In my story, the characters encounter someone who has been frozen cryogenically for a very long amount of time, and woken up.

Assuming we have the technology to put someone into suspended animation (BTW, not sure if I'm butchering these terms), what side effects might occur after someone wakes up after such a long period of time, and how long would someone be frozen for and be able to wake up, (for the most part, at least) alive?

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    $\begingroup$ I don't believe there are answers to your questions, because the technology does not exist, and science fiction answers to this vary wildly. Some have cryogenics for 500 years, others slumber for 500,000 or more. Some have us waking up with no side effects, others have us feel like we actually died. $\endgroup$
    – Cort Ammon
    Apr 21, 2016 at 1:16
  • $\begingroup$ Our current cryogenics involves constant maintenance of the frozen people, especially in defense against frostbite and maintaining steady electricity to keep the bodies cold. $\endgroup$
    – Marion
    Apr 21, 2016 at 1:27
  • $\begingroup$ I'm going to close vote this as opinion based, although I'm not entirely sure if that is what it should be closed under. The simple answer is that we do not know. We haven't yet developed the technology to do that yet, so we don't know about potential side effects.; $\endgroup$ Apr 21, 2016 at 1:56
  • $\begingroup$ Noted, perhaps the better question then, would be, how long can someone stay asleep for (Assuming they age at a slower rate, so that they can survive for longer) without suffering from any related injuries for? I know that there are people who have gone into a coma and woken up as late as 30 years later. I think that's as close as we can get to answering a cryogenics question. $\endgroup$ Apr 21, 2016 at 2:58
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    $\begingroup$ I'd say this is more about biology than Worldbuilding. Xandar is right, there is No way for us to know, as long as no one exact knows how this would even be done. $\endgroup$
    – T3 H40
    Apr 21, 2016 at 2:58

1 Answer 1


At present there is no method of successfully cryogenically freezing living mammals.

Even worse, even if we could successfully force crew into hibernation, cosmic rays and information loss would eventually kill the frozen crew (or embryos). They would have to be awoken from sleep during the trip so that the body's cellular repair processes could repair the damage induced over time.

I've recently seen a reference with the actual numbers but don't have it handy. I'll look for it an link it if I can find it.

FWIW, I thought I saw a calculation showing that a number on the order of 100 years would be the limit for sleep cycles. Then the crew (or individuals) would have to be awoken and given time for their body's to repair the damage.

  • $\begingroup$ would also add that diffusion processes keep going in freeze state, so depends also how deep is freezing. $\endgroup$
    – MolbOrg
    May 10, 2016 at 20:08
  • $\begingroup$ FWIW, I think this is the closest we've got to for suspending mammals. $\endgroup$
    – forest
    Feb 25, 2018 at 3:22

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