Gravitational Waves

When very massive objects accelerate — two black holes spiralling together, say — they shake spacetime itself, sending out ripples that stretch and squeeze space as they pass.^[1] Einstein predicted them in 1916 but doubted they could ever be measured; the effect is absurdly tiny. In 2015, a century later, the LIGO detectors caught the waves from two merging black holes over a billion light-years away, distorting a 4-km beam by less than a thousandth the width of a proton.^[2] It won the 2017 Nobel Prize and opened a whole new way to observe the universe.^[3]