Scale of temperature the Swedish astronomer Anders Celsius (1701–1744), who developed a similar temperature scale two years before his death. The degree Celsius (°C) can refer to a specific temperature on the Celsius scale as well as a unit to indicate a temperature "interval "(a difference between two temperatures or an uncertainty). From 1744 until 1954, 0 °C was defined as the freezing point of water and 100 °C was defined as the boiling point of water, both at a pressure of one standard atmosphere. Although these defining correlations are commonly taught in schools today, by international agreement the unit "degree Celsius" and
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