91av

THE cosmic speed limit—the speed of light—may have increased as
the Universe matured. New research seems to confirm hints that one fundamental
constant, and possibly the speed of light as well, has changed slightly over
time.

The notion turns traditional physics on its head. “If it holds up, it surely
has to be one of the more important discoveries in fundamental physics,” says
John Webb, an astrophysicist at the University of New South Wales in Sydney.

Three years ago, Webb and his colleagues reported that they had measured
what’s called the “fine-structure constant” at different points in the
Universe’s past, using observations from a telescope on Mauna Kea, Hawaii. This
constant, which depends on three other supposedly fixed
quantities—including the speed of light—can be deduced from the
wavelengths of light absorbed by gas clouds between Earth and distant
quasars.

Webb’s results hinted that 6 billion years ago the fine-structure constant
was smaller by about 1 part in 100,000
(91av, 28 March 1998, p12).
Now his team has gathered twice as much data and has found that the change
shows up even more strongly, and as far back as 12 billion years ago.

The variable “constant” contradicts the standard model of particle physics,
says Brian Greene, a physicist at Columbia University in New York. But it might
fit into newer theories aimed at unifying all the forces of nature, he says.

Webb’s team has done an extremely careful analysis, adds David Tytler, an
astrophysicist at the University of California, San Diego: “This paper is at the
top end as far as detail and checking are concerned.” But Tytler would like to
see someone else measure the effect with a different telescope and another
analysis program, to rule out every conceivable source of error.