BLACK HOLES!

A thread about the most fascinating and the most mysterious objects in the Universe! We will encounter their history, origin, how do they work and what happens if you fall into one?! Stay with me, I promise it will be amazing and a little bit scary!

Okay, a quick note on escape velocity first: it's the minimum velocity of an object required to escape the Gravitational pull of massive body. For the earth the escape velocity is about 11 km/s, get something moving that quickly and it's gone! It will never fall back down!

The sun which has a much stronger gravity than earth, it has an escape velocity of over 600 km/s!! That means you need to project something at this speed to escape sun's Gravitational pull!
The escape velocity of a neutron star is about half the speed of light!!!!!

Now in the 1700's John Mitchell asked himself a curious question: what would happen if you made a star so big and massive that the escape velocity at it's surface would be bigger than the speed of light? Light could not get away from those stars! He called them 'DARK STARS'

After that, this idea was forgotten, it was just a hypothesis after all. Okay, fast forward to 1915! This year Albert Einstein published his General Theory of relativity (I know it deserves it's own thread) the most groundbreaking discovery of the last century! What does it say?

Basically, General relativity says that any presence of mass/energy will warp & curve the fabric of space!(spacetime to be precise) like a bowling ball warping/bending the fabric of a trampoline! The massive the object is the more space it will curve around it! THIS IS GRAVITY!!

Soon after when Einstein published this astounding theory of gravity, An Astronomer Karl Schwarzschild solved the equations of relativity and he found something really really really weird! He saw that if you crush down a massive body like a star to a very small size.....

......Einstein's math will predict that the curvature of space around that body will be so strong and severe that LITERALLY NOTHING CAN ESCAPE, NOT EVEN LIGHT! this is like Mitchell's dark stars right? Oh my gosh, he was on to something

Now Astrophysicists began to take these weird objects seriously, but HOW IN THE WORLD WOULD ONE OF THESE OBJECTS FORM? People began to think about this in the 30's, 40's and 50's and finally they arrived at the most spectacular & Interesting answer!

Imagine a Star, not just any star but a star much more massive than our own sun, stars are formed when a giant molecular cloud starts to collapse under it's own weight as shown in this gif! Nuclear fusion lights up the star, it releases heat and pumps up the star

Stars are in a constant struggle between Gravity of their own weight trying to collapse them & their internal heat(due to nuclear fusion in their cores) trying to inflate them! But not for long, once the star has ended up all of it's fuel you don't have to be near it!

As the nuclear fusion in it's core stops! The star begins to collapse under its own weight due to gravity! WHAT FORCE CAN POSSIBLY STOP IT NOW? it turns out that none, there's no force in the Universe that can stop a star collapsing!!! The core of the star is about to go bye bye

As it collapses down, the size of the star starts to shrink it keeps getting smaller and smaller! AND EVENTUALLY IT EXPLODES! IT GOES BOOM IN AN INSANT! THIS EVENT IS CALLED THE SUPERNOVA! THIS IS HOW STARS DIE!!! This star collapses down to a single point of INFINITE DENSITY

So, Now what's left behind? A GIGANTIC BLACK HOLE, YES THIS IS HOW THESE MONSTERS ARE BORN! A black hole is the ultimate end state of a very high mass Star! Black holes are like dead stars, corpses of a dead star, there are about 100 million black holes in our own galaxy alone!

The blackish boundary you see is known as the Event horizon of a black hole, that is the point of no return, once you are in, you literally cannot come out, it becomes impossible for you to come and tell what happens inside!

These monsters come in different sizes:
1. Stellar black holes, these are the tiny ones, only 10x bigger than our sun.
2. Intermediate black holes, the average ones, about 1000x times bigger than our sun
3. Supermassive black holes! These are the biggest, a billion times.....

... heavier than our sun. Black holes mess up with our ideas of Space & time! As I mentioned they bend the fabric of spacetime so severely that at their centre all the known laws of physics break down! They don't work, Not even Quantum theory, not even General Relativity! Nothing

These monsters also allow for time travel! Yes I'm not kidding, this is withing the framework of Astrophysics, because they are so massive they bend 'time' too!! Omg this is crazy but yes it's true, here's how it goes:

Suppose you wanna see how earth will look like a million years from now, you go into your spaceship, hang around the vicinity of a black hole for like a few days & when u'll come back, u'll see that thousands of years have passed on earth but you are the same age! How??

This is because around the vicinity of a black hole 'time' slows down! As you go near & near to it, time will tick more slowly for you as compared to people on earth! At the centre, time essentially STOPS! This is how you can leap frog into the future!

Okay, we have come so far but there's one last thing, what would happen if you fall into one? It's scary so stay with me let's take a feet first dive into one, as you fall in you will feel a little bit strechy initially

Yea it feels good in the morning when we strech, but near a black hole THIS STRETCHING WONT STOP, the force of gravity on your feet will be thousands of times stronger than at your head, your feet will fall faster than your head! You'll be pulled like a long noodle, like a taffy.

the force of gravity will be so strong that it will exceed the intermolecular forces that hold your flesh together! And YOU WILL SNAP INTO 2 PIECES (at the base of your spine) and THEN THOSE 2 PIECES WILL SNAP INTO 4, SO YOU GO FROM 2 TO 4,8,16,32.......

You'll become this stream of particles/atoms decending down into this giant cosmic monster never to be heard of again! This is how a black hole will eat you? And we have a name for this, it is known as 'spaghettification'! Phew that was damn scary asf xD

Finally here's the ACTUAL IMAGE of a black hole captured by the Event horizon telescope, it is 6 billion times heavier than our sun & 55 million light years away, you see that disk around it, we call it the accretion disk, it was probably eating up a massive star!

It is hard to express how utterly remarkable and astoundingly delightful it is for our mathematical scribblings to predict something as bizarre as black holes and then, looking to the skies with sufficient diligence, we find them.

There's still a lot we don't know about these monsters, but that's all for thr next time, I hope you guys will enjoy it! Stay Curious, thank you

The* typo

Hey @starstrickenSF would you like to read this?