- the temperature of −273.16°C (−459.69°F), the hypothetical point at which all molecular activity ceases.
absolute temperature scale
- temperature (absolute temperature) as measured on a scale in which the hypothetical lowest limit of physical temperatures is assigned the value zero (absolute zero), as the Kelvin scale.
- the lowest temperature theoretically attainable, at which the particles constituting matter would be in the lowest energy states available; the zero of thermodynamic temperature; zero on the International Practical Scale of Temperature: equivalent to –273.15°C or –459.67°F
the idea dates back to 1702 and its general value was guessed to within a few degrees soon thereafter, but not precisely discovered until Lord Kelvin's work in 1848. It was known by many names, e.g. infinite cold, absolute cold, natural zero of temperature; the term absolute zero was among them by 1806.
- The temperature at which substances possess no thermal energy, equal to -273.15°C, -459.67°F, or 0 K.
absolute temperature scale
- A temperature scale having absolute zero as the lowest temperature. Absolute temperature scales only have positive numbers. The Kelvin scale and the Rankine scale are absolute temperature scales. Compare relative temperature scale.
- The lowest possible temperature, at which all molecules are have the least possible amount of kinetic energy. Absolute zero is equal to 0°K, -459.67°F, or -273.15°C. At temperatures approaching absolute zero, the physical characteristics of some substances change significantly. For example, some substances change from electrical insulators to conductors, while others change from conductors to insulators. Absolute zero has never been reached in laboratory experiments. See also Bose-Einstein condensate zero-point energy.
A Closer Look: The temperature of a substance is determined by the average velocity of its molecules: the faster they move, the warmer the substance. At absolute zero molecules have minimal kinetic energy (or zero-point energy) and heat energy cannot be extracted from them. The molecules are not motionless, however, due to the uncertainty principle of quantum mechanics, which entails that the atoms cannot have both a fixed position and zero momentum at the same time; instead, the molecules of a substance at absolute zero are always wiggling in some manner. Absolute zero is zero degrees Kelvin, equal to -273.15 degrees Celsius and -459.67 degrees Fahrenheit. The coldest known place in the universe is the Boomerang Nebula, where the temperature is -272° Celsius. Scientists at Massachusetts Institute of Technology have gone much lower than that by using laser traps and other techniques to cool rubidium to 2 X 10-9 degrees Kelvin.