"New Scientist"
                   Light may have slowed down
 
                   14:20   15  August  01
                   Adrian Cho
 
                   The cosmic speed limit - the speed of light - may have reduced 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.

                   Webb's team has done an extremely careful analysis, says 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."

                   The new analysis is based on measurements of what is called the "fine
                   structure constant". 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.
 

                   New theories

                   Three years ago, Webb and his colleagues reported that they had measured
                   the fine-structure constant at different points in the Universe's past, using
                   observations from a telescope on Mauna Kea, Hawaii.

                   The results hinted that six billion years ago, the fine-structure constant was
                   smaller by about 1 part in 100,000 (New Scientist, 28 March 1998, p 12).
                   Now Webb's 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.

                   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.

                   Journal reference: Physical Review Letters (vol 87, e091301)

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