Cryonics is the low temperature preservation of humans and other animals that can no longer be sustained by contemporary medicine until resuscitation may be possible in the future. Human cryopreservation is not currently reversible. In the United States, cryonics can only be legally performed on humans after clinical death. The rationale for cryonics is that the process may be reversible in the future if performed soon enough, and that cryopreserved people may not really be dead by the information-theoretic definition of death. Cryonics is derived from the Greek word κρύος (kryos), meaning icy cold.
Cryonics faces many obstacles, and is viewed with skepticism by most scientists and doctors today. However, there is a high representation of scientists among cryonics supporters. Scientific support for cryonics is based on studies showing substantial preservation of brain cell structure by current methods, and projections of future technology, especially molecular nanotechnology and nanomedicine. Some scientists believe that future medicine will enable molecular-level repair and regeneration of damaged tissues and organs decades or centuries in the future. Disease and aging are also assumed to be reversible. Many ethical questions revolve around the issue of whether cryonics can work.
The modern concept of cryonics as a general procedure to apply whenever patients are considered beyond help by the medicine of their time was originated in 1962 by Robert Ettinger. The largest current practitioners of cryonics are two member-owned, non-profit organizations, the Alcor Life Extension Foundation in Scottsdale, Arizona, with 77 cryopreserved patients and the Cryonics Institute in Clinton Township, Michigan with 84.
- 1 Premises of cryonics
- 2 Obstacles to success
- 3 Neuropreservation
- 4 Financial issues
- 5 Philosophical and ethical considerations
- 6 History
- 7 Culture
- 8 See also
- 9 References
- 10 External links
Premises of cryonics
The central premise of cryonics is that memory, personality, and identity are stored in the structure and chemistry of the brain. While this view is widely accepted in medicine, and brain activity is known to stop and later resume under certain conditions, it is not generally accepted that current methods preserve the brain well enough to permit revival in the future. Cryonics advocates point to studies showing that high concentrations of cryoprotectant circulated through the brain before cooling can largely prevent freezing injury, preserving the fine cell structures of the brain in which memory and identity presumably reside.
To its detractors, the justification for the actual practice of cryonics is unclear, given present limitations of preservation technology. Currently cells, tissues, blood vessels, and some small animal organs can be reversibly cryopreserved. Some frogs can survive for a few months in a partially frozen state a few degrees below freezing, but this is not true cryopreservation. Cryonics advocates counter that demonstrably reversible preservation is not necessary to achieve the present-day goal of cryonics, which is preservation of basic brain information that encodes memory and personal identity. Preservation of this information is said to be sufficient to prevent information theoretical death until future repairs might be possible.
Obstacles to success
Long-term cryopreservation requires cooling to near -196 °C, the temperature of liquid nitrogen. Cooling whole people to this temperature causes injuries that are not reversible with present technology. The common belief that water freezes inside cells causing them to burst is a myth, but damage from freezing can still be serious. When untreated tissue is slowly cooled below the freezing point of water, ice forms between cells, causing mechanical and chemical damage. Cryonics uses cryoprotectants to reduce this damage. Cryoprotectant solutions are circulated through blood vessels to remove and replace water inside cells with chemicals that prevent freezing. This can reduce damage greatly, but not enough for whole people to recover spontaneously from cryopreservation.
When used at high concentrations, cryoprotectants stop ice formation completely. Cooling and solidification without freezing is called vitrification. The first cryoprotectant solutions able to vitrify at very slow cooling rates while still being compatible with tissue survival were developed in the late 1990s by cryobiologists Gregory Fahy and Brian Wowk for the purpose of banking transplantable organs. These solutions were adopted for use in cryonics by the Alcor Life Extension Foundation, for which they are believed to permit vitrification of some parts of the human body, especially the brain. This has allowed animal brains to be vitrified, warmed back up, and examined for ice damage using light and electron microscopy. No ice crystal damage was found. The Cryonics Institute also uses a vitrification solution developed by their staff cryobiologist, Dr. Yuri Pichugin, applying it principally to the brain.
Vitrification in cryonics is different than vitrification in mainstream cryobiology because vitrification in cryonics is not reversible with current technology. It is only structural vitrification. When successful it can prevent freezing injury in some body parts, but at the price of toxicity caused by cryoprotectant chemicals. The nature of this toxicity is still poorly understood. Cryonicists assume that toxicity is more subtle and repairable than obvious structural damage that would otherwise be caused by freezing. If, for example, toxicity is due to denatured proteins, those proteins could be repaired or replaced.
Ischemia means inadequate or absent blood circulation that deprives tissue of oxygen and nutrients. At least several minutes of ischemia is an unavoidable part of cryonics because of the legal requirement that cryonics procedures do not begin until after blood circulation stops. The heart must stop beating so that legal death can be declared. When there is advance notice of impending clinical death, it is sometimes possible to deploy a team of technicians to perform a “standby”. The team artificially restores blood circulation and breathing using techniques similar to CPR as soon as possible after the heart stops. The aim is to keep tissues alive after legal death by analogy to conventional medical procedures in which viable organs and tissues are obtained for transplant from legally deceased donors. Contrary to popular belief, legal death does not mean that all the cells of the body have died.
Often in cryonics the brain is without oxygen for many minutes at warm temperatures, or even hours if the heart stops unexpectedly. This causes ischemic injury to the brain and other tissues that makes resuscitation impossible by present medical technology. Cryonicists justify preservation under such conditions by noting recent advances that allow brain resuscitation after longer periods of ischemia than the traditional 4 to 6 minute limit, and persistence of brain structure and even some brain cell function after long periods of clinical death. They argue that definitions of death change as technology advances, and the early stages of what is called “death” today is actually a form of ischemic injury that will be reversible in the future. They claim that personal survival during long periods of clinical death is determined by information theoretic criteria.
It is universally agreed by scientists and cryonics advocates that reversing human cryopreservation is not possible with “any near-term technology.” Those who believe that revival may someday be possible generally look toward advanced bioengineering, molecular nanotechnology, nanomedicine, or mind uploading as key technologies. Revival (except for mind uploading, the most speculative and hypothetical technique) requires repairing damage from lack of oxygen, cryoprotectant toxicity, thermal stress (fracturing), freezing in tissues that do not successfully vitrify, physical therapy to regain function of the body (similar to that of a long-term coma), and reversing the effects that caused the patient death. In many cases extensive tissue regeneration will be necessary. Hypothetical revival scenarios generally envision repairs being performed by vast numbers of microscopic organisms or devices. These devices would restore healthy cell structure and chemistry at the molecular level, ideally before warming. More radically, mind transfer has also been suggested as a possible revival approach if and when technology is ever developed to scan the memory contents of a preserved brain.
It has often been written that cryonics revival will be a last-in-first-out (LIFO) process. In this view, preservation methods will get progressively better until eventually they are demonstrably reversible, after which medicine will begin to reach back and revive people cryopreserved by more primitive methods. Revival of people cryopreserved by the current combination of neurovitrification and deep-cooling (technically not "freezing", as cryoprotectant inhibits ice crystallization) may require centuries, if it is possible at all.
It has been claimed that if technologies for general molecular analysis and repair are ever developed, then theoretically any damaged body could be “revived.” Survival would then depend on whether preserved brain information was sufficient to permit restoration of all or part of the personal identity of the original person, with amnesia being the final dividing line between life and death.
Neuropreservation is cryopreservation of the brain, usually within the head, with surgical removal and disposal of the rest of the body. Neuropreservation, sometimes called “neuro,” is one of two distinct preservation options in cryonics, the other being "whole body" preservation.
Neuropreservation is motivated by the fact that the brain is the primary repository of memory and personal identity. (For instance, spinal cord injury victims, organ transplant patients, and amputees retain their personal identity.) It is also motivated by the belief that reversing any type of cryonic preservation is so difficult and complex that any future technology capable of it must by its nature be capable of generalized tissue regeneration, including regrowth of a new body around a repaired brain. Some suggested revival scenarios for whole body patients even involve discarding the original body and regenerating a new one because tissues are so badly damaged by the preservation process. These considerations, along with lower costs, easier transportation in emergencies, and the specific focus on brain preservation quality, have motivated many cryonicists to choose neuropreservation.
The advantages and disadvantages of neuropreservation are often debated among cryonics advocates. Critics of neuropreservation note that the body is a record of much life experience, including learned motor skills. While few cryonicists doubt that a revived neuro patient would be the same person, there are wider questions about how a regenerated body might feel different from the original. Partly for these reasons (as well as for better public relations), the Cryonics Institute preserves only whole bodies. Some proponents of neuropreservation agree with these concerns, but still feel that lower costs and better brain preservation justify preserving only the brain. About three-quarters of the patients stored at Alcor are "neuros".
Costs of cryonics vary greatly, ranging from $28,000 for cryopreservation by Cryonics Institute, to $150,000 for whole body cryopreservation by Alcor. To some extent these cost differences reflect differences in how fees are quoted. The Cryonics Institute fee doesn’t include “standby” (a team that begins procedures at bedside), transportation costs, or funeral director expenses outside of Michigan, which must be purchased as extras. CI Members wanting Standby and Transport from cryonics professionals can contract for additional payment to the Florida-based company Suspended Animation, Inc.
While cryonics is sometimes suspected of being greatly profitable, the high expenses of doing cryonics are well documented. The expenses are comparable to major transplant surgeries. The largest single expense, especially for whole body cases, is the money that must be set aside to generate interest to pay for maintenance in perpetuity.
The most common method of paying for cryonics is life insurance, which spreads the cost over many years. Cryonics advocates are quick to point out that such insurance is especially affordable for young people. It has been claimed that cryonics is “affordable for the vast majority” of people in the industrialized world who really want it and plan for it in advance.
Philosophical and ethical considerations
Cryonics is based on a view of dying as a process that can be stopped in the minutes, and perhaps hours, following clinical death. If death is not an event that happens suddenly when the heart stops, this raises philosophical questions about what exactly death is. In 2005 an ethics debate in the medical journal, Critical Care, noted “…few if any patients pronounced dead by today’s physicians are in fact truly dead by any scientifically rigorous criteria.” Cryonics proponent Thomas Donaldson has argued that “death” based on cardiac arrest or resuscitation failure is a purely social construction used to justify terminating care of dying patients. In this view, legal death and its aftermath are a form of euthanasia in which sick people are abandoned. Philosopher Max More suggested a distinction between death associated with circumstances and intention versus death that is absolutely irreversible. Absolutely irreversible death has also been called information-theoretic death, which is destruction of the brain to such an extent that the original information content can no longer be inferred. Bioethicist James Hughes has written that increasing rights will accrue to cryonics patients as prospects for revival become clearer, noting that recovery of legally dead persons has precedent in the discovery of missing persons.
Ethical and theological opinions of cryonics tend to pivot on the issue of whether cryonics is regarded as interment or medicine. If cryonics is interment, then religious beliefs about death and afterlife may come into consideration. Resuscitation may be deemed impossible by those with religious beliefs because the soul is gone, and according to most religions only God can resurrect the dead. Expensive interment is seen as a waste of resources. If cryonics is regarded as medicine, with legal death as a mere enabling mechanism, then cryonics is a long-term coma with uncertain prognosis. It is continuing to care for sick people when others have given up, and a legitimate use of resources to sustain human life. Cryonics advocates complain that theological dismissal of cryonics because it is interment is a circular argument because calling cryonics "interment" presumes that cryonics cannot work. They believe future technical advances will validate their view that cryonics patients are recoverable, and therefore never really dead.
Alcor has published a vigorous Christian defense of cryonics, including excerpts of a sermon by Lutheran Reverend Kay Glaesner. Noted Christian apologist John Warwick Montgomery has defended cryonics. In 1969, a Roman Catholic priest consecrated the cryonics capsule of Ann DeBlasio, one of the first cryonics patients. Many followers of Nikolai Fyodorovich Fyodorov see cryonics as an important step in the Common Cause project (reference: Fedorov seminar in Moscow, Russia on 25.11.2006) and compatible with Orthodox Christianity.
Benjamin Franklin suggested in a famous 1773 letter that it might be possible to preserve human life in a suspended state for centuries. However, the modern era of cryonics began in 1962 when Michigan college physics teacher Robert Ettinger proposed in a privately published book, “The Prospect of Immortality”, that freezing people may be a way to reach future medical technology. Even though freezing a person is apparently fatal, Ettinger argued that what appears to be fatal today may be reversible in the future. He applied the same argument to the process of dying itself, saying that the early stages of clinical death may be reversible in the future. Combining these two ideas, he suggested that freezing recently deceased people may be a way to save lives.
Slightly before Ettinger’s book was complete, Evan Cooper (writing as Nathan Duhring) privately published a book called Immortality: Physically, Scientifically, Now that independently suggested the same idea. Cooper founded the Life Extension Society in 1965 to promote freezing people. Ettinger came to be credited as the originator of cryonics, perhaps because his book was republished by Doubleday in 1964 on recommendation of Isaac Asimov and Fred Pohl, and received more publicity. Ettinger also stayed with the movement longer. Nevertheless, cryonics historian R. Michael Perry has written “Evan Cooper deserves the principal credit for forming an organized cryonics movement.” Cooper founded the first cryonics organization in 1964, the Life Extension Society (LES).
The actual word “cryonics” was invented by Karl Werner in 1965 in conjunction with the founding of the Cryonics Society of New York (CSNY) by Curtis Henderson and Saul Kent that same year. This was followed by the founding of the Cryonics Society of Michigan (CSM) and Cryonics Society of California (CSC) in 1966, and Bay Area Cryonics Society (BACS) in 1969 (renamed the American Cryonics Society, or ACS, in 1985). CSM eventually became the Immortalist Society, a non-profit affiliate of the Cryonics Institute (CI), a cryonics service organization founded by Robert Ettinger in 1976, now the second-largest cryonics organization.
Although there was at least one earlier aborted case, it is generally accepted that the first person frozen with intent of future resuscitation was Dr. James Bedford, a 73-year-old psychology professor frozen under crude conditions by CSC on January 12, 1967. The case made the cover of a limited print run of Life Magazine before the presses were stopped to report the death of three astronauts in the Apollo 1 fire instead.
Cryonics suffered a major setback in 1979 when it was discovered that nine bodies stored by CSC in a cemetery in Chatsworth, California, thawed due to depletion of funds. Some of the bodies had apparently thawed years earlier without notification. The head of CSC was sued, and negative publicity slowed cryonics growth for years afterward. Of seventeen documented cryonics cases between 1967 and 1973, only James Bedford remains cryopreserved today. Strict financial controls and requirements adopted in response to the Chatsworth scandal have resulted in the successful maintenance of almost all cryonics cases since that era.
The largest cryonics organization today was established by Fred and Linda Chamberlain in 1972 as the Alcor Society for Solid State Hypothermia (ALCOR). In 1977 the name was changed to the Alcor Life Extension Foundation. In 1982, the Institute for Advanced Biological Studies (IABS) founded by Mike Darwin and Steve Bridge in Indiana merged with Alcor. During the 1980s Darwin worked with UCLA cardiothoracic surgery researcher Jerry Leaf at Alcor to develop a medical model for cryonics procedures. They pioneered the first consistent use of a cryonics procedure now known as a “standby”, in which a team waits to begin life support procedures at the bedside of a cryonics patient as soon as possible after the heart stops.
Cryonics received new support in the 1980s when MIT engineer Eric Drexler started publishing papers and books foreseeing the new field of molecular nanotechnology. His 1986 book, Engines of Creation, included an entire chapter on cryonics applications. Cryonics advocates saw the nascent field of nanotechnology as vindication of their long held view that molecular repair of injured tissue was theoretically possible. Alcor’s membership expanded tenfold within a decade, with a 30% annual growth rate between 1988 and 1992.
Alcor was disrupted by political turmoil in 1993 when a group of activists left to start the CryoCare Foundation, and associated for-profit companies CryoSpan, Inc. (headed by Paul Wakfer) and BioPreservation, Inc. (headed by Mike Darwin). Darwin and collaborators made many technical advances during this time period, including a landmark study documenting high quality brain preservation by freezing with high concentrations of glycerol. CryoCare ceased operations in 1999 when they were unable to renew their service contract with BioPreservation. CryoCare’s two patients stored at CryoSpan were transferred to Alcor. Several ACS patients stored at CryoSpan were transferred to CI.
There have been numerous, often transient, for-profit companies involved in cryonics. For-profit companies were often paired or affiliated with non-profit groups they served. Some of these companies, with non-profits they served in parentheses, were Cryonic Interment, Inc. (CSC), Cryo-Span Corporation (CSNY), Cryo-Care Equipment Corporation (CSC and CSNY), Manrise Corporation (Alcor), CryoVita, Inc. (Alcor), BioTransport, Inc. (Alcor), Trans Time, Inc. (BACS), Soma, Inc. (IABS), CryoSpan, Inc. (CryoCare and ACS), BioPreservation, Inc. (CryoCare and ACS), Kryos, Inc. (ACS), Suspended Animation, Inc. (CI, ACS, and Alcor). Only Trans Time and Suspended Animation still exist. Apparently none of the companies were ever profitable. The cryonics field seems to have largely consolidated around three non-profit groups, Alcor, Cryonics Institute (CI), and the American Cryonics Society (ACS), all deriving significant income from bequests and donations.
As research in the 1990s revealed in greater detail the damaging effects of freezing, there was a trend to use higher concentrations of glycerol cryoprotectant to prevent freezing injury. In 2001 Alcor began using vitrification, a technology borrowed from mainstream organ preservation research, in an attempt to completely prevent ice formation during cooling. Initially the technology could only be applied to the head when separated from the body. In 2005 Alcor began treating the whole body with their vitrification solution in a procedure called "neurovitrification with whole body cryoprotection". In the same year, the Cryonics Institute began treating the head of their whole body patients with their own vitrification solution.
Alcor currently maintains 77 cryonics patients in Scottsdale, Arizona. The Cryonics Institute maintains 84 human patients (along with about 50 pets) at its Clinton Township, Michigan facility. There are support groups in Europe, Canada, United Kingdom, and Australia. There is also a small cryonics facility in Russia storing two neuropatients called KrioRus, and plans for a facility in Australia.
Cryonics in mass culture
Procedures similar to cryonics have been featured in innumerable science fiction stories to aid space travel, or as means to transport a character from the past into the future. In addition to accomplishing whatever the character's primary task is in the future, he or she must cope with the strangeness of a new world, which may contain only traces of their previous surroundings. This prospect of alienation is often cited as a major reason for the unpopularity of cryonics.
Notable early science fiction short stories featuring human cryopreservation, deliberate or accidental, include Jack London's first published work "A Thousand Deaths" (1899), H.P. Lovecraft's "Cool Air" (1928), and Edgar Rice Burroughs' "The Resurrection of Jimber-Jaw" (1937). Many of the subjects in these stories are unwilling ones, although a 1931 short story by Neil R. Jones called "The Jameson Satellite", in which the subject has himself deliberately preserved in space after death, has been credited with giving Robert Ettinger the seed of the idea of cryonics, when he was a teenager. Ettinger would later write a science fiction story called The Penultimate Trump published in 1948, in which the explicit idea of cryopreservation of legally-dead persons for future repair of medical causes of death, is promulgated .
Relatively few stories have been published concerning the primary objective and definition of cryonics, which is medical time travel. Influential novels with this theme include the early The Door Into Summer by Robert A. Heinlein (1956), and The Age of the Pussyfoot (1966) by Fred Pohl. Also included are national best-seller The First Immortal by James Halperin, Tomorrow and Tomorrow by Charles Sheffield, Chiller by Sterling Blake (aka Gregory Benford), Ralph’s Journey by David Pizer, Formerly Brandewyne by Jude Liebermann, and I Was a Teenage Popsicle by Bev Katz Rosenbaum. A fictional book about cryonics specifically for children is 21st Century Kids by Shannon Vyff.
Fictional application of cryonics as rescue after freezing in space has continued since The Jameson Satellite in 1931. Arthur C. Clarke's 3001: The Final Odyssey reveals that Frank Poole, murdered by HAL 9000 in 2001: A Space Odyssey was cryopreserved by his exposure to space, and found and revived a thousand years later. The Larry Niven short story "Wait It Out" depicts a sort of emergency self-cryopreservation by men marooned on Pluto. The 1992 Hugo-winning novel A Fire Upon the Deep by Vernor Vinge features a protagonist who is resuscitated by a superintelligence, thousands of years after a spaceship accident.
In the children's TV Show Shaolin Showdown, there was one episode when a character was transported several hundred years into the past. To bring himself back to the present, he froze himself in a manner similar to cryonics. He remained there for the entire term until the ice was broken in the present day.
Movies featuring cryonics for medical purposes include the Woody Allen comedy, Sleeper, and the films Late for Dinner, Abre los Ojos (remade as Vanilla Sky) and Wes Craven's Chiller. One of the most famous movies regarding a cryonics-like process was 1992's Forever Young, starring Mel Gibson. Although not about cryonics per se, the Ron Howard film Cocoon has been hailed by cryonics advocates as expressing the values motivating cryonics better than any other film. More recently cryogenics has featured in the Austin Powers spoof series of films where Dr. Evil and Austin Powers were both cryogenically frozen between the 1960s and the 1990s. During the freezing process Dr. Evil's cat Mr Biggleworth went completely bald due to the apparent irreversible side effects of the freezing.
On television, producer David E. Kelley wrote well-researched portrayals of cryonics for the TV shows L.A. Law (1990 episode), Picket Fences (1994 episode), and Boston Legal (2005 episode). In each case, there was a dying plaintiff petitioning a court for the right to elective cryopreservation. Cryonics was also featured in an episode of Miami Vice called "The Big Thaw", the episode "When We Dead Awaken" of seaQuest DSV, the episode "The Neutral Zone" of Star Trek: The Next Generation, the last two television works of Dennis Potter, Karaoke and Cold Lazarus, and the anime Cowboy Bebop. Cryonics was also satirized by the comedy cartoon series Futurama.
The most famous cryopreserved patient is baseball player Ted Williams. The popular urban legend that Walt Disney was cryopreserved is false; he was cremated, and interred at Forest Lawn Memorial Park Cemetery. Robert A. Heinlein, who wrote enthusiastically of the concept, was cremated and his ashes distributed over the Pacific Ocean. Timothy Leary was a long-time cryonics advocate, and signed up with a major cryonics provider. He changed his mind, however, shortly before his death, and so was not cryopreserved.
Slayer wrote a song called Crionics
The subculture of cryonicists
Cryonicists have been able to form cryonics societies in highly populated areas (see history section), have regular meetings, publish magazines and hold conferences. Saul Kent and Evan Cooper as well as Fred and Linda Chamberlain were active in organizing cryonics conferences in the early years of cryonics. The magazines of the cryonics organizations have also helped keep members of the cryonics community informed about events and common problems. On July 24, 1988 a Ph.D. in computer science named Kevin Brown started an electronic mailing list called CryoNet that became a powerful tool of communication for the cryonics community. Numerous other mailing lists and web forums for discussing cryonics and the affairs of particular organizations have since appeared, but CryoNet remains a central point of contact for cryonicists.
Cryonicists have also had a common jargon, including their use of the words patient, deanimation and suspension. The phrase cryonic suspension to describe cryopreservation is falling into disfavor, partly because the abbreviation suspension is too easily misunderstood. As in other subcultures, some members of the community can have strong feelings about the use of "politically correct" cryonics language.
- Alcor Life Extension Foundation
- American Cryonics Society
- Cryonics Institute
- Engineered negligible senescence
- Immortality Institute
- Immortalist Society
- Information theoretical death
- Life extension
- Rejuvenation (aging)
- Super cooling
- Suspended animation
- Scientists' Open Letter on Cryonics. Immortality Institute. Retrieved on 2007-04-13.
- Donaldson, Thomas (1988). 24th Century Medicine. Davis Publications. Retrieved on 2006-03-17.
- Platt, Charles (1995). Effect of Human Cryopreservation Protocol on the Ultrastucture of the Canine Brain, 4, Alcor Life Extension Foundation. Retrieved on 2006-03-17.
- Mazur P (1984). "Freezing of living cells: mechanisms and implications". Am J Physiol 247: C125-142. American Physiological Society. Retrieved on 2007-04-29.
- Platt, Charles (1995). New Brain Study Shows Reduced Tissue Damage, 4, CryoCare Foundation. Retrieved on 2006-03-17.
- Fahy GM et al (1984). "Vitrification as an approach to cryopreservation". Cryobiology 21: 407-426. Academic Press. Retrieved on 2007-04-29.
- Fahy GM et al (2005). "Cryopreservation of organs by vitrification: perspectives and recent advances". Cryobiology 50: 157-178. Elsevier. Retrieved on 2007-04-29.
- New Cryopreservation Technology. Alcor Life Extension Foundation (October, 2005). Retrieved on 2007-04-29.
- Lemler J, Harris SB, Platt C, Huffman TM (2004). The arrest of biological time as a bridge to engineered negligible senescence, 1019:559-63, Annals of New York Academy of Sciences. Retrieved on 2006-03-31.
- Lemler J, Harris SB, Platt C, Huffman TM (2004). The Arrest of Biological Time as a Bridge to Engineered Negligible Senescence. Alcor Life Extension Foundation. Retrieved on 2006-03-31.
- Lemler J, Harris SB, Platt C, Huffman TM (2004). Alcor Presentation at Cambridge University. Alcor Life Extension Foundation. Retrieved on 2006-03-31.
- CI-VM-1 Cryoprotectant and CI-Carrier Solution Used for Vitrification. Cryonics Institute (2007). Retrieved on 2007-04-29.
- Wowk B. Cardiopulmonary Support in Cryonics. Alcor Life Extension Foundation. Retrieved on 2007-04-29.
- National Human Neuronal Stem Cell Resource Frequently Asked Questions. NHNSCR. Retrieved on 2007-04-29.
- Donaldson, Thomas (1976). A Brief Scientific Introduction to Cryonics. Alcor Life Extension Foundation. Retrieved on 2007-04-29.
- (March, 1988) "The Cryobiological Case for Cryonics". Cryonics: 23-36. Alcor Life Extension Foundation. Retrieved on 2007-04-29.
- Donaldson, Thomas (May, 1990). "Prospects of a Cure for “Death”". Cryonics: 26-35. Alcor Life Extension Foundation. Retrieved on 2007-04-29.
- Merkle R (1992). "The technical feasibility of cryonics". Med Hypotheses 39: 6-16. Churchill Livingstone. Retrieved on 2007-04-29.
- Whetstine L et al (2005). "Pro/con ethics debate: when is dead really dead?". Critical Care 9: 538-542. BioMed Central Ltd.. Retrieved on 2007-04-29.
- Crippen DW et al (2007). "Ethics review: dark angels—the problem of death in intensive care". Critical Care 11: 202. BioMed Central Ltd.. Retrieved on 2007-04-29.
- Scientists’ Cryonics FAQ. Alcor Life Extension Foundation. Retrieved on 2006-04-03.
- Nanofactory Collaboration http://www.MolecularAssembler.com/Nanofactory
- Robert A. Freitas Jr., Nanomedicine, Landes Bioscience; Vol I (1999), Vol IIA (2003) http://www.nanomedicine.com
- Merkle, R (1994). Molecular Repair of the Brain. Alcor Life Extension Foundation. Retrieved on 2006-04-04.
- (1991) “Realistic” Scenario for Nanotechnological Repair of the Frozen Human Brain. Alcor Life Extension Foundation. Retrieved on 2006-04-04.
- Drexler, E (1986). Engines of Creation. Ancor Press/Doubleday. Retrieved on 2006-04-04.
- Darwin, M (1988). Resuscitation: A Speculative Scenario for Recovery. Alcor Life Extension Foundation. Retrieved on 2006-04-04.
- O'Neal, Michael B. (1990). The Case for Whole Body Suspension. Alcor Life Extension Foundation. Retrieved on 2006-03-16.
- Darwin, Mike (1990). The Cost of Cryonics. Alcor Life Extension Foundation. Retrieved on 2006-03-17.
- Whetstine, Leslie; Stephen Streat, Mike Darwin, and David Crippen (2005-10-31). Pro/con ethics debate: When is dead really dead?. Critical Care Forum. Retrieved on 2006-03-17.
- Donaldson, Thomas (1990). Prospects of a Cure for "Death". Alcor Life Extension Foundation. Retrieved on 2006-03-17.
- More, Max (1995). The Terminus of the Self. Alcor Life Extension Foundation. Retrieved on 2006-03-17.
- Hughes, James J. (2001). The Future of Death: Cryonics and the Telos of Liberal Individualism, Volume 6, Jet Press. Retrieved on 2006-03-17.
- He's Dead, Jim, The Irreversibility of Death as a Circular Argument. Alcor Life Extension Foundation. Retrieved on 2006-03-17.
- Harris SB (1989). "Many are cold but few are frozen: a humanist looks at cryonics". Free Inquiry 9: 19-24. Council for Secular Humanism. Retrieved on 2007-06-08.
- Christianity and Cryonics. Alcor Life Extension Foundation. Retrieved on 2006-03-17.
- Montgomery, John Warwick (1968-05-10). Cryonics and Orthodoxy, 12, 816, Christianity Today. Retrieved on 2006-03-17.
- Curtis Henderson (Sep-Oct 1969). "Cryonic Suspension of Ann DeBlasio". CRYONICS REPORTS 4 (9-10): 10-15. Cryonics Society of New York, Inc..
- Franklin, Benjamin (1773). Letter to Jacques Duborg. Foresight Nanotech Institute. Retrieved on 2006-03-17.
- Ettinger, Robert C.W. (1964). The Prospect of Immortality, First, Doubleday.
- Ev Cooper. Retrieved on 2006-03-17.
- Cryonics. Retrieved on 2006-03-17.
- Perry, R. Michael (1992). Suspension Failures: Lessons from the Early Years. Alcor Life Extension Foundation. Retrieved on 2006-03-17.
- Drexler, K. Eric (1986). Engines of Creation, "A Door to the Future". Foresight Nanotech Institute. Retrieved on 2006-03-17.
- Drexler, K. Eric (1986). Engines of Creation, The Coming Age of Nanotechnology. Foresight Nanotech Institute. Retrieved on 2006-03-17.
- CryoCare Foundation. Retrieved on 2006-03-17.
- BioPreservation, Inc. - Cryopreservation Services. Retrieved on 2006-03-17.
- Platt, Charles (1995). Effect of Human Cryopreservation Protocol on the Ultrastructure of the Canine Brain. Cryocare. Alcor Life Extension Foundation. Retrieved on 2006-03-17.
- Trans Time, Inc.. Retrieved on 2006-03-17.
- Suspended Animation, Inc.. Retrieved on 2006-03-17.
- New Cryopreservation Technology. Alcor Life Extension Foundation. Retrieved on 2006-03-17.
- Ben Best. The Cryonics Institute's 69th Patient. Retrieved on 2006-06-07.
- Full text of Ettinger's "Penultimate Trump" short story:  Accessed June 8, 2007
- Formerly Brandewyne. Lee Books (1997).
- 21st Century Kids. 21CenturyKids (2007).
- (March 15, 2007) 21st Century Kids. Warren Publishing. ISBN 1886057001.
- (1985) Cryonics, Volume 6 Issue 61, Alcor Life Extension Foundation. Retrieved on 2006-03-17.
- "L.A. Law" The Good Human Bar (1990). IMDb. Retrieved on 2006-03-17.
- "Picket Fences" Frosted Flakes (1994). IMDb. Retrieved on 2006-03-17.
- "Boston Legal" Let Sales Ring (2005). IMDb. Retrieved on 2006-03-17.
- CryoNet. Retrieved on 2006-03-17.
- Cryonics FAQ
- Ralph Merkle's introduction to cryonics
- Alcor Life Extension Foundation
- Cryonics Institute
- American Cryonics Society
- About Cryonics
- Cryonics Europe
- Cryonics Society - Resources and Advocacy
- Cryonics Society of Canada
- The Immortality Institute
- Longevity Meme
- Cryonics UK
- Erroneous Predictions and Negative Comments Concerning Scientific and Technological Developmentsde:Kryoniknl:Cryonismefi:Kryoniikka