Friday 30 September 2016

Einstein was right: scientists detect 'ripples' in space time

Sarah Knapton in London

Published 12/02/2016 | 02:30

An image depicting two black holes colliding and creating gravitational waves that transport energy across the universe. The waves have never before been measured, though Albert Einstein said they were out there, according to his theory of relativity.
An image depicting two black holes colliding and creating gravitational waves that transport energy across the universe. The waves have never before been measured, though Albert Einstein said they were out there, according to his theory of relativity.

Ripples in space time have finally been detected, 100 years after they were first predicted by Albert Einstein.

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The discovery was last night hailed as "the biggest scientific breakthrough" of the century by scientists who said that it was even more significant than finding the Higgs Boson and marked the "birth of gravitational astronomy".

In 1915, Einstein announced his General Theory of Relativity which suggested that huge bodies in space, like planets or black holes, have so much mass that they actually bend space and time. It can be thought of as a giant rubber sheet with a bowling ball in the centre. Just as the ball warps the sheet, so a planet bends the fabric of space-time creating the force that we feel as gravity. Any object that comes near to the body falls towards it because of the effect.

It was most recently demonstrated in the film 'Interstellar' when the crew visited a planet which fell within the gravitational grasp of a huge black hole, so that time slowed down massively. Crew members on the planet barely aged while those who stayed on the ship were decades older on their return.

Einstein predicted that if two massive bodies came together, it would create such a huge ripple in space time that it should be detectable on Earth.

Yesterday, scientists at Laser Interferometer Gravitational-Wave Observatory (LIGO) in Washington announced they had detected such a ripple, believed to be caused by two black holes colliding.

"It's monumental - like Galileo using the telescope for the first time. It's been a very long road, but this is just the beginning. It happened when life on Earth was just beginning to spread and it took a billion years to come to Earth."

Professor Sheila Rowan, Director of the University of Glasgow's Institute for Gravitational Research, said: "It's amazing to realise that we turned on our detectors on the centenary of the year Einstein's general theory of relativity was published and at exactly the right time to receive this signal coming to us from 1.5 billion years ago - when far out in the Universe two black holes spiralled in to collide.

"This detection marks not only a confirmation of Einstein's theories but most exciting is that it is marks the birth of gravitational astronomy. This expands hugely the way we can observe the cosmos."

Not only does it prove the Theory of Relativity, it is the first physical proof that black holes exist.

Professor James Hough, a Glasgow University physicist and LIGO member, said: "Until you can actually measure something, you don't really know it's there.

"I think this is much more significant than the discovery of the Higgs boson. This is the biggest scientific breakthrough of this century."

"It's the first time the universe has spoken to us through gravitational waves. Until now we have been deaf to gravitational waves, but now we can hear."

Astronomer Royal Martin Rees said the discovery was one of the scientific highlights of the decade.

Mr Rees said: "This detection is indeed a big deal, one of the great discoveries of the decade, up there with the detection of the Higgs particle, which caused huge razzmatazz two years ago.

"Gravitational waves, vibrations in the fabric of space itself, are a crucial and distinctive consequence of Einstein's theory of general relativity.

"This theory tells us that the force of gravity is best understood as a 'warping' of space itself. And when gravitating objects move, they generate a 'ripple' in space itself. When such a ripple passes the Earth, our local space is alternately stretched and compressed, rather as, when a stone is thrown into a pond."

The wave has been picked up using an instrument called an interferometer, a device which splits a single laser beam into two and sends both beams shooting off at right angles to each other. The beams bounce of mirrors in a tunnel and should travel equal distances. But a passing gravitational wave can chance the distance that each bends relative to the other.

The gravitational waves change the length of the beams by a tiny amount, roughly 1/10,000th the width of an atom's nucleus.

To pick up such a tiny change, LIGO must filter out all other sources of noise, including earthquakes and nearby traffic.

Dr Danny Steeghs, University of Warwick Department of Physics, said: "This is a fantastic technical achievement by the LIGO team, a highly deserved reward after many years of effort and technology development. A century after Einstein's theory of general relativity was presented, we now have a convincing, direct detection of a gravitational wave signal produced by a pair of black holes.

"It was fortunate that such an event occurred so soon after the detector upgrades, and a long anticipated window on the Universe has now opened.

"We are about to deploy a telescope system that is dedicated to chase visible signatures of events detected with the advanced gravitational wave detectors, and are delighted to see LIGO deliver their first detection, with hopefully many more to follow."

Professor Kenneth Strain is principal investigator of the Advanced LIGO project team in the UK. He said: "Evidence of gravitational waves and the collision of black holes is more than we ever could have hoped for." (© Daily Telegraph London)

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