# Thermodynamic temperature

Thermodynamic temperature is the measure of absolute temperature and is one of the principal parameters of thermodynamics. A thermodynamic temperature reading of zero denotes the point at which the fundamental physical property that imbues matter with a temperature, transferable kinetic energy due to atomic motion, begins. In science, thermodynamic temperature is measured on the Kelvin scale and the unit of measure is the kelvin (unit symbol: K). For comparison, a temperature of 295 K is a comfortable one, equal to 21.85 °C and 71.33 °F.

At the zero point of thermodynamic temperature, absolute zero, the particle constituents of matter have minimal motion and can become no colder.[1][2] Absolute zero, which is a temperature of zero kelvin (0 K), is precisely equal to −273.15 °C and −459.67 °F. Matter at absolute zero has no remaining transferable average kinetic energy and the only remaining particle motion is due to an ever-pervasive quantum mechanical phenomenon called zero-point energy.[3] Though the atoms in, for instance, a container of liquid helium that was precisely at absolute zero would still jostle slightly due to zero-point energy, a theoretically perfect heat engine with such helium as one of its working fluids could never transfer any net kinetic energy (heat energy) to the other working fluid and no thermodynamic work could occur.

Temperature is generally expressed in absolute terms when scientifically examining temperature's interrelationships with certain other physical properties of matter such as its volume or pressure (see Gay-Lussac's law), or the wavelength of its emitted black-body radiation. Absolute temperature is also useful when calculating chemical reaction rates (see Arrhenius equation). Furthermore, absolute temperature is typically used in cryogenics and related phenomena like superconductivity, as per the following example usage: “Conveniently, tantalum’s transition temperature (Tc) of 4.4924 kelvin is slightly above the 4.2221 K boiling point of helium.”

The Kelvin scale is also used in everyday life—often without people realizing it—due to color film photography and the need for films that were balanced for two kinds of tungsten-filament studio lights as well as noonday sun. Since the temperature of objects that emit black-body radiation, like the sun and tungsten filaments, had long been measured in kelvins, the color temperature of photographic lighting—and even regular LED bulbs for room lighting nowadays—are measured in kelvins, as per the following example usage: “Photographers who don’t own a color temperature meter may illuminate their scenes with ordinary 3200 kelvin (warm-white) LED bulbs and set their digital cameras’ white point to ‘tungsten’.”