posted 05-18-2002 02:07 PM            

By Dr David Whitehouse
BBC News Online science editor

The Universe may be a stranger place than we imagined because of new evidence that appears to show the very laws of physics have changed since the cosmos was young. Analysis of the light coming from distant quasars suggests that a fundamental physical constant may have been increasing slightly over the past six billion years.

The so-called fine structure constant - which measures the strength with which subatomic particles interact with one another and with light - may have been smaller at earlier times in the history of the Universe.

"This has major implications for our understanding of physics," Dr John Webb of New South Wales University, Australia, told BBC News Online. "If this is correct, it will radically change our view of the Universe. We have to be cautious but it could be revolutionary. We have seen something in our data - but is it what we think?"

Fabric of the Universe
The team looked at so-called absorption lines in the spectra of quasars, the highly active, bright cores of galaxies at the farthest reaches of the Universe. Gas clouds between Earth and the quasars absorb some of this light at specific wavelengths and produce the spectral lines.

The spacing of the absorption lines depends upon one of nature's fundamental numbers: the fine structure constant or alpha. Alpha is something that is built into the very fabric of the Universe. It is a dimensionless number, the ratio between four physical constants: the speed of light, the quantum energy constant, the charge of the electron and pi. The value of alpha, currently about 1/137, determines much about the way the Universe works.

"These dimensionless numbers are much more important than any of the dimensional constants," said Michael Murphy, of the University of New South Wales.

Sources of error
Alpha determines the strength of interactions between charged particles and electromagnetic fields, and, as such, is central to the understanding of electromagnetism - one of the four fundamental forces of nature. "Alpha is the central parameter in anything to do with atoms, electricity, magnetism - everything except for gravity," Mr Murphy said.

The spacing between the wavelengths absorbed by the intervening atoms depends on alpha. If alpha changes, then so will the absorption pattern in the spectra. The researchers looked for this effect using the world's largest telescope: the 10-metre Keck facility in Hawaii.

Dr Webb and his co-workers found evidence that alpha was slightly smaller in the past than it is now. The team say there is a one in 10,000 chance that the result is a statistical fluke. They also say they have eliminated 13 potential sources of systematic error.

Strange, wrong but interesting
Since the 1930s, physicists have discussed whether the constants of the Universe that appear in the equations for the fundamental laws of physics - such as the speed of light in vacuum and the electron charge - are indeed constant. Dr Webb said: "It was Dirac and Milne who talked about this first. Their ideas were strange, wrong, but very interesting. When I came across them, they made me think." The current value of alpha could not have been very different in the past. A small variation in alpha would imply that carbon atoms could not be stable, and carbon-based life such as us could not have arisen.

In fact, modern attempts to unify gravity with the other fundamental forces do allow for Nature's constants to vary. Proposed theories can accommodate changes in alpha over time. Known as string theories, they allow either a 10- or 26-dimensional universe, rather than our 4D one.

Something in the data
Other scientists have reacted with interest and caution after reviewing the quasar data. Faced with the possibility of toppling cherished views on the Universe, Dr Webb condones this approach. "There is something in the data. There is a signal there. Others have looked at our data and agree there is something there, but is it real or some unknown instrumental effect?"