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.
Quantum "squeezer" improves detection capability
“This quantum noise is like a popcorn crackle in the background that creeps into our interferometer, and is very difficult to measure,” adds Nergis Mavalvala, the Marble Professor of Astrophysics and associate head of the Department of Physics at MIT. With the new squeezer technology, LIGO has shaved down this confounding quantum crackle, extending the detectors’ range by 15 percent. Combined with an increase in LIGO’s laser power, this means the detectors can pick out a gravitational wave generated by a source in the universe out to about 140 megaparsecs, or more than 400 million light years away. This extended range has enabled LIGO to detect gravitational waves on an almost weekly basis.
Quote from Nergis Mavalvala in Scientific American The Gravitational-Wave “Revolution” Is Underway
“I’ve really been amazed at what we’ve been able to achieve. It’s staggering both on the astrophysics side, and the immense improvements to the instruments that have come about.”
Nergis Mavalvala in Scientific American
The Gravitational-Wave “Revolution” Is Underway
Scientists detect tones in the ringing of a newborn black hole for the first time
Black Hole Vibrations
Now, physicists from MIT and elsewhere have studied the ringing of an infant black hole, and found that the pattern of this ringing does, in fact, predict the black hole’s mass and spin — more evidence that Einstein was right all along. “We all expect general relativity to be correct, but this is the first time we have confirmed it in this way,” says the study’s lead author, Maximiliano Isi, a NASA Einstein Fellow in MIT’s Kavli Institute for Astrophysics and Space Research.
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.