For its advocates, cryonics offers almost eternal life. To its critics, cryonics is pseudoscience; the idea that we could freeze someone today in such a way that future technology might be able to re-animate them is nothing more than wishful thinking on the desire to avoid death. Many who battle nonsense dressed as science have spoken out against it: see for example Nano Nonsense and Cryonics, a 2001 article by celebrated skeptic Michael Shermer; or check the Skeptic's Dictionary or Quackwatch entries on the subject, or for more detail read the essay Cryonics–A futile desire for everlasting life by "Invisible Flan".
That it seems so makes me sad, because to my naive eyes it seems like it might work and I would quite like to live forever, but I know that I don't know enough to judge. The celebrated Nobel prize winning physicist Richard Feynman tells a story of a US general who spoke to him at a party and explained that one big challenge in desert warfare is keeping the tanks fuelled given the huge distances the fuel has to travel. What would really help, the general said, would be if boffins like Feynman could invent a sort of engine that was powered by sand. On this issue, I'm in the same position as the general; in the same way as a tank fuelled by sand seems plausible enough to him, it makes sense to me to imagine that however your brain stores information it probably has something to do with morphology and chemistry, so there's a good chance it might not evaporate right away at the instant of legal death, and that freezing might be a way to keep the information there long enough for future societies to extract it with their future-technology scanning equipment.
And of course the pro-cryonics people have written reams and reams of material such as Ben Best's Scientific Justification of Cryonics Practice on why they think this is exactly as plausible as I might think, and going into tremendous technical detail setting out arguments for its plausibility and addressing particular difficulties. It's almost enough to make you want to sign up on the spot.
Except, of course, that plenty of totally unscientific ideas are backed by reams of scientific-sounding documents good enough to fool non-experts like me. Backed by the deep pockets of the oil industry, global warming denialism has produced thousands of convincing-sounding arguments against the scientific consensus on CO2 and AGW. Thankfully in that instance we have blogs like Tim Lambert's Deltoid, RealClimate, and many others tracking the various ways that the denialists mislead, whether through cherry-picking evidence, misleading quotes from climate scientists, or outright lies. Their hard work means that denialists can barely move or speak without someone out there checking what they have to say against science's best understanding and pointing out the misrepresentations and discrepancies. So before I pony up my £25 a month to sign up to cryonics life insurance, I want to read the Deltoid of cryonics - the articles that take apart what cryonics advocates write about what they do and really go into the scientific detail on why it doesn't hang together.
Nano Nonsense and Cryonics goes for the nitty-gritty right away in the opening paragraph:
To see the flaw in this system, thaw out a can of frozen strawberries. During freezing, the water within each cell expands, crystallizes, and ruptures the cell membranes. When defrosted, all the intracellular goo oozes out, turning your strawberries into runny mush. This is your brain on cryonics.
This sounds convincing, but doesn't address what cryonicists actually claim. Ben Best, President and CEO of the Cryonics Institute, replies in the comments:
Strawberries (and mammalian tissues) are not turned to mush by freezing because water expands and crystallizes inside the cells. Water crystallizes in the extracellular space because more nucleators are found extracellularly. As water crystallizes in the extracellular space, the extracellular salt concentration increases causing cells to lose water osmotically and shrink. Ultimately the cell membranes are broken by crushing from extracellular ice and/or high extracellular salt concentration. [...] Cryonics organizations use vitrification perfusion before cooling to cryogenic temperatures. With good brain perfusion, vitrification can reduce ice formation to negligible amounts.
Best goes on to point out that the paragraph I quote is Shermer's sole attempt to directly address the scientific claims of cryonics; once the opening paragraph has dispensed with the technical nitty gritty, the rest of the piece argues in very general terms about "[blind] optimistic faith in the illimitable power of science" and other such arguments. Shermer received many other responses from cryonics advocates; here's one that he considered "very well reasoned and properly nuanced".
The Quackwatch entry takes us little further; it quotes the debunked Shermer argument above, talks about the cost (they all talk about the cost and a variety of other issues, but here I'm focussing specifically on the issue of technical plausibility), and links to someone else making the same already-answered assertions about freezing damage.
The Skeptic's Dictionary entry is no advance. Again, it refers erroneously to a "mushy brain". It points out that the technology to reanimate those in storage does not already exist, but provides no help for us non-experts in assessing whether it is a plausible future technology, like super-fast computers or fusion power, or whether it is as crazy as the sand-powered tank; it simply asserts baldly and to me counterintuitively that it is the latter. Again, perhaps cryonic reanimation is a sand-powered tank, but I can explain to you why a sand-powered tank is implausible if you don't already know, and if cryonics is in the same league I'd appreciate hearing the explanation.
It does link to the one article I can find that really tries to go into the detail: Cryonics–A futile desire for everlasting life by "Invisible Flan". It opens on a curious note:
If you would like my cited sources, please ask me and I will give them to you.
This seems a very odd practice to me. How can it make sense to write "(Stroh)" in the text without telling us what publication that refers to? Two comments below ask for the references list; no reply is forthcoming.
And again, there seems to be no effort to engage with what cryonicists actually say. The article assets
it is very likely that a human would suffer brain damage from being preserved for a century or two (Stroh).
This bald claim backed by a dangling reference is, to say the least, a little less convincing than the argument set out in Alcor's How Cold is Cold Enough? which explains that even with pessimistic assumptions, one second of chemical activity at body temperature is roughly equivalent to 24 million years at the temperature of liquid nitrogen. Ben Best quotes eminent cryobiologist and anti-cryonics advocate Peter Mazur:
...viscosity is so high (>1013 Poise) that diffusion is insignificant over less than geological time spans.
Another part of the article points out the well-known difficulties with whole-body freezing - because the focus is on achieving the best possible preservation of the brain, other parts suffer more. But the reason why the brain is the focus is that you can afford to be a lot bolder in repairing other parts of the body - unlike the brain, if my liver doesn't survive the freezing, it can be replaced altogether. Further, the article ignores one of the most promising possibilities for reanimation, that of scanning and whole-brain emulation, a route that requires some big advances in computer and scanning technology as well as our understanding of the lowest levels of the brain's function, but which completely sidesteps any problems with repairing either damage from the freezing process or whatever it was that led to legal death.
Contrast these articles to a blog like Deltoid. In post after painstaking post, Lambert addresses specific public claims from global warming denialists - sometimes this takes just one graph, sometimes a devastating point-by-point rebuttal.
Well, if there is a Tim Lambert of cryonics out there, I have yet to find them, and I've looked as best I can. I've tried various Google searches, like "anti-cryonics" or "cryonics skeptic", but nearly all the hits are pro-cryonics. I've asked my LiveJournal friends list, my Twitter feed, and LessWrong.com, and found no real meat. I've searched PubMed and Google Scholar, and again found only pro-cryonics articles, with the exception of this 1981 BMJ article which is I think more meant for humour value than serious argument.
I've also emailed every expert I can find an email address for that has publically spoken against cryonics. Sadly I don't have email addresses for either Arthur W. Rowe or Peter Mazur, two giants of the cryobiology field who both have strongly anti-cryonics positions; I can only hope that blog posts like these might spur them into writing about the subject in depth rather than restricting themselves to rather brief and unsatisfactory remarks in interviews. (If they were to have a change of heart on the subject, they would have to choose between staying silent on their true opinions or being ejected from the Society for Cryobiology under a 1982 by-law.) I mailed Michael Shermer, Steve Jones, Quackwatch, and Professor David Pegg. I told them (quite truthfully) that I had recently started talking to some people who were cryonics advocates, that they seemed persuasive but I wasn't an expert and didn't want to fall for a scam, and asked if there was anything they'd recommend I'd read on the subject to see the other side.
The only one of these to reply was Michael Shermer. He recommended I read David Brin, Steve Harris and Gregory Benford. This is a pretty surprising reply. The latter two are cryonics advocates, and while Brin talks about a lot of possible problems, he agrees with cryonics advocates that it is technically feasable.
I expanded my search to others who might be knowledgable: Society of Cryobiology fellows Professor Barry Fuller and Dr John G Baust, and computational neuroscience Professor Peter Dayan. I received one reply: Dayan was kind enough to reply very rapidly, sounding a cautionary note on how much we still don't know about the structure of memory and referring me to the literature on the subject, but was unable to help in my specific quest for technical anti-cryonics articles.
In his 1994 paper The Molecular Repair of the Brain, cryptology pioneer Professor Ralph Merkle remarks
Interestingly (and somewhat to the author's surprise) there are no published technical articles on cryonics that claim it won't work.
Sixteen years later, it seems that hasn't changed; in fact, as far as the issue of technical feasability goes it is starting to look as if on all the Earth, or at least all the Internet, there is not one person who has ever taken the time to read and understand cryonics claims in any detail, still considers it pseudoscience, and has written a paper, article or even a blog post to rebut anything that cryonics advocates actually say. In fact, the best of the comments on my first blog post on the subject are already a higher standard than anything my searches have turned up.
If you can find any articles that I've missed, please link to them in the comments. If you have any expertise in any relevant area, and you don't think that cryonics has scientific merit - or if you can find any claim made by prominent cryonics advocates that doesn't hold up - any paragraph in Ben Best's Scientific Justification of Cryonics Practice, anything in the Alcor Scientists’ Cryonics FAQ or the Cryonics Institute FAQ, or anything in Whole Brain Emulation: A Roadmap (which isn't directly about cryonics but is closely related) - then please, don't comment here to say so. Instead, write a paper or a blog post about it. If you don't have somewhere you're happy to post it, and if it's better than what's already out there, I'll be happy to host it here.
Because as far as I can tell, if you want to write the best anti-cryonics article in the world, you have a very low bar to clear.
Related articles: Carl Schulman links to Robin Hanson's What Evidence in Silence or Confusion? on Overcoming Bias, which discusses what conclusions one can draw from this.