“For decisive contributions to the LIGO detector and the observation of gravitational waves,” the Royal Swedish Academy of Sciences has awarded the 2017 Nobel Prize in Physics to Rainer Weiss, Barry C. Barish, and Kip S. Thorne. Weiss will receive half of the approximately $1.1 million prize. Barish and Thorne will share the other half.
Weiss is an emeritus professor of physics at Massachusetts Institute of Technology. Barish and Thorne are emeritus professors of physics at California Institute of Technology.
LIGO, the Laser Interferometer Gravitational-Wave Observatory, is a highly sensitive optical instrument designed to detect “ripples in space-time” that were predicted by Albert Einstein just over 100 years ago. According to his theory, as gargantuan bodies such as black holes accelerate because of gravity, they emit vast amounts of energy and generate gravitational waves that propagate through the universe, sometimes passing through Earth.
Those waves remained elusive for a century. But in 2015, LIGO’s enormous and ultrasensitive interferometers for the first time picked up the tiny signals, which in the past had been swamped by numerous sources of noise. One of the instruments is located in Livingston, La.; the other is in Hanford, Wash.
The instruments consist of a powerful laser and an interferometer with a pair of 4-km-long arms. A gravitational wave passing through the area of the detector causes a momentary subatomic-scale change in the length of one arm relative to the other.
The LIGO team had just completed an upgrade of their optical equipment when they finally saw the signal they had been searching for. They eventually determined that it came from gravitational waves that were generated 1.3 billion years ago. The waves formed as two black holes—roughly 29 and 36 times the mass of the sun—merged, forming a single black hole. A few months later, in December 2015, the LIGO team detected another black-hole merger.
At the press conference announcing this year’s prize, Weiss, who spoke by phone, said that like many of his team members, he did not believe that the first signal detected in 2015 was real. The signal could have been a fake result that was injected into the data stream to test the equipment and the team’s ability to recognize such signals. It took team members two months to convince themselves that the observations were real, Weiss said.
“Gravitational waves are allowing us to open a completely new window on the cosmos,” says University of Pisa physicist Massimiliano Razzano. He’s a member of the team that runs Virgo, the new gravitational-wave detector near Pisa, Italy. In late September, the LIGO and Virgo teams announced jointly that all three detectors measured signals that correspond to yet another black-hole merger.
Reflecting on the honor of winning the Nobel Prize, Weiss said, “It’s really wonderful. It recognizes the work of 1,000 people that has been going on for nearly 40 years.” He added that the team continues to work on increasing the sensitivity of the detectors. The goal, he said, “is to look deeper and deeper into the universe and to study its beginnings.”
NOTE: This story was updated on Oct. 5, 2017, to include new information.