Gravity wave detector is go

All bets are off

A key prediction of Einstein's Theory of General Relativity is set to be tested, as a German/UK research group powers up its gravitational wave detector GEO600 for an 18-month stint of continual operation.

Gravitational waves are a consequence of the equations of Einstein's famous theory. He predicted that two stars in orbit around one another would gradually lose energy from their orbits in the form of gravitational radiation. The orbits would gradually collapse, resulting in shorter and shorter orbital periods.

Although there is some circumstantial evidence to support the theory, no one has been able to test directly for their existence in the real world. Now a lab in Hanover will be watching the skies for these waves, which ought to be produced when a star explodes as a supernova.

"If there is a supernova in our vicinity during the next couple of months, our chances of detecting and measuring the resulting gravitational waves are good," said says Professor Karsten Danzmann, head of the International Centre for Gravitational Physics.

Detecting the waves would mean that the first step towards gravitational wave astronomy had been taken, he continued: "at last allowing us to observe the 96% of our universe which have been hidden to us up to now".

Vast swathes of the invisible universe would suddenly be accessible to astronomers. Using gravitational waves, researchers would be able to investigate the nature of the hypothetical dark matter and dark energy, thought by some to account for the majority of the mass in the universe.

The team working with GEO600 has been running tests of the detector since 2002, and have considerably increased the instrument's sensitivity since then. In 2002 its scope was limited to just a small fraction of our home galaxy.

"Today our sensitivity has increased by a factor of 3000 and we can detect events in distances many times greater than the distance between us and our galactic neighbour, the Andromeda Galaxy," Danzmann explains.

The detector is a super-sensitive Michelson laser interferometer, with laser beams running in two underground vacuum tubes which are 600m long. It incorporates absorption-free optics and a highly sophisticated vibration damping arrangement that allows it to measure the tinychanges to the lengths of the laser beams.

Using the GEO600, astronomers will be able to chart the distribution of neutron stars and black holes in the Universe, and discover more about the formation of black holes. The detector might even be able to spot the gravitational waves thought to have been left behind by the big bang.

The GEO600 is bad news for betting shop Labrokes. In 2004, the firm offered odds of 500/1 against gravity waves being spotted before 2010. After hoards of physicists rushed to take the betting shop up on the offer, Ladbrokes had to shorten the odds to 6/1.

The book on this one has been closed for a while, Ladbrokes says. "Even a few fifty quid bets at the original odds represents a substantial liability," a spokesman told us.

"We've had our fill of science bets for the time being. And we've got this thing called the World Cup on at the moment, which is keeping us busy." ®

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