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  • Writer's pictureDev Trivedi


Gravitational waves, space-time’s very own structural ripples. Their existence was first predicted by well obviously, Einstein himself in the General Theory of Relativity of 1915. And about 100 years later at 6 AM, on September 14, 2015, scientists witnessed the wondrous spectacle of the collision of two black holes.

Thirty times our Sun’s size and after orbiting each other millions of years, due to the massive gravitational pull they got closer together they orbited each other faster and faster and finally merged to become a bigger black hole, a fraction of a second before their crash they send a vibration across the universe and 1.3 billion years later this vibration was detected on the LIGO or the Laser Interferometry Gravitational-wave Observatory. This signal only lasted a mere tenth of a second but opened the door for millions of new possibilities for theories predicting the working of the universe.

But what are these ripples in space? Let’s start with gravity, gravity is the attractive force pulling any two objects together. Einstein imagined gravity as a curve in a surface called space-time (like a trampoline stretching across the entire length of the universe) a mass (like a star or a planet) creates a depression in space-time. Larger the mass, the greater the depression and more the gravity. When this mass moves it sends ripples in the fabrics of space-time called gravitational waves. These waves are invisible and travel extremely fast at 300,000 m/s (or a billion times faster than when children run at the AVM athletic meet).

By the time these waves reach the earth these waves become extremely weak and that’s where LIGO comes in for the rescue. The LIGO has two very long arms, 4 kilometres in length whose length is measured with lasers. When a gravitational wave passes by it causes a minute change in the length of the arms hence detecting a gravitational wave. Not only collisions of black holes but the explosion of a star or a supernova, big neutron stars orbiting each other, all of these events cause gravitational waves.

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