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Gravitational Waves: listening to the universe

Computer simulation of two black holes merging that lead to the detection of gravitational waves. Photo credit: The Simulating eXtreme Spacetimes

‚ÄčAhead of premiering our new work Gravitational Waves by Iris ter Schiphorst, we asked astrophysicist Professor Bernard Schutz to give us a rundown on this  breakthrough discovery of our time. It's the perfect manual before we launch into outerspace this week, heading on our concert tour to Snape Maltings Concert Hall (4 Aug), Symphony Hall Birmingham (5 Aug), and the BBC Proms (6 Aug).


What is a gravitational wave?
Einstein taught us that nothing can move faster than light. So when gravity changes in one place, then these changes move out through space at the speed of light. These ripples of gravity are what we call gravitational waves.


How were they discovered?
Gravity is such a weak force that we don’t feel the gravitational waves that pass through us all the time. It took a worldwide collaboration of physicists three decades to develop the ultra-sensitive measurement technology for the two identical Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors in the United States, and for others around the world that will soon expand the detector network. This past February, LIGO announced that both of its detectors had simultaneously registered the tiny effect of a passing gravitational wave. Since then they have found two more waves, and many more are expected.


How were they produced?
In a galaxy more than a billion light years away, two massive black holes had been orbiting one another for billions of years, getting ever closer, ever faster; and finally they merged into a single black hole. Their motion disturbed gravity around them more and more strongly, and the resulting waves of gravity rippled out in all directions. They finally reached LIGO on September 14 last year.


Why is this important? 
Because Einstein himself predicted these waves in 1916, but it took a century to develop the technology to         observe them! 

Because the waves came from that other prediction of Einstein, black holes! 

Because we can convert the gravitational wave signal into sound, and so we are beginning to listen to the universe! This is a totally new kind of astronomy. The increasing frequency of the waves recorded by LIGO converts into an audible sound with a rising pitch, which we call a 'chirp'. This is the true music of the spheres!


Professor Bernard Schutz of Cardiff University, one of the leaders of the LIGO project. Schutz helped set up the UK gravitational wave research team in the 1980s, and then went to Germany in the 1990s to help found the Albert Einstein Institute near Berlin, which gave a further push to the scientific effort going into the LIGO collaboration. Now back in Cardiff, he is applying the lessons of LIGO data analysis to problems of Big Data. He is known for his work on communicating science to the public, especially for his Scienceface website.


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