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ONE of the most elusive phenomena in the Universe could soon be measured for the first time after an Anglo-German team of scientists switched on a revamped detector designed to pick up gravitational waves. 
 
The Geo600 laboratory near Hanover is set to become the first to prove the existence of the waves — ripples in the fabric of space and time predicted by Albert Einstein’s general theory of relativity but never actually observed.

The detector, which consists of two 600-metre arms in an L-shape in a field, has begun 18 months of continuous observations after it was refitted to make it sufficiently sensitive. The ripples, created by events such as supernovas and collisions between black holes, deform space and time, squeezing and expanding matter as they pass through the Earth.

Their influence, however, is extremely weak: over the distance between Earth and Alpha Centauri — 4.3 light years — a gravity wave would warp space by as little as the thickness of a human hair. At Geo600, this means the length of its arms would fluctuate by one ten thousandth of the diameter of an atomic nucleus. The refit, however, should enable it to pick up such minute changes.

“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 Karsten Danzmann, one of the leaders of the research. “The first step towards gravitational wave astronomy has been taken, at last allowing us to observe the 96 per cent of our Universe hidden to us up to now. We are opening a wholly new chapter in the long history of astronomy with the direct observation of the ‘dark side’ of our universe – black holes, dark matter and the reverberations of the Big Bang.”

Geo600 will work in conjunction with three similar detectors in the US, which together form the Laser Interferometer Gravitational Wave Observatory [Ligo] collaboration. If and when a gravity wave passes through any of them, one arm will shrink very slightly, while the other lengthens by an equivalent amount. The same thing should happen at all the detectors, confirming the accuracy of the observation.