White Hole: A wonder

Now-a-days we all are familiar with the term "black hole". We all know that a black hole is an extremely dense object from which nothing can escape, not even light. What if I tell you that there could be some object where nothing can enter! Won't you be surprised? May be a little bit confused as well. It is, however, not impossible for such object to be in existence in our Universe. At least theoretically we can predict the existence of such object, called "white hole". A Russian theoretical astrophysicist and cosmologist named Igor Dimitriyevich Novikov put forward the possibility of the existence of white holes in 1964. White holes are predicted as part of a solution to the Einstein field equations known as the maximally extended version of the Schwarzschild metric describing an eternal black hole with no charge and no rotation.

 

This visualization shows a jet blasting from a black hole near the speed of light. In theory, a white hole looks similar to a black hole, but instead of sucking matter in, a white hole pushes matter away. (Image credit: NASA/JPL-Caltech)

White holes have mass, charge and angular momentum, similar to the black holes. They also attract matter like any other mass, but anything falling towards the white hole would never reach beyond event horizon of the white hole. It seems that space-time is extending outward from the white hole with the speed of light, se anything falling towards the white hole must have a speed more than that of light in order to enter into the event horizon of the white hole. A good analogy is tap water, water falling from the tap moves away from the place of fall with a high speed compared to other portion of water. Anything must have more speed to reach the place of fall. If the speed of the moving water from the place of fall is the speed of light then nothing can enter into the place of fall. That's a white hole.

All of this is still a prediction. If we think in terms of quantum mechanics, the black hole emits Hawking radiation and so it can come to thermal equilibrium. Stephen Hawking argued that the time reversal of a black hole in thermal equilibrium results in a white hole in thermal equilibrium. Consequently this may imply that black holes and white holes are the same structure wherein the Hawking radiation from an ordinary black hole is identified with a white hole's emission of energy and matter!

A paper published in 2012 argues that big bang itself is a white hole. It further suggests that the emergence of a white hole, which was named a 'Small Bang' is spontaneous - all the matter is ejected at a single pulse. Thus, unlike black holes, white holes cannot be continuously observed; rather, their effects can be detected only around the event itself.

Let's hope for a paper which will clarify the fact to us and dispel all our confusion.

Courtesy: Wikipedia.