Gravitational Waves: The Colossal Clash of the Giants

Introduction

In 1915, in perhaps one of the most influential scientific papers, Einstein introduced the world to the General Theory of Relativity, which went on to revolutionize our understanding of gravity and the grand architecture of the universe. In that paper, Einstein proposed that gravity is a crumple or curvature in the geometric fabric of a higher-dimensional space, which we call spacetime. This extraordinary collection of mathematical equations and theories yielded some of the most amazing concepts such as, the existence of black holes, time dilation, gravitational wells, gravitational waves and many others.

What are gravitational waves?

In 1916, Einstein pointed out that when massive celestial objects accelerate asymmetrically, they cause disturbance in the spacetime by sending ripples away from them. These ripples were termed gravitational waves, which propagates with the speed of light. It is theorized that, if a gravitational wave were to encounter an observer, then the observer will find spacetime around him to be distorted, where he would notice that distances between the objects increase and decrease as the wave rhythmically passes. Consider throwing a rock into a pond, the ripples caused by the rock in the pond, is exactly the kind of phenomenon is being talked about at the scale of massive celestial objects.

Clash of the giants

The best example of how these gravitational waves can form is the merging of two massive black holes. Just imagine for a moment the aftermath of a collision on that scale. We are talking about two massive black holes, whose core itself could be as big as the sun, or perhaps thousands of times bigger, colliding with each other after an all-out chaos of gravitational pull. Consider that even one of these things holds so immense power that it literally creates a gravitational well in spacetime, due to their enormous concentration of mass at singularity. Of course, after such an event, chaos and destruction are meant to follow. In the aftermath, the two would merge into an even larger black hole, combining their masses into one. Such heart-pounding event, as one can imagine, significantly affects the flexible structure of spacetime by sending powerful ripples across the spacetime at the speed of light, like a stone thrown into a pond would cause on the surface of water, but only with an unimaginable magnitude.

Such is the origin of gravitational waves. Other events that could potentially produce such waves would be neutron star collisions, supernova explosions, and even The Big Bang.

The discovery of gravitational waves

On September 14, 2015, LIGO (Laser Interferometer Gravitational-wave Observatory) succeeded in discovering gravitational waves with Rainer Weiss , Kip Thorne , and Barry Barish being the lead scientists discovered the first evidence of gravitational waves.

The team behind this discovery, engineered an experiment where they fired a laser beam, and by using a beam splitter, the laser beam was split into two perpendicular beams. Each of these laser beams travelled a distance of four kilometres in a vacuum tube in two separate arms (as you can see in the photo) at right angle to each other. The beams are then reflected back and forth by mirrors multiple times, increasing the path length to hundreds of kilometres. In the end, the beams meet again at the beam splitter and interfere with each other, forming an interference pattern.

Usually, this interference pattern would cancel out due to destructive interference, but in case of gravitational waves, the path length of these split beams would have been affected, leading to a change in interference pattern when the beams combine. LIGO was able to detect this change and hence succeeded in discovering the first evidence of gravitational waves.

For this groundbreaking discovery the lead physicists ended up winning the 2017 Nobel Prize in physics, the highest honour of appreciation to the collaboration of over a thousand scientists from twenty different countries, making this experiment one of the largest physics collaborations ever. Thank you for reading this article, I appreciate it. Please share your views in the comments.