Existence of Einstein’s gravitational waves confirmed

Scientists have for the first time detected gravitational waves passing over the Earth.

The waves were caused by the collision of two massive black holes that crashed together 1.3 billion years ago.

"We have detected gravitational waves. We did it," Prof Dave Reitze, executive director of LIGO, declared to a packed press conference at the Washington Press Club on Thursday.

Gravitational waves are much the same as the waves produced by throwing a pebble into a pond. A stone is enough to cause them on water, but gravitational waves are triggered by cataclysmic events such as colliding black holes.

The discovery was made by the LIGO collaboration, an international initiative led by the US National Science Foundation involving 1,000 scientists in 16 countries.

L-shaped detectors

LIGO used two huge L-shaped laser-using detectors based in Louisiana and Washington state to discover the waves.

The invisible and harmless waves pass through matter, but as they pass they stretch and squeeze space-time, the fabric of the universe.

As a wave passes by it distorts space-time, briefly changing the length of the L-shaped arms by as little as one thousandth the diameter of a hydrogen atom, enough to confirm a wave is passing.

The detectors emit a "chirp" if a wave is detected, said Prof Gabriela Gonzales of Louisiana State University, spokeswoman for the consortium.

“Not only will we be able to see the wave, we are going to hear it chirp,” she said at Thursday’s press conference.

Such is the importance of the discovery that most scientists agree the LIGO consortium is almost certain to receive a physics Nobel Prize for its efforts.

Being able to read gravitational waves means being able to see events such as black hole mergers across the universe, said Prof Luke Drury, director of the school of cosmic physics at the Dublin Institute for Advanced Studies.

Pass through anything

The waves pass through anything without disturbance. "You can see right back through the fog to the Big Bang itself," he said. "We may also have early warning of impending collisions so we can watch as they happen. It is also a proof of the final major prediction made in Albert Einstein's Theory of General Relativity, " he said.

LIGO's success allows "a whole new way to observe the universe", said Prof Adrian Ottewill, professor of mathematical physics at University College Dublin, who worked in the consortium for 10 years.

“It is as though we can now hear the universe while previously we could only see it. We will be able to see very different things. It is incredibly exciting times for astronomy,” he said.

The first detection of the waves "marks a significant new advance in modern physics and simultaneously opens up a new frontier in astronomy", said Dr Cormac O'Raifeartaigh, lecturer in physics at Waterford Institute of Technology and a Fellow of the Royal Astronomical Society.