Olof Celsius Olof Celsius was made a member of the Royal Swedish Academy of Sciences in 1739. 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
International Temperature Scale of 1990 record cold temperature achieved by the NIST in 1994). Estimates of the differences between thermodynamic temperature and the ITS–90 ("T"-"T") were published in 2010. It had become apparent that ITS–90 deviated considerably from PLTS-2000 in the overlapping range of 0.65 K to 2 K. To address this, a new He vapor pressure scale was adopted, known as PTB-2006. For higher temperatures, expected values for "T"-"T" are below 0.1 mK for temperatures 4.2 K – 8 K, up to 8 mK at temperatures close to 130 K, at 0 K (by definition) at the triple point of water (273.16 °C), but