Scientist suggests big loop theory of the universe

Is the universe stuck in a Groundhog Day? Is the universe stuck in a Groundhog Day?

Difficult to tell if the Groundhog Day lasts for billions of years, but a leading Princeton physicist will today put forward the theory of a cyclical universe stuck in a never-ending loop.

Speaking at the Institute of Physics conference Physics 2005 at Warwick University, Professor Paul Steinhardt will present new work which could reinvigorate research into future universes.

Drawing on recent findings that the universe's expansion is speeding up, and that the majority of energy in the universe must therefore be gravitationally repulsive "dark energy", Prof Steinhardt, who is the Albert Einstein professor in science at Princeton University, will explain how this could mean that the universe is destined to repeat its own history.

Physicists propose several options for the future of the universe, but most dramatic is the possibility that the current acceleration is the prelude to a period of contraction. The "big crunch" which followed would create new matter and radiation, triggering another big bang, and a rejuvenated universe would emerge from the fireball like a phoenix from the flames.

Prof Steinhardt argues that what happens in the future could also have happened in our past. The big bang may not have been the beginning of space and time, but a bridge to a pre-existing era of contraction. Instead, the evolution of the universe could be cyclic, with regularly repeating periods of expansion and contraction.

If this theory is correct, it could help to explain one of the puzzles of cosmology - how the galaxies, stars and planets came into being. The big bang should leave a boring, featureless universe, but not if it was preceded by a big crunch. The random quantum fluctuations in the collapsing universe might be the very ripples which seed the galaxies in the subsequent expansion.

The cyclic picture can be tested using experiments which are already underway. Physicists are looking for propagating ripples in space known as gravitational waves. Prof Steinhardt says that the spectrum of the waves detected should reveal whether or not the universe existed before the big bang.