LIGO Hears Gravitational Waves Einstein Predicted
About a hundred years ago, Einstein predicted the existence of gravitational waves, but until now, they were undetectable.
By DENNIS OVERBYE, JONATHAN CORUM and JASON DRAKEFORD on February 11, 2016. Photo by Artist's rendering/Simulating eXtreme Spacetimes. Watch in Times Video »
Rainer Weiss, a professor at the Massachusetts Institute of Technology, and Kip Thorne and Barry Barish, both of the California Institute of Technology, were awarded the Nobel Prize in Physics on Tuesday for the discovery of ripples in space-time known as gravitational waves, which were predicted by Albert Einstein a century ago but had never been directly seen.
In announcing the award, the Royal Swedish Academy called it “a discovery that shook the world.”
That shaking happened in February 2016, when an international collaboration of physicists and astronomers announced that they had recorded gravitational waves emanating from the collision of a pair of massive black holes a billion light years away, it mesmerized the world. The work validated Einstein’s longstanding prediction that space-time can shake like a bowlful of jelly when massive objects swing their weight around, and it has put astronomers on intimate terms with the deepest levels of physical reality, of a void booming and rocking with invisible cataclysms.
Why Did They Win?
Dr. Weiss, 85, Dr. Thorne, 77, and Dr. Barish, 81, were the architects and leaders of LIGO, the Laser Interferometer Gravitational-wave Observatory, the instrument that detected the gravitational waves, and of a sister organization, the LIGO Scientific Collaboration, of more than a thousand scientists who analyzed the data.
Dr. Weiss will receive half of the prize of 9 million Swedish Krona, or more than $1.1 million, and Dr. Thorne and Dr. Barish will split the other half.
Einstein’s General Theory of Relativity, pronounced in 1916, suggested that matter and energy would warp the geometry of space-time the way a heavy sleeper sags a mattress, producing the effect we call gravity. His equations described a universe in which space and time were dynamic. Space-time could stretch and expand, tear and collapse into black holes — objects so dense that not even light could escape them. The equations predicted, somewhat to his displeasure, that the universe was expanding from what we now call the Big Bang, and it also predicted that the motions of massive objects like black holes or other dense remnants of dead stars would ripple space-time with gravitational waves.
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These waves would stretch and compress space in orthogonal directions as they went by, the same way that sound waves compress air. They had never been directly seen when Dr. Weiss and, independently, Ron Drever, then at the University of Glasgow, following work by others, suggested detecting the waves by using lasers to monitor the distance between a pair of mirrors. In 1975, Dr. Weiss and Dr. Thorne, then a well-known gravitational theorist, stayed up all night in a hotel room brainstorming gravitational wave experiments during a meeting in Washington.
Dr. Thorne went home and hired Dr. Drever to help develop and build a laser-based gravitational-wave detector at Caltech. Meanwhile, Dr. Weiss was doing the same thing at M.I.T.
The technological odds were against both of them. The researchers calculated that a typical gravitational wave from out in space would change the distance between the mirrors by an almost imperceptible amount: one part in a billion trillion, less than the diameter of a proton. Dr. Weiss recalled that when he explained the experiment to his potential funders at the National Science Foundation, “everybody thought we were out of our minds.”
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The foundation, which would wind up spending $1 billion over the next 40 years on the project, ordered the two groups to merge, with a troika of two experimentalists, Drs. Weiss and Drever, and one theorist Dr. Thorne, running things. The plan that emerged was to build a pair of L-shaped antennas, one in Hanford, Wash., and the other in Livingston, La., with laser light bouncing along 2.5-mile-long arms in the world’s biggest vacuum tunnels to monitor the shape of space.
In 1987, the original three-headed leadership of Drs. Weiss, Drever and Thorne was abandoned for a single director, Rochus Vogt of Caltech. Dr. Drever was subsequently forced out of the detector project. But LIGO still foundered until Dr. Barish, a Caltech professor with a superb pedigree in managing Big Science projects, joined in 1994 and then became director. He reorganized the project so that it would be built in successively more sensitive phases, and he created a worldwide LIGO Scientific Collaboration of astronomers and physicists to study and analyze the data. “The trickiest part is that we had no idea how to do what we do today,” he commented in an interview, giving special credit to the development of an active system to isolate the laser beams and mirrors from seismic and other outside disturbances.
“Without him there would have been no discovery,” said Sheldon Glashow, a Nobel Prize-winning theorist now at Boston University.
The most advanced version of LIGO had just started up in September 2015 when the vibrations from a pair of colliding black holes slammed the detectors in Louisiana and Washington with a rising tone, or “chirp,” for a fifth of a second.
An Earthling’s Guide to Black Holes
Welcome to the place of no return — a region in space where the gravitational pull is so strong that not even light can escape it. This is a black hole.
It was also the opening bell for a whole new brand of astronomy. Since then LIGO (recently in conjunction with a new European detector, Virgo) has detected at least four more black hole collisions, opening a window on a new, unsuspected class of black holes, and rumors persist of even more exciting events in the sky.
“Many of us really expect to learn about things we didn’t know about,” Dr. Weiss said this morning.
Who Are the Winners?
Dr. Weiss was born in Berlin in 1932 and came to New York by way of Czechoslovakia in 1939. As a high school student, he became an expert in building high-quality sound systems and entered M.I.T. intending to major in electrical engineering. He inadvertently dropped out when he went to Illinois to pursue a failing romance. After coming back, he went to work in a physics lab and wound up with a Ph.D. from M.I.T.
Dr. Thorne was born and raised in Logan, Utah, receiving a bachelor’s degree from Caltech and then a Ph.D. from Princeton under the tutelage of John Archibald Wheeler, an evangelist for Einstein’s theory who popularized the term black holes, and who initiated Dr. Thorne into their mysteries. “He blew my mind,” Dr. Thorne later said. Dr. Thorne’s enthusiasm for black holes is not confined to the scientific journals. Now an emeritus professor at Caltech, he was one of the creators and executive producers of the 2014 movie “Interstellar,” about astronauts who go through a wormhole and encounter a giant black hole in a search for a new home for humanity.
Dr. Barish was born in Omaha, Neb., was raised in Los Angeles and studied physics at the University of California, Berkeley, getting a doctorate there before joining Caltech. One of the mandarins of Big Science, he had led a team that designed a $1 billion detector for the giant Superconducting Supercollider, which would have been the world’s biggest particle machine had it not been canceled by Congress in 1993, before being asked to take over LIGO.
Subsequently, Dr. Barish led the international effort to design the International Linear Collider, which could be the next big particle accelerator in the world, if it ever gets built.
Reached by telephone by the Nobel committee, Dr. Weiss said that he considered the award as recognition for the work of about a thousand people over “I hate to say it — 40 years.”
He added that when the first chirp came on Sept. 14, 2015, “many of us didn’t believe it,” thinking it might be a test signal that had been inserted into the data. It took them two months to convince themselves it was real.
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Einstein presented his general theory of relativity 100 years ago this month.
In an interview from his home, Dr. Thorne said that as the resident theorist and evangelist on the project he felt a little embarrassed to get the prize. “It should go to all the people who built the detector or to the members of the LIGO-Virgo Collaboration who pulled off the end game,” he said.
“An enormous amount of rich science is coming out of this,” he added. “For me, an amazing thing is that this has worked out just as I expected when we were starting out back in the 80s. It blows me away that it all come out as I expected.”
Dr. Barish said he had awoken at 2:41 am in California and when the phone didn’t ring he figured he hadn’t won. Then it rang. “It’s a combination of being thrilled and humbled at the same time, mixed emotions,” he said. “This is a team sport, it gets kind of subjective when you have to pick out individuals.” LIGO, he said, is very deserving. “We happen to be the individuals chosen by whatever mechanism.”
For the National Science Foundation, the Nobel was a welcome victory lap for an investment of 40 years and about $1 billion. In a news release, France Córdova, the foundation’s director, said: “Gravitational waves contain information about their explosive origins and the nature of gravity that cannot be obtained from other astronomical signals. These observations have created the new field of gravitational wave astronomy.”
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