Findings: Mystery mass fills universe

June 14, 2002

The vacuum of space is teeming with a mysterious "dark energy" that accounts for 70 per cent of the universe yet is a complete puzzle to science, writes Steve Farrar.

High-precision images of the universe when it was just 1/50,000th of its present age have provided fresh evidence of this baffling hidden side to the cosmos.

Scientists at Cambridge University, with collaborators at Manchester University and the Instituto de Astrofisica de Canarias, used a novel telescope called the Very Small Array to study the relic of the primeval fireball that followed the Big Bang.

At this time, matter had yet to clump together to form the first galaxies.

VSA, sited on Mount Teide in Tenerife, combined signals from 14 aerial-like elements to detect subtle ripples in the radiation that pervades space. This is called the microwave background and is thought to be a relic of the fireball.

The telescope detected variations of 1/10,000th of a degree C in the three patches of the sky it studied.

Statistical analysis of the pattern of these ripples provided data that will help resolve the fundamental parameters of the universe.

So far, they are in line with results from other efforts to map the microwave background.

The research suggests that normal matter, of the sort we see around us on earth and in space, accounts for just 5 per cent of the total mass of the universe.

So-called cold, dark matter, which exerts a gravitational pull but does not interact with light, makes up a further 25 per cent.

The balance - 70 per cent of the universe - is a mystery. Dubbed vacuum dark energy, it is not understood by scientists but is believed to be making the contents of the universe accelerate away from each other.

The findings are to be published in the Monthly Notices of the Royal Astronomical Society.

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