The National Science Foundation announced that scientists have officially detected ripples in spacetime, 100 years after Albert Einstein predicted the existence of such phenomena.

“Ladies and gentlemen, we have detected gravitational waves,” said Laser Interferometer Gravitational-wave Observatory (LIGO) Executive Director David Reitze at a press conference hosted today in Washington, D.C.  

On Sept. 14, 2015, both LIGO detectors detected gravitational waves emanating from the merging of two black holes. These black holes, which each stuff about 30 solar masses in a space a little over 150 km in diameter, circled one another 1.3 billion years ago. As they approached each other, they increased in acceleration and warped the surrounding space before coalescing into a single black hole at about half the speed of light. The collision sent a ripple emanating outwards into the universe.

“This is the first time that this kind of system has ever been seen,” said Reitze. “It’s proof that binary black holes exist in the universe.”

The study behind the discovery was accepted for publication in Physical Review Letters.

The signal picked up by LIGO was detected by the detector in Livingston, La. about seven milliseconds before it was detected by the Hanford, Wash. counterpart.

“It’s the first time the universe has spoken to us through gravitational waves,” said Reitze. “We were deaf to them” before.

The LIGO detectors, operated by the California Institute of Technology (Caltech) and the Massachusetts Institute of Technology (MIT), are designed to detect the most diminutive disturbances in spacetime. The detectors, which are L-shaped and about 4 km long, shoot laser beams, which are split into two, down the length of their arms. Mirrors positioned at the end of the arms are monitored by the beams. A gravitational wave is capable of changing the distance between the mirrors, and LIGO can detect changes down to one-ten-thousandth the diameter of a proton.

“The Advanced LIGO detectors are a tour de force of science and technology, made possible by a truly exceptional international team of technicians, engineers, and scientists,” said the project’s leader David Shoemaker, of MIT.  

Reitze said the discovery is on par with Galileo Galilei’s breakthrough with observational astronomy, and will change the way we look at the universe. It introduces to the world of science the field of gravitational wave astronomy.