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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Cryonics | 1/3 | https://en.wikipedia.org/wiki/Cryonics | reference | science, encyclopedia | 2026-05-05T09:18:26.108623+00:00 | kb-cron |
Cryonics (from Greek: κρύος kryos, meaning "cold") is the low-temperature freezing (usually at −196 °C or −320.8 °F or 77.1 K) and storage of human remains in the hope that resurrection may be possible in the future. Cryonics is regarded with skepticism by the mainstream scientific community. It is generally viewed as a pseudoscience, and its practice has been characterized as quackery. Cryonics procedures can begin only after the "patients" are clinically and legally dead. Procedures may begin within minutes of death, and use cryoprotectants to try to prevent ice formation during cryopreservation. It is not possible to reanimate a corpse that has undergone vitrification (ultra-rapid cooling), as this damages the brain, including its neural circuits. The first corpse to be frozen was that of James Bedford, in 1967. As of 2014, remains from about 250 bodies had been cryopreserved in the United States, and 1,500 people had made arrangements for cryopreservation of theirs. Even if the resurrection promised by cryonics were possible, economic considerations make it unlikely cryonics corporations could remain in business long enough to deliver. The "patients", being dead, cannot continue to pay for their own preservation. Early attempts at cryonic preservation were made in the 1960s and early 1970s; most relied on family members to pay for the preservation and ended in failure, with all but one of the corpses cryopreserved before 1973 being thawed and disposed of.
== Conceptual basis == Cryonicists argue that as long as brain structure remains intact, there is no fundamental barrier, given our current understanding of physics, to recovering its information content. Cryonics proponents go further than the mainstream consensus in saying that the brain does not have to be continuously active to survive or retain memory. Cryonicists controversially say that a human can survive even within an inactive, badly damaged brain, as long as the original encoding of memory and personality can be adequately inferred and reconstituted from what remains. Cryonics uses temperatures below −130 °C, called cryopreservation, in an attempt to preserve enough brain information to permit the revival of the cryopreserved person. Cryopreservation is accomplished by freezing with or without cryoprotectant to reduce ice damage, or by vitrification to avoid ice damage. Even using the best methods, cryopreservation of whole bodies or brains is very damaging and irreversible with current technology. Cryonicists call the human remains packed into low-temperature vats "patients". They hope that some kind of presently nonexistent nanotechnology will be able to bring the dead back to life and treat the diseases that killed them. Mind uploading has also been proposed.
== Cryonics in practice == As of 2018, the cost of preparing and storing corpses using cryonics ranged from US$28,000 to $200,000. At high concentrations, cryoprotectants can stop ice formation completely. Cooling and solidification without crystal formation is called vitrification. In the late 1990s, cryobiologists Gregory Fahy and Brian Wowk developed the first cryoprotectant solutions that could vitrify at very slow cooling rates while still allowing whole organ survival, for the purpose of banking transplantable organs. This has allowed animal brains to be vitrified, thawed, and examined for ice damage using light and electron microscopy. No ice crystal damage was found; cellular damage was due to dehydration and toxicity of the cryoprotectant solutions. Costs can include payment for medical personnel to be on call for death, vitrification, transportation in dry ice to a preservation facility, and payment into a trust fund intended to cover indefinite storage in liquid nitrogen and future revival costs. As of 2011, U.S. cryopreservation costs can range from $28,000 to $200,000, and are often financed via life insurance. KrioRus, which stores bodies communally in large dewars, charges $12,000 to $36,000 for the procedure. Some customers opt to have only their brain cryopreserved ("neuropreservation"), rather than their whole body. As of 2014, about 250 corpses have been cryogenically preserved in the U.S., and around 1,500 people have signed up to have their remains preserved. As of 2022, five facilities retained cryopreserved bodies: three in the U.S., one in Russia, and one in Berlin. It seems extremely unlikely that any cryonics company could exist long enough to take advantage of the supposed benefits offered; historically, even the most robust corporations have only a one-in-a-thousand chance of lasting 100 years. Many cryonics companies have failed; as of 2018, all but one of the pre-1973 batch had gone out of business, and their stored corpses have been defrosted and disposed of.
== Obstacles to success ==
=== Preservation damage === Medical laboratories have long used cryopreservation to maintain animal cells, human embryos, and even some organized tissues, for periods as long as three decades, but recovering large animals and organs from a frozen state is not considered possible now. Large vitrified organs tend to develop fractures during cooling, a problem worsened by the large tissue masses and very low temperatures of cryonics. Without cryoprotectants, cell shrinkage and high salt concentrations during freezing usually prevent frozen cells from functioning again after thawing. Ice crystals can also disrupt connections between cells that are necessary for organs to function. Some cryonics organizations use vitrification without a chemical fixation step, sacrificing some structural preservation quality for less damage at the molecular level. Some scientists, like João Pedro Magalhães, have questioned whether using a deadly chemical for fixation eliminates the possibility of biological revival, making chemical fixation unsuitable for cryonics. Outside of cryonics firms and cryonics-linked interest groups, many scientists are very skeptical about cryonics methods. Cryobiologist Dayong Gao has said, "we simply don't know if [subjects have] been damaged to the point where they've 'died' during vitrification because the subjects are now inside liquid nitrogen canisters." Based on experience with organ transplants, biochemist Ken Storey argues that "even if you only wanted to preserve the brain, it has dozens of different areas which would need to be cryopreserved using different protocols".