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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.

Go deeper

Federal court blocks Biden's vaccine mandate for health workers in 10 states

President Biden delivers remarks on the Omicron COVID-19 variant following a meeting with his COVID-19 response team. Photo: Anna Moneymaker via Getty Images

A federal court in Missouri has blocked the Biden administration from enforcing a coronavirus vaccine mandate for health care workers at federally-funded facilities in 10 states.

Why it matters: Monday's decision is the first victory for opponents of the rule, which requires health care workers to get vaccinated by Jan. 4, 2022. The case is one of four lawsuits challenging the Centers for Medicare & Medicaid Services' (CMS) rule and argues that the mandate will exacerbate staffing shortages.

Twitter's next act

Illustration: Annelise Capossela/Axios

Twitter co-founder and CEO Jack Dorsey is exiting the company he helped build at a time when its future has never been so uncertain.

Why it matters: The person who controls Twitter controls the de facto public square — with implications for politics, media and free speech.

45 mins ago - Health

CDC strengthens COVID booster recommendation

Rochelle Walensky. Photo: Chip Somodevilla/Getty Images

The Centers for Disease Control and Prevention (CDC) on Monday strengthened its previous recommendation for booster shots, saying that everyone 18 and older "should" receive a booster dose.

Why it matters: Last month, CDC director Rochelle Walensky accepted a key advisory committee's recommendation that adults "may" get the shot. The slight, but strengthened, change in wording comes amid the emergence of the Omicron coronavirus variant.