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’s 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. “It is by far the lowest temperature a big mass like that has ever achieved,”…
