Cryogenic stasis has been a staple of sci-fi for decades. A person goes into deep freeze, comes out some time later, hasn’t aged a day. Sometimes it’s used for long prison sentences, or long-term space transportation. Sometimes, very ill people will be put into stasis until medical science can cure them.
Is this even theoretically possible, with what we know about cryogenics, physics, aging, and biology?
It’s been done with tardigrades, but not mammals. I believe the damage to the cell membranes is too great. Could it theoretically be done in the future once they solve those problems? Time will tell.
No, for the same reason that you can’t freeze lettuce. Well, technically you can freeze lettuce, but you might not want to eat it afterwards.
There are many plants and animals that can survive freezing, but they usually use a biological trick or two to do it.
Plants that can survive freezing often have a cell structure that gives the water someplace to go when it expands during freezing. Plants that don’t have these types of structures, like lettuce, suffer from major cell damage when frozen, which is why frozen lettuce is mushy and unpleasant when you thaw it out.
Alligators and crocodiles can go for really long periods of time without eating, which is how they managed to survive the extinction event that killed the dinosaurs. They do need to breathe, if slowly, so when the pond or lake that they are in starts to freeze over, they just stick their nose up through the ice and let the lake freeze. They get stuck in the ice and can’t move, but with their nose up in the air they can still breathe. It gets them through the winter but they couldn’t survive a sci-fi type of long term deep freeze.
Some types of frogs can produce a protein that basically sucks all the water out of their cells. They also produce a thick sugary syrup to replace the water so that their cells don’t freeze completely. Other animals can also produce a sugary “anti-freeze” that prevents them from freezing completely solid.
Humans lack any of these biological adaptations, so once you freeze a human, they’re done for. The mere act of freezing them causes massive cell damage all throughout their body. It doesn’t matter how you thaw them out. They aren’t recovering from that. You’ve turned their brains into mush, so even if you could grow a replacement body through more sci-fi magic, they still aren’t surviving.
For humans to survive a cryogenic freeze, you need to figure out some way to freeze them without damaging their cells. No one has figured out how to do that yet.
Please note that currently cryogenics, when it comes to humans, consists of freezing dead humans or human body parts(usually the head) in hope that someone in the future will figure out how defreeze that dead body or body part…and bring that body back to life or, or bring the dead body part back to life and somehow be able to create a new body AND be able to reattach that unfrozen part to it successfully.
Has anybody ever completely stopped brain activity and then restarted it without erasing the mind that once inhabited it? Even if you could repair tissue; how do you restore personality and memory?
Nobody has ever “restored personality and memory”, but there is a saying among ER docs that you’re not dead until you are warm and dead.
Patients have been brought in with extremely low body temperatures (for example someone who “drowned” in an icy cold lake) who have no pulse and no brain activity, but who have recovered once they warmed up. Sometimes they end up with permanent brain damage from the ordeal, so it’s not necessarily a complete recovery.
I wasn’t sure at exactly what temperature brain activity stops, so I poked around on google a bit and found this:
So brain activity stops long before the brain actually freezes.
Which makes one wonder if instead of freezing someone we just get really close to that point and revive later.
Would that provide any long term benefits? (e.g. long space trips)
Some form of hibernation is likely possible the subject’s metabolism & aging could be slowed down for months or even years before awakening, but this would only be useful for interplanetary travel not interstellar (unless we could get very close to lightspeed).
You would also need to either figure out a way to safely thaw & reanimate those cells, or (more likely) take incredibly detailed brain-scans and “print” a new brain for implantation in a cloned body. And if the latter is possible then there’s no real reason to bother keeping the brain in storage or shipping it anywhere. Even if you were reanimating the subject’s original body, they’d “only” be able last a few millennia on ice before the radioactive decay of the isotopes in their own bodies rendered them non-viable.
I think its less likely than FTL travel being possible. But more likely than time travel.
So basically, not possible.
To the best of our current knowledge, FTL travel and time travel are the same thing. But I’d have to say that cryostasis is easier than both: We know that there are some animals that can do it, so it’s not outside the bounds of possibility that we might someday find a way to modify humans to do it, too.
Though that won’t do any good for the folks whose heads have already been frozen, because they weren’t suitably modified first.
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As I understood the “theory” from assorted SciFi, the discussion was that a person who was supercooled very quickly to liquid nitrogen temperatures would result in non-crystaline “ice”, so no damage to the body.
The theory would be to put the person into a near-hibernation state, then apply standard sci-fi magic to get them to the -170° range ASAP. The issue is of course whether a body can be completely frozen that fast - especially the brain, because it’s not like you can lace it throughout the interior with freezing tubes.
(In one of Larry Niven’s stories, the difficult part was getting them unfrozen successfully. Whereas individual organs could be successfully revived if they were a match for someone in need of a transplant.) Another thought was that super-frozen hair is very fragile and will break off, which explains Dr. Evil’s cat that becomes hairless in the last Austin Powers movie.
To be fair, this has more to do with the nature of tardigrades than with any sort of cryogenic breakthrough. Tardigrades uniquely can survive almost anything …
Tardigrades are among the most resilient animals known, with individual species able to survive extreme conditions …
… Tardigrades are thought to be able to survive even complete global mass extinction events caused by astrophysical events, such as gamma-ray bursts, or large meteorite impacts. Some of them can withstand extremely cold temperatures down to 0.01 K (−460 °F; −273 °C) (close to absolute zero), while others can withstand extremely hot temperatures up to 420 K (300 °F; 150 °C)[37] for several minutes, pressures about six times greater than those found in the deepest ocean trenches, ionizing radiation at doses hundreds of times higher than the lethal dose for a human, and the vacuum of outer space.
Therein lies the problem. Near hibernation is 33°. Then they need to get to -170° (so, a 200° F swing in moments). Their core temp will be higher than the external temp and have to freeze from the outside in. Movies aside, no one freezes in an instant. Those ice crystals are gonna happen.
I meant to say:
“Near freezing is 33°” rather than, Near hibernation is 33°.
Tardigrades are nigh indestrucable. You could put them into your transporter and beam them out into deep space on wide dispersal, and not kill them.
Yes, that’s the reality check. The question becomes, what is the speed of conduction of heat through meat? MY totally unscientific, unprofessional opinion, based on how fast heat goes the other way when you cook, is the guess that a few millimeters is about the limit for how deep super-fast cooling might go.
So unless there’s a technique for putting hibernating humans. then putting them through the deli slicer before dipping them in liquid nitrogen, and then reassembling them during thaw, I doubt cryo-preservation will do anything. All those people who paid to have their body (or head) frozen at death are out of luck.
Plan B is to use the same scifi magic to produce some sort of cryo-bio-friendly fluid to replace enough of the water in our bodies that we can be frozen without damage. Might work, but I hope it doesn’t taste like that colostomy preparation stuff if you have to drink several gallons of it and nothing else for a few days…
I agree with this. Cryostasis is difficult but at least theoretically possible under the basic understanding of physics we have.
There are sort of two questions here:
They are both theoretically plausible, but might rely on very different technologies or assumptions about physical reality. The first one requires that the mind is fully composed of some structure that is not destroyed at or in transition to and from low temperatures given the proper chemical or other preparation, and that such a chemical preparation exists.
The second requires that the mind is fully composed of some structure that was not destroyed in the haphazard transition to low temperature that can be scanned and replicated.
My understanding of biochemistry and computer science make me think that the second is actually more likely to happen first (if either happens). We already have simulated the brains of relatively simple organisms and (maybe?) the only thing that remains to do is scale up the simulation by a factor of 2^N. There may be fundamental constraints encountered on the way up, but historically computer hardware design as a field has been amazingly good at generating 2^N/dollar transistors a few years after we could create 2^(N-1)/dollar .
What about the millions of tiny robots? It is simple.
Are you serious?