I mean, sure, there is mummification and and some bodies being naturally preserved due to coldness or dryness, but I’m talking more about the idea of cryonics- the idea that you could stop a biological organism’s entire metabolism in some kind of suspended animation and then later thaw them out and be able to continue living. Most of this is just science fiction though and greatly exaggerated. All of the people who have gotten their bodies cryopreserved as adults are people who have died and it’s essentially just mummification instead of suspended animation.
In: Biology
The big reason most living things can’t survive freezing is because large, sharp ice crystals form in their cells and pop them like balloons from the inside – that’s basically what frostbite is. When something freezes really quickly all at once, the resulting ice crystals are a lot smaller than if that thing is frozen slowly. For a more accessible example, that’s part of the reason why ice cream is smooth but if you put cream in your freezer it’ll turn out slushy – commercial ice cream is frozen extremely quickly so the ice crystals are small enough that you can’t detect them.
So the reason we’re not currently able to cryopreserve, say, a whole human, is because it would take a lot of time for the parts in the middle of the body to actually freeze and you’d get large ice crystals which damage the cells beyond repair. You’d really effectively preserve the skin while causing massive internal frostbite. Small things like sperm or embryos (or lots of other cells that we freeze to preserve) are small enough to survive that process because they freeze all the way through so quickly. Additionally we tend to use compounds called cryoprotectants in that process which also reduce the size of ice crystals.
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