How do I convert Kelvin in Celsius? What is Fahrenheit scale based on? What is the temperature in Réaumur?
Here, the temperatures in different temperature scales can be converted.
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Establishing a temperature scale requires two fixed points. For this purpose temperatures were selected that have a special physical meaning.
Kelvin (SI unit): In the Kelvin scale, which was introduced in 1848 by Lord Kelvin, the absolute zero point serves as the lower fixed point. According to the third law of thermodynamics this point can't be reached. However, it is possible to approach arbitrarily close to that point. As second fixed point the triple point of water was set as 273.16 K. At this point and at a pressure of 661.657 Pa water is at the same time solid, liquid and gaseous. The scale division was chosen so that it coincides with the Celsius scale: ΔT = 1K = 1°C.
Celsius: The Celsius scale of 1742 is probably the most illustrative scale, because the phase transitions of water are used as fixed points which are well known from nature. The zero point was fixed by the transition "solid-liquid" (0°C). As second fixed point the boiling temperature of water was defined as 100°C.
Fahrenheit: This temperature scale which is common mostly in the U.S. was developed by Daniel Fahrenheit inspired by Rømer. To avoid negative temperatures in daily use he chose the lowest temperature measured in Danzig in 1714 as zero. He reproduced this temperature using a frigorific mixture. As upper fixed point he defined the human body temperature at 96°F. A further fixed point is the melting point of ice at 32°F.
Réaumur: The Réaumur scale of 1740 uses the phase transitions of water like the Celsius scale. However the boiling temperature was set to 80°Ré. This scale is nowadays rarely used.
Newton: The Newton scale uses the fixed points of the Celsius scale as well, with the boiling temperature defined as 33°N.
Rankine: The Rankine scale relates to absolute zero like the Kelvin scale. However the scale division doesn't correspond to the Celsius scale but to the Fahrenheit scale.
Rømer: The Rømer-scale of 1701 was developed using the freezing temperature of a brine (0°Rø). According to this, the melting temperature of ice (7.5 °Rø) and the boiling temperature of water (60°Rø) were used as fixed points. Fahrenheit tried to improve this scale and introduced the Fahrenheit scale some years later.
Delisle: The Delisle scale, likewise, uses the temperatures of the phase transitions of water whereas the boiling temperature was defined as zero and the melting temperature as 150°De. For this reason the Delisle scale runs the other way around than the other here mentioned scales.