I would not be surprised if the measurement is right. . . . (I have) a nervous feeling that we have become too complacent (in cosmology), having gone too long without a shocking new experimental discovery."

Source: Deseret News (Salt Lake City)

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