…we can’t freeze a fully developed human and thaw them later and they’ll live?
In: Biology
An embryo weighs a fraction of a gram
An adult weighs several tens of thousands of grams
To freeze an embryo they have to replace the water in it with something which doesn’t expand when frozen, then it is frozen almost instantly with liquid nitrogen. Because it’s very small it’s very easy to replace the water, and because it’s very small it’s also very quick to go from alive temperature to totally frozen temperature.
An adult would take a long time to replace all the water in, as you’d have to pump out tens of litres of liquid from blood, lymph, intracellular fluid, etc. and replace it all with the freeze juice. You also take a LONG time to cool down from 37c to -100c. During that freezing process, and that fluid replacement process, you would be in a state untenable for life but also not so cold that you wouldn’t be dying.
Additionally, a very small fraction of frozen embryos survive the freezing. If a (very generous) 5% survive that’s fine because you can just use the survivors. If only 5% of the cells in your adult body survive, and the other 95% die, you die.
And the last issue is that there are many complex systems in your body that are larger than a single cell. The heart needs to pump, the kidneys need to filter, etc and the brain needs to think. We aren’t good at making those things start going again after they stop, and freezing would stop them. The brian in particular, as you can imagine, is important here.
It’s about how quickly the freezing agent can enter tissues. One cell is easy. Something the size of a gerbil, surprisingly, is easy – we can freeze and thaw them out. Interestingly, this task – thawing frozen gerbils – spurred the invention of the first microwave oven. A human is just too big to flash freeze.
Here’s Tom Scott with the story about frozen gerbils and the first microwave. He even interviews the scientist who invented it and thawed the gerbils. https://m.youtube.com/watch?v=2tdiKTSdE9Y
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