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 ______________________________________________________ Get Your Private, Free Email at http://www.hotmail.com Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=13306