WHITE HOLES

White holes, which are theoretically the exact opposite of black holes, could constitute a major portion of the mysterious dark matter that's thought to make up most of the matter in the universe. And some of these bizzare white holes may even predate the Big Bang. A black hole is one prediction of Einstein's theory of general relativity. Another is known as a a white hole, which is like a black hole in reverse. Whereas nothing can escape from a black holes event horizon, nothing can enter a white holes horizon. It has been suggested that matter and energy falling into a black hole could possibly emerge from a white hole either somewhere else in the cosmos or in another universe entirely. It could also be that when black holes die they could become white holes. Once a black hole evaporated to a degree where it could not shrink any further because space-time could not be squeezed into anything smaller, the dying black hole when then rebound to form a white hole. It has been estimated that it would take a black hole with a mass equal to that of the Sun about a quadrillion times the current age of the universe to convert into a white hole. Even white holes with microscopic diameters could still be quite massive, just as black holes smaller than a grain of sand can weigh more than the moon. Future research will explore how white holes from a previous universe might help to explain why time flows only forward in this current universe and not also in reverse.