Re: [FT] sensors

On 3 Dec 2004 at 19:44, Samuel Penn wrote:
> On Friday 03 December 2004 18:09, Thomas Westbrook wrote:
> > I thought that it is the generally accepted theory that nothing,
> > including light in all is forms, could escape the grasp of the black
> > hole if it was past the event horizion (though I haven't kept up on
> > most of the new theories).	It would seem that any matter being
> > "eaten" by the black hole, would not have any detectable radiation,
> > except that on the "normal" side of the event horizion.
> 
> Look up Hawking radiation.

The shortish version is that space continually creates particle/anti-
particle pairs via quantum fluctuations. Normally these pairs 
anihilate each other in a very short period of time. Energy is 
conserved as the energy liberated when the anihilated equals the 
energy used to create them.

However, at the very edge of the event horizon one half of the pair 
may get pulled into the black hole whilst the other half escapes. 
Hence the black hole will seemingly emit the escaping halves.

In order to conserve mass, energy, momentum, and most importantly the 
entropy of ths system the black hole must effectively lose mass in 
order to compensate for this effect.

Look, Hawkings came up with this, I did a degree in physics and I 
just about understand the very simple version....

> Basically, black holes evaporate given
> enough time. A *lot* of time is needed, but micro black holes formed
> at the time of the big bang have had long enough to evaporate by now.
> No idea how big a 'micro' black hole is however.

One of the key points is that smaller black holes lose mass via this 
method faster than big black holes. So if you're a small black hole 
you get stuck in a vicious circle and end up going 'poof'.

	Steve
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Steve Pugh   <steve@pugh.net>	<http://steve.pugh.net/>