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Not to be confused with cryobiologyWikipedia (the study of living things at low temperatures), cryotherapyWikipedia (the use of cold in medicine), cryogenicsWikipedia (subjecting things to cold temperatures in general), or Whole-body cryotherapy (alternative medicine for the living).
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That is not dead which can eternal lie.
And with strange aeons even death may die.
H.P. Lovecraft

Cryonics is the practice of freezing clinically-dead people in liquid nitrogen (N2) with the hope of future reanimation.

Many scientists will admit that some sort of cryogenic preservation and revival does not provably violate known physics. But they stress that, in practical terms, freezing and reviving dead humans is so far off as to hardly be worth taking seriously; current cryonics practices are speculation at best and quackery and pseudoscience at worst.

Nevertheless, cryonicists will now accept considerable amounts of money for procedures based only on vague science fiction-level speculations, with no scientific evidence that any of their present actions will help achieve their declared aims. (Cryonicists often point to presently-nonexistent "sufficiently advanced" nanotechnology or mind uploading as favored methods for revival.) They consider this an obviously sensible idea — so common-sense that one would have to be stupid not to sign up.

History and impact[edit]

Origins of cryonics[edit]

Alcor's "bigfoot" dewar can contain 4 whole-bodies and 6 brains immersed in liquid nitrogen

Robert Ettinger,Wikipedia a teacher of physics and mathematics, published The Prospect of Immortality in 1964. He then founded the Cryonics Institute and the related Immortalist Society. Ettinger was inspired by "The Jameson Satellite" by Neil R. Jones (Amazing Stories, July 1931).[1] Many science fiction fans and early transhumanists then seized upon the notion with tremendous enthusiasm.

Corpses were frozen in liquid nitrogen by the early 1960s, though only for cosmetic preservation. The first person to be frozen with the aim of revival was James Bedford, frozen in early 1967. Bedford remains frozen (at Alcor Life Extension Foundation) to this day.

New hope came with K. Eric Drexler's Engines of Creation, postulating nanobots as a mechanism for cell repair in 1986. That Drexlerian nanobots are utterly impossible has not affected cryonics advocates' enthusiasm for them, and they remain a standard proposed revival mechanism.[2]

A major advance in tissue preservation came in the late 1990s with vitrification, where chemicals are added to the tissue to allow it to freeze as glass rather than as ice crystals. This eliminated ice crystal damage at the cost of toxicity of the chemicals.

(Cryonicists are very big on asserting that putting a human substantially made of water into liquid nitrogen at -196°C, turning them into a lump of ice, is not "freezing" at all but vitrification if you add enough antifreeze, and will get very shirty at people calling it "freezing" and claim this makes every further criticism wrong. In real medical technology, e.g., embryo preservation, vitrification is spoken of as a kind of freezing, which, of course, it is.)

Upon his death in 2011, Ettinger was stored at the Cryonics Institute in Detroit, the 106th person to be stored there. About 250 people had been "preserved" as of 2015.[3] About 2000 living people presently signed up with Alcor or the Cryonics Institute — the cryonics subculture is tiny for its cultural impact.

In popular culture[edit]

Cryonics, in various forms, has become a theme in science fiction,[4] either as a serious plot device (The Door into Summer, the Alien tetralogy) or a source of humor (Futurama, Sleeper). Its usual job is one-way time travel, the cryonics itself being handwaved (as you are allowed to do in science fiction, though not in reality) as a pretext for one of various Rip Van Winkle scenarios.

As a fictional concept, "cryogenics" generally refers to a not-yet-invented form of suspended animation rather than present-day cryonics, in that the worst technical issue to be resolved (if at all) in the far future is either aging or the cause of death/whatever killed you.

Timothy Leary, the famous LSD-dropper, was also famously interested in the "one in a thousand" chance of revival. He signed up with Alcor soon after it opened.[5] Eventually, the cryonicists creeped him out so much[6] that he opted for cremation.[7]

Walt Disney — often believed (in urban legend) to have had his head or body frozen — died in December 1966, a few weeks before the first cryonic freezing process in early 1967.

Hall of Fame baseball player and all-time Red Sox great Ted Williams was frozen after he died in 2002. A nasty fight broke out between his oldest children, who had a will saying he wished to be cremated, and his youngest son, John-Henry, who produced an informal family agreement saying he was to be frozen. This resulted in a macabre family feud for much of the summer of 2002. Williams was eventually frozen.[8]

So, how would cryonics actually work?[edit]

Cryonics enthusiasts will allow that a person is entirely dead when they reach "information-theoretic death", where the information that makes up their mind is beyond recovery.

The purpose of freezing the recently dead is to stop chemistry. This is intended to allow hypothetical future science and technology to recover the information in the frozen cells and repair or reconstruct the person, or at least their mind. We have literally no idea how to do the revival now or how it might be done in the future — but cryonicists believe that scientific and technological progress will, if sustained for a sufficient time, advance to the point where the information can be recovered and the mind restarted, in a body (for those who see cryonics as a medical procedure) or a computer running an emulator (for the transhumanists).

Most of the problems with cryonics relate to the massive physical damage caused by the freezing process. Attempts to alleviate this cause chemical damage.

The current state of cryonics[edit]

Whoo-hoo-hoo, look who knows so much. It just so happens that your friend here is only mostly dead. There's a big difference between mostly dead and all dead.
—Miracle Max, The Princess Bride[9]
The whole deal was a long shot but I figured what the hell, might as well give them the dough instead of leaving it to my ex-wives. But you know, son, I figured it was all just a bunch of hooey.
—Sonny, Star Trek: The Next Generation[10]

Cryonics for dead humans currently consists of a ritual that many find reminiscent of those performed by practitioners of the world's major religions:

  1. Freeze the body.
  2. Wait for a miracle.

As the Society for Cryobiology puts it:[11]

The Society does, however, take the position that the knowledge necessary for the revival of live or dead whole mammals following cryopreservation does not currently exist and can come only from conscientious and patient research in cryobiology and medicine. In short, the act of preserving a body, head or brain after clinical death and storing it indefinitely on the chance that some future generation may restore it to life is an act of speculation or hope, not science, and as such is outside the purview of the Society for Cryobiology.

Current procedure[edit]

In the US, cryonics is legally considered a highly elaborate form of burial (at Cryonics Institute in Michigan)[note 1] or as a donation to science (at Alcor in Arizona) and cannot be performed on someone who has not been declared medically dead (i.e., "brain dead"). Once you are declared legally dead, your fellow cryonicists swoop in to preserve you as quickly as possible.

The body, or just the head, is given large doses of anti-clotting drugs and infused with cryoprotectant chemicals to allow vitrification. It is then frozen by being put into a bath of liquid nitrogen at -196°C. At this temperature, chemical reactions all but stop.

The body is stored upside down so that if staff cannot "top off" the liquid nitrogen in the tank, the head will be the last part to thaw. The Cryonics Institute only allows for full-body freezing, but Alcor will let you freeze only your head. The heads are stored in the center of their dewars (big aluminum frozen coffins), so if your head is close to the top and they can't refill it with nitrogen, then you're just out of luck.

You can also have your pet frozen because future societies will be able and willing to resurrect centuries-old humans and Fido (or Seymour).

Scientific evidence for the efficacy of the current practice[edit]

Long-term memory is stored in physical form in the neural network as proteins accumulated at a chemical synapse to change the strength of the interconnection between neurons. So if you freeze the brain without crystals forming, the information may not be lost. As such. Hopefully. Though we have no idea if current cryonics techniques preserve the physical and chemical structure in sufficient detail to recover the information even in principle. Samples look good, though at least one working scientist with a strong interest in preserving the information disagrees.[13]

Recovering the information is another matter. We have not even an idea how to get it back out again. No revival method is proposed beyond "one day we will be able to do anything!" Some advocates literally propose a magic-equivalent future artificial superintelligence that will make everything better as the universal slam-dunk counterargument to all doubts.[14]

Ben Best, CEO of the Cryonics Institute, supplies in Scientific Justification of Cryonics Practice[15] a list of cryobiology findings that suggest that cryonicists might not be entirely wrong; however, this paper (contrary to the promise of its title) also contains a liberal admixture of "then a miracle occurs." His assertions as to what cited papers say also vary considerably from what the cited papers' abstracts state.

Alcor Corporation calls cryonics "a scientific approach to extending human life" and compares it to heart surgery.[16] This is a gross misrepresentation of the state of science and technology and verges on both pseudoscience and quackery. Alcor also tends to use invented pseudomedical terminology in its suspension reports.[17][18]

To date, the strongest evidence for cryonics comes from experiments with mammal brains. In 2016, researchers showed that a rabbit's brain could be frozen and thawed while keeping interconnections between neurons intact.[19]

Major problems facing cryonics[edit]

Engineering problems[edit]

Keeping the head or entire body at -196°C stops chemistry, but the freezing process causes massive physical damage to the cells. The following problems (many of which are acknowledged by cryonicists[20]) would all need to be solved to bring a frozen head or body back to life. Many would need breakthroughs in engineering and scientific understanding, which we simply cannot predict.

  • Liquid nitrogen at -196°C will not flash-freeze a head to the center; any more than a deep fryer set to 200°C will flash-defrost something frozen dropped into it. It takes minutes; crystals will form, cells will break, and proteins will denature.
  • Freezing organs recoverably. (We already do this routinely with embryos, and there's good work, though little success as yet, on freezing and recovering organs. It attracts lots of cryobiology funding.)
  • Cloning most of a body from recoverable DNA. (We're closer to this one than the others below.)
  • Nanobots. The popular conception of nanobots, which too many cryonics advocates also seem to share,[21] is bollocks. Drexler's computer-controlled nanoscopic miracle workers would need to violate physics.[22][23] Nanobots won't resemble the popular image of macroscopic industrial robots a billionth of the size with their own built-in supercomputers — they'll be carefully designed chemicals, much like cells or enzymes (the real-life examples of nanobots). Things are different at nanoscale.
    • "Nanobots!" is not the magic answer to everything more than "really small tweezers!" is. Fixing the damage would have to be physically possible — which it may not be — and humans would still need to know how to actually fix whatever it was to program the nanobots.
  • Cryonicists often say it will be a "last in, first out" situation. This means that the last people to be frozen will be the first people revived, as the last people will be frozen using more "advanced" methods, and then eventually, science will be able to revive those frozen under more "primitive" methods. Without knowing how they will be revived, there is no way of matching a freezing method to the revival or knowing which methods are more advanced than any other.
  • Fixing the freezing damage to the original frozen brain. The dendrites (10,000 connections for each of the 100 billion neurons — that's 1015 dendrites to check) are cracked badly by the freezing process — "acoustic fracturing events," like when you drop an ice cube into a drink. What is the process for fixing a frozen brain that's cracked into several or hundreds of pieces, with dendrites shattered at a microscopic level? This is a problem even with vitrification.[24]
    • The damage may not be mappable, let alone repairable. Damaging energies are required to scan at 5 nm resolutions, where things start going quantum.[25]
  • Reattaching a severed head or transplanting the brain.
    • Alternately: reading the patterns from the original brain and writing those to the cloned brain (uploading and downloading minds). Cryonicists speak of mind-uploading as a mere technical detail just around the corner rather than something that we don't know can be meaningfully discussed.
  • The cryopreservatives that prevent ice crystal damage are themselves toxic and would need to be removed from the tissues. (This is a minor problem compared to everything else listed herein.)
  • Cryonics must preserve a high proportion of the mind to live up to its promise. But what is an acceptable threshold? A typical stroke patient loses ~5% of their brain (over 10% in some severe strokes).[26] A severe stroke can be associated with the loss of large chunks of personality and memory, and the sufferer is frequently severely disabled afterward, although stroke victims are still considered to be the same person (occupying the same body and all that). For comparison, adults naturally lose up to 0.5% of their brain volume yearly.[27] For another comparison, hemispherectomy,Wikipedia removing half a person's brain (as pioneered by everyone's favorite neurosurgeon[28]), is survivable with, thanks to neuroplasticity, surprisingly tolerable effects on memory, personality, and cognitive function, particularly in young children.[29] Of course, there is no evidence that cryonics preserves more than 0%.
  • Once you've fixed the body's cells and the brain paths, you have a recovered corpse. Your next task is to resurrect the dead.

Organizational problems[edit]

This is the big problem. The existing cryonics facilities are charities with large operational expenses run by obsessive enthusiasts. They are small and financially shaky.[30][31] In 1979, the Chatsworth facility (Cryonics Company of California, run by Robert Nelson) ran out of money, and the frozen bodies thawed.[32][33] The cryonics movement was outraged, and facility operators are much more careful these days. But it's an expensive business to operate as a charity.

The general problem is that many cryonicists are libertarians and, unsurprisingly, have proven rather bad at putting together highly social nonprofits designed well enough to work in society on timescales of decades, let alone centuries. The movement has severe and obvious financial problems — the cash flows aren't sustainable, and Alcor relies on occasional large donations from rich members to make up the deficit.[34][35]

Insurance companies are barely willing to consider cryonics. You will have to work hard to find someone to sell you the policy. There are, however, cryonicist insurance agents who specialize in the area.[36]

Furthermore, Alcor is distressingly slapdash and amateur in its procedures, as per the famed case of Kim Suozzi's 2013 cryopreservation:[37]

Within minutes of taking custody of the body, the bumbling Alcor team began experiencing a series of equipment failures. A temperature monitor didn't work because, as it turned out, the batteries were dead. Shortly thereafter, their expensive mechanical chest-compression device stopped functioning. Then, having moved Suozzi’s body into a tub of ice, the Alcor team realized they'd forgotten to bring along a key piece of cooling equipment. Alcor's after-action report, compiled from the haphazard "free-form" observations of an unnamed but "experienced" observer, determined that such mistakes could in the future be remedied by "the use of a checklist." Now there’s a thought.

Eliezer Yudkowsky of LessWrong signed up with the Cryonics Institute but recommends Alcor as the "high-priced high-quality organization".[38]

Only James Bedford remains from the early frozen corpses due to tremendous effort from his surviving relatives. Though they didn't do anything to alleviate ice crystals, so his remains are likely just broken cell mush by now.

Specific scenarios that would keep today's cryonics from working[edit]

  • Insufficient information is being preserved by today's cryonics.
  • Nanoscopic repair, mind uploading, or other "reanimation" technologies have never been invented or turned out not possible, even if current techniques preserve sufficiently well and recovery doesn't defy physics.
  • A steep learning curve for future scientists. There will be much trial and error if efforts are made to revive corpses. If it is possible to revive a corpse, the first attempts will fail. An individual cannot know if they'll be one of the "experimental" revivals or will only be revived after it's perfected.
  • Organizational or social problems mean the frozen people aren't preserved long enough.
  • High future reanimation costs.
  • Lack of interest from the future society. After they've revived a few thousand medieval peasants (from their perspective), why do they care about reviving you?
  • The collapse of society or massive catastrophe.
  • Who needs another corpsicle? It's not like there will be a shortage of humans in the foreseeable future. The bodies could be treated the way mummies from Ancient Egypt have been, being unwrapped at "parties," put in museums, or worse. The corpses might just get thrown on a pyre for entertainment.
  • The requisite technologies to successfully reanimate someone who died today into a healthy new body after being frozen for at least half a century could be used to restore youth in *any* person. That means eternal life would be available for everyone already alive and fighting for space… if they are still staying on a planet with limited space.
  • The magical handwaved nano-tech abilities could also turn any brain into a super-brain. Whatever super-brains are in the future probably won't care too much about typical human worries, and any matter in your brain and its final form won't be up to you. The temptation will simply be too great to avoid making "improvements." One way or another, it won't be you who revives.

Reintegration issues after revival[edit]

Terry [dramatically]: Welcome to the world of tomorrow!!
Lou: Why do you always have to say it that way?
—Applied Cryogenics technicians greeting the newly thawed, Futurama[39]

Many medical issues are connected with reanimation, but a reanimated person faces numerous non-medical issues after returning to society. These might include:

  • Culture shock — given that many older people have trouble keeping up with technology, etc., someone out of the loop for decades or even centuries will experience quite a different world.
  • Language — which will have changed substantially in the intervening period or been replaced by one the person does not know.
  • Finance etc. — the person would presumably have to support or fund themselves (or worse, be an indentured servant to pay for the unanticipated electrical bills from centuries of freezing). Many technical qualifications will be obsolete. The person's assets may have also been mismanaged or their money made worthless by currency changes.
  • Isolation — all of the person's friends and relatives will presumably be dead.
  • Ambiguous/complex legal status — Are you a citizen in the future? Are you free to go anywhere else as someone born in that time would be?
  • Moral Presentism — Future societies may view actions taken by the person in their original lifetime, considered normal by contemporaries, as anathema.

All of these could cause the person great social, not to mention psychological, problems after revival. The person may also experience an identity crisis or delusions of grandeur.

Mainstream scientific and medical opinion on cryonics[edit]

Cryonics is not considered a part of cryobiology, and cryobiologists consider cryonicists nuisances. The Society for Cryobiology banned cryonicists from membership in 1982, specifically those "misrepresenting the science of cryobiology, including any practice or application of freezing deceased persons in anticipation of their reanimation."[note 2] (This specific provision was not present in the 2017 revision of the bylaws.[41]) As they put it in an official statement:

The act of freezing a dead body and storing it indefinitely on the chance that some future generation may restore it to life is an act of faith, not science.

The Society's planned statement was considerably toned down (it originally called cryonics a "fraud") after threats of litigation from Mike Darwin of Alcor.[42]

It can be difficult to find scientific critics willing to bother detailing why they think what the cryonics industry does is silly,[43] though some will detail just why the fundamental notions of present-day cryonics practice are biologically ludicrous.[13] Mostly, scientists consider that cryonicists are failing to acknowledge the hard, grinding work needed to advance the several sciences and technologies that are prerequisites for their goals.[44] Castles in the air are a completely acceptable, indeed standard, part of turning science fiction into practical technology, but you do have to go through the brick-by-brick slog of building the foundations underneath. Or, indeed, inventing the grains of sand each brick is made of.

Cryonicists, like many technologists, also frequently show arrogant ignorance of fields not their own — not just sciences[45] but even directly-related medicine[46][47] — leaving people in those fields disinclined to take them seriously.

William T. Jarvis, president of the National Council Against Health Fraud, said, "Cryonics might be a suitable subject for scientific research, but marketing an unproven method to the public is quackery."[48] Mostly, doctors ignore cryonics and consider it an expensive long shot.

Cryonics advocacy[edit]


Demographically, cryonics advocates tend to intersect strongly with transhumanists and singularitarians: almost all well-educated, mostly male — to the point where the phrase "hostile wife syndrome" is commonplace[49] — mostly atheist or agnostic but with some being religious and disproportionately involved in mathematics, computers, or physics.[50] Belief in cryonics is required on LessWrong to be accepted as "rational."[51]

Hardly any celebrities have signed up to be frozen in hopes of being brought back to life in the distant future.[52] (This may be a net win.)

Discussion tropes[edit]

Cryonicists are some of the smartest people you will ever meet and provide sterling evidence that humans are just monkeys with shiny toys who mostly use intelligence to implement stupidity faster and better.

When arguing their case, cryonics advocates tend to conflate nonexistent technologies that might someday be plausible with science-fiction-level speculation and speak of "first, achieve the singularity" as if it were a minor detail that will just happen, rather than a vast amount of work by a huge number of people working out the many, many tiny details.

The proposals and speculations are so vague as to be pretty much unfalsifiable. Solid objection to speculation is met with another speculation that may (but does not necessarily, or sometimes even probably) escape the problem. Cryonicists often tell you there isn't any proof it won't work. You will find many attempts to reverse the burden of proof and demand that you prove given speculation isn't possible. Answering can involve trying to compress a degree in biology into a few paragraphs.[45] Most cryonicists' knowledge of biology appears severely deficient.

Cryonicists also tend to assert unsupported high probabilities for as-yet nonexistent technologies and as-yet nonexistent science.[53][54][55] Figures are derived based on no evidence concerning the behavior of systems we've built nothing like and therefore have no empirical understanding of — they even assert probabilities of particular as-yet unrealized scientific breakthroughs occurring. (Saying "Bayesian!" is apparently sufficient support with no further working being shown under any circumstances.) If someone gives a number or even says the word "probable," ask them to show their working.

One must also make exact queries, distinguishing between, "Is some sort of cryogenic suspension and revival not theoretically impossible with as yet unrealized future technologies?" and "Is there any evidence that what the cryonics industry is doing right now does any good at all?" Cryonics advocates who have been asked the second question tend to answer the first, at which point it is almost impossible to pry a falsifiable claim out of them.

When you ask about a particularly tricky part, and the answer is "but, nanobots!" take a drink. If it's "but, future nigh-magical artificial superintelligence!", down the bottle.

Incompetence rather than malice[edit]

See the main article on this topic: Hanlon's razor

Cryonicists are almost all sincere and exceedingly smart people. However, they are also absolute fanatics and believe that freezing your freshly-dead body is the best hope of evading permanent death and that the $30–200,000 this costs is an obviously sensible investment in the distant future. There is little, if any, deliberate fraud going on.

Some cryonicists considered the Chatsworth facility going broke to be due to fraud, but there's little to suggest it wasn't primarily the owner just being out of his depth.

Alcor has multiple reports of being incredibly careless with the frozen heads in their care.[56] Despite suing to get a book on the subject dropped from publication[57] and threatening further legal action, their carelessness further came to light in the case of Kim Suozzi, a breathtaking saga of slapdash amateurism, particularly for an organization that has been doing this for four decades.[37]

One cryonics fanatic, scientist Kurt Pilgeram, had been giving lectures for Alcor since 1971.[58] Only his head was preserved by Alcor after his death in 2015, but according to a lawsuit by his son, Laurence Pilgeram, Alcor had been mandated to preserve all of his father's remains, no matter how damaged.[58]

Pascal's wager[edit]

See the main article on this topic: Pascal's wager

Cryonics enthusiasts are fond of applying a variant of Pascal's wager to cryonics[59] and saying that being a Pascal's Wager variant doesn't make their argument fallacious.[54][55][60] Ralph Merkle gives us Merkle's Matrix:

 It works  It doesn't work
Sign up Live Die, lose life insurance
Do nothing Die Die

The questionable aspect here is omitting the bit where "sign up" means "spend $30,000 (at the Cryonics Institute), $80,000 (at Alcor; head-only), or $200,000 (at Alcor; whole-body) of your children's inheritance for a spot in the freezer and a bunch of completely scientifically unjustified promises from shaky organizations run by strange people who are medical incompetents." It also assumes that living at some undetermined future date is sufficiently bonum in se that it is worth spending all that money that could be used to feed starving children now. Or, if you care only about your own survival, on medicine today, which is much more likely to extend your life.

Cooling processes known to work[edit]

When you freeze a steak and bring it back to edible, I'll believe it.
—Mike Godwin[61]

The basic notion of freezing and reviving an animal, e.g., a human, is far from entirely implausible.


  • Cryogenics has proven usably effective for multicellular embryos (up to about eight cells) — it is widely used in in vitro fertilization to store them for later implantation, and the kids grow up just fine.
  • There are many reported cases of humans (adult and child) who have had a severely lowered core temperature and been brought back to full health once warmed. (Of course, there are many more reported cases where they just died. And there are, of course, no cases of a human being frozen solid and surviving the process.)
  • Targeted Temperature Management (which replaced the former practice of therapeutic hypothermia) is sometimes practiced in hospitals to reverse ischemia damage after a successful cardiac arrest resuscitation, although the practice has faced increasing scrutiny.


  • Experiments have been done involving suspended animation at temperatures higher than freezing, in which the life processes of a mammal subject[62] are reduced to almost nothing for a short period and then brought back. Pigs can be taken down to 10°C and revived.[63]
  • The nematode Caenorhabditis elegans is one of the simplest creatures with a nervous system. C. elegans often survive freezing in liquid nitrogen with cryoprotectant chemicals,[64] and the revived nematode is happily parasitic upon trees.[65] This bears some resemblance to what current cryonics does. It's a favorite of cryonics discourse as the simplest possible example. Alcor claims in a 2015 paper[66] that revived C. elegans remember things they've learned. The paper's circumstances are dubious (obscure journal operated by transhumanists, one of the two methods not described & deferred to a still-unpublished paper), but at least someone did the obvious experiment at last.
  • Alaskan beetle larvae appear to vitrify in nature.[67]
  • Some frogs have been frozen and revived quite reliably and actually appear to have evolved to survive partial freezing.[68] In general, cold-blooded animals are rather better at dealing with cold than mammals or birds.
  • Insects freeze and revive pretty well.[69] Freezing and reviving houseflies is reliable enough to make a nice magic trick.[70]
  • Tardigrades can survive being chilled for days at −200 °C (-328 °F).[71] Some can even survive cooling to −272 °C (~1 degree above absolute zero or -458 °F)[72] for a few minutes.
  • A bacterium was revived after 120,000 years in a Greenland ice sheet.[73]
  • Small mammals freeze and revive surprisingly well, according to Smith et al. (1957),[74] a sterling piece of mad science with remarkable success half a century ago. Mice dropped in beakers of liquid N2 revived fairly reliably with careful warming, artificial respiration, and electrical shocks because they were so small they flash-froze. However, the females were infertile because large oocyte cells were susceptible to ice crystals, and they suffered slightly diminished remaining lifespans for various related reasons. Bushbabies (a type of prosimian) were revived but died within 24 hours. The only problem with this apparently-promising study is the complete lack of replication in the past 50-odd years.


  • Work continues in trying to revive neuron networks, which is one of the big prizes. So far, a few neurons frozen under ideal (not current cryonics) conditions and thawed look like they might work, though they weren't actually restarted.[75]
  • Transplant teeth are preserved with expected viability of 40 years by supercooling to -10°C in a magnetic field, instant-freezing with no crystals when the magnetic field is switched off.[76] This avoids toxic cryoprotectants.
  • Best claims that cryobiologists have taken out a rat hippocampus,Wikipedia frozen it, inspected it, and declared that it would possibly be viable (presumably, working when replaced).[15] This would be very promising, except that the abstract of the cited paper does not claim any such success and only claims that the slice looked good.[77] (The authors of the paper are cryonicists and cryobiologists but appear to understand what brick-by-brick science and technology entail.)
  • Viable eggs are recoverable from frozen mouse ovaries.[78] This is, of course, not the same as recovering a working organ. Ovaries are not as complex as kidneys or hearts. This paper states that complete mouse ovaries were cryopreserved at liquid nitrogen temperature and rewarmed to produce live pup birth rates comparable to that seen with fresh ovaries.[78]
  • A rabbit kidney (cryobiologists like rabbit kidneys and experiment on them a lot) was frozen to -135°C, retransplanted, and supported life.[79] Best[15] claims it "functioned well enough as the sole kidney to keep the rabbit alive indefinitely," but the original paper does not go that far. The 2009 paper shows that when rewarmed, the vitrified rabbit kidney was able to function as the sole functioning kidney — but only for a few days, not "indefinitely"; its serum creatinine, a marker of kidney function, was high enough that death was imminent. The kidney also suffered a stress fracture only a few minutes below the vitrification temperature and some ice crystal formation. Best has since admitted that this was an erroneous interpretation on his part but maintains that the study nonetheless has significance in demonstrating continued functionality in complex organs.[80]
  • Trials are being undertaken to rapidly unfreeze frozen tissues using nanoparticles and magnetic fields.[81][82] This is the first step in the long-term storage of frozen organs.

In conclusion[edit]

While the chances of immortality may be slim, dozens of people still commit their bodies or brains to cryonics each year. If their remains aren’t mismanaged or allowed to disintegrate, and if their relatives don’t go to court over the body, there is now a good chance that they will remain frozen for decades. Unfortunately, they will come out of the process cracked into a million pieces, and the prospect of putting them back together again is purely science fiction for the foreseeable future. It’s a grim practice with ghoulish results; at least it makes for some fascinating stories and a bit of dark humor.
—Horror stories of cryonics: The gruesome fates of futurists hoping for immortality (Big Think, 2022)[83]

See also[edit]

External links[edit]


  1. The Cryonics Institute used to be legally constituted as a private cemetery! [12]
  2. "Upon a two-thirds vote of the Governors in office, the Board of Governors may refuse membership to applicants, or suspend or expel members (including both individual and institutional members), whose conduct is deemed detrimental to the Society, including applicants or members engaged in or who promote any practice or application which the Board of Governors deems incompatible with the ethical and scientific standards of the Society or as misrepresenting the science of cryobiology, including any practice or application of freezing deceased persons in anticipation of their reanimation." [Sec. 2.04 of the bylaws of the Society for Cryobiology].[40]


  1. Cryonics Robert T. Carroll, Skeptic's Dictionary
  2. For example, the Drexler-Smalley debate or the book Nanomedicine by Robert Freitas.
  3. Moen, OM (August 2015). "The case for cryonics". Journal of Medical Ethics 41 (18): 493–503. PMID 25717141. 
  4. Human Popsicle (TV Tropes)
  5. Dr. Leary Joins Up (Cryonics, Volume 9(9), September, 1988, Issue #98)
  6. Re: Timothy Leary Renounces Cryonics (David Cosenza, CryoNet mailing list, 07 May 1996)
  7. Timothy Leary Renounces Cryonics (Charles Platt, CryoNet mailing list, 06 May 1996)
  8. Ted Williams Frozen In Two Pieces by David Hancock (December 20, 2002, 10:30 AM) CBS News (AP).
  9. Princess Bride, The (1987) Screenplays for You.
  10. The Neutral Zone; Stardate: 41986.0; Original Airdate: 16 May, 1988 Chrissie's Transcripts Site.
  11. Society for Cryobiology Position Statement: Cryonics
  12. 2013 version of their FAQ.
  13. 13.0 13.1 PZ Myers freezes tiny zebrafish brains for a living, and details just how ridiculously hard it is to even get physical preservation with the best possible present techniques, let alone chemical. And more.
  14. A breathtaking example.
  15. 15.0 15.1 15.2 Abstract: Benjamin P. Best. Scientific Justification of Cryonics Practice. Rejuvenation Research. April 2008, 11(2): 493-503. doi:10.1089/rej.2008.0661. Full text (PDF)
  16. Christianity and Cryonics: Questions and Answers (Alcor)
  17. Cryonics Meets Medicine: Catherine Baldwin Just Another Participant in Cryonics Fraud by AboutCryonics (September 28, 2010) Blogspot.
  18. Cryonics Meets Medicine: Cryonics Quackery by AboutCryonics (October 1, 2010) Blogspot.
  19. Mammal brain frozen and thawed out perfectly for first time by Helen Thomson (February 11, 2016). New Scientist.
  20. Cryonics, Cryptography, and Maximum Likelihood Estimation (Ralph Merkle, Xerox PARC, Proceedings of the First Extropy Institute Conference, 1994)
  21. Cryonicists' sunk costs reasoning about Drexler's "nanotech." (Mark Plus, The Life of Man Qua Man on Earth blog, 2010-08-31)
  22. Rupturing The Nanotech Rapture: Biological nanobots could repair and improve the human body, but they'll be more bio than bot Richard A.L. Jones, IEEE Spectrum, June 2008
  23. Nano-nonsense: 25 years of charlatanry (Scott Locklin, Locklin on science blog, August 24th 2010)
  24. Q: What about fracturing? (Alcor FAQs)
  25. David Matthewman on the Whole Brain Emulation roadmap (Paul Crowley, blog post, 20 Feb 2010)
  26. Jeffrey L. Saver. "Time is brain - quantified." Stroke 2006;37:263-266.
  27. Abstract: Anna M. Hedman et al. "Human brain changes across the life span: A review of 56 longitudinal magnetic resonance imaging studies." Human Brain Mapping 2012;33(8):1987-2002.
  28. SCIENTIST AT WORK: Benjamin S. Carson; For Many, Pediatric Neurosurgeon Is a Folk Hero (Robin Marantz Henig, The New York Times, June 8, 1993)
  29. Margaret B. Pulsifer et al. "The Cognitive Outcome of Hemispherectomy in 71 Children." Epilepsia 2004;45(3):243-54.
  30. Alcor's Financial Statements (Jennifer Chapman, Alcor News)
  31. Re: CryoNet #31623 (Ron Havelock, CryoNet mailing list, 20 Apr 2009)
  32. Suspension Failures: Lessons from the Early Years (R. Michael Perry, Cryonics, February 1992)
  33. Mistakes Were Made. An extraordinary episode of radio documentary series This American Life tells the funny, bizarre, and tragic story of a cryonics facility owner and client family for whom things didn't go quite as planned with the frozen body thing. It's an excellent cautionary primer to the complexities of actually running such a facility.
  34. Charles Platt. Cryoptimism. Part 1, part 2.
  35. "Cryopreservation Funding and Inflation: The need for Action; A Discussion Article by the Management and Board of Directors of Alcor." Cryonics 2011Q4. Summary, PDF.
  36. Interview with cryonics funding specialist Rudi Hoffman (Aschwin de Wolf, Depressed Metabolism, 2009-10-10). A cryonicist life insurance salesman sets out precisely what you need to do. He's also writing a book on the subject of how to arrange all this financially.
  37. 37.0 37.1 Everybody Freeze! The extropians want your body by Corey Pein (2016) The Baffler.
  38. You Only Live Twice by Eliezer_Yudkowsky (12 December 2008 07:14PM) LessWrong.
  39. Applied Cryogenics The Infosphere, the Futurama Wiki
  40. 1995 version of the bylaws.
  41. 2017 revision
  42. Society for Cryobiology statements on cryonics (Paul Crowley, blog post, 12 Feb 2010)
  43. An open letter to scientific critics of cryonics (Paul Crowley, blog post, 14 February 2010)
  44. Corpsicles in the New Yorker (Ouroboros, 5 Feb 2010)
  45. 45.0 45.1 See, for example, PZ Myers versus Ray Kurzweil:
  46. Cryonics Meets Medicine: Destroying Cryonics by AboutCryonics (October 6, 2010) Blogspot.
  47. Cryonics Meets Medicine: Reprint of Old Post from Cold Filter Cryonics Forum by AboutCryonics (October 10, 2010) Blogspot.
  48. Is Cryonics Feasible? by Stephen Barrett (revised on September 2, 2005) Quackwatch.
  49. Is That What Love is? The Hostile Wife Phenomenon in Cryonics, Michael G. Darwin, Chana de Wolf, and Aschwin de Wolf (archived by The Wayback Machine, complete in this TWB pdf)
  50. Quigley, Christine (1998). Modern Mummies: The Preservation of the Human Body in the Twentieth Century. McFarland. p. 143. ISBN 0786404922. According to Wikipedia.
  51. "I'm going to come out and say it: If you don't sign up your kids for cryonics then you are a lousy parent." (Eliezer Yudkowsky, Normal Cryonics, 19 Jan 2010)
  52. Category:Cryonically preserved peopleWikipedia on Wikipedia. What, you don't trust Wikipedia?
  53. Debates about Cryonics with Skeptics ( When told that the revival rate is 0% (as far as we know), and that it is therefore too soon to be charging for it, Mr Best repeatedly tells skeptics "You are treating cryonics as if it were sex with minors." He then puts this on his web page as if accusing opponents of reductio ad Hitlerum makes him look good.
  54. 54.0 54.1 Rationality, Cryonics and Pascal's Wager (Roko,, 08 April 2009)
  55. 55.0 55.1 The Pascal's Wager Fallacy Fallacy (Eliezer Yudkowsky,, 17 March 2009); slightly different version at The Pascal's Wager Fallacy Fallacy (Eliezer Yudkowsky, LessWrong, 18 March 2009)
  56. Ted Williams' frozen head for batting practice at cryogenics lab: book (Nathaniel Vinton, New York Daily News, 2nd October 2009).
  57. Alcor Sues to Block Book Expose of Ted Williams Cryonics (Ethics Soup, 06 October 2009)
  58. 58.0 58.1 Calif. scientist's son suing cryonics nonprofit for incorrectly freezing father's body by Annie Vainshtein (3:12 pm PDT, September 10, 20180 SF Gate.
  59. Pascal's Wager and cryonics (
  60. Pascal’s Wager taken out of deep freeze (Michael Cook, BioEdge, 24 Oct 2009
  61. Bar conversation with a RationalWikian.
  62. Most notably Miles the Beagle, suspended for an hour in 1987. (dead link — anyone got a good ref?)
  63. Stuck Pig (Bijal P. Trivedi, Wired 14.07)
  64. One C. elegans specialist noted in 1974 the cryopreservation process was convenient and "has proved completely reliable", with simple methods giving 20%-40% rates, and improvements have been made pushing revival rates up to 84%
  65. E. Riga and J. M. Webster. "Cryopreservation of the Pinewood Nematode, Bursaphelenchus spp." J. Nematol. 1991 October; 23 (4): 438–440.
  66. Vita-More & Barranco 2015, "Persistence of Long-Term Memory in Vitrified and Revived C. elegans." Rejuvenation Research doi: 10.1089/rej.2014.1636
  67. Deep supercooling, vitrification and limited survival to -100°C in the Alaskan beetle Cucujus clavipes puniceus (Coleoptera: Cucujidae) larvae by T. Sformo et al. (2010) J. Exp. Biol. 213(3):502-9. doi:10.1242/jeb.035758.
  68. Ask the expert: Jon Costanzo (NovaScience Now, PBS, April 2005)
  69. Frozen Flies Safeguard Research, Screwworm Eradication Efforts (ScienceBlog, 04 Feb 2005)
  70. Reviving a Dead Fly Magic Trick
  71. Survival of Tardigrades in Extreme Environments: A Model Animal for Astrobiology by Daiki D. Horikawa (2011) In: Anoxia: Evidence for Eukaryote Survival and Paleontological Strategies, edited by Alexander V. Altenbach, et al. Springer. pp. 205-217.
  72. Becquerel P. (1950). "La suspension de la vie au-dessous de 1/20 °K absolu par démagnétisation adiabatique de l'alun de fer dans le vide le plus élevé" (in French). C. R. Hebd. Séances Acad. Sci. Paris 231: 261–263. 
  73. 'Resurrection bug' revived after 120,000 years (Andy Coghlan, New Scientist, 15 June 2009)
  74. Smith, A.U. (1957) "Problems in the Resuscitation of Mammals from Body Temperatures Below 0°C" Proceedings of the Royal Society of London. Series B, Biological Sciences, 147(929):533-544 (14 pages.) Excerpt: "Two of the galagos [bushbabies] regurgitated and inhaled bicarbonate from the stomach during administration of artificial respiration. The other two galagos which had been treated with bicarbonate and then frozen for 45 minutes seemed to make an excellent recovery after thawing. One of them regained an appetite as well as normal posture and behaviour. Within 24 hours they both died. At post mortem the stomach was normal, but in one animal the duodenum and jejunum contained bloodstained fluid. In both instances there was oedema of the lungs and froth in the trachea. This may have been a terminal event. Survival may have been limited by some other physico-chemical or physiological derangement which, if diagnosed, might well have been susceptible to treatment. It was therefore decided to postpone further experiments on freezing the larger mammals until the effects on other organs of freezing in vivo and in vitro were better understood." (p. 538) Figure 60 on Plate 25 ("A frozen galago is being rewarmed with diathermy. It lies inside a Perspex tube surrounded by the output coil of the diathermy apparatus. Artificial respiration is being given by insufflating air into a tracheal cannula.") is awesome.
  75. Ma W., et al. (2006) "Cryopreservation of adherent neuronal networks" Neuroscience Letters, 403(1-2):84-9.
  76. Food Freezing Technology Preserves Human Teeth. Organs Next? by Constance J. Woodman (Jan 23, 2011) Singularity Hub.
  77. Cryopreservation of rat hippocampal slices by vitrification by Yuri Pichugin et al. (2006) Cryobiology 52(2):228-40.
  78. 78.0 78.1 Pup birth from mouse oocytes in preantral follicles derived from vitrified and warmed ovaries followed by in vitro growth, in vitro maturation, and in vitro fertilization by A. Hasegawa et al. (2006) Fertil. Steril. 86 Suppl 4:1182-92.
  79. Fahy GM, Wowk B, Wu J, Phan J, Rasch C, Chang A, Zendejas E. Cryopreservation of organs by vitrification: perspectives and recent advances. Cryobiology. 2004 Apr;48(2):157-78.
  80. Physical and biological aspects of renal vitrification by G. M. Fahyet al. (2009) Organogenesis 5(3):167-75.
  81. A new way to warm up frozen tissue could help with the organ shortage as seen in the Verge
  82. A new way to warm up frozen tissue could help with the organ shortage as seen in the Verge
  83. Tom Hartsfield, Horror stories of cryonics: The gruesome fates of futurists hoping for immortality. Big Think, 3 August 2022.
  84. Plastination versus Cryonics (Gwern Branwen,