From: Anders Sandberg (asa@nada.kth.se)
Date: Tue May 27 2003 - 13:40:34 MDT
On Tue, May 27, 2003 at 10:47:30AM -0700, Party of Citizens wrote:
> Speaking of black holes, can anyone help me with this question. It seems
> to me the ed tv coverage on black holes is saying that black holes DO emit
> radiation. At the same time we are told that all mass-energy entering a
> black hole "disappears". How are these two notions reconciled?
Hwaking radiation (as it is called, it was Stephen Hawking's first claim
to fame) is due to quantum effects near the horizon, as Mike answered.
The original analysis of black holes was done using classical mechanics
(general relativity) and there they are utterly black. But the quantum
fuzziness of things change the predicted behavior in interesting ways.
There are multiple ways of viewing why the radiation occurs:
http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/011125b.html
http://casa.colorado.edu/~ajsh/hawk.html has some nice explanations
about its behavior.
http://library.thinkquest.org/C007571/english/advance/english.htm has
some very educational calculations.
Since large black holes have very little Hawking radiation and absorb
energy they would make nice cooling systems. Small ones on the other
hand would be (rather unstable) energy sources if fed matter at the
right rate.
-- ----------------------------------------------------------------------- Anders Sandberg Towards Ascension! asa@nada.kth.se http://www.nada.kth.se/~asa/ GCS/M/S/O d++ -p+ c++++ !l u+ e++ m++ s+/+ n--- h+/* f+ g+ w++ t+ r+ !y
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