It can be hard to get factual information about Cryonics and most wiki pages appear as if they were written by Cryonics Enthusiasts or PR men - Below is a comprehensive list of the most factual websites. The main body of text is from: http://rationalwiki.org/wiki/Cryonics
"Cryonics is the practice of freezing clinically dead people in liquid nitrogen with the hope of future reanimation.
Presently-nonexistent nanotechnology or mind uploading are the favored methods envisioned for revival.
Scientists will admit that some sort of cryogenic preservation and revival does not provably violate known physics. But they stress that, in practical terms, freezing and reviving dead humans is so far off as to hardly be worth taking seriously; present cryonics practices are speculation at best, and quackery and pseudoscience at worst.
Nevertheless, cryonicists will accept considerable amounts of money right now for procedures based only on vague science-fiction-level speculations, with no scientific evidence whatsoever that any of their present actions will help achieve their declared aims. They sincerely consider this an obviously sensible idea that one would have to be stupid not to sign up for.
Cryonics should not be confused with cryobiology (the study of living things and tissues at low temperatures), cryotherapy (the use of cold in medicine) or cryogenics
There is no scientific evidence whatsoever that any of what cryonicists currently do will make revival any easier, or even that it does preserve the neural information — they just think it sounds like a plausible hypothesis that it will.
There is no scientific evidence that it will be more effective than the preservation technology the ancient Egyptians used on their pharaohs, viz., taking the brain out in pieces via the nose and putting it in a jar next to the mummy for safekeeping — with their knowledge and beliefs at the time suggesting a non-zero probability that this would work. They could just as easily have said, "In 6000 years we'll be able to do anything!" But even the so-called technological singularity won't be enough to get the pharaohs back.
Ben Best, CEO of the Cryonics Institute, supplies in Scientific Justification of Cryonics Practice a list of cryobiology findings that suggest that cryonicists might not be completely wrong; however, this paper (contrary to the promise of its title) also contains a liberal admixture of "then a miracle occurs." His assertions as to what cited papers say also vary considerably from what the cited papers' abstracts state.
Alcor Corporation calls cryonics "a scientific approach to extending human life" and compares it to heart surgery. This is a gross misrepresentation of the state of both the science and technology and verges on both pseudoscience and quackery.
Keeping the head or body at -196°C stops chemistry, but causes massive damage to the cells. The following problems (many of which are acknowledged by cryonicist) would all need to be solved to bring a frozen head or body back to life. Many would need breakthroughs not merely in engineering, but in scientific understanding itself, which we simply cannot predict.
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WARNING - The Cryonics page on Wikipedia appears like it was written by a PR Expert working for a Cryonics company see here: http://en.wikipedia.org/wiki/Talk%3ACryonics