SOMEWHERE in the Netherlands, a cold ball of metal named MiniGRAIL has begun listening for the sound of exploding stars and colliding black holes.
Violent events like these are thought to generate gravitational waves, which squeeze and stretch anything they pass through by a tiny amount, but no such waves have yet been detected.
Researchers expect strong gravitational waves to set MiniGRAIL鈥檚 1.4-tonne ball of copper-aluminium alloy ringing. To cut down the noise, the ball has been cooled to within 0.068 degrees of absolute zero. 鈥淚t is by far the lowest temperature a big mass like that has ever achieved,鈥� says Giorgio Frossati, head of the MiniGRAIL team at Leiden University in the Netherlands.
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Frossati thinks miniGRAIL will pick up waves from as far away as the Virgo galaxy cluster, 50 million light years away. And for frequencies around 3 kilohertz, MiniGRAIL could be more sensitive than LIGO, the detector in the US that uses interfering laser beams to listen for gravity waves. But because of the relatively narrow bandwidth, MiniGRAIL is unlikely to be first to detect a gravity wave.
MiniGRAIL has one big advantage: at around 鈧�1 million it comes far cheaper than the hundreds of millions of dollars LIGO is costing. 鈥淚f many universities would build one so that there are 100 throughout the world, no interferometer could beat them,鈥� Frossati says.
