American scientists Rainer Weiss, Barry Barish and Kip Thorne won the 2017 Nobel Prize for Physics on Oct. 3 for their pioneering role in the detection of gravitational waves. (Reuters)

Rainer Weiss, Barry C. Barish and Kip S. Thorne have won the 2017 Nobel Prize in physics. The three Americans are members of the LIGO-Virgo detector collaboration that discovered gravitational waves. The prize was awarded “for decisive contributions to the LIGO detector and the observation of gravitational waves,” the committee said in a news release.

“This year’s prize is about a discovery that shook the world,” said the Nobel committee representative Göran K. Hansson in Stockholm on Tuesday.

Albert Einstein predicted in his 1915 general theory of relativity that distortions in gravity would travel through space-time like a shock wave. It took nearly a century to confirm that these distortions exist, a feat that required huge contraptions in two locations to detect an ultra-tiny ripple in the fabric of space.

One half of the prize went to Weiss, born in Berlin and now a U.S. citizen, who is a physics professor at the Massachusetts Institute of Technology. The other half was split by Barish, a Nebraska native, and Thorne, who was born in Utah. Both work at the California Institute of Technology.

“When we first discovered them back in September 2015, many of us didn't believe it,” said Weiss, calling in by phone to the Stockholm conference. It took months for the scientists to convince themselves that the detectors found gravitational waves, he said.

Two black holes collided more than a billion light-years away, converting a mass equivalent to three suns into energy. As the violent belch passed by Earth, the twin LIGO detectors, in Livingston, La., and Hanford, Wash., caught the wave. The detectors registered the wave as a spike in frequency — a tone nicknamed the “cosmic chirp.”

The Nobel physics prize selection process is notoriously secretive. But that does not curb speculation. The detection of black hole gravitational waves has been floated as a contender both this year and last. This year, the predictions came true.

Detectors sensed three other gravitational waves since the first, all from merging black holes. The LIGO team, plus the Italian Virgo detector, announced the most recent cosmic distortion discovery in September.

A team of more than 1,000 scientists, researchers and technicians make up the LIGO Scientific Collaboration. Yet three people at most can share a Nobel Prize, a rule that critics say is too restrictive.

“It is unfortunate that, due to the statutes of the Nobel Foundation, the prize has to go to no more than three people, when our marvelous discovery is the work of more than a thousand,” Thorne said in a news release Tuesday. He said the prize “rightly belongs” to the scientists and engineers who constructed the detectors and who plucked the signal from noisy data.

Scientists proposed using lasers to measure gravitational waves in the 1960s. Weiss conceived of the first L-shaped laser interferometers while teaching a course on general relativity at MIT decades ago.

The device consists of twin laser beams shot down an interferometer's branching arms, both of equal length. At the end of each arm is a mirror. The lasers bounce off the mirror to return at precisely the same time. If something has jiggled the fabric of space — like the long-ago collision of a black hole — one arm elongates or contracts out of sync with the other. These distortions are so small as to be inconceivable: a wobble a thousandth the width of an atom's nucleus. The lasers' mismatched return, however slight, signifies that space has warped.

Meanwhile, Thorne helped advance the theory of gravitational waves. He described how the waves, which could be the product of merging black holes or colliding neutron stars, stretch space and time. (Aside from his work on LIGO, Thorne is known for his theories about time travel. He was a consultant on the sci-fi movie “Interstellar” and came up with a wormhole plot device that allows an astronaut in the film to go back in time.)

“LIGO would not exist without Kip's vision for the scientific potential of gravitational waves and his amazing gift for sharing that vision with other scientists,” said Caltech's Stan Whitcomb, a LIGO Laboratory scientist, in a statement.

Military grants to develop small interferometers gave way to an ambitious proposal. In 1984, MIT and Caltech agreed to design and construct LIGO, the Laser Interferometer Gravitational-Wave Observatory, together. The National Science Foundation “married MIT and Caltech with a shotgun,” joked Rochus Vogt, LIGO's first project director, to the Scientist magazine in 1988.

Disagreements between the two institutes and a lack of funding almost crippled the experiment. Barish, who replaced Vogt, is credited with reviving the project after its early problems and managing the unwieldy collaboration.

“I always wanted to be an experimental physicist and was attracted to the idea of using continuing advances in technology to carry out fundamental science experiments that could not be done otherwise,” Barish said in a statement Tuesday. “LIGO is a prime example of what couldn't be done before.”

The particle physicist earned a “sterling reputation,” Science magazine reported in 2016, blemished by a recent talk he gave in which his opening slide included a woman's bare back and “cartoonish racial caricature.” Barish apologized.

Barish was not included in some previous awards to the LIGO team, and as Science magazine reported, some experts worried that he would miss a shot at a Nobel Prize. The death in March of Ronald Drever, a LIGO physicist who was included in previous awards, may have cleared the way for Barish to be included.

“Barish, in my opinion, is the most brilliant leader of large science projects that physics has ever seen,” Thorne said.

LIGO's hunt for the cosmic ripples began in 2002. It succeeded more than a dozen years later. “Einstein was right!” President Barack Obama wrote in a congratulatory tweet to LIGO.

The search continues. The machines alternate between periods of active detection and pauses for technical refinement. As The Washington Post reported from LIGO in Louisiana this year:

The two observatories in Louisiana and Washington state had to be built in remote, seismically stable locations. The dominant feature of each facility is the pair of 2.5-mile-long beam lines, set perpendicularly. These are tubes in which laser beams pass through an almost perfect vacuum.

“We had to correct for the curvature of the Earth,” said Amber Stuver, a LIGO physicist, standing on a bridge overlooking one of the beam line tubes as it receded into the pineywoods — timber land owned primarily by Weyerhaeuser. “From the corner there to the end of the arm, the Earth curves down away a little bit more than four feet.”

A reporter drove a rental car the length of the arm, with Stuver serving as narrator. The beam line is encased in heavy concrete. Stuver said that so few atoms and molecules remain in the vacuum tubes that if you could gather them all up, from the entire 2.5-mile length, and compress them to normal atmospheric pressure, they'd amount to one thimbleful of air.

Hunting stands are nearby in the woods, but they point away from the beam lines. The scientists met with local hunting clubs, and made one simple request: Don't shoot the observatory.

LIGO is funded by the National Science Foundation. All told, the detectors had a $1.1 billion price tag. President Trump proposed a budget cut of 11 percent to the NSF, but Congress has been more supportive of the agency.

The Nobel committee has awarded a prize in physics 111 times since 1901. Last year, three researchers won for their work in the field of topology. Topology, as The Post reported, is the study of state changes more intricate than the pivot from liquid to solid. The 2016 laureates discovered exotic transformations that turn matter into superconductors or frictionless liquids, able to swirl in a never-slowing vortex.

Winners of the Nobel Prize in physics join a rarefied group that counts Einstein, Marie Curie and Niels Bohr as members. More recent laureates include University of Manchester scientists Andre Geim and Konstantin Novoselov, who won the 2010 prize. They performed groundbreaking experiments with graphene, a lattice of carbon a single atom thick. In 2013, François Englert and Peter Higgs won for predicting a subatomic particle called the Higgs boson, the existence of which was confirmed by the Large Hadron Collider in 2012.

The Nobel Prize in chemistry will be announced Wednesday, the literature prize Thursday and the peace prize Friday. An award in economics, not one of the original prizes but now conducted in memory of Alfred Nobel, will be announced Monday.

Joel Achenbach contributed to this report. This post has been updated.

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