Kelvinasteikkoon

Kelvinasteikkoon, known internationally as the Kelvin scale, is the base unit of thermodynamic temperature measurement in the International System of Units (SI). It is named after the Scottish physicist William Thomson, 1st Baron Kelvin. The Kelvin scale is an absolute temperature scale, meaning that its zero point, 0 K, is absolute zero, the theoretical temperature at which all molecular motion ceases. This contrasts with scales like Celsius or Fahrenheit, which have arbitrary zero points.

The Kelvin scale is defined by setting the Boltzmann constant to 1.380649 × 10⁻²³ J/K. This definition was adopted in 2019 as part of a redefinition of the SI base units. Before this redefinition, the Kelvin scale was defined based on the triple point of water, which is the temperature and pressure at which water can exist in equilibrium as solid, liquid, and gas. The triple point of water is 273.16 K.

The relationship between Kelvin and Celsius is simple: 0 K is equal to -273.15 °C, and 1 K is equal to 1 °C. Therefore, to convert from Celsius to Kelvin, one adds 273.15. For example, room temperature, approximately 20 °C, is 293.15 K. The Kelvin scale is widely used in science and engineering, particularly in fields such as thermodynamics, physics, and chemistry, due to its absolute nature.