X-Message-Number: 13306
From: "john grigg" <>
Subject: putting Humpty Dumpty back together again......
Date: Fri, 25 Feb 2000 18:22:41 PST

On these two posts from the Extropian list, Billy Brown and Hal Finney 
discuss seeming information loss and whether it can be reversed.


Date: Tue, 22 Feb 2000 13:55:10 -0600From: "Billy Brown" 
<>
Subject: RE: Why  wrote:
>I think the problem with the cryptographic analogy is that cryptographic
>transformations are, by design, reversible.  All the information in
>the plaintext is intentionally preserved, in scrambled form, in the
>ciphertext.
Actually, that isn't true.  There have been lots of systems that essentially 
sucked information out of the message and embedded it in the decryption. 
algorithm.  The situation with cryonics seems analogous - most of the 
information that is "destroyed" by chemical reactions can be codified in a 
form that lets you add it back in, provided you can recognize which reaction 
you are dealing with.
>However, chemical reactions are biased in the direction of increasing
>entropy.  The body's metabolic reactions have to constantly fight
>this trend in order to maintain order.  Once there is injury or death,
>the forces of entropy will come into play.  Increase of entropy means
>loss of information.  So I think it is likely that most injuries,
>including trauma, ischemic and freezing injury, will involve some loss
>of information.
The fact that chemical reactions tend to increase entropy in the long run 
does not necessarily imply that they destroy information in this sense.  If 
you know what the reaction is, and you know what the reactants and the end 
products look like, you can just look at the end result and say "oh, this is 
decay reaction X, so this protein must have stated out like so..."  Doing 
the same thing when you have lots of different reactions going on is more 
complicated, but that just increases the computational requirements.  As 
long as the end state is uniquely determined by the initial state and the 
know history of the system, you can in principle compute the initial state.
Billy Brown


Date: Tue, 22 Feb 2000 13:24:25 -0800From: 
Subject: RE: Why CryonicsBilly Brown, <>, writes:
>The fact that chemical reactions tend to increase entropy in the long run
>does not necessarily imply that they destroy information in this sense.  If
>you know what the reaction is, and you know what the reactants and the end
>products look like, you can just look at the end result and say "oh, this 
>is
>decay reaction X, so this protein must have stated out like so..."  Doing
>the same thing when you have lots of different reactions going on is more
>complicated, but that just increases the computational requirements.  As
>long as the end state is uniquely determined by the initial state and the
>know history of the system, you can in principle compute the initial state.
Sure, in principle, but then you are back to Eugene's super-gods who can 
reconstruct everyone from atmospheric molecule motions.  Once information 
has degraded into heat, there is no practical technology which is going to 
be able to re-create that information.  And such degradation is exactly what 
happens in chemical reactions that increase entropy.

Distinguishable states transform into indistinguishable states.  Macro scale 
information (at least at the molecular and structural level) changes into 
micro scale information (meaning heat). If you grant the impossibility of a 
technology which can analyze random molecular thermal motion and "play it 
back" to recreate the entire past in microscopic detail, then you must 
accept that an increase in entropy is a loss of information.  From the final 
state there are multiple initial states which could have produced it, and 
the only way to distinguish them is in the micro-information of the thermal 
motions.  Put another way, from decay products alone you cannot construct a 
unique set of initial compounds which would have decayed to form these 
results, in general.

I maintain that given our current state of knowledge, we simply don't
know whether there is sufficient information in frozen tissue to
reconstruct its initial state to any particular degree of precision.Hal



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