Re: [asa] another physics question-information

From: <>
Date: Tue Oct 30 2007 - 17:48:03 EDT

He's talking about entropy.? There are many different states that matter can be in as it falls into a black hole, representing high entropy and high information.? However, if it truly fell all the way into the singularity in the black hole then it would all be going into exactly one state, since a singularity is a singularity is a singularity -- exactly one state.? Hence, the entropy of the universe (the number of available states) would be diminished as matter falls into black holes and the information describing which particular state the matter was in would have been destroyed.? Hawking discovered that the matter doesn't actually fall into a singularity.? Instead, it spreads out across the event horizon surrounding the black hole.? There are many ways that it could spread out across the event horizon -- many states -- and so the entropy is not diminished and information in the universe is not destroyed as matter falls into a black hole.? The information stays written acros
 s the face of the event horizon.

I don't know how he came to the idea that information is not destroyed.? His earlier view in cosmology was that the universe is symmetric in time, so that a Big Bang exists on each end of time.? Thus, after passing the half-way point of time, entropy would begin to diminish toward the Big Bang in the future.? It would be as if all matter is falling into a singularity and indeed all information would be slowly destroyed.? But this kind of reduction in information and in entropy makes no sense if all information flows only in the forward direction of time, since it would require a highly improbable sequence of unplanned events to make things become increasingly symmetric and ordered.??But if to the contrary the laws of physics are symmetric in time, so that information actually does flow both ways, then there is no reason why entropy cannot reduce in (what is to us) the forward time direction.? The only catch is that we cannot go to those locations to observe it happening, beca
 use our minds depend on increasing entropy to operate.? In fact, it is the direction of increasing entropy that defines forward time for us.? But somehow Hawking came to the conclusion that information flow in the most fundamental basis physics is not time symmetric and hence entropy can only increase with respect to the forward time direction in all regions of the universe, and information is therefore never diminished anywhere in the Universe, so that there is no Big Bang at the opposite end of time and similarly matter does not fall into a singularity at a black hole.


-----Original Message-----
From: David Campbell <>
Sent: Tue, 30 Oct 2007 12:12 pm
Subject: Re: [asa] another physics question-information

The question on space and distance brings to mind a question I had
about conservation of information. As popularly used in
antievolutionary arguments, the principle of conservation of
information is a fiction invented for the purpose of denying
evolution. Mutations do happen, and every new mutation (or even every
new combination of genes occurring through recombination, sexual
reproduction, etc.) produces novel information. However, I saw
mention that the principle of conservation of information had led
Hawkings to reconsider his thoughts on black holes. What does that
assert and how is it compatible with the observation that new
information is generated all the time? (E.g., the information that I
just sent a note to the ASA list today is new information.)

Dr. David Campbell
425 Scientific Collections
University of Alabama
"I think of my happy condition, surrounded by acres of clams"
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Received on Tue Oct 30 17:49:44 2007

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