First, we need a conceptual framework. The whole point of cryonics is to stop chemistry, so if you’re cryopreserved and then exposed to ionizing radiation over any period of time, you’ll experience the same amount of damage as if you were alive and exposed to that much radiation all at once. (Being alive and exposed to radiation over a period of time is different; you experience less damage because your cells have time to repair themselves.)
Wikipedia says “Estimates are that humans unshielded in interplanetary space would receive annually roughly 400 to 900 milli-Sieverts (mSv) (compared to 2.4 mSv on Earth)”. Wikipedia also says that an acute exposure of 4500 to 5000 mSv is “LD50 in humans (from radiation poisoning), with medical treatment”. Now, LD50 isn’t LD100, but we can agree that it’s a Very Bad Dose.
Generously, assuming that the Very Bad Dose is 5000 mSv, and Outer Space’s Death Rays are 400 mSv/yr, being Cryopreserved In Space will give you a Very Bad Dose in 12.5 years. This is compared to roughly 2000 years on Earth.
That answers one half of Eliezer’s question. My answer to the other half (is this significant in information-theoretic terms) is mu. When you’re cryopreserved, you’re double dead—dead from whatever killed you, and dead again from cryopreservation damage. You’re betting that the future can fix this, but you shouldn’t give the future even more work to do, and being triple dead from radiation damage wouldn’t help.
This fits in with something I’ve been wondering in general just for Earth based cryopreservation. How much effort do cryonic organizations make to ensure that there’s a minimum of radiation exposure to the cryopreserved individuals? Even background radiation matters a lot more than it would for a living person since there’s no ongoing repair mechanisms. I suspect that the bodies are not being subject to much external radiation simply because the cryochambers themselves would block most of it. But, the bodies themselves will generate some radiation, primarily from the decay of potassium 40 and carbon 14. Naively if one were trying absolutely to minimize this one would try to have people who knew they were likely to die soon (due to terminal illness) to eat diets which have less potassium. One could also conceive of having foods made made with carbon that had a low amount of c-14. But given the proportions I’m pretty sure that the bulk of the radiation will be from potassium 40. Robert Ettinger at one point presented a back of the envelope calculation that showed that the radiation just from potassium 40 is unlikely to be a problem if one is the range of 50-100 years, but if one is interested in longer ranges then this becomes a more serious worry.
Remember that it takes a lot more radiation to erase someone than to merely kill them.
To information-theoretically erase a person would seem to require that at least 40% of the molecules in their brains are altered, which would seem to imply at least 10^24 or so radioactive particles. This is extremely high.
I’m curious where you are getting the 40% number. I’m not completely sure what we mean by erasing a person since the mind isn’t a binary presence that is there or not. Damage can result in loss of some aspects of personality or some memories without complete erasure. Presumably, most people would like to minimize that issue.
Given your 40% claim I tentatively agree with your 10^24 number. There’s a minor issue of cascading particles but that shouldn’t be a problem since most of the radiation is going to be low energy beta particles. I am however concerned slightly that radiation could result in additional free radicals which are able to jump around and do unpleasant chemical stuff even at the temperatures of liquid nitrogen. I suspect that this would not be a major issue either but I don’t think I have anywhere near enough biochem knowledge to make a strong conclusion about this.
Additionally, as STL pointed out, we don’t want to make things more difficult for the people reviving them. This combines badly with the first-in-last-out nature of cryonics- the bodies which have been around longer will have more radiation damage and will already be much more technically difficult to revive. Moreover, some people will strongly prefer being reanimated in their own bodies rather than as simulations on computers. The chance that that can occur is lower if the bodies have serious problems due to radiation damage.
Say you randomly alter 1% of the molecules in the brain. Then almost every neuron would still recognizably be a neuron, and still have synapses that connected to the right things, and any concentration of neurotransmitter X would still recognizably be type X (rather than Y). There is no way I see for 1% random destruction to erase the person information-theoretically.
The difference between 1% and 40% is not actually so much… 10^22 vs 10^24. Still huge.
Say you randomly alter 1% of the molecules in the brain. Then almost every neuron would still recognizably be a neuron, and still have synapses that connected to the right things, and any concentration of neurotransmitter X would still recognizably be type X (rather than Y). There is no way I see for 1% random destruction to erase the person information-theoretically.
Would this be enough to keep thresholds for action potentials correct? I’m more familiar with neural nets for computational purposes than with actual neural architecture, but for neural nets this matters a lot. You can have wildly different behavior even with the same neurons connected to each other just by changing the potential levels. Learning behavior consists not just in constructing or removing connections but also in strengthening and weakening existing connections.
I don’t know why you mention the concentrations of neurotransmitters since that’s a fairly temporary thing which (as far as I’m aware) doesn’t contain much in the way of actual data except about neurons which have fired very recently.
Would this be enough to keep thresholds for action potentials correct
What determines the threshold for an action potential? If it’s something bigger than a few dozen molecules, it seems that a random 1% destruction can’t erase it.
There is no way I see for 1% random destruction to erase the person information-theoretically.
I suspect you are right. Since the important structures involved are significantly larger than one molecule, most of the single molecule alterations will be rather obvious and easy to reverse (for a given kind of ‘easy’).
Shopping is hard, let’s do math!
First, we need a conceptual framework. The whole point of cryonics is to stop chemistry, so if you’re cryopreserved and then exposed to ionizing radiation over any period of time, you’ll experience the same amount of damage as if you were alive and exposed to that much radiation all at once. (Being alive and exposed to radiation over a period of time is different; you experience less damage because your cells have time to repair themselves.)
Wikipedia says “Estimates are that humans unshielded in interplanetary space would receive annually roughly 400 to 900 milli-Sieverts (mSv) (compared to 2.4 mSv on Earth)”. Wikipedia also says that an acute exposure of 4500 to 5000 mSv is “LD50 in humans (from radiation poisoning), with medical treatment”. Now, LD50 isn’t LD100, but we can agree that it’s a Very Bad Dose.
Generously, assuming that the Very Bad Dose is 5000 mSv, and Outer Space’s Death Rays are 400 mSv/yr, being Cryopreserved In Space will give you a Very Bad Dose in 12.5 years. This is compared to roughly 2000 years on Earth.
That answers one half of Eliezer’s question. My answer to the other half (is this significant in information-theoretic terms) is mu. When you’re cryopreserved, you’re double dead—dead from whatever killed you, and dead again from cryopreservation damage. You’re betting that the future can fix this, but you shouldn’t give the future even more work to do, and being triple dead from radiation damage wouldn’t help.
This fits in with something I’ve been wondering in general just for Earth based cryopreservation. How much effort do cryonic organizations make to ensure that there’s a minimum of radiation exposure to the cryopreserved individuals? Even background radiation matters a lot more than it would for a living person since there’s no ongoing repair mechanisms. I suspect that the bodies are not being subject to much external radiation simply because the cryochambers themselves would block most of it. But, the bodies themselves will generate some radiation, primarily from the decay of potassium 40 and carbon 14. Naively if one were trying absolutely to minimize this one would try to have people who knew they were likely to die soon (due to terminal illness) to eat diets which have less potassium. One could also conceive of having foods made made with carbon that had a low amount of c-14. But given the proportions I’m pretty sure that the bulk of the radiation will be from potassium 40. Robert Ettinger at one point presented a back of the envelope calculation that showed that the radiation just from potassium 40 is unlikely to be a problem if one is the range of 50-100 years, but if one is interested in longer ranges then this becomes a more serious worry.
Remember that it takes a lot more radiation to erase someone than to merely kill them.
To information-theoretically erase a person would seem to require that at least 40% of the molecules in their brains are altered, which would seem to imply at least 10^24 or so radioactive particles. This is extremely high.
I’m curious where you are getting the 40% number. I’m not completely sure what we mean by erasing a person since the mind isn’t a binary presence that is there or not. Damage can result in loss of some aspects of personality or some memories without complete erasure. Presumably, most people would like to minimize that issue.
Given your 40% claim I tentatively agree with your 10^24 number. There’s a minor issue of cascading particles but that shouldn’t be a problem since most of the radiation is going to be low energy beta particles. I am however concerned slightly that radiation could result in additional free radicals which are able to jump around and do unpleasant chemical stuff even at the temperatures of liquid nitrogen. I suspect that this would not be a major issue either but I don’t think I have anywhere near enough biochem knowledge to make a strong conclusion about this.
Additionally, as STL pointed out, we don’t want to make things more difficult for the people reviving them. This combines badly with the first-in-last-out nature of cryonics- the bodies which have been around longer will have more radiation damage and will already be much more technically difficult to revive. Moreover, some people will strongly prefer being reanimated in their own bodies rather than as simulations on computers. The chance that that can occur is lower if the bodies have serious problems due to radiation damage.
Say you randomly alter 1% of the molecules in the brain. Then almost every neuron would still recognizably be a neuron, and still have synapses that connected to the right things, and any concentration of neurotransmitter X would still recognizably be type X (rather than Y). There is no way I see for 1% random destruction to erase the person information-theoretically.
The difference between 1% and 40% is not actually so much… 10^22 vs 10^24. Still huge.
Would this be enough to keep thresholds for action potentials correct? I’m more familiar with neural nets for computational purposes than with actual neural architecture, but for neural nets this matters a lot. You can have wildly different behavior even with the same neurons connected to each other just by changing the potential levels. Learning behavior consists not just in constructing or removing connections but also in strengthening and weakening existing connections.
I don’t know why you mention the concentrations of neurotransmitters since that’s a fairly temporary thing which (as far as I’m aware) doesn’t contain much in the way of actual data except about neurons which have fired very recently.
What determines the threshold for an action potential? If it’s something bigger than a few dozen molecules, it seems that a random 1% destruction can’t erase it.
I don’t know enough about the mechanisms to to comment. Do we have any more biologically inclined individuals here who can?
I suspect you are right. Since the important structures involved are significantly larger than one molecule, most of the single molecule alterations will be rather obvious and easy to reverse (for a given kind of ‘easy’).
Life is tough. Unlife is tougher.