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Re: Blackholes And Absolute Zero

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Posted by Tom Bernard/">Tom Bernard on July 7, 1997 18:45:06 UTC

: : Is a blackhole at absolute zero??? : Well, black holes definetely do exist. Considering that they : suck many a star inside, as well as anything else in its : destructive forcefield. I think that they could possibly be a : time machine almost. Back in time most likely, considering : I belive that there is no such thing as fate. : They might just be an absolute zero, Where time : stands still.

I think the original question was more in reference to the temperature of the black hole, not whether or not time stands still. The question is, if nothing, not even radiation can escape from a black hole, could it's temeperature be considered absolute zero. Well, as Hawking points out, black holes actually do emit some radiation. The following is an excerpt from a simmilar question on the "How Things Work Homepage" I hope it is of some help.

To begin with, matter always emits radiation. That's because, at any temperature above absolute zero, the electrically charge particles in matter are in thermal motion and they accelerate frequently. Any time an electrically charged particle accelerates, it emits electromagnetic radiation. If you could cool matter to absolute zero, the thermal motion would vanish and the matter wouldn't emit radiation. However, absolute zero is an unreachable destination--it can't be achieved--so everything experiences thermal motion and emits radiation.

The issue of radiation emitted by a black hole is another story. For decades, people thought of a black hole as perfectly black--it absorbed radiation perfectly but emitted none itself. However, Stephen Hawking showed that a black hole does emit radiation and that it behaves like a normal black-body: an object that emits thermal radiation characteristic of its temperature. The temperature of a black hole is inversely proportional to its mass. For black holes of any reasonable size, this temperature is so extraordinarily low that the black hole emits very little Hawking radiation.

This radiation originates in the vicinity of the event horizon, the surface inside which the black hole's gravity finally becomes strong enough to prevent even light from escaping. At that surface, quantum fluctuations in which particles are temporarily created and destroyed can occasionally lead to the creation of a particle that escapes the black hole forever. In effect, two particles are created simultaneously, one of which falls into the black hole and is lost and the other of which escapes forever. The particle that falls into the black hole actually decreases the mass of the black hole, and the missing mass escapes with the other particle. As for whether the black hole causes this emission or is actually doing the emission, there is no difference. The only feature that the black hole has (other than electric charge and angular momentum) is its event horizon (actually a characteristic of its mass). If the event horizon is causing the particles to be created, then the black hole itself is at work creating those particles.

Tom "absolut zero" Bernard

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