Scientists battle 'dark energy' theory of universe

ROME - A small group of physicists are battling what they see as the cosmological equivalent to the bogeyman: an enormous dark force, that nobody has ever seen, driving galaxies apart.

Conventional wisdom holds that the mysterious force, called "dark energy," may make up 70 per cent of the universe, and could be the determining factor in whether it is eventually destroyed billions of years from now. But Italian and American cosmologists are offering a controversial alternative to explain the accelerating expansion of the universe. They say it's not dark energy, but an overlooked after-effect of the "Big Bang" -- which cosmologists believe gave birth to the universe.

"No mysterious dark energy is required," said Antonio Riotto at Italy's National Nuclear Physics Institute in Padova.

"If dark energy were the size that theories predict ... it would have prevented the existence of everything we know in our cosmos," he told Reuters.

Since the late 1990s, scientists have used dark energy to explain an apparent anti-gravity force pushing galaxies away from each other at an accelerating rate, and using a variety of theories -- like new dimensions -- to justify its existence.

Albert Einstein once proposed a similar "cosmological constant," entering an anti-gravity factor into his general theory of relativity to offset gravity and create a balanced, static universe.

WAS EINSTEIN RIGHT OR WRONG?

When he later discovered that the universe was expanding, he called the cosmological constant his "greatest blunder," but dark energy revived the idea of an anti-gravity force.

However, according to the new study, no anti-gravity factor like dark energy or cosmological constant is needed to explain the forces of the universe.

"We think Einstein was right when he said he was wrong," said Edward W. Kolb of the US Department of Energy's Fermi National Accelerator Laboratory.

Kolb and the Italians say the universe's accelerating expansion is the result of long ripples in the fabric of space-time created by the big bang, during an "inflation" phase of rapid expansion of the universe, which have not been properly accounted for since they stretch beyond the observable universe.

"These long wavelength swells grow with time and give an extra expansion to the universe," Kolb said.

Not all cosmologists are buying into the theory, which will be poured-over following its submission this month to the journal Physical Review Letters.

"Their paper is going to get enormous scrutiny, and my own guess is that in the end, they'll be wrong," said cosmologist Michael Turner at the University of Chicago, who coined the term "dark energy," and published a paper with Kolb in 1990.

"But they may get the last laugh. And the interesting thing is, if they get the last laugh, I doubt that this is the only effect of these long ripples. We may have to make some other changes," he told Reuters.

That could include changes to theories about the ultimate fate of the universe, particularly whether it will collapse in a "big crunch," be completely blown apart in a "big rip" or just drift steadily until galaxies are so far away from each other they cannot be seen -- in effect taking stars from the sky.

The ramifications of the "long ripples" proposal would be infinite drift and "cosmic darkness," Riotto said.

"The next generations of experiments that are done should be able to distinguish or tell us which if any of the ideas are correct. Whether it's dark energy or our proposal," said Kolb.

- REUTERS