Cryonics is the use of very cold temperatures (below -150°C) to preserve a person who can no longer be supported by current medical technology, and is implemented after clinical death has been legally pronounced. This is done with a view to restoring the life of the person when future medical technology allows rejuvenation in some manner.
Continuing progress in medical science strongly suggests that treatments will be found for most currently fatal conditions, including disease, injury and aging. It is also anticipated that the cryonic processes will eventually be reversible as new technologies become available, allowing either reanimation of a deceased person whose tissues have been appropriately preserved, or replacement with newly grown tissue, or scanning and uploading of the memories encoded in preserved brain tissues, or a combination of these and other rejuvenation technologies.
Vitrification is now the leading method of cryonic suspension. The practice of cryonics has advanced beyond previous methods, which could cause the formation of ice in the body and brain, damaging the cells. With vitrification, cryoprotectants are used to minimise the formation of harmful ice crystals at extremely low temperatures. This achieves a glass-like state of the bodily organs, with minimal damage to their structure at any level. Once the patient reaches a sufficiently low temperature, all biological and chemical activity is suspended, and can remain suspended for centuries if necessary.
Freezing is an older method of cryonic suspension, and is still practised in some cases where vitrification is not warranted because of cost or other factors. In contrast to the more modern cryoprotectants that are used for vitrification, freezing uses chemicals based on glycerine.
Below is a comparison of the risks for both methods.
- Low risk of ice crystal formation in the brain, and therefore a much lower risk of brain damage.
- Very high risk during long-range transportation, due to high sensitivity to temperature variations. CryoPath has a solution for the temperature sensitivity and can greatly mitigate this risk.
- High risk of ice crystal formation in the brain, which could cause brain damage.
- Lower risk during long-range transportation, due to a much lower sensitivity to temperature variations.
Note that no method is currently available for the reanimation of the cryonically suspended human body. For this, cryonics depends on future developments in medical technology.
The following websites are good sources of information about cryonics.
Ben Best, former president of Cryonics Institute
‘The Engines of Creation’, a book by Eric Drexler, written in 1986 — see the chapter on Cryonics
‘At What Moment are You Dead?’, a 5-minute TED-Ed lesson by Randall Hayes
‘The Three Camps of Brain Preservation’, an introduction to the technologies and options, written by John Smart from the Brain Preservation Foundation