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Blackhole Evolution....

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Posted by Mark on August 21, 2001 18:46:01 UTC

There is a classical law of blackhole evolution, according to general relativity, that the surface area of a blackhole may only increase with time and never decrease. This is due to the fact that infalling matter will cause the event horizon to expand outward and in order for the event horizon to contract, matter must escape to the outside universe; (such an act would violate many principles of realtvity and a few laws of physics). There is no limit to the amount of matter that can fall in. So it's safe to say that since nothing escapes from a blackhole, they'll only get bigger over time.....or is it...??

There is a loop-hole to this scenario and once again quantum physics breaks the rules of classicle physics. It was conjectured and later proved by Hawking and a few of his collegues that blackholes could radiate energy. This process is now known as the Hawking Radiation Effect. To explain the process simply (VERY simply): particle/anti-particle pairs can "burp" up into existance and annihiliate quick enough that it wouldn't be considerred a violation of the law conservation of energy. The main mechanism responsible for this exotic phenomenon is the Heisenberg Uncertainty Principle. Well should this happen close enough to the event horizon of a blackhole, the anti-particle can be captured while the particle escapes. Negative energy is imparted the blackhole while positive energy rockets the particle outward in the form of radiation. The net effect is a reduction in blackhole size due to the captured negative energy. The process happens quickly for quantum sized blackholes but is rather negligable for blackholes the size of a few solar masses or more. It could take upwards of 10^60 years for a blackhole of that size to completely evaporate.

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