Universal Constants May Not Be
(From the November/December 2001 issue of StarDate magazine)
Astrophysicists are having to adjust their beliefs regarding two of the constants they rely on to describe the universe.
The gravitational constant, or “big G,” was first proposed by Isaac Newton in the 18th century to describe the gravitational attraction between two masses. Experiments over the last decade or so have come up with widely varying values for this constant.
“It’s a huge embarrassment for modern physics, where we think we know everything so well and other constants are defined to many, many digits,” said Jens Gundlach, a physicist at the University of Washington. “Gravity is the most important large-scale interaction in the universe, there’s no doubt about it. Yet it is relatively little understood.”
Now an experiment carried out by the Bureau International des Poids et Mesures (BIPM) in France and the University of Birmingham in England is in somewhat close agreement with the measurement made by Gundlach and his collaborator Stephen Merkowitz last year. Both experiments show that the official value of “G” needs to be increased.
Whereas the value of the gravitational constant may be adjusted, there is evidence that the so-called “fine structure constant” (referred to as alpha) may not be a constant at all. Alpha, which measures how strongly subatomic particles interact with light and with each other, may be increasing over time.
John Webb of Australia’s University of New South Wales used the Keck telescopes in Hawaii to study the features of light coming from quasars millions of light-years away. The differences between the light from quasars at relatively nearby, and those at great distances (thus revealing an earlier time in the universe’s evolution) show that the laws of physics may have been different in the distant past. Rebecca Johnson
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