Physicists Rainer Weiss, Kip Thorne and Barry Barish received the 2017 Nobel prize in physics for their work detecting ripples in space-time predicted by Einstein over 100 years ago.
Why it matters: Einstein's theory of general relativity predicts that massive objects — like black holes — distort space-time. We feel that as gravity. Because space-time can't be directly seen or measured, scientists instead study it indirectly, for example by searching for gravitational waves that Einstein predicted would be emitted when two massive objects collide. So far, observations by the Laser Interferometer Gravitational-Wave Observatory have confirmed Einstein's theory.
Since 2015, LIGO detectors — one in Washington and another in Louisiana — have observed gravitational waves from black hole collisions four times, most recently in August. These gravitational waves contain enough energy to bend space-time itself in measurable ways and are a window into understanding the fundamental nature of gravity.
"[G]ravitational waves are direct testimony to disruptions in spacetime itself. This is something completely new and different, opening up unseen worlds. A wealth of discoveries awaits those who succeed in capturing the waves and interpreting their message." -- The Nobel committee
How it works: Each observatory is essentially a 2.5-mile-long, L-shaped antenna with beams of laser light bouncing back and forth between mirrors at either end. When a gravitational wave passes through Earth, the distance between those mirrors should change ever so slightly as space-time contracts and expands, if Einstein's general theory of relativity holds.
It takes hugely energetic events — like the collision of black holes or neutron stars — to generate a measurable perturbation. Even then, the waves, which travel billions of light years before they pass Earth, move the mirrors just a fraction of the diameter of a proton. (LIGO can detect a change as small as 1/10,000 the width of a proton.)
Who they are: Weiss is an emeritus professor of physics at MIT (where he flunked out as an undergraduate) who — along with Ronald Drever, who died earlier this year — led the design and construction of the LIGO detectors. Barish, a professor emertius at Caltech, was LIGO's director and managed the team as well as making technical contributions. Thorne is a professor of theoretical physics at Caltech who figured out what exactly the detectors should be looking for.
Some history: Joseph Taylor Jr. and Russell Hulse received the 1993 Nobel prize in physics for their discovery of a pulsar-neutron star pair capable of producing gravitational waves. In the 1960s, Weiss came up with the idea for detecting these waves, which was realized as LIGO when Weiss and Drever began working together in the mid-1980s. More than 1,000 people around the world now work on the international collaboration.