Gravitational waves were detected for the first time by LIGO, the Laser Interferometer Gravitational-Wave Observatory, it was announced in February. These are predicted by Einstein's theory of general relativity, which says that massive objects warp space-time around them. When these objects accelerate, they form gravitational waves, ripples in the fabric of space-time. Their presence was inferred in 1974, but none had been observed directly – until now. In May, Neanderthals were credited with building a series of mysterious large stalagmite structures in a French cave. Roughly 175,000 years old, they are made from 400 individual stalagmites snapped from the cave floor and laid in a circle.