A century after Einstein predicted their existence, the LIGO project has finally detected gravitational waves. LIGO, the Laser Interferometer Gravitational-wave Observatory, consists of two identical facilities in Livingston, LA and Hanford, WA; the two work together because their physical separation means they should detect waves at slightly different times. From a source somewhere in the southern sky and about 1.3 billion light years away, gravitational waves rippled outward to make a tiny, barely perceptible blip in the instruments. This event is believed to have been generated by a pair of black holes colliding, which also makes this a new piece of direct evidence for the existence of the quixotic and unfathomably dense objects.
Now that the principle has been demonstrated for the first time, the team and others worldwide are already making plans for successor instruments, as the new field of gravitational wave astronomy opens up!