This is the definition that was used up until 2019, when the kelvin was redefined based on the definitions of the second, meter, and kilogram.Ĭurrent use: The Celsius scale replaced the Fahrenheit scale in most countries in the mid to late 20 th century. In 1954, the unit, 'degree Celsius,' as well as the Celsius scale were again re-defined to instead be based on absolute zero (-273.15 ☌) and the triple point of VSMOW (specially purified water). Celsius as a unit and a scale was not widely used until this original definition was inverted. This was not always the case, and originally 0☌ was defined as the boiling point of water and 100☌ was defined as the melting point of snow. History/origin: From 1743 until 1954, the Celsius scale was based on 0☌ for the freezing point of water and 100 ☌ for the boiling point of water, both at a pressure of one standard atmosphere, using mercury as the working material. The kilogram, meter, and second, are defined based on Planck's constant, h, the speed of light, c, and cesium frequency, Δ νCs. The kelvin (and thus Celsius) is defined based on the Boltzmann constant, k, which equals 1.380649 × 10 -23 when expressed in the unit J The Celsius and Kelvin scales are precisely related, with a one-degree change in Celsius being equal to a one degree-change in kelvin. It is defined based on the SI unit of temperature, the kelvin. Definition: The Celsius (symbol: ☌) is an SI (International System of Units) derived unit of temperature.

Fer by C.C. W