Imagine you are floating on a raft at sea on a calm summers day. There is no wind

and (for the moment), the sea is flat and motionless, no waves, no turbulence, just

flatness as far as the eye can see. This is what spacetime, the fabric of the universe

that  links our three physical dimensions as well as time itself, looks like. Well I’m

simplifying a  little here. This is what space time looks like for the vacuum. You

may  have  heard that planets  and stars ”bend” or ”warp” spacetime. What is

happening  here is akin to how  on you in your raft are  causing a (all be it slight)

displacement  of the water beneath you. Your raft in  order to float has sunk

down  a little into the  sea, bending and warping the water’s surface!


Now just as you are enjoying your day along comes someone to mess it all up.

You hear an obnoxiously loud whirring of an engine, as speed boat enters the bay.

This is speed boat is captained by its new and untrained owner, who has taken

to riding the boat around in circles just about a kilometre away from you. After a

short period of time you begin to notice that your raft is beginning to rock back

and forth. Much to your annoyance small waves from the speed boat’s antics

have rippled across the water and are shattering the tranquillity of what was a

wonderful day. These waves that occur due to the motion of large objects are also

seen in the fabric of spacetime! These are, as you may have guessed from the

title, Gravitational waves!

Gravitational waves were predicted as far back as 1916, by the  well known

Albert Einstein, using his newly developed theory of general relativity. But

it wasn’t  until almost 100 years later in 2015, that gravitational waves were

detected  in the Laser Interferometer Gravitational-Wave Observatory (LIGO).

 LIGO detected waves, which are theorised to be produced from the collision

 of two black holes. This detection is done by sending light beams down two

 perpendicular long tunnels and measuring the length change of the tunnels,

 by  detecting any changes in the time it takes for the light to travel down the

tunnel and back.


Gravitational waves are slightly different to the waves on water that we were

describing in our analogy. First of all the surface of water is a 2D surface where

as we  live in 3D! The water waves also only have one way to oscillate, that is

they can  move up and down. However gravitational waves have two possible

directions  of oscillation.  If a gravitational wave was to pass through your body,

it  could warp space so that you get taller, or it could warp space so that you get


As researchers continue to refine their techniques for detecting and

interpreting  gravitational waves, we can expect to unlock even more secrets

about the  nature of spacetime  and the universe at large. It’s a thrilling journey

that promises to revolutionise our understanding of the cosmos and inspire awe

and wonder for generations to come.

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