LIGO finds first direct evidence of gravitational waves

Nature : On 14 September 2015 the two detectors of the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) in Livingston, Louisiana, and Hanford, Washington, saw a 0.04-second oscillation in the data stream. The identical signals at the two sites were 7 milliseconds apart. Earlier today at a press conference in Washington, DC, representatives from LIGO announced that they had spotted the signals and had ruled out terrestrial sources. The only conclusion, they said, was that a gravitational wave had passed through Earth and been detected. From the signal they were able to estimate that the gravitational wave originated 1.3 billion years ago from the collision of two black holes, each around 30 solar masses. Not only is it the first direct detection of a gravitational wave, it is also the first observation of a black hole merger.