Jennifer Oullette in Gizmodo:
Excited rumors began circulating on Twitter this morning that a major experiment designed to hunt for gravitational waves—ripples in the fabric of spacetime first predicted by Albert Einstein—has observed them directly for the very first time. If confirmed, this would be one of the most significant physics discoveries of the last century.
Move a large mass very suddenly—or have two massive objects suddenly collide, or a supernova explode—and you would create ripples in space-time, much like tossing a stone in a still pond. The more massive the object, the more it will churn the surrounding spacetime, and the stronger the gravitational waves it should produce. Einstein predicted their existence in his general theory of relativity back in 1915, but he thought it would never be possible to test that prediction.
LIGO (Laser Interferometer Gravitational Wave Observatory) is one of several experiments designed to hunt for these elusive ripples, and with its latest upgrade to Advanced LIGO, completed last year, it has the best chance of doing so. In fact, it topped our list of physics stories to watch in 2016.