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Friday, November 5, 1999 Published at 16:09 GMT


Sci/Tech

Viper telescope probes Big Bang 'echo'

The Viper telescope: Well placed for observation

By BBC News Online Science Editor Dr David Whitehouse

The Viper microwave telescope situated at the Amundsen-Scott South Pole base has detected ripples in the so-called microwave background radiation - the "echo" from the Big Bang.

Such variations were first detected by the Cosmic Background Explorer satellite (Cobe) in 1992 and are regarded as being of fundamental importance in understanding the birth of galaxies from a featureless young cosmos.

The new observations cast new light on the origin of the so-called "seeds" of the galaxies and provide more evidence that gravity is a more complex force than many believe.

The Viper telescope is situated at one of the best and probably also the worst places on Earth to put a telescope.

Perched on the vast plateau of ice surrounding the South Pole, it boasts atmospheric conditions that make it the best in the world to observe the Universe in millimetre and sub-millimetre wavelengths.

This is because the thin, dry air over Antarctica has the lowest water vapour content of any comparable observatory site. This means that the interference or "noise" created by such water vapour, which is a serious obstacle in astronomical research, is minimised.

Matter and radiation

For over a year, Viper has been observing the cosmic microwave background radiation (CMB) that originated when the Universe was only 300,000 years old.

It was formed when matter and radiation "decoupled". The matter went on to form galaxies and stars. The CMP then just spread out into space - where it still is and can be detected. Some scientists describe it as the "echo" from the Big Bang. The CMB was first observed in 1965.

Tiny fluctuations in the CMB give astronomers information about the distribution of matter in the early Universe - how galaxies and clusters, stars, planets and quasars might have evolved from the "primordial soup" of free-floating protons and electrons.

Without doubt, Viper has seen the ripples in the background radiation with the results to be published in a forthcoming issue of the Astrophysical Journal.

But the ripples cannot be fully explained by a simple idea that the Universe began in a Big Bang some 15 billion years ago and has been expanding ever since with only gravity affecting the expansion.

The best explanation for the observations requires that over large distances gravity becomes a repulsive force, not an attractive one.

It is not a new suggestion and according to some astronomers there is a growing body of evidence to support the idea. But it is not something that many astronomers feel particularly comfortable with at the moment.



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