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Scientists may be on the brink of discovering a new phenomenon reverberating throughout the cosmos: a steady thrum of ripples in space-time.
Albert Einstein first predicted that colliding massive objects like black holes would create such ripples, called gravitational waves. But he thought that the noise and vibrations on Earth would prevent us from ever being able to detect these waves. In that aspect, Einstein was wrong. One of the most remarkable experiments in history — the Laser Interferometer Gravitational-Wave Observatory (LIGO) — detected gravitational waves for the first time in 2015.
Those waves came from two black holes that crashed 1.3 billion light-years away, sending out ripples that eventually traveled through our planet and registered in LIGO’s giant, L-shaped detectors in Washington and Louisiana. Three researchers who helped conceive of the experiment earned a Nobel Prize in physics.
Since that first discovery, LIGO and its Italian counterpart, Virgo, have detected likely gravitational waves at least 50 times, from various combinations of black holes and neutron stars colliding.
But these are just the most obvious instances of gravitational waves — violent bursts of radiation from some of the most massive collisions in the universe. Theoretically, the cosmos should also be vibrating with a constant low-level hum of gravitational waves reverberating from merging galaxies across the universe.
Scientists think that the center of every large galaxy contains a supermassive black hole that’s millions or even billions of times more massive than the colliding objects that LIGO and Virgo have detected. These supermassive black holes should merge when galaxies crash into each other and slowly become one. The hypothetical hum from that activity throughout the universe is referred to as the “gravitational-wave background,” or GWB.
But nobody has discovered definitive evidence of it yet.
That’s where the new research comes in. Astrophysicists at the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) have detected what may be the first signs of this background radiation in space-time. Their research was published in the The Astrophysical Journal Letters.
“These enticing first hints of a gravitational-wave background suggest that supermassive black holes likely do merge, and that we are bobbing in a sea of gravitational waves rippling from supermassive black hole mergers in galaxies across the universe,” Julie Comerford, an astrophysicist on the NANOGrav team and an associate professor at the University of Colorado Boulder, said in a press release.
A gravitational-wave observatory the size of our galaxy
To search for the gravitational-wave background, the NANOGrav researchers sought to imitate LIGO on a much larger scale.
LIGO works by shooting out a laser beam and splitting it in two. The light then travels down the detector’s two 2.5-mile-long arms. The beams bounce off mirrors at the ends of those arms and converge back near the beam splitter, where they should cancel each other out. But when a gravitational wave comes through, it warps space-time — making one tube slightly longer and the other shorter for a brief moment. As a result, the two beams return to the splitter …read more
Source:: Business Insider