## Black Holes are not so Black (Part 3) – Gravitational Waves

The existence of Gravitational Waves have been confirmed. But you probably have heard that. In this post, we will break down this profound discovery into comprehend-able chunks.

This is going to be a amazing journey. Ready ?

## Redefining Gravity

When we usually talk of Gravitation we are bound to think like Newton,
where objects are assumed to exerting a force upon each other.

Like
imaginary arrows of force in space. But this picture, although good for
high school crumbled, with the advent of Einstein’s theory of
Relativity.

## What is the Space-Time Fabric?

Think of space-time fabric as
an actual cloth of fabric. ( An analogy )

When you place an object on the fabric, the
cloth curves. This is exactly what happens in the solar system as well.

The
sun with such a huge mass bends the space-time fabric. And the earth
and all the planets are kept in orbit by following this curvature that
has been made by the sun.

Attributing to the various masses of objects, the way they bend this fabric also varies.

## What are Gravitational Waves?

If you drop an object in a medium such as water, they produce ripples that propagate as waves through the medium.

Similarly, Gravitational waves are ripples in space-time fabric produced when you drag heavy objects through space time.

And the nature of these waves is that they don’t require a medium to propagate.

## How do you make one?

Everything with mass/energy can create these waves.

Source

Two persons dancing around each other in space too can create gravitational waves. But the waves would be extremely faint.

You need something big and massive accelerating through space-time in order to even detect them.

And orbiting binary stars/black holes are valuable in this retrospect.

## How can you detect them?

Let’s turn to the problem to detecting them assuming you do find binary stars/black-holes in the wondrous space to suite your needs.

Well, for starters you cannot use rocks/ rulers to measure them because as the space expands and contracts, so do the rocks. ( the distances will remain same in both the cases )

Here’s where the high school fact that the speed of Light is a constant no matter what plays an important and pivotal role.

If the space expands, the time taken for light to reach from A to B would be longer. And if it contracts, the time taken for it to reach from A to B would be smaller.

PC: PHDComics

By allowing the light waves from the contraction and expansion to interfere with each other, such as done in any interferometry experiment we can detect the expansion or contraction. Voila!

And this is exactly what they did! ( on a macroscopic level ) at LIGO (Laser Interferometer Gravitational-Wave Observatory)

## 14 September 2015

Two Black Holes with masses of 29 and 36 solar masses merged together some 1.3 Billion light years away.

Two Black Holes colliding is the header animation of the ‘Black Holes are not so Black Series’, in case if you haven’t noticed.

The merger of these two black holes results in the emission of energy equivalent to 3 solar masses as Gravitational Waves.

This signal was seen by both LIGO detectors, in Livingston and Hanford,
with a time difference of 7 milliseconds.

And with the measurement of this time difference, physicists have pronounced the existence of Gravitational Waves.

Source

All this is most certainly easily said than done and requires meticulous and extensive research, not to mention highly sensitive instruments.

Had they not have measured this time difference,
we might have had to wait for the merger for more massive black holes
to collide and maybe even build more sensitive instruments to detect these waves.

## And Einstein predicted this a 100 years back!

Mind Blown!

Note: Hope you are able to understand and appreciate the profundity of the discovery done by mankind.

** All animations used here are merely for Educational purposes. If you have any issues, please write to us at : 153armstrong@gmail.com

## Why is this discovery a Big Deal ?

Gravitational waves gives
us another way to observe celestial phenomenon. These waves also form
when supernovae explode, when black holes collide and during many other
space activities.

Detecting them might give us a new
perspective into the cosmic events. There is hell of a lot of space that
is left unexplored or lies beyond human exuberance and this discovery
might shed some light on it. ( like the big bang per se )

The ultimate goal is to
understand the fundamental laws of the universe. It is a quest through
the oblivion towards a theory of everything.

Although it is
unknown how many years/decades it might take to get us there, but these discoveries
are markers to getting there.

## What is this Image that i see everywhere?

This is not the photograph of the actual event but a simulation run by NASA of two black holes merging.

A2A: Anonymous

## How does the actual experimental setup look like ?

The actual experimental setup is a bit complex in its entirety. But the guardian has an elegant image that seems to cover its essence:

A2A: Anonymous

Have a great day!

## Nobel Prize in Physics 2017

The Nobel Prize
in Physics 2017 was divided, one half awarded to Rainer Weiss, the other
half jointly to Barry C. Barish and Kip S. Thorne “for decisive contributions to the LIGO detector and the observation of gravitational waves”.