The very short guide to why gravitational waves matter

Measurements of gravitational waves confirm a key prediction integral to Albert Einstein’s 1915 general relativity, an explanation of how forces in the universe interact.

Gravitational waves are disturbances in spacetime – imagine dragging your hand through water and you can visualise the pattern of waves which follow in its path and spread out towards the edges of the pool.

A similar thing happens when massive objects (such as neutron stars or black holes) orbiting each other ‘disrupt’ space-time in such a way that ‘waves’ of distorted space radiate from the source,. These ripples travel at the speed of light through the Universe, carrying with them information about their origins.

Gravitational waves are also an important way to study space. For instance, waves from the formation of the Universe could explain more about how everything we know today came into being. Basically detecting these waves can allow us to “see” or “hear” into the past and the huge cosmic events that occurred billions of years ago. At the same time they can also deepen our understanding of fundamental laws of the universe.

A very short history of human interaction with gravitational waves

While gravitational waves have been around as long as time, at least in the sense we understand it, and were predicted by Einstein a century ago, our own experiences of actually detecting them are remarkably short.

On September 14, 2015, LIGO (Laser Interferometer Gravitational-Wave Observatory, based in the USA) first physically spotted distortions in spacetime caused by passing gravitational waves generated by two colliding black holes nearly 1.3 billion light years away.

On August 14 this year, VIRGO (the European Gravitational Observatory, based in Italy) recorded gravitational waves from the collision of a pair of black holes 1.8 billion light years away from Solar System. It was the fourth time in the last two years that astronomers have detected such ripples but the first time they had been able to use three different observations to pinpoint their origin.

LIGO and Virgo

Having a three-detector global (two in the USA and one in Italy) network opens new prospects for astronomy. The European Virgo collaboration consists of more than 280 physicists and engineers belonging to 20 different European research groups including the Centre National de la Recherche Scientifique (CNRS) in France; the Istituto Nazionale di Fisica Nucleare (INFN) in Italy; the Netherlands with Nikhef; the MTA Wigner RCP in Hungary; the POLGRAW group in Poland; Spain with the University of Valencia; and EGO, the laboratory hosting the Virgo detector near Pisa in Italy.
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