I'm a little bit puzzled how this conversation is occurring. This is the commonest question people have/criticism they make about cryonics. They say: "Sure you can be frozen, but can you come back to life?" The answer from cryonicists: "Well, we certainly hope so! We can't do it now, but with the wonders of technology in 100-200 years, maybe it will be doable!" If you're wondering
in principle if it's possible to bring a frozen human being (including, crucially, their nervous system) back to life, I'd tentatively say yes. I think it's clear that it's possible
in principle to make biological machines (
step 1 happened this year), to make nanotechnology that can manipulate matter down to the individual atom, to become a
Type III civilization, to use
mind uploading, and even to become superintelligent. Furthermore, I think it's quite plausible that biological machines, advanced nanotech, Type III energy supplies, mind uploading, and superintelligence will become realities
eventually -- whether it takes 200 or 10,000 or 3,000,000 years -- as long as civilization keeps progressing smoothly like (more or less) it has been since the Scientific Revolution.
Let's try a fanciful thought experiment: the second after a person's heart stops (legal death), their body is instantly preserved down to the atom (I said it was fanciful). Long later, with the 5 technologies I listed in the last paragraph in full swing, can we revive the patient? I don't know how you could doubt that we can, with the ability to use bio/nano machines manipulate the patient's body down to every atom.
So the real 3 worrying questions about cryonics are:
1) Is the
vitrification process good enough to preserve a person's mind just as it was before they were legally declared dead? The legal declaration is only based on the fact that our medical technology isn't good enough yet to revive someone if we can't get their heart beating again right away. "Flatlining", the first second of the heart beat falters completely, would be our legal death if we didn't have defibrillators. A positive sign is that people have, on rare occasions, been revived
minutes after they were declared legally dead (after the defibrillators failed). Their minds were in the same state they were beforehand. So if we can vitrify brains to preserve minds to the level of
two-minutes-after-declaration-of-legal-death, worry (1) is a worry no more! But that remains to be seen. We will only really know once we bust out our nanobots.
2) How fast will a vitrified brain deteriorate in preservation quality over time? This, I think, is a small worry compared to (1), although still a worry. Estimates I've heard say there is virtually no change until sometime between a few hundred years and 40,000 years [
citation needed :p]. Worry (2) is inextricable from worry (3):
3) Will the 5 technologies (or just as many as are necessarily -- e.g. just biotech and nanotech) arrive on time to save the frozen patients? Or will the deterioration just discussed in (2) outpace the growth of technology?
In other words, for anyone interested in cryonics, the two main uncertainties are: how good is the vitrification we do
now? and how
fast will advanced nanotech arrive on the scene? Whether it is
in principle possible to revive a human being is not a main worry, because the answer is
yes,
so long as the vitrification we do now is good enough. How good is good enough? We don't know yet, and probably won't know until we get advanced nanotech and try to revive cryonics patients. That is the whole idea of cryonics. It is an informed gamble: a cost-benefit analysis everyone must make for themself.
P.S. The second most common objection to cryonics is that cryonics is unfordable to the average person. This is almost universally believed, but not true: cryonics ranges from a total lifetime cost ranging from
$29,250 to a maximum of
$200,000. These may seem like a lot, but if you purchase a good life insurance plan when you are relatively young and healthy, the actual total lifetime cost to you is much lower. Also, in the latter example I linked to, you can pay significantly less than $200,000 if you plan ahead and pay membership dues.
Edited by Trent, 24 September 2010 - 04:00 AM.