WHAT CAN GRAVITATIONAL WAVES TELL US?

“THE HOPE IS THAT GRAVITATIONAL WAVES WILL LEAD US TO A LONG-SOUGHT QUANTUM THEORY OF GRAVITY”

Gravitational waves have the potential to point towards a better, deeper theory of gravity. We know that Einstein’s theory breaks down in the infinitely dense ‘singularity’ found at the heart of a black hole and at the beginning of time in the Big Bang. The hope is that gravitational waves will lead us to a long-sought quantum theory of gravity.

They also have the potential to reveal the behaviour of super-dense matter inside neutron stars. Perhaps, even more excitingly, they could tell us about the birth of the Universe. In the standard picture, the Universe in its first split-second of existence went through an incredibly violent expansion known as inflation. This should have left a relic background of gravitational waves in today’s Universe, which we may be able to detect and decode.

Gravitational waves truly provide us with a new ‘sense’. We have always been able to see the Universe, with our eyes and telescopes. Now, for the first time, we can hear the Universe too. Gravitational waves are the ‘ voice of space’. So far, we have heard some sounds at the edge of audibility. Nobody knows what the cosmic symphony will sound like, but as we improve the sensitivity of gravitational wave detectors, we hope that we will discover things of which nobody has ever dreamed.

1. CATCHCH A WAVE Einstein’s General Theory of Relativity tells us that if two massive objects, such as two black holes, are bound together by gravity, they should create ripples in the fabric of space- time. These ripples are called gravitational waves.

On 14 September 2015, first in Livingston, then in Hanford, LIGO’s arms repeatedly expanded and contracted by a hundred-thousandth the diameter of an atom, marking the first ever direct detection of gravitational waves. 3. DETECT IT

2. SPACE GYMNASTICS As a wave travelling at the speed of light passes through space- time, it first stretches space in one direction and squeezes it in the perpendicular plane, then reverses the process.