Detecting Gravitational Waves
A century after first predicted, scientists validated Einstein by listening to invisible ripples in the universe.
Albert Einstein’s general theory of relativity predicted the existence of gravitational waves — distortions in spacetime — but assumed that they would be virtually impossible to detect from Earth.
On Sept. 14, 2015, at approximately 5:51 a.m. EDT, a gravitational wave — a ripple from a distant part of the universe — passed through the Earth, generating an almost imperceptible, fleeting wobble that would have gone completely unnoticed save for two massive, identical instruments, designed to listen for such cosmic distortions.
Since this first discovery, LIGO has detected other gravitational wave signals, also generated by pairs of spiraling, colliding black holes. The latest discovery of a neutron-neutron star merger producing gravitational waves opens the field of a long-awaited “multi-messenger astronomy” to understand astrophysical events in both gravitational waves and electromagnetic waves — our cosmic messengers.
Gravitational waves could reveal how fast our universe is expanding
Scientists from MIT and Harvard University have proposed a more accurate and independent way to measure the Hubble constant, a unit of measurement that describes the rate at which the universe is expanding. Using gravitational waves emitted by a relatively rare system: a black hole-neutron star binary, a hugely energetic pairing of a spiraling black hole and a neutron star, should yield the most accurate value yet for the Hubble constant.
Why do gravitational waves matter?
Science in light and sound
Since LIGO’s first detection of gravitational waves, we’ve gained unexpected insight into the cosmos. Theorists had predicted that what follows the initial fireball of a neutron star merger is a “kilonova” — a phenomenon by which leftover material from a collision glows with light. Using gravitational waves, scientists could pinpoint and then record new light-based observations indicating that heavy elements, such as lead and gold, are created in these kilonova and subsequently distributed throughout the universe — opening the window of a long-awaited “multi-messenger” astronomy.
Neutron stars collide
Ushering in the new era of multi-messenger astronomy with a bang
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LIGO signal revealed first observation of two massive black holes colliding
Gravitational waves emanating from the collision of two black holes holes was detected for the first time by LIGO. This computer simulation shows two black holes, each roughly 30 times the mass of the sun, about to merge together 1.3 billion years ago.
One small chirp for humankind
Listen to the collision of two black holes
And yet despite the crazy, Matt Evans and his colleagues did it. The LIGO team used those L-shaped buildings to detect gravitational waves that were produced by a collision of two black holes more than a billion light years away.