Cryogenics is the study of the very cold, how to produce extremely low temperatures and the behavior of materials at those temperatures.

It began as an area separate from refrigeration when two French scientists first liquefied oxygen in 1877.

In 1892, when James Dewar invented the vacuum flask that bears his name, the science really heated up.

Today the delineation of cryogenics is the boiling temperature of oxygen at minus-280 degrees, which is 150 degrees colder than dry ice.

An easy way to visualize the extreme cryogenic temperatures of liquefied gases is to think of a building with 300 stories. This requires some imagination since the tallest buildings today have scarcely more than 100 floors.

The top floor represents a typical day on Earth, about 60 degrees Fahrenheit. Oxygen boils at the 90th floor, nitrogen at the 77th, hydrogen at the 20th and helium a mere four stories up. The ground floor represents absolute zero, the coldest possible temperature where molecular motion stops.

In World War II researchers discovered that metals subjected to low temperatures showed increased resistance to wear. Cryogenic tempering increased the density of near-surface molecules similar to quenching hot metals or glass in cold water.

This discovery led to many applications of cryogenic hardening, including increasing the sweet spot on baseball bats and golf clubs, greater performance of racing engines, tempering of knives, razor blades, brake rotors and firearms.

The results turned out to be unstable. Some metals shattered under thermal shock when cooled quickly or at low temperatures, but in the 1980s pieces of the head of the Statue of Liberty were processed with liquid nitrogen to strengthen and extend the life of the century-old metal.

The most common cryogenic liquid is nitrogen. It is abundant, comprising nearly 80 percent of the atmosphere. It boils at minus-320 degrees and costs only about $1 per gallon to produce commercially.

The Space Shuttle was launched with rockets burning hydrogen and oxygen that were stored on board as liquids in 383,000- and 43,000-gallon tanks, respectively.

Recycling of the more than 300 million tires discarded yearly in the United States is aided by liquid nitrogen. Steel belts and fibers are difficult to separate from rubber, but after spraying with liquid nitrogen the tires shatter like glass when run through a hammer mill. Afterward, magnets remove metal shards, and the remaining rubber ‘crumb’ is used in sports fields, rubber mats and playgrounds.

Ceramic high-temperature superconductors that function at liquid nitrogen temperatures (as opposed to the low temperature of liquid helium) encased in liquid nitrogen can carry five or more times the amount of electricity.

Cryogenics might bring to mind the freezing of cadavers or brains in hope of reviving them in the future when medical science might be able to reanimate them. Although to date 825 remains are preserved, there is no evidence that revival is possible or even likely.

Richard Brill is a professor of science at Honolulu Community College. Email questions and comments to rickb@hcc.hawaii.edu.