First observation of gravitational waves

On 14/09/2015, the Laser Interferometer Gravitational-Wave Observatory recorded the first direct observation of gravitational waves, confirming a prediction from Albert Einstein’s general theory of relativity. The signal, later named GW150914, was detected almost simultaneously by LIGO’s twin interferometers located in Livingston, Louisiana, and Hanford, Washington. The measured disturbance represented ripples in spacetime generated by the merger of two black holes approximately 1.3 billion light years from Earth. The detection lasted about 0.2 seconds and matched theoretical models of binary black hole coalescence. Analysis indicated that the two black holes had masses of roughly 36 and 29 times that of the Sun. As they spiraled inward and merged, they formed a single black hole of about 62 solar masses. The remaining mass, equivalent to roughly three Suns, was converted into energy emitted as gravitational waves. LIGO measured the event using laser interferometry, which detects minute changes in distance smaller than the diameter of a proton as gravitational waves pass through Earth. The signal reached the Livingston detector first and then the Hanford detector about 7 milliseconds later, consistent with a wave traveling at the speed of light. The discovery provided the first direct confirmation of gravitational waves and the first observational evidence of a binary black hole merger. It also marked the beginning of gravitational wave astronomy, allowing scientists to study cosmic events through spacetime distortions rather than electromagnetic radiation alone. The observation was publicly announced on 11/02/2016 after extensive verification, and subsequent detections by LIGO and partner observatories expanded the catalog of gravitational wave events.