Thread by @nellaiseemai

What are gravitational waves?
#Einstein predicted in 1916.
It took almost a century to realize that.
He was "way ahead of his time".
When a gravitational wave passes through objects will elongate and shrink alternatively.

#Gravity #GravitationalWave 1/n

But #GravitationalWaves are tiny so does the elongation and shrinking.

So scientists build an "L" shaped tunnel and sending laser from the middle point to both the edges and back continuously.

The length of the L shaped tunnel is 2.5 miles each side.

#gravity 2/n

The idea is when #gravitationalwaves pass through the L shape tunnel, one side will shrink and the other side will elongate bcoz they are diagonally opposite to each other.

The instrument is so sensitive that it can measure a change in length as small as 1/1000 of a proton. 3/n

Now we have to keep watching the reading and observe any change in length of the L shaped tunnel.

It needs a massive body to move in a short time to generate measurable #gravitationalwaves.

Without knowing us, two black bodies of twin stars were doing at farther distance. 4/n

Multiple #LIGO facilities (L shaped tunnels) built world over. 2 in the USA, 2 in Europe and 2 in Asia. Thus if change in the reading happens at the same time in all the facilities confirm the #gravitationalwaves passing and scientists are able to locate from where it is coming.

First such #gravitationalwaves detection was observed in 2015 from two massive colliding #blackholes which are 1.3 billion light years away. This means, the collision happened 1.3 billion years before and we are "seeing" it now.
#gravity 5/n