Kelvin (K)
Kelvin is the SI base unit of thermodynamic temperature defined by fixing the numerical value of the Boltzmann constant to 1.380649×10⁻²³ J·K⁻¹. It uses absolute zero as its null point and increments equal to those of the Celsius scale. One kelvin equals one degree Celsius in magnitude but starts at absolute zero, representing the lowest physically possible temperature [bipm-si-brochure].
Origin
The kelvin scale was named after William Thomson, 1st Baron Kelvin, who proposed an absolute thermodynamic temperature scale in 1848. It was formally adopted as an SI base unit in 1967–1968 by the CGPM to provide a universal temperature standard based on fundamental constants [cgpm-resolutions].
Worldwide Use
Kelvin is the standard temperature unit in scientific research, thermodynamics, and engineering worldwide. It is the official unit for temperature in physics and chemistry according to the International System of Units (SI), used globally including by NIST and BIPM member countries [nist-si-guide].
Common References
- Absolute zero is 0 K, equivalent to −273.15 °C
- Water freezes at 273.15 K and boils at 373.15 K under standard pressure
- Room temperature is approximately 293–298 K
- Human body temperature averages about 310 K
- Stars like the Sun have surface temperatures around 5778 K