How do scientists detect gravitational waves from colliding black holes?
Quick Answer
They use ultra-sensitive laser interferometers that can detect changes in length far smaller than a proton. The first direct detection was announced by LIGO in 2016 from a 2015 event.
The Full Story
Gravitational waves are ripples in spacetime caused by massive accelerating objects such as merging black holes or neutron stars. LIGO in the United States and Virgo in Europe detect them using laser interferometers with long arms, where tiny distortions change the interference pattern of laser light. The first direct detection, announced in 2016, came from a black-hole merger observed on 14 September 2015 and was named GW150914. Since then, dozens of events have been detected, opening a new way to observe the universe. These measurements let astronomers study systems that emit little or no light.
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