Celsius Celsius scale are defined by absolute zero and the triple point of Vienna Standard Mean Ocean Water (VSMOW), a specially purified water. This definition also precisely relates the Celsius scale to the Kelvin scale, which defines the SI base unit of thermodynamic temperature with symbol K. Absolute zero, the lowest temperature possible, is defined as being exactly 0 K and −273.15 °C. The temperature of the triple point of water is defined as exactly . This means that a temperature difference of one degree Celsius and that of one kelvin are exactly the same. In 1742, Swedish astronomer Anders Celsius
Thomas Henderson (astronomer) is not recorded on the Adie grave; Adie himself died 14 years after Henderson. A blue plaque is installed on his house at 1 Hillside Crescent. It refers to him as "Thomas J. A. Henderson", similar to middle names wrongly added to Wikipedia around 2007. A larger memorial (naming him "Thomas Henderson") is incorporated in the external wall of the City Observatory. Thomas Henderson (astronomer) Thomas Henderson FRSE FRS FRAS (28 December 1798 – 23 November 1844) was a Scottish astronomer and mathematician noted for being the first person to measure the distance to Alpha Centauri, the major component of