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 said.

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.

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.

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.?Reuters