Gravitational Waves

One hundred years after Einstein’s prediction, the LIGO experiment with the two Michelson interferometers in Hanford and Livingston discovered the first gravitational-wave signal from the fusion of two black holes in 2015. Just as Pauli thought in 1930 that “his” neutrino could never be measured experimentally, Einstein believed that the slight rippling of space-time by gravitational waves could never be detected. With this discovery, made possible by an extremely vibration-free positioning of the interferometer mirrors and the use of “squeezed” laser light (with a phase-dependent reduced blur), a new method for studying cataclysmic processes in the universe has emerged in gravitational-wave astronomy.