Tuesday, 23 February 2016

Gravitational Waves: Revealing the Secrets of the Universe

by Elliot Ebert

The science world rejoiced earlier this month with news of a groundbreaking discovery - The existence of gravitational waves. These waves should allow scientists to further explore the secrets of the Universe and hopefully answer questions that were previously unanswerable.

But what are gravitational waves?

Gravitational waves are essentially ripples in spacetime caused by a supermassive collision, predicted in Albert Einsteins Theory of General Relativity which he published in 1915. This followed his Special Theory of Relativity. Einsteins Theory of General Relativity, in short, dictates that we exist in a four dimensional spacetime, (three dimensions of space, one of time) and that the concentration of energy and mass can bend this spacetime.According to his theory, this is the origin of the force of gravity. It can be pictured in a three dimensional sense by a rubber sheet, on which a bowling ball is placed, deforming the sheet. If a marble is then rolled into the deformed area, it will spiral towards the bowling ball. The idea is the same in four dimensions rather than three and, of course, on a much larger scale. Einsteins Theory also predicts that masses moving through spacetime produce gravitational waves which are contortions of spacetime that propagate outwards, much like the wake from a moving boat. These ripples in spacetime can also be produced (more noticeably so) by violent events which occur in the cosmos. And this is precisely what happened in this latest discovery.

The spike in gravitational waves was in fact recorded on the 14th of September 2015 by the LIGO (Laser Interferometer Gravitational-Wave Observatory) detectors in the US. However, it was not clear what had caused the spike. So began the process of simulating events which would result in the waves which were detected. Only recently, on the 11th of February, was it confirmed that these waves were caused by a black hole merger, 1.3 billion light years away. This would have been an incredibly violent event, with each of the black holes having a mass about 30 times greater than our sun. Just before the black holes merged, they were orbiting one another at a rate of 250 times per second and the energy released during the collision was equal to 1.4 times the mass of our sun (Energy being equivalent to mass through the equation E=mc2, another one of Einsteins equations, where E is energy, m is mass and c is the speed of light). This was what was picked up by LIGO - the ripples in space time as a result of this monumental release of energy, many light years away.

So what use is the discovery?

Gravitational waves form a new avenue through which scientists can explore the Universe. Mankind has already almost used electromagnetic radiation to its full extent in examining the Universe (Radio waves, light and the Cosmic Microwave Background, amongst others). Furthermore, gravitational waves will triumph where light failed. For example, in the event which led to this latest discovery, previous methods would have been useless for its determination as, intrinsically, the black holes do not emit electromagnetic radiation. However, through gravitational waves, scientists were able to correctly determine the course of events which produced the detected waves and will, in future, be able to better detect dark objects, such as black holes and dark matter. As an example, scientists have, so far,  been unable to accurately determine the origins of the Universe. This is due to the fact that for the first 400,000 years in the lifetime of the Universe, all was dark and light could not travel due to the concentration of other particles blocking the light. However, gravitational waves would have been able to propagate in this environment and so scientists may now be able to correctly determine the origin of the Universe all of the way back to the mystery that still remains to be solved, the Big Bang singularity.

Most importantly, this latest discovery further supports Einsteins Theory of General Relativity and may ultimately lead to a better understanding of the laws that govern our Universe. This will help scientists on the way to a Grand Unified Theory. 

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