What is White hole.

 A white hole is a hypothetical astronomical object that is the reverse of a black hole. While a black hole is known for its incredibly strong gravitational pull, a white hole is postulated to be an object that expels matter and energy, rather than absorbing them.

This is because a white hole would theoretically be the exit point of a black hole, where the matter and energy that was absorbed by the black hole would be released.

According to general relativity, a black hole is formed when a massive star collapses under its own gravitational force. This creates a region in space where gravity is so strong that nothing, not even light, can escape from it. On the other hand, a white hole is considered to be the "opposite" of a black hole in the sense that it emits matter and energy but not allow anything to enter.

In other words, while a black hole is a region of space-time from which matter and energy cannot escape, a white hole is a region of space-time where matter and energy cannot enter. It is believed that a white hole is the "exit" of a black hole, where matter and energy are expelled after entering a black hole.

White holes are not directly observed in nature, and there is currently no conclusive evidence for their existence. They are primarily explored as a theoretical concept derived from Einstein's field equations in general relativity. The equations suggest that while black holes have an event horizon beyond which nothing can escape, a white hole could have an event horizon from which nothing can enter. Instead, matter and energy would be expelled outwards.

White holes have been studied as an alternative to black holes as a way to explain the Big Bang Theory and the origin of the universe. While they are still a theoretical concept, the equations of general relativity suggest that they could exist, and that matter and energy could be expelled from them outward.

It is important to note that white holes remain highly speculative and have not been observed or confirmed through astronomical observations. They are primarily discussed in the context of theoretical physics and cosmology, serving as a thought experiment to explore the nature of space, time, and gravity.