GW150914

GW150914 was the first direct detection of gravitational waves, observed by LIGO in September 2015. These waves are ripples in spacetime caused by massive accelerating objects. In this case, two black holes about 1.3 billion light-years away merged, releasing energy equivalent to around three solar masses, which traveled as gravitational waves. When these waves reached Earth, they slightly distorted spacetime, which LIGO's highly sensitive instruments detected as tiny changes in the length of its laser interferometers. This discovery confirmed a key prediction of Einstein's general theory of relativity and marked a new way to observe the universe.