An extensive upgrade has made LIGO more sensitive than everNutsinee Kijbunchoo/ANU/LIGO Hanford By Daniel CossinsTHE search for gravitational waves is back on, and this time we are expecting a deluge. The Laser Interferometer Gravitational-Wave Observatory (LIGO) in the US made a huge splash in 2016, when it announced the detection of faint ripples in space-time produced by the collision of a pair of black holes. It has since spotted 10 more gravitational-wave events. Now, following upgrades, LIGO should see one a week when it starts up again on 1 April. “We’re making the transition from having a slow drip of events to opening the faucet,” says Luis Lehner … Article amended on 29 March 2019 We clarified that looking for spin alignment is one way to find out what brings black holes together