The concept of black holes is best explained by the

The theory of special relativity

The theory of general relativity

Proposed by Albert Einstein, but the theory of special relativity was latter said to have weak points and was replaced by the theory of general relativity which dealt with the gravitational wave to explain the concept.

The major figure in understanding the black hole was Stephen Hawking.

What is a Black hole?

A black hole is a dense spherical object with size very less to mass. Due to high gravitational pull even light cannot escape a black hole (let G be the gravity r radius and k some constant and given relation G=k/r^{2 }, so if r decreases the gravitational pull increases).

Till date no one knows exactly how a black hole is from the inside, there are only guesses with 2 output

The inner effect: – which no one is sure of.

The outer effect: – which is a known set of events that leads to a certain conclusion (conclusions formed by comparing with what we see) and based on that the inner effects are proposed (i.e. might be possible activities that are going on inside a black hole).

An important term that comes up here at this point is the event horizon.

The event horizon is a bright region on the extreme edge of the black hole where the light is trapped.

A new concept that has come to the horizon is the string theory, Sting theory describes things about the black hole which cannot be explained by the theory of relativity. The string theory for the time only explains what happens in the event horizon and not what’s going inside the black hole.

New technology that is being discussed by the scientist to explore more about what is there inside the black hole is the gravitational waves.

For more knowledge and reference on the black hole, the most popular referrals are written by Kip Throns, Stephen Hawking.