Ideally the subject(s) would be stashed deep in a cave, and the process would be timed to wake him(them) up after 10,000 years have passed. Because of the low-tech nature of the future and the absence of electrical infrastructure, freezing is not really an option. Ideas?

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    $\begingroup$ Why couldn't you have a freezing mechanism? You'd want to have an isolated, tamper-proof power source, but that's no more impossible than the freezing tech itself. $\endgroup$ – Cadence Sep 29 '18 at 11:15
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    $\begingroup$ There is a nice list of literary time travel devices on Wikipedia. Just saying. I am partial to time travel by means of a fairy. $\endgroup$ – AlexP Sep 29 '18 at 11:27
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  • $\begingroup$ Welcome to WB.SE! When you have a moment, please click here to learn more about our culture and take our tour. The SE Q&A model is one-specific-question/one-best answer, meaning that undirected idea generation is often unsuitable and regularly off-topic. Please visit our help center and review our posts about high concept questions and open-ended questions for details. $\endgroup$ – JBH Sep 29 '18 at 18:52

It is uncertain today if Cryonics is viable.

10,000 years is a long time, and using current knowledge to prevent major tissue damage the body needs to be frozen below -130 degrees Celsius.

It may be possible to freeze someone for that long, perhaps in a location where in 10,000 years the environment can be predicted to warm further enough to thaw someone, however the real issue lies in when someone is unfrozen their bodies need to contend with:

  • Cryogenic antifreeze chemicals (which may be toxic) used to preserve cell structures
  • Fractures in organs during the freezing process
  • Brain functions, of which there are dozens of areas which need to be unfrozen carefully to ensure full brain function

None of the above points have been able to be dealt with successfully, and those that are currently preserved, for which there are roughly 1500, may not be revivable at all.

Certainly the unfreezing process will require enormous expertise effort and research, of which you have stated there is none in the future. Although popular in science fiction, I'm afraid the reality of Cryonics is quite different.

All other time delay solutions are currently not plausible using current day technology.

However it may be possible to have a small society in the cave for 10,000 years. Given a constant supply of food and complete isolation, the society may be possible to exist for this amount of time. However, the same persons would not be the ones entering the cave than the ones exiting. Memories could be told of via stories passed down the generations (Australian Aborigines have stories passed down which have been demonstrated to be 20,000 years old, including memories of the formation of the Great Barrier Reef).

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This is no cave solution, but I hope this helps you anyway.

A different way to survive 10,000 years into the future is with time dilation via very fast spaceships. The problem is that we do not have technology to go anywhere near the speed of light, but then again, we don't have cryogenics and probably never will due to its inherent problems. Travelling close to the speed of light, on the other hand, is more plausible.

Time dilation occurs when travelling near the speed of light. Actually it occurs all the time, but it is not noticible unless you are travelling close to the speed of light. In special relativity, time dilation is calculated with this formula:

$$ T = \frac{T_0}{\sqrt{1 - \frac{v^2}{c^2}}} $$

$T_0$ is the proper time (the time as experienced by the person going very very fast), as opposed to $T$, which is the time experienced by an observer. $v$ is the velocity of the person moving fast, and $c$ is the speed of light. This means that if I were flying in a plane at 1000 km/h, which converts to about 277 m/s, then the plane would experience virtually no difference to someone standing on the ground. However, if I were going at 86.6% the speed of light in a spaceship headed for the stars, then, compared to someone standing on the Earth, I would experience "half" the time that the person on Earth experiences, so if I set the ship's computer to come back to Earth after 5 years, then after 5 years, the person on Earth would have aged 10 years.

Time dilation is asymptotic as it approaches the speed of light. The difference in time dilation between 1% and 2% of the speed of light is minor, but the difference between 98* and 99% is great, as is 99.99% and 99.99999% the speed of light.

The speed of light is roughly 299,792,458 m/s. If I were to go 1.5 m/s shy of the speed of light, for every year I travelled, roughly 10,000 years would pass for the observer. So that means your subject could be sent on a spaceship for a year-long vacation, and come back to find that everyone they ever knew was long dead! Now, there are problems with going that fast. For example, you are going to need a lot of energy to do that, but either way, this is a way to "time travel" into the future.

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  • $\begingroup$ One followup question: could the year-long vacation take place in Earth orbit or does it have to be a trip into outer space? $\endgroup$ – user55810 Sep 30 '18 at 12:32
  • $\begingroup$ @user55810 it can be anywhere, even right here on Earth. The problem is that if you going at near light speed in orbit around the Earth, you would need to make a complete circle around the Earth a few times a second, which would involve insanely high centrifugal forces. If you went in a straight line to outer space then you would only need to worry about your own acceleration. $\endgroup$ – KITTENDESTROYER-9000 Sep 30 '18 at 12:45
  • $\begingroup$ Ok thanks, that super-helpful. How about near-lightspeed travel inside a very contained space, like looping around a kind of accelerator? $\endgroup$ – user55810 Sep 30 '18 at 14:33
  • $\begingroup$ @user55810 We do that with tiny subatomic particles, but with a person, again, the centrifugal forces would be far too great for someone to survive. $\endgroup$ – KITTENDESTROYER-9000 Sep 30 '18 at 14:55
  • $\begingroup$ Thank you! I think between the advice you've given me and literary license I'll be able to pull it off. Gratitude to all. $\endgroup$ – user55810 Sep 30 '18 at 22:35

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