Einstein’s gravitational waves ‘seen’ from black holes

Einstein’s gravitational waves ‘seen’ from black holes

Einstein’s gravitational waves ‘seen’ from black holes

Written by Staff Writer

12 Feb, 2016 | 8:05 am

Scientists are claiming a stunning discovery in their quest to fully understand gravity.

They have observed the warping of space-time generated by the collision of two black holes more than a billion light-years from Earth.

The international team says the first detection of these gravitational waves will usher in a new era for astronomy.

It is the culmination of decades of searching and could ultimately offer a window on the Big Bang.

The research, by the LIGO Collaboration, has been published yesterday(11) in the journal Physical Review Letters.

The collaboration operates a number of labs around the world that fire lasers through long tunnels, trying to sense ripples in the fabric of space-time.

Expected signals are extremely subtle, and disturb the machines, known as interferometers, by just fractions of the width of an atom.

But the black hole merger was picked up by two widely separated LIGO facilities in the US.

The merger radiated three times the mass of the sun in pure gravitational energy.

Prof Karsten Danzmann, from the Max Planck Institute for Gravitational Physics and Leibniz University in Hannover, Germany, is a European leader on the collaboration.

He said the detection was one of the most important developments in science since the discovery of the Higgs particle, and on a par with the determination of the structure of DNA.

The LIGO laser interferometers in Hanford, in Washington, and Livingston, in Louisiana, were only recently refurbished and had just come back online when they sensed the signal from the collision. This occurred at 10.51 GMT on 14 September last year.

On a graph, the data looks like a symmetrical, wiggly line that gradually increases in height and then suddenly fades away.

Being able to detect gravitational waves enables astronomers finally to probe what they call “dark” Universe – the majority part of the cosmos that is invisible to the light telescopes in use today.

Not only will they be able to investigate black holes and strange objects known as neutron stars (giant suns that have collapsed to the size of cities), they should also be able to “look” much deeper into the Universe – and thus farther back in time. It may even be possible eventually to sense the moment of the Big Bang.

In addition, the study of gravitational waves may ultimately help scientists in their quest to solve some of the biggest problems in physics, such as the unification of forces, linking quantum theory with gravity.

At the moment, General Relativity describes the cosmos on the largest scales tremendously well, but it is to quantum ideas that we resort when talking about the smallest interactions. Being able to study places in the Universe where gravity is really extreme, such as at black holes, may open a path to new, more complete thinking on these issues.

Scientists have sought experimental evidence for gravitational waves for more than 40 years.

Einstein himself actually thought a detection might be beyond the reach of technology.

His theory of General Relativity suggests that objects such as stars and planets can warp space around them – in the same way that a billiard ball creates a dip when placed on a thin, stretched, rubber sheet.

Gravity is a consequence of that distortion – objects will be attracted to the warped space in the same way that a pea will fall in to the dip created by the billiard ball.

Einstein predicted that if the gravity in an area was changed suddenly – by an exploding star, say – waves of gravitational energy would ripple across the Universe at light-speed, stretching and squeezing space as they travelled.

Although a fantastically small effect, modern technology has now risen to the challenge.

Much of the R&D work for the Washington and Louisiana machines was done at Europe’s smaller GEO600 interferometer in Hannover.

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