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Anders Celsius's original thermometer used a reversed scale, with 100 as the freezing point and 0 as the boiling point of water.. In 1742, Swedish astronomer Anders Celsius (1701–1744) created a temperature scale that was the reverse of the scale now known as "Celsius": 0 represented the boiling point of water, while 100 represented the freezing point of water. [5]
In 1948, the Celsius scale was recalibrated by assigning the triple point temperature of water the value of 0.01 °C exactly [35] and allowing the melting point at standard atmospheric pressure to have an empirically determined value (and the actual melting point at ambient pressure to have a fluctuating value) close to 0 °C.
A maximum–minimum thermometer. The scales are Fahrenheit on the inside of the U and Celsius on the outside. The current temperature is 23 degrees Celsius, the maximum recorded is 25, and the minimum is 15; both read from the base of the small markers in each arm of the U tube.
From 1787 to 1802, it was determined by Jacques Charles (unpublished), John Dalton, [20] and Joseph Louis Gay-Lussac [21] that, at constant pressure, ideal gases expanded or contracted their volume linearly (Charles's law) by about 1/273 parts per degree Celsius of temperature's change up or down, between 0° and 100° C. This suggested that ...
Since 1982, STP has been defined as a temperature of 273.15 K (0 °C, 32 °F) and an absolute pressure of exactly 1 bar (100 kPa, 10 5 Pa). NIST uses a temperature of 20 °C (293.15 K, 68 °F) and an absolute pressure of 1 atm (14.696 psi, 101.325 kPa). [3] This standard is also called normal temperature and pressure (abbreviated as NTP).
Unlike the degree Fahrenheit and degree Celsius, the kelvin is no longer referred to or written as a degree (but was before 1967 [1] [2] [3]). The kelvin is the primary unit of temperature measurement in the physical sciences, but is often used in conjunction with the degree Celsius, which has the same magnitude. Other scales of temperature:
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Most scientists measure temperature using the Celsius scale and thermodynamic temperature using the Kelvin scale, which is the Celsius scale offset so that its null point is 0 K = −273.15 °C, or absolute zero. Many engineering fields in the US, notably high-tech and US federal specifications (civil and military), also use the Kelvin and ...