Re: [asa] another physics question-information

From: Randy Isaac <>
Date: Tue Oct 30 2007 - 18:27:55 EDT

    As is often the case, this topic gets a little clearer if we define some
terms and concepts. The term "information" is used in many different ways.
We usually think of loss of information as the inability to ascertain the
meaning of an intended communication. If static drowns out a telephone
conversation, we think we lost the information. But the concept of
conservation of information doesn't work quite that way. Information may get
scrambled and unintelligible but it isn't lost. It's just converted into a
form which we can't decipher. The concern that Hawking had over the years
was the absolute loss of information, not just the scrambling that makes it
hard to decode. That debate isn't over yet and for those of you interested
in this topic, here are a couple of articles with a little more clarity.

   Note also that in this context "information" is not the communication of
a sentient being. Rather, entropy is the measurement of the information
content. The two types of information are not necessarily totally
independent of each other but the concepts are quite different.

    Relating this to DNA, there simply is no way that the conservation of
information principle has anything to do with constraining the possible
changes of DNA code. For one thing, energy is expended in the process of
cell replication so it doesn't violate the second law of thermodynamics,
which is essentially the same thing in this context. The entropy or
information content of cellular DNA can increase or decrease without any
violation of a conservation law.


----- Original Message -----
From: "David Campbell" <>
To: <>
Sent: Tuesday, October 30, 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 18:28:45 2007

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