Cryogenics is a field of study gaining momentum these days. Cryogenics is the branch of physics dealing with the production and effects of very low temperatures. It studies how materials behave at those temperatures.
Cryogenics constitutes various subsets which include Cryobiology, Cryoconservation, Cryosurgery, Cryoelectronics, Cryotronics and Cryonics.
Cryogenics took its shape as reality through the efforts of 19th-century scientists. These scientists and researchers discovered cryogenics while trying to liquefy gases that were thought to be permanent at exceedingly low temperatures. The gases tested on included Oxygen, Hydrogen, Nitrogen, Methane and NitricOxide.
Temperature plays a crucial role in any kind of material. According to the variation in the temperature, the motion of molecules within a material alters. In cryogenics, temperature varies between -100°C (-148°F) to absolute zero (0 Kelvin) or -459°F.
Low temperatures can be produced through various techniques. Joule-Thomson effect is where a real is gas is forced through an insulated porous plug or valve, there is a temperature drop. Adiabatic demagnetization is another technique in which special paramagnetic salts are used to produce some of lowest temperatures. Heat conduction and evaporative cooling are also used to produce low temperatures.
Cryogenics is useful and fulfils numerous purposes. It is used to transfer liquefied natural gas from carriers to storage tanks. It enables space research as the cryogenic hydrogen or oxygen is used to propel the rocket into orbit. Nuclear Magnetic Resonance Spectroscopy (NMR) produces strong magnetic fields by supercooling electromagnets. It is also used in food processing medical fields.
Human Cryopreservation was started in 1967. As of 2014, about 250 people were cryopreserved in the US with 1500 more slated for the procedure after their legal death. There are four Cryonic facilities available all over the world- three in the US and one in Russia.
To preserve a human cryogenically, the person needs to be dead though not completely. Some brain activity has to be there while the heart stops beating. Cryonic aims at preserving the remaining cell function so that the person can be revived in future. It costs around $200,000 at present to preserve the whole body.
There are options to preserve only the brain with a view that the future technology will be able to regenerate the rest of the body. There has been no successful revival using cryogenics. Primarily because the complete technology to preserve humans using cryogenics has not been built.