By tracking the shifting patterns through time, researchers can watch a gravitational wave ripple through the facility. Those length changes alter the time it takes the laser beams to bounce back and forth, which in turn changes the pattern the beams make where they meet. When a gravitational wave passes through Earth, it slightly stretches one of the arms and compresses the other. Each L-shaped facility consists of two arms more than two miles long that meet at a right angle.īy bouncing lasers back and forth within each arm, physicists can measure their lengths with an accuracy so astonishing, it would be like measuring the distance between us and Alpha Centauri-the closest star outside our solar system-to within a hair's width. The observatory consists of two facilities: one in Louisiana, the other in Washington State. Starting in the 1970s, physicists including Rainer Weiss, Kip Thorne, and Barry Barish sketched out the idea that later became LIGO. In 2017, three of LIGO's founding scientists were honored with the Nobel Prize in physics. Scientists formally announced the success in February 2016. Laser Interferometry Gravitational-Wave Observatory-aka LIGO-detected the rumble that two colliding black holes gave off 1.3 billion years ago. The first direct detection of gravitational waves took place on September 14, 2015, when the U.S. Calculations made clear that this energy loss came in the form of gravitational waves-a discovery that won Taylor and Hulse a Nobel Prize in 1993. As the pair of pulsars spun around each other, they grew closer together, which indicated that they were giving off energy. In 1974, astronomers Joe Taylor and Russell Hulse tracked a pair of spinning stellar corpses called pulsars. Though Einstein later doubted the waves' existence, we have had indirect evidence of them since the 1970s. Detecting gravitational wavesĮinstein's general theory of relativity first predicted the existence of gravitational waves, which the famous scientist himself noted in 1916. It just takes the right instrument to hear them.ĭetecting gravitational waves on Earth was a challenge that took roughly a century to complete, since the ones that wash through the planet are incredibly tiny. For gravitational waves, spacetime is the medium. The difference is that sound waves vibrate through a medium, like water or soil. We can hear gravitational waves, in the same sense that sound waves travel through water, or seismic waves move through the earth. And unlike the gentle drop of a stone in a pond, the events that trigger gravitational waves are among the most powerful in the universe. But unlike sound waves pond ripples, which spread out through a medium like watter, gravitational waves are vibrations in spacetime itself, which means they move just fine through the vacuum of space. Gravitational waves are distortions in the fabric of space and time caused by the movement of massive objects, like sound waves in air or the ripples made on a pond's surface when someone throws a rock in the water.
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