Black Holes have always been a mysterious object to space community for its unique characteristics and also draw interests among common people also. The advent of Einstein’s theory of relativity gave a new thrust to the study of black holes. A black Hole is a region of space-time whose gravitational force is massive that sucks everything inside it and nothing can escape including light. This is due to the gravitational potential energy of the collapsed star that equals to the kinetic energy  possessed by light. So if light cannot escape from this region anything and everything is dragged back by the gravitational field as nothing can move faster than the speed of light. When a black hole is formed, the core of a star collapses where even the atomic nuclei are squeezed together and the whole mass of the star collapse to a single point having infinite density. Surrounding the black hole is a mathematically defined surface where the escape velocity from the hole just equals the speed of light and that marks the point of no return known as the Event Horizon or surface of a black hole. 

During the death of a massive star, its matter becomes compressed to enormous densities and the strength of gravity at the surface of this rapidly shrinking sphere also increases. The distortion of space and time around the star increases gradually and finally escape velocity from the dying star’s surface equals the speed of light which makes the star invisible. At this stage, space becomes so severely curved that a hole is punched in the fabric of the Universe. The dying star disappears into this cavity leaving behind a black hole and this cavity is known as Singularity. The entire mass of the star is crushed to infinite density at this point at the center of the black hole.

The multi-universe concept arise due to some physicists, who over the years have explored the properties of the black hole’s core using Einstein’s equation, revealing the wild possibility that it might be a gateway to another universe which tenuously attaches to ours only at a Black Hole’s center. We can say it in this manner that, where time in our universe comes to an end, time in the attached universe just begins. The interior of the Black Holes are deeply mysterious places, forever beyond our view, where the accepted laws of physics provide no guide. One idea is that the shrinking interior of a black hole shrinks only that much before it rebounds as another universe with slightly different laws of physics. Not in our universe, mind it, because it is a law of black holes that nothing that is inside can ever get out again, but somewhere else. Black Holes give birth to baby universes that are geared up to produce the most black holes will spawn the most offspring universes. It develops the idea of the multi universe and all other theoretical speculations relating to black holes.

White holes are a solution of valid mathematical calculations but it doesn’t mean that they actually exist in nature. Here again come the equations of general relativity which have an interesting property that, they are symmetric in time. That means we can take any solution to the equations and imagine that time flows backward rather than forward and we will get another valid solution to the equations. If we apply this rule to the solution that describes black holes, we get an object known as White Holes. Since a black hole is a region of space from which nothing can escape, the time reversed version of a black hole is a region of space into which nothing can fall. In fact, just as a black hole can only suck things in, white holes can only spit things out. White Holes are a perfectly valid mathematical solution to the equations of general relativity. But we know infentisimal about our vast space and who can deny the fact that one day maybe we will be able to discover the actual existence of a white hole.