The conventional wisdom says the universe was created from nothing by a unique "Big Bang" and has since expanded in size, eventually becoming an empty, cold vacuum.
Not according to two American scientists, however. Big Bang, they say, was not such a big deal after all. In fact, similar events occur roughly every trillion years. The universe's life is really made up of a cycle of "big bangs" and "big cycles", which suggest that it is timeless – it will never end.
The research may not seem too relevant since the universe – at the latest estimate – is just 14 billion years old, and therefore some way off from either a "big bang" or a "big crunch".
But the paper – published today in the journal Science by Paul Steinhardt and Neil Turok, of Princeton University – may help to settle a scientific conundrum. Albert Einstein himself could not understand why the universe was still expanding at a growing rate, even though its expansion was propelled by an event 14 billion years back in time. He identified the "anti-gravitational force" responsible for it, but he tweaked his equations to eliminate it.
Professor Steinhardt explains that the universe is being driven by big bangs and crunches occurring in another dimension – without our being able to detect them.
"We would not perceive the 'crunch' as a change in the size of our universe, because it's not happening in our dimension. It would be a hold-up in expansion; then with a big bang – not the Big Bang – there would be much more matter and energy created in the universe and expansion would begin again."
The idea received a cautious welcome from Professor Sir Martin Rees, Britain's Astronomer Royal. "It's speculative, an alternative way of looking at what is observed," he said. "The really big mystery that we need to explain is why the energy in empty space which causes this anti-gravity effect is not zero."
Professor Rees said that the latest theory is yet another to add to the many which try to explain the proportion of matter and energy in the universe today. "The universe seems to be comprised of about 4 per cent atoms, 30 per cent dark matter – which are things that we know are out there but can't observe directly – and the remainder in 'dark energy' out in empty space."
It is the "dark energy" – energy that makes itself felt out in the far distance of space in the gaps between the stars and galaxies – that is driving the universe apart. Thus a volume of what looks like empty interstellar space actually has energy, rather like a ball sitting on top of a hill has energy yet is doing nothing.
That "dark energy" is being added to the kinetic energy that the universe got when the Big Bang occurred. And that, the scientists suggest, is what is driving the extra expansion of the universe at the moment.
By chance, a separate group of scientists working with the Hubble telescope said yesterday that they had the best evidence yet that the universe is 14 billion years old. They based this on the discovery of the oldest burnt-out stars, which were 12 to 13 billion years old, and the knowledge that it would take between one and two billion years for those stars to form.
To Professor Steinhardt, the "original" Big Bang might have been nothing more than a point in the road. "Time does not have to have a beginning," he said. Instead, what scientists theorise as the dawn of time might, in fact, be "only a transition from a pre-existing phase to the present expanding phase".
Professor Rees is unconvinced. "What we really need is a single theory to unify everything – gravity, electromagnetism, atomic theory. But we're really very far from understanding the relevant physics."