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
Introduction to the metric system volt and farad in honour of Georg Ohm, Alessandro Volta and Michael Faraday respectively. This proposal had the support of William Thomson (Lord Kelvin) who had been instrumental in forming the Committee of Electrical Standards of the British Association for the Advancement of Science. The use of scientists' names for such units was subsequently extended to other units, including the watt named after James Watt and the degree Celsius named after Anders Celsius. Historically, individual units evolved which were based on the size and context of what was being measured. These units could avoid the need to use large numbers