This morning, the Royal Swedish Academy of Sciences awarded the Nobel Prize in Physics to three U.S.-based physicists, Rainer Weiss of the Massachusetts Institute of Technology as well as Kip S. Thorne and Barry C. Barish of the California Institute of Technology for their work behind the discovery of gravitational waves—a type of ripple in the fabric of space-time that was first predicted by Albert Einstein over 100 years ago.
As Dennis Overbye at The New York Times reports, the three laureates were the driving force behind the Laser Interferometer Gravitational-wave Observatory (LIGO), an instrument designed to detect gravitational waves. They led a consortium of over 1,000 scientists who worked for decades to collect, analyze and improve the detectors. And in 2015, their efforts finally paid off with the detection of a tiny chirp emitted from two black holes colliding over a billion years ago.
While the time between the discovery and the award—just two years—is short by Nobel standards (even Einstein waited 16 years for his award), the seeds of the project were over 40 years in the making.
The detection of gravitational waves shook the physics community, confirming one of the central tenants of Einstein's General Theory of Relativity. According to this theory, the motions of super massive objects, such as black holes, causes ripples through the fabric of space-time—like waves from a pebble dropped in a pond. But for decades, physicists doubted that these waves truly exist—or could ever be detected.
As a PhD student in the early 1960s, Kip Thorne believed they they were out there. And by the 1970s, new modeling and thought experiments began convincing an increasing number of researchers. "The music was out there. They just hadn’t heard it yet," Jennie Rothenberg Gritz wrote for Smithsonian in 2017 when the trio was honored with the magazine's American Ingenuity Award.
In 1972, Weiss published a paper with his initial conception of a so-called Laser Gravitational Wave "antenna," teaming up with Thorne to refine and execute the ambitious plan. It was a radical idea: create a detector that was sensitive enough to detect a ripple in space-time smaller than the diameter of a proton.
Barish, previously head of the Superconducting Supercollider project, joined the team later, becoming director of LIGO in 1994. He is often credited for reorganizing and managing the project, which was struggling to continue at the time. But eventually LIGO was born.
LIGO consists of two L-shaped detectors, one in Louisiana and one in Washington State—separated by 1,865 miles. Each detector, Gritz reports, has two 2.5 mile-long arms with the world’s smoothest mirror at each end. As physicist Brian Greene wrote for Smithsonian.com last year, the detector measures the time it takes a super-powerful laser beam to bounce between the two mirrors, measuring any minute differences. Tiny changes in the travel time of the lasers are indicators of a passing gravitational wave.
For its first eight years, the observatory struggled, and was shut down in 2010 for a $200 million retool. But in September 2015, soon after relaunching, LIGO detected its first ripple. Since then, another three gravitational waves have been detected, one, a collaboration between LIGO and the Italian Virgo observatory, was announced just last week.
While only three researchers are recognized by the prize, it took a legion of researchers for the detector to succeed, reports Hannah Devlin and Ian Sample at The Guardian. “I view this more as a thing that recognizes the work of about 1,000 people,” says Weiss. “I hate to tell you but it’s as long as 40 years of people thinking about this, trying to make a detection … and slowly but surely getting the technology together to do it.”
Devlin and Sample report that there was a fourth member of the team who would have likely also received the prize. Scottish physicist Ronald Drever, another core member of the LIGO team passed away from dementia in March. The Nobel committee does not typically award the prize posthumously.
The discovery is a game changer for astronomers and physicists, providing a new tool to study the universe. As Green wrote last year, unlike light, x-rays, gamma rays, infrared or other signals astronomers use to study the sky, gravitational waves pass through everything and cannot be blocked. So the waves could be used to examine realms that are "off-limits" to light—including perhaps the "wild rumble of the big bang itself, 13.8 billion years ago.”
As Green writes: “History will look back on the discovery as one of those few inflection points that change the course of science.”