Temperature

The highest recorded weather temperature on Earth was 136°F (57.8°C), observed in North Africa in 1922. The record low temperature is -129°F (-89.2°C), observed in the Antarctic in 1983. Elsewhere in the universe, temperature extremes are much greater. The average surface temperatures of the most distant planets in our solar system (Uranus, Neptune, Pluto) are about 53K (-364°F; - 220°C;). Although temperatures on and within the sun vary, the core is about 27 million° F (15 million° C). (At very high temperatures Celsius and Kelvin temperatures are virtually identical; the 273 is negligible).

Temperatures produced in laboratories can be even more extreme. The study of very low temperatures, called cryogenics, is an active field of scientific research because of the unusual properties of many substances when they are close to absolute zero. Using magnetic techniques, temperatures below one microkelvin have been achieved. (A microkelvin, μ K, is 0.000001K.) Absolute zero itself, however, has not yet been reached.

Less extreme low temperatures can be obtained relatively easily with dry ice or liquid nitrogen. Dry ice, solid carbon dioxide, vaporizes (sublimes) under normal pressures rather than melting to a liquid. The sublimation temperature of dry ice is 195K (-198°F; 78°C). Liquid nitrogen can be used to obtain even lower temperatures. It is used at its normal boiling point, which is of liquid nitrogen is 77K (-321°F; -196°C).

Scientific interest in very high temperatures is largely due to the hope of achieving controlled nuclear fusion—the energy producing process in the sun and stars. By the use of powerful lasers, temperatures over 400 million kelvins have been achieved for short periods of time.