Black Hole

A black hole is a region of space from which nothing, not even light, can escape.  It is called "black" because it absorbs all the light that hits the horizon, reflecting nothing, just like a perfect black body in thermodynamics.Black holes of stellar mass are expected to form when heavy stars collapse in a supernova at the end of their life cycle. After a black hole has formed it can continue to grow by absorbing mass from its surroundings. By absorbing other stars and merging with other black holes, super massive black holes of millions of solar masses may be formed. Quantum mechanics predicts that black holes emit radiation like a black body with a finite temperature. This temperature is inversely proportional to the mass of the black hole, making it difficult to observe this radiation for black holes of stellar mass or greater.

Despite its invisible interior, the presence of a black hole can be inferred through its interaction with other matter. Astronomers have identified numerous stellar black hole candidates in binary systems, by studying their interaction with their companion stars. There is growing consensus that supermassive black holes exist in the centers of most galaxies. In particular, there is strong evidence of a black hole of more than 4 million solar masses at the center of our Milky Way.
The theory of general relativity predicts that a sufficiently compact mass will deform space time to form a black hole. Around a black hole there is a mathematically defined surface called an event horizon that marks the point of no return.
Time travel: Scientists predict that if anything is able to just escape form the event horizon, then that thing will not be sucked into a black hole. Time travelling that has been thought of from long times, is said to be possible for a person who has escaped the event horizon. A body of huge amount of mass in it is said to slow time because of its own gravitation. So for a person in the gravitational field of the black hole, the time will run slower. So he might as well make time travel possible because he'd reach the past. This has only been though of and not proved in reality.


A body of huge mass