I don’t know so much about C-14, but wouldn’t potassium decay’s effects be small on timescales ~10,000 years? The radioactive natural isotope K-40 has a ridiculously long half life (1.25 billion years, which is why potassium-argon dating is popular for dating really old things) and only composes 0.012% of natural potassium. Potassium’s also much less abundant in the body than carbon—only about 140g of a 70kg person is potassium, although admittedly it might be more concentrated in the brain, which is the important part.
ETA—I did calculations, and maybe there is a problem. Suppose 0.012% of K is K-40 by mass. Then I get 0.0168 grams of K-40 in a body, which comes out as 0.00042 moles, 2.53e20 K-40 atoms. With a 1.25 billion year half life that makes 1.40e15 decays after 10,000 years. In absolute terms that’s a lot of emitted electrons and positrons. I don’t know whether the absolute number (huge) or the relative number (miniscule) is more important though.
I don’t have enough background to estimate how serious the decay would be. But with 1.40e15 decays after 10,000 years that’s around 3000 decay events a second (in practice most of that will be in the first few thousand years given that decay occurs exponentially). It seems that part of the issue also is that there’s no repair mechanism. When something is living it can take a fair bit of radiation with minimal negative results. In some circumstances living creatures can even benefit from low levels of radiation. But radiation is going to be much more damaging to cells when they can’t engage in any repairs.
Edit:Also note that the majority of the radiation that people are subject to is from potassium 40 so if this is ok then we’re generally ok. It seems that radiation is not a major limiting factor on long-term cryonic storage.
It’s true that radiation is more damaging to cells when they can’t engage in repairs. But damage is nothing to worry about in this case. When e.g. a gamma ray photon breaks a protein molecule, that molecule is rendered nonfunctional; enough such events will kill a cell. But in the context of cryonics, a broken molecule is as good as an intact one provided it’s still recognizable. Rendering it impossible to tell what the original molecule was, would take far more thorough destruction.
From Wikipedia, “The worldwide average background dose for a human being is about 2.4 millisievert (mSv) per year.” Even a lethal prompt dose is a couple of thousand times this quantity. And you can take maybe 10 times the lethal dose and still be conscious for a little while. So that’s 20,000 years of background radiation verified to not even significantly damage, let alone erase, the information in the brain. I’d be surprised if the timescale to information theoretic death by that mechanism was very much less than a billion years.
The lack of an automatic repair mechanism makes things hairier, but while frozen, the radiation damage will be localized to the cells that get hit by radiation. By the time you get the tech to revive people from cryonic freezing, you’ll most likely have the tech to fix/remove/replace the individual damaged cells before reviving someone. I think you’re right that radiation won’t be a big limiting factor, though it may be an annoying obstacle.
I don’t know so much about C-14, but wouldn’t potassium decay’s effects be small on timescales ~10,000 years? The radioactive natural isotope K-40 has a ridiculously long half life (1.25 billion years, which is why potassium-argon dating is popular for dating really old things) and only composes 0.012% of natural potassium. Potassium’s also much less abundant in the body than carbon—only about 140g of a 70kg person is potassium, although admittedly it might be more concentrated in the brain, which is the important part.
ETA—I did calculations, and maybe there is a problem. Suppose 0.012% of K is K-40 by mass. Then I get 0.0168 grams of K-40 in a body, which comes out as 0.00042 moles, 2.53e20 K-40 atoms. With a 1.25 billion year half life that makes 1.40e15 decays after 10,000 years. In absolute terms that’s a lot of emitted electrons and positrons. I don’t know whether the absolute number (huge) or the relative number (miniscule) is more important though.
I don’t have enough background to estimate how serious the decay would be. But with 1.40e15 decays after 10,000 years that’s around 3000 decay events a second (in practice most of that will be in the first few thousand years given that decay occurs exponentially). It seems that part of the issue also is that there’s no repair mechanism. When something is living it can take a fair bit of radiation with minimal negative results. In some circumstances living creatures can even benefit from low levels of radiation. But radiation is going to be much more damaging to cells when they can’t engage in any repairs.
Edit:Also note that the majority of the radiation that people are subject to is from potassium 40 so if this is ok then we’re generally ok. It seems that radiation is not a major limiting factor on long-term cryonic storage.
It’s true that radiation is more damaging to cells when they can’t engage in repairs. But damage is nothing to worry about in this case. When e.g. a gamma ray photon breaks a protein molecule, that molecule is rendered nonfunctional; enough such events will kill a cell. But in the context of cryonics, a broken molecule is as good as an intact one provided it’s still recognizable. Rendering it impossible to tell what the original molecule was, would take far more thorough destruction.
From Wikipedia, “The worldwide average background dose for a human being is about 2.4 millisievert (mSv) per year.” Even a lethal prompt dose is a couple of thousand times this quantity. And you can take maybe 10 times the lethal dose and still be conscious for a little while. So that’s 20,000 years of background radiation verified to not even significantly damage, let alone erase, the information in the brain. I’d be surprised if the timescale to information theoretic death by that mechanism was very much less than a billion years.
The lack of an automatic repair mechanism makes things hairier, but while frozen, the radiation damage will be localized to the cells that get hit by radiation. By the time you get the tech to revive people from cryonic freezing, you’ll most likely have the tech to fix/remove/replace the individual damaged cells before reviving someone. I think you’re right that radiation won’t be a big limiting factor, though it may be an annoying obstacle.