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gjm comments on PSA: Very important policy change at Cryonics Institute - Less Wrong
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I see people saying things like
but I'd thought the truth was nearer to
Do I have a mistaken idea of how useless mere freezing is for cryopreservation?
You do not. If you're frozen instead of cryopreserved, there is absolutely no chance that any simple procedure will be able to read out your mindstate.
However, there is still a chance[1] that a sufficiently smart intelligence would be able to time-reverse the ice damage and resurrect you that way, or at least extract enough data to construct a reasonable facsimile for your family and friends that's more than simply their memories. That might still be worth paying for, if you believe such intelligences will exist.
1: Pulling a number out of my ass, I'd say about 5% of the chance that vitrification works. I don't have much faith in the information-scattering abilities of ice crystals. I do, however, consider it possible that important data is stored in volatile form.
It may be a bit difficult for most individuals to visualize ice formation with enough clarity and detail. It is not just the expansion of water upon freezing that is a problem. Ice crystals don't appear out of nothing. They are formed out of water that is there. During freezing, the ice crystals initially get made of pure water, forcing everything else into inter-crystal spaces (smashing it together into smaller volume).
In addition to the already grave damage of shredding something that is made of fairly identical parts, the cell membrane fragments get to float in the concentrated brine (as the pure water was removed), which would assuredly restrict the space of possible states of multitude of proteins in the receptor gates and the like, losing information irreversibly. Which is also the case for most "cryoprotectants".
At molecular scale, there's no tiny scratches, lost hairs, and the like, that the future superintelligent Sherlock Holmes can look at with a better magnifying glass.
True. If the molecular scale matters, we're boned. :P
It definitely does, i.e. the ion gates and receptors and such are molecular complexes, and most of the information is virtually certain to be in the states of molecules (shapes for those that can be in either shape, adhesion of molecules, etc etc), the sort of stuff that will get irreversibly lost when proteins denature due to either high salinity or "cryoprotectants".
I'm skeptical that the brain could be this delicate in operation and still work as robustly as it does.
edit: I suppose it's plausible that memories could be stored this way if they're done so redundantly, in which case a systematic unraveling of proteins might destroy them in a way that normal wear-and-tear wouldn't.
"Virtually certain" seems like overreaching as far as I'm aware though - is this the standard point of view among biologists?
States of molecules are in no way delicate. There's points plotted on a line:
delicate----------------not so delicate------------robust--------------------will withstand solvent replacement or brine.
The molecules that unravel and change their shapes (and detach, and lose state information) upon the changes involved would never (for any practical meaning of never) change their shape in such ways in normal conditions. It is not delicate - it is just that changes in the properties of solvents are very non delicate kind of change at all.
There isn't so much of a "standard point of view" because the people in the area just really don't take cryonics seriously at all.
Here is a comment from one of the previous threads on the topic, with ensuing discussion.
Not even a superintelligence can restore an ice sculpture from a glass of water.
Yes.
It may be helpful to outline what exactly - in terms of information - makes an ice sculpture irrecoverable or recoverable. It is the fact that distinct ice sculptures will result in precisely identical glass of water. Even if you look at the individual water molecules in the glass and try to retrace their motion backwards, due to the introduction of unknowns (interaction of those molecules with the molecules in the actual glass, then in the air, etc etc), they map to every possible ice sculpture.
The ice sculpture is irrecoverable because the final state corresponds to many possible initial states.
Likewise, massive changes in the solvent - which occur in either cryoprotected or non-cryoprotected cryonics - will force bistable molecules and molecular complexes to transition into a third state, losing their state information. This is because changes in the solvent affect intermolecular forces between parts of a protein (making proteins denature, i.e. unfold or re-fold into a different shape), and between different proteins.
Cryonics as it is can not be seen as science fictional stasis field with cracking and distortion that can in principle be undone someday. It involves massive, many-to-one chemical changes.
It is clear that if the cryonics involved cooking your head in a pot and then freezing it - or even letting the head remain at room temperature for a few hours - the chances would seem fairly minuscule to you, due to extensive many to one chemical changes that would occur during cooking. Likewise, the chances of cryonics - without any cooking - seem fairly minuscule to me due to extensive many to one chemical changes that result from either the introduction of the "cryoprotectants" (at concentrations which denatures some proteins) or due to the concentration of all solutes including salt in the inter crystal boundaries (which also denatures proteins). This is all quite far outside the range of any "robustness" against normal environmental conditions, too - I do not expect memories to be any more delicate than rest of the changeable chemical state (By the way, more chemically 'robust' storage would also require more energy for writing memories).
Now, of course, given the unknowns, we can't tell for sure that cryonics does not work. But we can have no reasonable expectation for cryonics to work better than, say, doing good deeds in the hope that it raises chances at resurrection through some sort of look-into-the-past technology utilizing unknown laws of physics, or resurrection possibilities in simulated worlds, or the like - all the other things that no one can prove impossible.
I don't think that's a good analogy; IIRC organs (eg rabbit kidneys) have been successfully frozen and revived (good enough to implant), so it's more a matter of whether that can be extended to human brains (which, sure, may be more delicate) rather than being something inherently absurd.
Rabbit kidneys are much smaller than human brains.
The square-cube law is the main showstopper: you can remove heat form a thing at a rate proportional to its surface area, while its heat capacity is proportional to mass and thus to volume. Therefore, maximum attainable cooling speed decreases with size (if you try to cool any faster, youl'll just crack the surface).
Rabbit kidneys can be vitrified without using a toxic concentration of cryprotectants, moreover, IIUC the circulatory system of a kidney allows higher flow and pressure (a kidney is just a blood filter, after all), making cryoprotectant perfusion easier. Even then, cryopereservation isn't perfect: microscopic damage has been observed.
I am an absolute amateur, but wasn't vitrification about replacing the ice-crystal-generating water in the brain/body with a liquid that turns into a glass when cooled? If you can get that liquid into the furthest reaches of the brain, wouldn't you also be able to distribute coolant through its interior, turning the effective cooling surface area proportional to the volume?
Thanks for the information, but that suggests that preserving a human brain will be difficult and may require more advanced techniques than currently used, not necessarily that it's some crazy impossible thing that shouldn't even be thought about. Hell, maybe it would be possible to carefully cut up the brain into smaller chunks before freezing it (a sharp cut along the right line being perhaps not so damaging compared to bad freezing).
A lot of it is going to come down to exactly how memories are stored and how redundant they are. Last time I checked this wasn't yet fully understood. If they really do depend on fine details of molecules that are inevitably irreversibly scrambled by freezing, then it probably is impossible after all.
It's an exaggeration, but not far off. The information seems pretty damn fragile. From the linked thread: "The damage that is occurring - distortion of membranes, denaturation of proteins (very likely), disruption of signalling pathways. Just changing the exact localization of Ca microdomains within a synapse can wreak havoc, replacing the liquid completely? Not going to work."
The counterarguments appear to be "but do we really need all that detail for a good-enough copy of the person?" Which is a "prove my negative" - the people arguing that don't know either.
It's a double-edged negative... not only do we not know how good the copy will be, we don't know how good is good enough. (Of course, if our standards for "good enough" are sufficiently low, then they can be satisfied by other people being born.)
Ultimately the cryonics argument is that the value to me of someone who meets my standards for being me existing in the future is so high that any increase, however small, in the chance of that happening has a higher expected value than anything else I could do with the resources consumed by post-mortem cryonic preservation of my brain (or at least, higher EV than many things I am currently doing with them, which I should therefore give up doing in favor of cryonics).
That argument seems to me to be based on an incredibly oversimplified view of what the recovery process would look like. It's not going to involve restoring operation to the system.
Quite. We don't know, so what are the chances?
They don't need to be very high for cryonics to be an improvement on, y'know, definitely dying.
What does that sentence even mean?
"Figure out the past state from the current state". Or at least some close approximation of the past state.
Which involves attempting to time-reverse the laws of physics, on some level. Which is impossible, strictly speaking, but you may be able to get close enough for government purposes.