Universally changing

A recent research throws light on the possibility that the laws of physics were different in the past

Published: Sunday 30 September 2001

Dazzled: scientists claim that (Credit: Science photo library) it is one of the unwritten assumptions of physics that the laws of nature are the same not only in all parts of the Universe but also at all times. This assumption is what allows us to say meaningful things about very distant realms of our Universe and also about very old times. But now analysis of light by a research team indicates that billion of years ago the laws of physics might have been slightly different. New observations from the world's biggest telescope indicate that one of the nature's supposedly immutable constants has changed over the 15 billion-year history of the Universe. "This has fundamental implications for our understanding of physics," said John Webb, a professor at the University of New South Wales in Sydney, Australia, who led the research.

Webb and his colleagues found that six billion years ago, the fine structure constant -- a number that determines the strength of electromagnetic force and thus the speed of light -- might have a value some .001 per cent smaller than what it is today. At present its value is thought to be 1/137.

The idea that fundamental constants of nature like the speed of light or the gravitational constant might depend on time has been around since the 1930s. The notion is that the equations of physics remain the same while the constants appearing in them might vary at different times. To analyse the validity of this idea, the researchers used the Keck telescope atop Hawaii's Mauna Kea to peer at some of the most distant objects in the Universe. They aimed the telescope at 17 different quasars, which are extremely bright objects associated with black holes. The quasars are so far away -- about 12 billion light years -- that the light they produced at the dawn of the Universe is only now reaching Earth. Light travelling from them usually passes through gas clouds along its way, which absorb some of it. The wavelength of absorbed light depends on the elements present in the clouds. The patterns of absorption are indication of some characteristics of the light, especially its speed because the fine structure constant determines how fast it goes. "This phenomena is like a car headlight on a foggy night. When the headlight shines through the fog, you can see the change on the background light because of the fog's presence," Webb told Associated Press. The researchers looked at dark lines in the spectrum of light coming from the quasars and accurately measured the absorption wavelengths of several metals in the clouds. After a comprehensive analysis of the absorption lines, they found that the value of the fine structure constant has been increasing with time.

Several scientists are sceptical about the team's conclusion and say that there are other factors that could cause the same kind of effects in the absorption spectrum. "It is just a very nice piece of information, if it stands up," says John Bahcall of the Institute for Advanced Study in Princeton, usa. "But it is a big if. I would be quite cautious about believing such conclusions," added Bahcall.

But if other experiments confirm the result and the sources of errors are understood, then the finding will be a very significant one. It would radically change the way we have been looking at the Universe, especially in relation to its past. For example, it might prove that our calculation about the stability of carbon atoms is very different from the current value. If this is so, then carbon atoms will not be stable and life as we know would not be possible.

But for some physicists, the finding is not alarming but good news because proposed theories can accommodate changes in the fine structure constant over a period of time. Known as string theories, they allow either a 10 or 26 dimensional Universe, rather than a four-dimensional one. If the finding proves to be true, the extra dimensions would be curled or folded so that they would be impossible to detect in everyday life or even in any physics experiments. "This would be a clue to help guide how you convert string theories into something relevant," said Gordon Kane, a physicist at the University of Michigan, usa. The scientists hope to confirm their results using a different telescope, perhaps the very large telescope at the European Southern Observatory in Chile.

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