What is a Black Hole?

Generally, stars glow because of the nuclear fusion (process in which two lighter nuclei from one heavy nucleus) processes which convert its Hydrogen(atmospheric gas) into Helium. This nuclear process which later creates thermal pressure will support the star from collapsing itself due to the star's massive gravity.

When time passes, the star will eventually exhaust its nuclear fuel which no more creates an explosion that later create thermal pressure to maintain gravity. In this case, the star will become a dwarf star(little star) when its gravity is less and cant contract more. But, when the gravity is more, the star will collapse into itself and form an infinite density at a single point called a singularity. This singularity marks the end of time itself there. Now, this type of behavior by a star is called a Black Hole. 

In easier words, it is a uniform spherical star which contracts itself to one point.


Detecting a black hole is very hard because even light can't escape the massive gravitational field of it. The black hole is so mysterious that all our known physics laws fail inside the black hole. It straight disproves Einstein's General Relativity on Space-Time. It consists of an edge at the start and once something slips down the edge, technically Event Horizon, you cannot come back and are pulled into the black hole. Now, this event horizon is the place where you decide to go into a black hole or not. Once the decision is made, you never coming back again. One can only observe something sucked into a black hole upto event horizon and then the object will just disappear due to no light beyond that region. This event horizon acts like a boundary where something enters, it will be pulled into the black hole.

And once you're over the edge and keep getting nearer to the singularity, the higher will be the gravitational pull. Imagine you slide through event horizon by your legs first and hear next, the gravitational pull will be more on your legs than your head. This causes your legs to detach from your body and body from the head and this continues. This only happens when the mass(gravity) of the star is smaller. In the case of a bigger star, it won't have that big influence of gravity on your tiny body. If you ever want to go inside a black hole then choose a big one. I heard the one in the center of the milky way galaxy is bigger, go give it try.

Some unproven theories say that a black hole can be an entrance to other universe or at least another side of our universe. Some also believe including Stephen Hawking that a small black hole about a mountain size can give away x-rays and gamma rays at a rate of 10 million MegaWatts which will be enough to power the Earth's whole electricity. Some other theories say that inside black hole other dimensions of space can be unlocked like in  Interstellar movie.