Gravitational Waves Discovery - Why is it Such a Big Deal?

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If you're at all interested in science, then you've probably heard on the grapevine that gravitational waves have been discovered a full 100 years after Einstein predicted them. 
But what are gravitational waves? And why is this important?

On Sep 14 5:51 am 2015 (eastern daylight time)  the Twin Laser Interferometer Gravitational-wave observatory (LIGO) finally detected that gravitational waves exist, and this has recently been verified and released to the public.

Livington's LIGO detector
LIGO is a huge and financially risky construction funded by the National Science Foundation and consists of  two detectors spaced so that one is sat in Livington,Louisiana, and the other in in hanford, Washington. Each detector interacts with a  laser beam that is split in two and forced down two  2 and a half mile long perpendicular tunnels. When they hit the mirrors at the end of the tunnel, the laser is fired back and the two split lasers recombine, allowing scientists to detect any infinitesimally small variations in the makeup of the laser beam. If a gravitational wave is present, the distance that the light of the lasers has to travel will have changed, and the form of the beam will be different.

But why would the distance of travel change? 

This is down to Albert Einstein's general theory of relativity, an aspect of which relates to gravitational waves. Imagine the solar system - with the planets happily spinning around one another due to gravity: primary school level science, right? While we laymen commonly imagine why this happens is due to a mix of  centrifugal force and the idea of the 'push' and 'pull' forces keeping the planets in space and moving, in reality it's all down to how big gravitationally 'heavy' objects interact with the fabric of Spacetime. This comic explains it beautifully, but basically imagine this: space is light a taut bedsheet (secured at each corner) and a hefty object (like a star) is like dropping a bowling ball onto the sheet - it creates a dip. It distorts spacetime. And these sorts of distortions emanate outwards and create waves. Now, gravity really is an incredibly weak force, despite all the dramatic things it can do (you right now are defying a whole planet's worth of gravity by lifting your arm!), so it takes something truly massive to be detectable. Up until now Einstein theorised that these waves should exist, but there was no way that we could prove this. Without proof, it's very hard to put it to practical use.

According to Einstein's general theory of relativity, if a pair of black holes orbited each other they would gradually lose energy through the emission of gravitational waves and in doing so would be pulled closer and closer to one another until they would collide to create a single massive black hole that would create a final huge burst of gravitational waves.
Cue a pair of black holes 1.3 billion years ago and their collision that was dramatic enough that LIGO could finally pick up the signal after over 40 year's work.

So what does this mean for science?

Dr Ed Daw of the University of Sheffield (one of the founding collaborators of the consortium of universities) is understandably excited. LIGO's detection, and the further development of the facility in the effort to understand gravitational waves has the potential to create a whole new field of astronomy in how we understand the universe.
"Essentially," he said, "it's like listening to the cosmos, when we've only been able to look before."

As well as proving that gravitational waves exist at all, it also has shown that these waves move at the speed of light (which is why we have been able to only detect this 1.3 billion year old event now). Proving this enables scientists to sure up their calculations no end. What's more, in detecting this event LIGO has confirmed the first intermediate mass black hole ever found (as opposed to the smaller versions we know about). It is thought that when these intermediate black holes merge they might produce the supermassive black holes - the kind of black holes that sit in the centre of whole galaxies.

So what's next?

The natural plan is to keep moving forward with even bigger, more accurate versions of the LIGO detector so that we can pick up more subtle gravitational waves. One ambitious project on the horizon (currently scheduled for the 2030s) is 'LISA' - an attempt to create  a LIGO-like detector up in space that uses satellites at huge distances apart to measure the travels of their lasers, allowing for even more accuracy.

Whatever the future holds, it's clear that the discovery of gravitational waves has opened up an exciting branch of science to be explored.

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Stay curious!

-The Star
-Ligo Caltech Website
-Gravitational Waves explained
-IFL Science
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