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From: sharp@noao.UUCP (Nigel Sharp)
Newsgroups: net.physics
Subject: Re: Re: "big bang" a big bust?
Message-ID: <444@aquila.noao.UUCP>
Date: Wed, 5-Dec-84 12:01:39 EST
Article-I.D.: aquila.444
Posted: Wed Dec  5 12:01:39 1984
Date-Received: Sun, 9-Dec-84 03:26:32 EST
References: <127@sdcc12.UUCP> <17266@lanl.ARPA>
Organization: Natl. Optical Astronomy Observatories, Tucson, AZ USA
Lines: 37

> Information does NOT escape from a black hole.
 Correct.  The information was always there, locally.  As the state of the
object changes towards being a black hole, changes in the locally obtained
information about that state propagate outwards at the speed of light.
(Incidentally, the available parameters are mass, angular momentum, charge
and [mathematically acceptable] magnetic monopole moment.)

> Note also that light DOES escape from a black hole.  A black hole radiates
> like a blackbody whose temperature .....
NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO
This is precisely the sort of remark which confuses people.  The quantum
mechanical effect by which a black hole radiates energy as a black body,
and therefore loses mass, eventually disappearing in a puff whose properties
noone has adequately calculated, is NOT THE ESCAPE OF LIGHT FROM THE HOLE.
Using the word `escape' implies that something inside gets to the outside,
whereas what is happening is very difficult to explain - energy transfer
is happening by the addition of energy to external states and the removal
of energy from internal states - in fact, the addition of negative energy
states.  I'm not explaining this very well: I have still to come up with
an adequate way.  The mathematics seems to make sense, and the radiated
spectrum is black body, but there is no possibility of anything moving
from the inside to the outside.  The black body nature is a reflection
of the destruction of information.

> ................ but no information
> about the internal structure of the black hole (if any) is carried by this
> radiation.

The original poster (post-person ? post-being ?  :-) ) probably knows what
he's talking about, and this is correct, but I have been trying for some time
to persuade people to be very careful about their language when explaining
any of a black hole's effects.  It is difficult to translate mathematics,
and we have more trouble explaining why, when x said y, he really didn't mean
it, than we do explaining the phenomena.  (`But Carl said ....'  `Yes, but
what he meant was ...'  `Then why did he say ...'   Sigh.)
-- 
	Nigel Sharp   [noao!sharp  National Optical Astronomy Observatories]