X-Message-Number: 11748
From: 
Date: Fri, 14 May 1999 12:58:50 EDT
Subject: freezing and information loss

Eugene Leitl writes:

 >I was speaking about _irreversible information loss_ due to scrambling of
>the tissue. 

How do you know when it is irreversible?

>That there is severe information loss is obvious to any who
>cares to take a look at the EM photographs -- 

"Severe" is not the same as "irreversible."

>a lot of the structure has been
>altered in a non-backtrackable manner. 

How do you know? In any case, back-tracking trajectories of particles is not 
the only way of postdicting information. There are manifold and intricate 
relationships which can be used, partly analogous to a jig-saw puzzle.

>Lacking detailed three-dimensional 
>data it is difficult to define a metric, 

"Difficult" relative to current capabilities, yes, but that is not the 
criterion. 

>however the qualitative
>statement itself is accurate enough for anyone who cares to look.
 
Not accurate enough for me, and I have looked until I was crosseyed.

Also this reminder to everyone who thinks it is easy to lose information 
irretrievably: In sending messages, cryptographers TRY to make information 
unreadable, yet cryptanalysts often break the codes and read the information 
anyway, even when it is mingled with a lot of noise. Nature on the other hand 
is not malicious--merely indifferent; she does not deliberately try to hide 
clues. 

>Do you think arguments from information theory are inapplicable?
>Here's a bit vector large parts of which have been altered by a truly
>stochastic process. 

There are no truly stochastic processes, except putatively at the quantum 
level. Certainly there might exist or arise challenges that in practice we 
cannot meet successfully, but it is extremely premature to make any such 
judgment now.

>How [could a frozen patient be restored if] I
>use the kitchen mixer to stir up your brains prior to suspension?

The implications here are (a) that freezing does as much damage as a mixer, 
and (b) that the mixer effectively destroys necessary information. Not only 
is there no proof of that, but to a large extent it is contrary to known 
fact. After all, many biological specimens HAVE been revived after freezing, 
and frozen/thawed nervous tissue has shown retention of considerable 
structure and even function. Pichugin demonstrated coordinated electrical 
activity in networks of neurons in pieces of rabbit brains after thawing from 
liquid nitrogen temperature. 

Also Merkle, for example, has studied in detail the question of whether 
freezing produces turbulent flow, and concluded that essentially it does not. 
Absent turbulent flow (and maybe even with it) you do not get hopelessly 
jumbled brains, even though it may look that way to the contemporary eye.

In my opinion, a gloomy view at this stage is just a personal choice, and not 
a realistic one.

Robert Ettinger
Cryonics Institute
Immortalist Society
http://www.cryonics.org

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