The two huge interferometers belonging to one of the world's biggest physics experiments, the Laser Interferometer Gravitational-Wave Observatory (LIGO), experience a simultaneous burst of energy. The interferometers are separated by around 3000 kilometres, one in Louisiana and one in Washington state, and such interesting coincident pulses are just what the scientists are looking for...
That was in September 2007. Chance aside, a coincidence across that distance had to be caused by something interesting, so it began to look as if this was the nearest thing to a believable gravitational wave anyone had seen in 50 years of searching.
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