The cosmic speed limit 鈥� the speed of light 鈥� 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. 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.
Webb鈥檚 team has done an extremely careful analysis, says 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�
Advertisement
The new analysis is based on measurements of what is called the 鈥渇ine structure constant鈥�. This constant, which depends on three other supposedly fixed quantities 鈥� including the speed of light 鈥� 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鈥檚 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 杏吧原创, 28 March 1998, p 12). Now Webb鈥檚 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.
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)