In Depth

What are gravitational waves and why are they important?

Discovery hailed as this century's biggest scientific breakthrough that could answer questions about the Big Bang itself

Scientists have today confirmed the existence of gravitational waves – exactly a century after they were first predicted by Albert Einstein.

"Their discovery... is certain to earn a Nobel Prize," said The Guardian's science editor, Ian Sample.

What are they and who has been looking for them?

Gravitational waves represent movements in the fabric of space-time created by major cosmic events, such as the collision of black holes. They can be likened to ripples in a pond.

Their existence was first proposed by Einstein and formed a key part of his general theory of relativity, but they have never before been detected. 

However, in recent weeks, rumours began circulating that the decades-long search was over. Hundreds of scientists working on the Advanced Laser Interferometer Gravitational-Wave Observatory experiment in Washington State have been using laser detectors to seek out the cosmic ripples.

"They have constructed [two] tubular channels several kilometres long, down which they fire laser beams that bounce off a mirror at the far end," says the BBC's Phillip Ball.

"A gravitational wave would change one channel length more than the other, depending on its direction, slightly altering the interference between the two beams."

Why have they been so hard to find?

Because of the small size of the displacement created by the ripple, says The Guardian. "A wave from millions of light years away would distort a four kilometre laser beam by less than a thousandth of the diameter of the nucleus of an atom. Which is hard to spot."

Why are they important?

Their discovery, confirmed this afternoon, has been hailed by scientists as "the biggest scientific breakthrough of the century". It's claimed the find is even more significant than the discovery of the Higgs boson and marks the "birth of gravitational astronomy", says the Daily Telegraph.

"Quite apart from offering a completely new vindication of Einstein's theory, these results will deepen our understanding of stars and galaxies," British cosmologist Sir Martin Reese writes.

It could also answer fundamental questions about the moment of creation. "It will give a window into some of the most violent and energetic events in the cosmos; exploding stars, colliding black holes, maybe even the Big Bang itself," says Professor Martin Hendry, from the University of Glasgow.

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