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| Laureates (L-R) Rainer Weiss, Barry C. Barish and Kip S. Thorne are pictured on a display during the announcement of the 2017 Nobel Prize winners in Physics on October 3, 2017, at the Royal Swedish Academy of Sciences in Stockholm. |
Predicted by Albert Einstein a century ago as part of his theory of general relativity, gravitational waves are "ripples" in space-time — the theoretical fabric of the cosmos.
They are the aftermath of violent galactic events, such as colliding black holes or imploding massive stars, and can reveal events that took place billions of years ago.
The first detection of gravitational waves happened in September 2015 at the US-based Laser Interferometer Gravitational-wave Observatory (LIGO), where the three Nobel laureates worked.
"Their discovery shook the world," said Goran K. Hansson, the head of the Swedish Royal Academy of Sciences which selects the Nobel laureates.
Announced in February 2016 to great excitement in the scientific community, the discovery was hailed as the historic culmination of decades of research. It has clinched numerous astrophysics prizes.
Traveling at speed of light
In 1984, Thorne, now 77, and Weiss, 85, co-created LIGO at the prestigious California Institute of Technology, which has taken home 18 Nobels since the prizes were first awarded in 1901.
Barish, 81, joined the project in 1994 and helped bring it to completion. LIGO is now a collaboration between more than 1,000 researchers from 20 countries.
The 2015 observation was of two black holes smashing into each other some 1.3 billion light-years away.
"Although the signal was extremely weak when it reached Earth, it is already promising a revolution in astrophysics," the Nobel academy said.
"Gravitational waves are an entirely new way of following the most violent events in space and testing the limits of our knowledge."
Gravitational waves are minuscule, and near-undetectable because they interact very weakly with matter and travel through the universe at the speed of light unimpeded.
The ripples emitted by a pair of merging black holes, for example, would stretch a one-million-kilometer (621,000-mile) ruler on Earth by less than the size of an atom.
Since 2015, the enigmatic ripples have been detected three more times: twice by LIGO and once by the Virgo detector located at the European Gravitational Observatory (EGO) in Cascina, Italy.
"Einstein was convinced it would never be possible to measure them," the jury said.
"The LIGO project's achievement was using a pair of gigantic laser interferometers to measure a change thousands of times smaller than an atomic nucleus, as the gravitational wave passed the Earth."
'Universe full of music'
Black holes emit no light, and can only be observed through gravitational waves that occur when they collide and violently merge — offering scientists a means of studying them.
"If we could hear all the waves and not only the strongest ones, the entire universe would be full of music, like birds chirping in a forest, with a louder tone here and a quieter one there," the academy said.
Weiss was awarded half the prize, which comes with nine million Swedish kronor (about $1.1 million or 940,000 euros), while Barish and Thorne shared the rest.
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