Scientists detect gravitational waves, space-time ripples that Einstein predicted 100 years ago – Los Angeles Times

In a groundbreaking discovery, scientists say they have finally detected gravitational waves —  ripples in space-time from a violent collision 1.3 billion light-years away — that serve as a resounding confirmation of a prediction made by Albert Einstein a century ago. 

The detection, made with the Laser Interferometer Gravitational-Wave Observatory, known as LIGO, is the culmination of a decades-long search for signs of this elusive phenomenon.

The discovery, described in a paper in Physical Review Letters, will open a new window onto the universe, said LIGO Executive Director David Reitze. 

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“Until now we have been deaf to gravitational waves — but today we are able to hear them,” Reitze told a packed room at a news briefing in Washington, D.C. 

Astronomers rely on light of all wavelengths to detect the universe. Visible light reveals the starry heavens; infrared allows us to penetrate further back in time to see older, more distant stars; radio waves reveal the afterglow of the universe’s violent birth; and X-rays showcase violent encounters in the cosmos, including the supernova deaths of massive stars.

With the exception of the nascent field of neutrino astronomy, scientists have nearly always relied on their (or their telescope’s) “eyes” to view the distant heavens. But now, researchers will be able to sense the universe in a whole new way: with their “ears.” 

The telltale ripples were picked up just before 2:51 a.m. Pacific Daylight Time on Sept. 14 by the twin LIGO detectors — one in Hanford, Wash., and the other in Livingston, La., — a mere three days after the detectors had gone live following a five-year upgrade. The L-shaped detectors send laser beams down each leg of the L, which have the exact same length. If a gravitational wave passes through the detector, it will squeeze one leg and stretch the other, causing the distance to change and thus creating slight differences in timing.  

Gravitational waves occur as objects move through space, almost like a boat moving on a lake sends ripples through the water’s surface. But they’re so tiny that until now it’s been nearly impossible to detect them, even those caused by something as large as a planet moving around the sun. (The fact that they’re imperceptible on these scales is probably a good thing — objects lose energy as they emit gravitational waves, and if a body like the Earth lost too much, it would eventually fall into the Sun.) 

So to pick up this signal, scientists have to look for massive, violent events in the universe. This particular signal appears to have been caused by a collision between two black holes (20 and 36 solar masses) that occurred some 1.3 billion years ago.


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