Olof Celsius Olof Celsius Olof Celsius (the elder) (19 July 1670 – 24 June 1756) was a Swedish botanist, philologist and clergyman, He was a professor at Uppsala University, Sweden. Celsius was a mentor of the botanist and scientist Carl Linnaeus. Celsius wrote his most famous book on biblical plants, "Hierobotanicon", in 1745-47. Olof Celsius's nephew Anders Celsius was an astronomer who invented a temperature scale where 100 represented the freezing point of water and 0 represented the boiling point. Jean-Pierre Christin, in 1744 reversed the scale to create the centigrade scale, renamed in 1948 to the Celsius scale in use today.
Negative temperature Negative temperature In quantum thermodynamics, certain systems can achieve negative temperature; that is, their temperature can be expressed as a negative quantity on the Kelvin or Rankine scales. A system with a truly negative temperature on the Kelvin scale is "hotter" than any system with a positive temperature. If a negative-temperature system and a positive-temperature system come in contact, heat will flow from the negative- to the positive-temperature system. A standard example of such a system is population inversion in laser physics. Temperature is loosely interpreted as the average kinetic energy of the system's particles. The existence of negative temperature,