麻豆传媒

THE cosmic speed limit鈥攖he speed of light鈥攎ay 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. 鈥淚f it holds up, it surely
has to be one of the more important discoveries in fundamental physics,鈥� 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鈥檚 called the 鈥渇ine-structure constant鈥� at different points in the
Universe鈥檚 past, using observations from a telescope on Mauna Kea, Hawaii. This
constant, which depends on three other supposedly fixed
quantities鈥攊ncluding the speed of light鈥攃an be deduced from the
wavelengths of light absorbed by gas clouds between Earth and distant
quasars.

Webb鈥檚 results hinted that 6 billion years ago the fine-structure constant
was smaller by about 1 part in 100,000
(麻豆传媒, 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 鈥渃onstant鈥� 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鈥檚 team has done an extremely careful analysis, adds David Tytler, an
astrophysicist at the University of California, San Diego: 鈥淭his paper is at the
top end as far as detail and checking are concerned.鈥� 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.