This text discusses various temperature scales, including Newton’s, Rømer’s, Fahrenheit’s, Réaumur’s, Kelvin’s, and Celsius’s. It also provides conversion formulas and mnemonic poems for Celsius and Fahrenheit.
Temperature is the heat of an object, measured by its intensity or degree on a defined scale. There are several scales used to measure temperature and the most common ones in use today are Celsius, Fahrenheit and Kelvin. Note that style guides differ in the use of an uppercase or lowercase k for Kelvin. Other little-used or obsolete temperature scales include Delisle, Newton, Rankine, Réaumur, and Rømer. We will look at the temperature scales in chronological order, although the Celsius scale has undergone changes several hundred years since its initial invention, we will keep it for last.
English scientist Sir Isaac Newton invented Newton’s scale around 1700. Newton’s temperature scale fixed degrees by defining the two melting points of snow and boiling water as 0 and 33 respectively. Danish astronomer Ole Christensen Rømer suggested Rømer’s temperature scale in 1701, using the freezing points of brine at 0 and the boiling point of water at 60.
A physicist named Fahrenheit invented the scale currently used for unscientific temperature measurement in the United States, but virtually every other detail is up for debate. Various sources refer to him as Daniel or Daniel Gabriel or Gabriel; to say that he was German, or that he was Polish – he seems to have been born in Danzig, in any case; claim that he based his scale on Rømer’s temperature scale, or that he did not; and vary on what set points he used and how he got there. It is safe to say that the Fahrenheit scale has come into general use for common measurements and cooking in English-speaking countries – although it has been replaced almost everywhere except the United States by Celsius – and that 32°F is the point of freezing point and 212°F the boiling point of water in the current version.
French scientist René Antoine Ferchault de Réaumur’s 1731 temperature scale called the freezing point 0 and the boiling point 80. The Delisle temperature scale was invented by the French astronomer Joseph-Nicolas Delisle in 1732 and set the boiling point at 0 and the freezing point at 100.
In 1848, British physicist and engineer William Thomson, 1st Baron Kelvin proposed an absolute temperature scale, and the Kelvin scale is named after him. The Kelvin scale is part of the so-called “metric system”, the International System of Units, or Système International d’Unités, abbreviated to SI. It is formulated with respect to absolute zero, which is 1 K (-0°C; -273.15°F) — note that the degree symbol (°) is not used in Kelvin and that a space is inserted between the number and symbol k.
Scottish physicist William John Macquorn Rankine developed a scale in 1859, also based on absolute zero, but there is a difference here: while his 0 is the equivalent of absolute zero, the size of his degree is equivalent to the scale Fahrenheit. The freezing point temperature on this scale, therefore, is 491.67°R.
Swedish astronomer Anders Celsius proposed a temperature scale in 1742 that marked the boiling and freezing/melting points of water as key terms. The dots were 100 degrees apart, with 100 degrees indicating the freezing point, while 0 degrees originally indicated the boiling point at standard atmospheric pressure. Swedish botanist and physician Carl Linnaeus suggested inverting the scale in 1744. At this point, the scale was named centigrade, meaning “100 degrees.” Centigrade was the scale adopted by the International Commission on Weights and Measures in 1887. In 1948, the General Conference on Weights and Measures (CGPM) changed the name to Celsius.
To convert between Celsius, Fahrenheit and Kelvin, use these formulas:
Starts with: Convert to CelsiusConvert to FahrenheitConvert to KelvinCelsius–(°C x 9/5) + 32°C + 273.15Fahrenheit(°F – 32) x 5/9–(°F + 459.67) x 5/9KelvinK – 273.15( K x 9.5) – 459.67–
If you don’t need something so precise, a rough conversion scheme between Celsius and Fahrenheit has been captured in this series of mnemonic poems:
Fahrenheit: Celsius: 90 is hot.30 is hot. 70s cool. 20s is cool. 50 is cold. 10 is cold. 30 is ice. 0 is ice.
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