X-Message-Number: 13321 From: Eugene Leitl <> Date: Mon, 28 Feb 2000 03:36:36 -0800 (PST) Subject: Re: Message #13318 Charles Platt wrote: > I think your assumption is not correct, Steve. I have received private > email from Ralph Merkle (who apparently prefers not to get entangled in > the discussions here) emphasizing the applicability of encryption > algorithms, while acknowledging the limited onboard power of nanomachines. Excuse me, Charles, but we're totally ignoring the relevant issue here (some deja vu, anybody?). At first, the assumed navigation and computation bottlenecks do not exist if use destructive imaging (i.e. disassembling the system, transiently creating a molecular map which we either use for extraction of a computational model, or, after advanced digital retouche tricks, for reconstruction verbatim, in the (still frozen) flesh). Time is not a problem, since the system is being processed in the vitrified state, and processivity is also not a problem since the tissue can microtomed into sufficient number of sections which get processed in parallel. So here our ass is covered. Ok? Now for the bad part: the cryptography analogy is unfortunately totally bogus. The damage description in http://www.merkle.com/cryo/cryptoCryo.html bears only tenuous connection to reality, and the assumption that there is no information loss in the system because "The laws of physics are reversible, and so in principle recovery of complete information about the original state should be feasible" is not valid. Now, even assuming that Edward Fredkin's thesis about Digital Physics http://cvm.msu.edu/~dobrzele/dp/Publications/Fredkin/Finite-Nature/ http://cvm.msu.edu/~dobrzele/dp/Publications/Fredkin/New-Cosmogony/ is true (despite no experimental evidence whatsoever, but we're on CryoNet here so let this not deter us), and we're indeed living in exactly such a universe, this is unfortunately not very helpful if the information is still Out There, but is meanwhile spread over a lightcone with (say) 100 lightyears radius, and is still receding fast, at the quite formidable speed of light in vacuum, or whatever upper speed the universe rule dictate). So, still assuming that we're living in a reversible-rule universe, this requires the Omega point with its Aleph-null MIPS (either as indiscriminate, brute force resurrection as computational models, or reconstruction extracted from the information contained in the collapsing, closed spacetime) to work. We're firmly on religious turf here. Deus ex machina, indeed. I'm sorry for having to resort to this truly surreal out-of-this world type of arguments, but unfortunately this is the type of (theoretical, head-in-the-clouds, homing-in-on-the-irrelevant) argumentation type prevailing here. Mea culpa, etiam. So from the practical point of view there indeed are dissipative physical processes, where information is erased. As a gedanken, drop an arbitrarily shaped cube of sugar into your hot beverage, and stir until dissolved. Can we computationally reverse the time arrow? No. This wouldn't even work in a perfectly Newtonian world, barring infinite precision of both measurement and computation. ? Exactly. A construed example? Sure. Do information-erasure processes appear in the frozen brain? Certainly. Let us take a look at the typical state of a patient's brain: http://4.3.78.106/cryo/ccr8.jpg This is a piece of rabbit hippocampus with the ice removed by freeze-substitution process, seen in light microscopy (below scala is in that heathen unit mm). Let us take a closer look: http://4.3.78.106/cryo/ccr3.jpg To my layman's eye, the damage pattern is fractal, i.e. showing self-similiarity on all scales. One could compute the fractal dimension from the image, but that's not relevant here. Gauging from the white/black pixel ratio, the compression ratio is high. 1:3, 1:4? Exact figure doesn't matter now. Due to volume expansion during freezing the pressures generated within occluded yet unfrozen regions are very high. Displacement of structures is high amplitude, light microscopic observations show anisotropic high velocity flow during the freezing process. Ultrastructurally, because lipid bilayers are self-assembling, when torn apart they form new (vesicular/lammellar) structures, thus further destroying information about their original shape. Alas, this is not exactly neatly shattered china, ready for puzzlework. Please nobody now say "Reynolds number", because that's strictly irrelevant. This is about as far from an isotropic macroscale model as it gets. Then why not a bandersnatch. Even after above caricature of an analysis, please do not attempt weak humour, and mention "reversibility" to me. So, that's the bad part. Is there a good part? Let's see. At first, this is not vitrification. Vitrificiation does much better. (How much better, I can hopefully soon demonstrate in high-res images, both light and electromicrographs accompanied by lots of juicy prose by gurus we all know and love instead of my embarrassing attempts. So, hang on there). What is missing, is information about what happens to the system at molecular scale. Fortunately, technology marches on, so this is knowable in principle. http://www.people.Virginia.EDU/~js6s/zsfig/figureindex.html This is still technology in statu nascendi, and can be probably modified to image in the bulk. We don't need better resolution than what CryoAFM can provide. (Well, at least I call that good enough:) http://www.people.Virginia.EDU/~js6s/zsfig/salt1.jpg The other part of the puzzle missing is how much structural details do we need to reconstruct the function of the original molecular machinery, and either confabulate an functionally equivalent meatspace model, or a purely computational model in machina (yesss!). However, chances are good we will know, relatively soon. The human genome project is rapidly nearing completion, Blue Gene & bioinformatics promises to help us making sense of all the sequence data, people have recently started making all kinds of neat things like http://www.e-cell.org/ http://www.nrcam.uchc.edu/ and generically neural simulation involving digitized neuranatomy is making steady progress. So the question whether cryonics can or can not work will be anwerable, hopefully in the foreseeable future. Blanket optimism, however, is less than helpful in the attempt of answering that question. Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=13321