Kelvinscale

Kelvinscale, commonly called the Kelvin scale, is the thermodynamic temperature scale used in science and engineering. It assigns temperature values to physical states using the Kelvin (K) as the unit of measure. The kelvinscale is absolute, beginning at absolute zero, the theoretical lowest possible temperature.

The Kelvin scale is defined by fixing the numerical value of the Boltzmann constant k exactly 1.380649×10^-23 J/K. Consequently, 0 K equals -273.15 C, and temperatures in Kelvin can be obtained from Celsius by adding 273.15. The kelvinscale is one of the seven base units of the International System of Units (SI), and it provides a direct link between temperature and energy through thermodynamic relations.

As an absolute scale, all Kelvin temperatures are nonnegative; ratios of temperatures can reflect energy relationships in many contexts. For instance, 600 K represents a higher energy state than 300 K in relevant thermodynamic equations. The kelvinscale is widely used in physics, chemistry, cryogenics, and spectroscopy because it avoids the complications associated with negative temperatures on other scales.

Historical notes: The scale is named after Lord Kelvin (William Thomson). It was developed in the 19th century and standardized as an SI base unit in the latter half of the 20th century. The 2019 redefinition anchors the kelvinscale to a fixed value of the Boltzmann constant, reducing reliance on physical artifacts as reference points.

In practice, temperatures are commonly reported in Kelvin in scientific and engineering contexts, while everyday temperatures are often given in Celsius or Fahrenheit; conversion between scales is straightforward using K = C + 273.15. See also: Celsius scale, Fahrenheit scale, Boltzmann constant, absolute zero.