White Holes



A black hole is a place where gravity works to its highest that even light can’t escape it. The gravity there is very strong as matter has been squeezed into a tiny space. This can happen when a star is dying. In general relativity, a white hole is a hypothetical region of space-time which cannot be entered from the outside but matter and light can escape from it. The property of a white hole is complete reverse of a black hole.

White holes appear in the theory of eternal black holes. In 2006 occurrence of a white holes remains inconclusive. Similar to black holes, white holes have properties like mass, but objects falling towards a white hole would never actually reach the white hole. In quantum mechanics, the black hole emits hawking radiation and so can come to thermal equilibrium with a gas of radiation. Because a thermal-equilibrium state is time-reversal-invariant, Stephen Hawking argued that the time reserve of a black hole in thermal equilibrium is again a black hole in . This may imply that the time reverse of a black holes and white holes are the same object. The Hawking radiation from an ordinary black hole is then identified with the white-hole emission. hawking’s semi-classical argument is reproduces in a quantum mechanical AdS/CFT treatment, where a black hole in anti-de sitter space is described by a thermal gas in a gauge theory, whose time reversal is the same as itself. Most black holes are formed when stars collapse in a supernova explosion. However, it has been suggested that black holes end their lives by transforming in to white holes which explosively pour out the information that had been swallowed by the black hole. According to this model, the transition of a black hole to white hole would occur right after the formation of the former. As a black hole is formed, it is shielded by its event horizon however at one point the star that is collapsing under its own gravity will reach a point beyond which it can’t shrink any further. At this moment, it experiences and outward pressure called a quantum balance which transforms a black hole into a white hole. If black holes turns into white holes and release all of their innards out again, it could provide the solution to the most troublesome question in thermodynamics. However white holes are highly hypothetical.

Approximately 137 billion years ago, the matter in the universe was compresses into a single, infinitesimally small point. This point then enlarged in heated explosion, and is still expanding today. There are great amount of evidences for this such as the galaxies moving away from us. However, an intriguing idea has been suggested by physicists revolving around the concept of white hole. It has been suggested that the white hole could be the reason behind the Big Bang- for it would explain how such a gigantic amount of energy and matter just spontaneously appeared.

By Saambavi Sivanraj

13E (2017)

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