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
Anders Henrik Bull Anders Henrik Bull Anders Henrik Bull (25 January 1875 – after 1909) was a Norwegian electrical engineer. He was born in Minneapolis as the son of ophthalmologist Ole Bornemann Bull (1842–1916) and his first wife Marie Cathrine Lund (1843–1884). The family moved to Norway in 1876. He took his engineering education in Kristiania and Hannover. He returned to Norway from Hannover in 1901, and became noted in the engineering community for his pioneering work on wireless telegraphy. He also worked for Norsk Hydro, as a consultant to Kristian Birkeland, from 1906 to 1909, in that company's formative phase. He married