The Celsius scale, also known as the centigrade scale,[1][2] is a temperature scale used by the International System of Units (SI). As an SI derived unit, it is used by all countries except the United States,[3] the Bahamas, Belize, the Cayman Islands and Liberia. It is named after the Swedish astronomer Anders Celsius (1701–1744), who developed a similar temperature scale. The degree Celsius (symbol: °C) can refer to a specific temperature on the Celsius scale or a unit to indicate a difference between two temperatures or an uncertainty. Before being renamed to honor Anders Celsius in 1948, the unit was called centigrade, from the Latin centum, which means 100, and gradus, which means steps.

From 1743, the Celsius scale is based on 0 °C for the freezing point of water and 100 °C for the boiling point of water at 1 atm pressure. Prior to 1743, the scale was also based on the boiling and melting points of water, but the values were reversed (i.e. the boiling point was at 0 degrees and the melting point was at 100 degrees). The 1743 scale reversal was proposed by Jean-Pierre Christin.

By international agreement, since 1954 the unit degree Celsius and the Celsius scale are defined by absolute zero and the triple point of Vienna Standard Mean Ocean Water (VSMOW), a specially purified water. This definition also precisely relates the Celsius scale to the Kelvin scale, which defines the SI base unit of thermodynamic temperature with symbol K. Absolute zero, the lowest temperature possible, is defined as being exactly 0 K and −273.15 °C. The temperature of the triple point of water is defined as exactly 273.16 K (0.01 °C).[4] This means that a temperature difference of one degree Celsius and that of one kelvin are exactly the same.[5]

On 20 May 2019, the kelvin, and along with it the degree Celsius, will be redefined so that its value will be determined by definition of the Boltzmann constant.

A thermometer calibrated in degrees Celsius
General information
Unit systemSI derived unit
Unit ofTemperature
Named afterAnders Celsius
1 °C in ...... is equal to ...
   K   c + 273.15
   °F   (c × 9/5) + 32


Celsius original thermometer
An illustration of Anders Celsius's original thermometer. Note the reversed scale, where 100 is the freezing point of water and 0 is its boiling point.

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.[6] In his paper Observations of two persistent degrees on a thermometer, he recounted his experiments showing that the melting point of ice is essentially unaffected by pressure. He also determined with remarkable precision how the boiling point of water varied as a function of atmospheric pressure. He proposed that the zero point of his temperature scale, being the boiling point, would be calibrated at the mean barometric pressure at mean sea level. This pressure is known as one standard atmosphere. The BIPM's 10th General Conference on Weights and Measures (CGPM) later defined one standard atmosphere to equal precisely 1,013,250 dynes per square centimetre (101.325 kPa).[7]

In 1743, the Lyonnais physicist Jean-Pierre Christin, permanent secretary of the Académie des sciences, belles-lettres et arts de LyonAcadémie des sciences, belles-lettres et arts de Lyon, working independently of Celsius, developed a scale where zero represented the freezing point of water and 100 represented the boiling point of water.[8][9] On 19 May 1743 he published the design of a mercury thermometer, the "Thermometer of Lyon" built by the craftsman Pierre Casati that used this scale.[10][11][12]

In 1744, coincident with the death of Anders Celsius, the Swedish botanist Carl Linnaeus (1707–1778) reversed Celsius's scale.[13] His custom-made "linnaeus-thermometer", for use in his greenhouses, was made by Daniel Ekström, Sweden's leading maker of scientific instruments at the time, whose workshop was located in the basement of the Stockholm observatory. As often happened in this age before modern communications, numerous physicists, scientists, and instrument makers are credited with having independently developed this same scale;[14] among them were Pehr Elvius, the secretary of the Royal Swedish Academy of Sciences (which had an instrument workshop) and with whom Linnaeus had been corresponding; Daniel Ekström[[[SV]]], the instrument maker; and Mårten Strömer (1707–1770) who had studied astronomy under Anders Celsius.

The first known Swedish document[15] reporting temperatures in this modern "forward" Celsius scale is the paper Hortus Upsaliensis dated 16 December 1745 that Linnaeus wrote to a student of his, Samuel Nauclér. In it, Linnaeus recounted the temperatures inside the orangery at the University of Uppsala Botanical Garden:

...since the caldarium (the hot part of the greenhouse) by the angle of the windows, merely from the rays of the sun, obtains such heat that the thermometer often reaches 30 degrees, although the keen gardener usually takes care not to let it rise to more than 20 to 25 degrees, and in winter not under 15 degrees...

Centigrade, hectograde and Celsius

Since the 19th century, the scientific and thermometry communities worldwide have used the phrase "centigrade scale". Temperatures on the centigrade scale were often reported simply as degrees or, when greater specificity was desired, as degrees centigrade (symbol: °C). Because the term centigrade was also the Spanish and French language name for a unit of angular measurement (1/10000 of a right angle) and had a similar connotation in other languages, the term centesimal degree (known as the gradian, "grad" or "gon": 1ᵍ = 0.9°, 100ᵍ = 90°) was used when very precise, unambiguous language was required by international standards bodies such as the BIPM. More properly, what was defined as "centigrade" then would now be "hectograde".

To eliminate any confusion, the 9th CGPM and the CIPM (Comité international des poids et mesures) formally adopted "degree Celsius" in 1948,[16][a] formally keeping the recognized degree symbol, rather than adopting the gradian/centesimal degree symbol.

For scientific use, "Celsius" is the term usually used, with "centigrade" remaining in common but decreasing use, especially in informal contexts in English-speaking countries.[17] It was not until February 1985 that the weather forecasts issued by the BBC switched from "centigrade" to "Celsius".[18]

Common temperatures

Some key temperatures relating the Celsius scale to other temperature scales are shown in the table below.

Key scale relations
Kelvin Celsius Fahrenheit
Absolute zero (exactly) 0 K −273.15 °C −459.67 °F
Boiling point of liquid nitrogen 77.4 K −195.8 °C[19] −320.4 °F
Sublimation point of dry ice 195.1 K −78 °C −108.4 °F
Intersection of Celsius and Fahrenheit scales 233.15 K −40 °C −40 °F
Melting point of H2O (purified ice)[20] 273.1499 K −0.0001 °C 31.9998 °F
Water's triple point (exactly) 273.16 K 0.01 °C 32.018 °F
Normal human body temperature (average)[21] 310.15 K 37.0 °C 98.6 °F
Water's boiling point at 1 atm (101.325 kPa)
(approximate: see Boiling point)[b]
373.1339 K 99.9839 °C 211.971 °F

Name and symbol typesetting

The "degree Celsius" has been the only SI unit whose full unit name contains an uppercase letter since the SI base unit for temperature, the kelvin, became the proper name in 1967 replacing the term degrees Kelvin. The plural form is degrees Celsius.[22]

The general rule of the International Bureau of Weights and Measures (BIPM) is that the numerical value always precedes the unit, and a space is always used to separate the unit from the number, e.g. "30.2 °C" (not "30.2°C" or "30.2° C").[23] The only exceptions to this rule are for the unit symbols for degree, minute, and second for plane angle (°, ′, and ″, respectively), for which no space is left between the numerical value and the unit symbol.[24] Other languages, and various publishing houses, may follow different typographical rules.

Unicode character

Unicode provides the Celsius symbol at code point U+2103 DEGREE CELSIUS. However, this is a compatibility character provided for roundtrip compatibility with legacy encodings. It easily allows correct rendering for vertically written East Asian scripts, such as Chinese. The Unicode standard explicitly discourages the use of this character: "In normal use, it is better to represent degrees Celsius "°C" with a sequence of U+00B0 ° DEGREE SIGN + U+0043 C LATIN CAPITAL LETTER C, rather than U+2103 DEGREE CELSIUS. For searching, treat these two sequences as identical."[25]

Shown below is the degree Celsius character followed immediately by the two-component version:

℃ °C

When viewed on computers that properly support Unicode, the above line may be similar to the image in the line below (enlarged for clarity):

Unicode degree Centigrade comparison
Unicode degree Centigrade comparison

The canonical decomposition is simply an ordinary degree sign and "C", so some browsers may simply display "°C" in its place due to Unicode normalization.

Temperatures and intervals

The degree Celsius is subject to the same rules as the kelvin with regard to the use of its unit name and symbol. Thus, besides expressing specific temperatures along its scale (e.g. "Gallium melts at 29.7646 °C" and "The temperature outside is 23 degrees Celsius"), the degree Celsius is also suitable for expressing temperature intervals: differences between temperatures or their uncertainties (e.g. "The output of the heat exchanger is hotter by 40 degrees Celsius", and "Our standard uncertainty is ±3 °C").[26] Because of this dual usage, one must not rely upon the unit name or its symbol to denote that a quantity is a temperature interval; it must be unambiguous through context or explicit statement that the quantity is an interval.[c] This is sometimes solved by using the symbol °C (pronounced "degrees Celsius") for a temperature, and C° (pronounced "Celsius degrees") for a temperature interval, although this usage is non-standard.[27] Another way to express the same is "40°C ± 3 K", which can be commonly found in literature.

Celsius measurement follows an interval system but not a ratio system; and it follows a relative scale not an absolute scale. For example, 20 °C is not twice the heat energy of 10 °C; and 0 °C is not the lowest Celsius value. Thus, degrees Celsius is a useful interval measurement but does not possess the characteristics of ratio measures like weight or distance.[28]

Coexistence of Kelvin and Celsius scales

In science and in engineering, the Celsius scale and the Kelvin scale are often used in combination in close contexts, e.g. "a measured value was 0.01023 °C with an uncertainty of 70 µK". This practice is permissible because the magnitude of the degree Celsius is equal to that of the kelvin. Notwithstanding the official endorsement provided by decision #3 of Resolution 3 of the 13th CGPM,[29] which stated "a temperature interval may also be expressed in degrees Celsius", the practice of simultaneously using both °C and K remains widespread throughout the scientific world as the use of SI-prefixed forms of the degree Celsius (such as "µ°C" or "microdegrees Celsius") to express a temperature interval has not been well-adopted.

Melting and boiling points of water

One effect of defining the Celsius scale at the triple point of Vienna Standard Mean Ocean Water (VSMOW, 273.16 K and 0.01 °C), and at absolute zero (0 K and −273.15 °C), is that neither the melting nor boiling point of water under one standard atmosphere (101.325 kPa) remains a defining point for the Celsius scale. In 1948 when the 9th General Conference on Weights and Measures (CGPM) in Resolution 3 first considered using the triple point of water as a defining point, the triple point was so close to being 0.01 °C greater than water's known melting point, it was simply defined as precisely 0.01 °C.[30] However, current measurements show that the difference between the triple and melting points of VSMOW is actually very slightly (<0.001 °C) greater than 0.01 °C. Thus, the actual melting point of ice is very slightly (less than a thousandth of a degree) below 0 °C. Also, defining water's triple point at 273.16 K precisely defined the magnitude of each 1 °C increment in terms of the absolute thermodynamic temperature scale (referencing absolute zero). Now decoupled from the actual boiling point of water, the value "100 °C" is hotter than 0 °C – in absolute terms – by a factor of precisely 373.15/273.15 (approximately 36.61% thermodynamically hotter). When adhering strictly to the two-point definition for calibration, the boiling point of VSMOW under one standard atmosphere of pressure is actually 373.1339 K (99.9839 °C). When calibrated to ITS-90 (a calibration standard comprising many definition points and commonly used for high-precision instrumentation), the boiling point of VSMOW is slightly less, about 99.974 °C.[31]

This boiling-point difference of 16.1 millikelvins between the Celsius scale's original definition and the current one (based on absolute zero and the triple point) has little practical meaning in common daily applications because water's boiling point is very sensitive to variations in barometric pressure. For example, an altitude change of only 28 cm (11 in) causes the boiling point to change by one millikelvin.

Celsius temperature conversion formulae
from Celsius to Celsius
Fahrenheit [°F] = [°C] × ​95 + 32 [°C] = ([°F] − 32) × ​59
Kelvin [K] = [°C] + 273.15 [°C] = [K] − 273.15
Rankine [°R] = ([°C] + 273.15) × ​95 [°C] = ([°R] − 491.67) × ​59
For temperature intervals rather than specific temperatures,
1 °C = 1 K = ​95 °F = ​95 °R
Comparisons among various temperature scales

See also


  1. ^ According to The Oxford English Dictionary (OED), the term "Celsius' thermometer" had been used at least as early as 1797. Further, the term "The Celsius or Centigrade thermometer" was again used in reference to a particular type of thermometer at least as early as 1850. The OED also cites this 1928 reporting of a temperature: "My altitude was about 5,800 metres, the temperature was 28° Celsius." However, dictionaries seek to find the earliest use of a word or term and are not a useful resource as regards to the terminology used throughout the history of science. According to several writings of Dr. Terry Quinn CBE FRS, Director of the BIPM (1988–2004), including "Temperature Scales from the early days of thermometry to the 21st century" (PDF). (146 KiB) as well as Temperature (2nd Edition/1990/Academic Press/0125696817), the term Celsius in connection with the centigrade scale was not used whatsoever by the scientific or thermometry communities until after the CIPM and CGPM adopted the term in 1948. The BIPM was not even aware that "degree Celsius" was in sporadic, non-scientific use before that time. It is also noteworthy that the twelve-volume, 1933 edition of OED didn't even have a listing for the word Celsius (but did have listings for both centigrade and centesimal in the context of temperature measurement). The 1948 adoption of Celsius accomplished three objectives:
    1.    All common temperature scales would have their units named after someone closely associated with them; namely, Kelvin, Celsius, Fahrenheit, Réaumur and Rankine.
    2.    Notwithstanding the important contribution of Linnaeus who gave the Celsius scale its modern form, Celsius's name was the obvious choice because it began with the letter C. Thus, the symbol °C that for centuries had been used in association with the name centigrade could remain in use and would simultaneously inherit an intuitive association with the new name.
    3.    The new name eliminated the ambiguity of the term "centigrade", freeing it to refer exclusively to the French-language name for the unit of angular measurement.
  2. ^ For Vienna Standard Mean Ocean Water at one standard atmosphere (101.325 kPa) when calibrated solely per the two-point definition of thermodynamic temperature. Older definitions of the Celsius scale once defined the boiling point of water under one standard atmosphere as being precisely 100 °C. However, the current definition results in a boiling point that is actually 16.1 mK less. For more about the actual boiling point of water, see VSMOW in temperature measurement. A different approximation uses ITS-90, which approximates the temperature to 99.974 °C
  3. ^ In 1948, Resolution 7 of the 9th CGPM stated, "To indicate a temperature interval or difference, rather than a temperature, the word 'degree' in full, or the abbreviation 'deg' must be used." This resolution was abrogated in 1967/1968 by Resolution 3 of the 13th CGPM, which stated that ["The names "degree Kelvin" and "degree", the symbols "°K" and "deg" and the rules for their use given in Resolution 7 of the 9th CGPM (1948),] ...and the designation of the unit to express an interval or a difference of temperatures are abrogated, but the usages which derive from these decisions remain permissible for the time being." Consequently, there is now wide freedom in usage regarding how to indicate a temperature interval. The most important thing is that one's intention must be clear and the basic rule of the SI must be followed; namely that the unit name or its symbol must not be relied upon to indicate the nature of the quantity. Thus, if a temperature interval is, say, 10 K or 10 °C (which may be written 10 kelvins or 10 degrees Celsius), it must be unambiguous through obvious context or explicit statement that the quantity is an interval. Rules governing the expressing of temperatures and intervals are covered in the BIPM's "SI Brochure, 8th edition" (PDF). (1.39 MiB).


  1. ^ "Celsius temperature scale". Encyclopædia Britannica. Retrieved 19 February 2012. Celsius temperature scale, also called centigrade temperature scale, scale based on 0 ° for the freezing point of water and 100 ° for the boiling point of water at 1 atm pressure.
  2. ^ Helmenstine, Anne Marie (December 15, 2014). "What Is the Difference Between Celsius and Centigrade?". Chemistry.about.com. About.com. Retrieved March 16, 2015.
  3. ^ https://www.vox.com/2015/2/16/8031177/america-fahrenheit
  4. ^ "SI brochure, section". International Bureau of Weights and Measures. Archived from the original on 26 September 2007. Retrieved 9 May 2008.
  5. ^ "Essentials of the SI: Base & derived units". Retrieved 9 May 2008.
  6. ^ Celsius, Anders (1742) "Observationer om twänne beständiga grader på en thermometer" (Observations about two stable degrees on a thermometer), Kungliga Svenska Vetenskapsakademiens Handlingar (Proceedings of the Royal Swedish Academy of Sciences), 3 : 171–180 and Fig. 1.
  7. ^ "Resolution 4 of the 10th meeting of the CGPM (1954)".
  8. ^ Don Rittner; Ronald A. Bailey (2005): Encyclopedia of Chemistry. Facts On File, Manhattan, New York City. p. 43.
  9. ^ Smith, Jacqueline (2009). "Appendix I: Chronology". The Facts on File Dictionary of Weather and Climate. Infobase Publishing. p. 246. ISBN 978-1-4381-0951-0. 1743 Jean-Pierre Christin inverts the fixed points on Celsius' scale, to produce the scale used today.
  10. ^ Mercure de France (1743): MEMOIRE sur la dilatation du Mercure dans le Thermométre. Chaubert; Jean de Nully, Pissot, Duchesne, Paris. pp. 1609–1610.
  11. ^ Journal helvétique (1743): LION. Imprimerie des Journalistes, Neuchâtel. pp. 308–310.
  12. ^ Memoires pour L'Histoire des Sciences et des Beaux Arts (1743): DE LYON. Chaubert, París. pp. 2125–2128.
  13. ^ Citation: Uppsala University (Sweden), Linnaeus' thermometer
  14. ^ Citation for Daniel Ekström, Mårten Strömer, Christin of Lyons: The Physics Hypertextbook, Temperature; citation for Christin of Lyons: Le Moyne College, Glossary, (Celsius scale); citation for Linnaeus's connection with Pehr Elvius and Daniel Ekström: Uppsala University (Sweden), Linnaeus' thermometer; general citation: The Uppsala Astronomical Observatory, History of the Celsius temperature scale
  15. ^ Citations: University of Wisconsin–Madison, Linnæus & his Garden and; Uppsala University, Linnaeus' thermometer
  16. ^ "CIPM, 1948 and 9th CGPM, 1948". International Bureau of Weights and Measures. Retrieved 9 May 2008.
  17. ^ "centigrade, adj. and n." Oxford English Dictionary. Oxford University Press. Retrieved 20 November 2011.
  18. ^ 1985 BBC Special: A Change In The Weather on YouTube
  19. ^ Lide, D.R., ed. (1990–1991). Handbook of Chemistry and Physics. 71st ed. CRC Press. p. 4–22.
  20. ^ The ice point of purified water has been measured at 0.000089(10) degrees Celsius – see Magnum, B.W. (June 1995). "Reproducibility of the Temperature of the Ice Point in Routine Measurements" (PDF). Nist Technical Note. 1411. Archived from the original (PDF) on July 14, 2007. Retrieved 11 February 2007.
  21. ^ Elert, Glenn (2005). "Temperature of a Healthy Human (Body Temperature)". The Physics Factbook. Retrieved 22 August 2007.
  22. ^ "Unit of thermodynamic temperature (kelvin)". The NIST Reference on Constants, Units, and Uncertainty: Historical context of the SI. National Institute of Standards and Technology (NIST). 2000. Retrieved 16 November 2011.
  23. ^ BIPM, SI Brochure, Section 5.3.3.
  24. ^ For more information on conventions used in technical writing, see the informative SI Unit rules and style conventions by the NIST as well as the BIPM's SI brochure: Subsection 5.3.3, Formatting the value of a quantity. Archived 2014-07-05 at the Wayback Machine
  25. ^ "22.2". The Unicode Standard, Version 9.0 (PDF). Mountain View, CA, USA: The Unicode Consortium. July 2016. ISBN 978-1-936213-13-9. Retrieved 20 April 2017.
  26. ^ Decision #3 of Resolution 3 of the 13th CGPM.
  27. ^ H.D. Young, R. A. Freedman (2008). University Physics with Modern Physics (12th ed.). Addison Wesley. p. 573.
  28. ^ This fact is demonstrated in the book Biostatistics: A Guide to Design, Analysis, and Discovery By Ronald N. Forthofer, Eun Sul Lee and Mike Hernandez
  29. ^ http://www.bipm.fr/en/CGPM/db/13/3/
  30. ^ "Resolution 3 of the 9th CGPM (1948)". International Bureau of Weights and Measures. Retrieved 9 May 2008.
  31. ^ Citation: London South Bank University, Water Structure and Behavior, notes c1 and c2

External links

The dictionary definition of Celsius at Wiktionary

Anders Celsius

Anders Celsius (27 November 1701 – 25 April 1744) was a Swedish astronomer, physicist and mathematician. He was professor of astronomy at Uppsala University from 1730 to 1744, but traveled from 1732 to 1735 visiting notable observatories in Germany, Italy and France. He founded the Uppsala Astronomical Observatory in 1741, and in 1742 proposed the Celsius temperature scale which bears his name.

Backyard Babies

Backyard Babies are a rock band from Nässjö, Sweden. The band was formed in 1989 and over the years they have released seven studio albums and won two Swedish Grammy Awards. The band is now located in Stockholm.

They are largely attributed with popularizing sleaze rock in Scandinavia and Sweden. Their single "Minus Celsius" appears as a playable bonus track in Guitar Hero III: Legends of Rock and "Degenerated" is available as a downloadable song for Guitar Hero World Tour.

Bishop Bay – Monkey Beach Conservancy

Bishop Bay – Monkey Beach Conservancy is a nature conservancy in British Columbia, Canada. It is 3,374 hectares in size and is accessible only by floatplane or boat. It features boat anchorage and tent platforms as well as a hotspring fed bath house. The temperature of the hotsprings is approximately 41.3 degrees Celsius at the source and about 38.8 degrees Celsius in the bath house. It is located 25 km east of Hartley Bay and 75 km south of Kitimat. The conservancy was established in 2007.


The calorie is a unit of energy. The Calorie (note the capital C) is 1,000 calories.

That capital C, distinguishing Calorie from calorie, is a long-established scientific convention but is not always understood more widely. Where the context is clearly about food, nutrition and exercise, the term often appears without the capital C. The Calorie is also termed the large calorie or kilocalorie — symbols: Cal, kcal — or food calorie, defined as the heat energy involved in warming one kilogram of water by one degree Celsius.The small calorie (symbol: cal) was later defined as the heat energy to raise the temperature of one gram of water — rather than a kilogram — by the same amount. (See below for details of the definitions.)

Although both units relate to the metric system, they have been considered obsolete, or deprecated, in scientific usage, since the adoption of the SI system. (The SI unit of energy is the joule.) But the small calorie is still often used in laboratory measurements and calculations, with the values thus established typically being reported in kilocalories.

Celsius (comics)

Celsius is the superhero alias of Arani Desai, a fictional character in the DC Comics series, Doom Patrol. She first appeared in Showcase #94 (September 1977), and was created by Paul Kupperberg and Joe Staton. She is among the very few superheroes of South Asian heritage, and may be the first ever such hero created by DC Comics.Celsius appeared in her first live adaptation on the first season of the Doom Patrol television series for the new DC streaming service played by Jasmine Kaur and Madhur Jaffrey.

Celsius (crater)

Celsius is a small lunar impact crater that is located in the rugged terrain in the southern hemisphere on the Moon's near side. It is named after Swedish astronomer, physicist and mathematician Anders Celsius. It lies less than one crater diameter to the south-southwest of the crater Zagut, and due north of Büsching.

This is a heavily worn crater with a southwest rim that has been damaged by multiple small crater impacts. There is a valley-like gap in the northern rim that joins Celsius with Celsius A. The interior floor of Celsius is almost featureless, except for a small craterlet in the northern half.

Christer Fuglesang

Arne Christer Fuglesang (Swedish pronunciation: [ɑ:ɳɛ krɪstɛr fʉ:glɛsaŋ]) (born March 18, 1957 in Stockholm) is a Swedish physicist and an ESA astronaut. He was first launched aboard the STS-116 Space Shuttle mission on December 10, 2006, at 01:47 GMT, making him the first Swedish citizen in space.Married with three children, he was a Fellow at CERN and taught mathematics at the Royal Institute of Technology before being selected to join the European Astronaut Corps in 1992. He has participated in two Space Shuttle missions and five spacewalks, and is the first person outside of the United States or Russian space programs to participate in more than three spacewalks.

Conversion of units of temperature

This is a collection of temperature conversion formulas and comparisons among eight different temperature scales, several of which have long been obsolete.


The Fahrenheit scale is a temperature scale based on one proposed in 1724 by Dutch–German–Polish physicist Daniel Gabriel Fahrenheit (1686–1736). It uses the degree Fahrenheit (symbol: °F) as the unit. Several accounts of how he originally defined his scale exist. The lower defining point, 0 °F, was established as the freezing temperature of a solution of brine made from equal parts of ice, water and salt (ammonium chloride). Further limits were established as the melting point of ice (32 °F) and his best estimate of the average human body temperature (96 °F, about 2.6 °F less than the modern value due to a later redefinition of the scale). The scale is now usually defined by two fixed points: the temperature at which water freezes into ice is defined as 32 °F, and the boiling point of water is defined to be 212 °F, a 180 °F separation, as defined at sea level and standard atmospheric pressure.

At the end of the 2010s, Fahrenheit was used as the official temperature scale only in the United States (including its unincorporated territories), its freely associated states in the Western Pacific (Palau, the Federated States of Micronesia and the Marshall Islands), the Bahamas, the Cayman Islands and Liberia. Antigua and Barbuda and other islands which use the same meteorological service, such as Anguilla, the British Virgin Islands, Montserrat and Saint Kitts and Nevis, as well as Bermuda, Belize and the Turks and Caicos Islands, use Fahrenheit and Celsius. All other countries in the world officially now use the Celsius scale, named after Swedish astronomer Anders Celsius.


ISO 1 is an international standard set by the International Organization for Standardization that specifies the standard reference temperature for geometrical product specification and verification. The temperature is fixed at 20 °C, which is equal to 293.15 kelvin and 68 degrees Fahrenheit.Due to thermal expansion, precision length measurements need to be made at (or converted to) a defined temperature. ISO 1 helps in comparing measurements by defining such a reference temperature. The reference temperature of 20 °C was adopted by the CIPM on 15 April 1931, and became ISO recommendation number 1 in 1951. It soon replaced worldwide other reference temperatures for length measurements that manufacturers of precision equipment had used before, including 0 °C, 62 °F, and 25 °C. Among the reasons for choosing 20 °C was that this was a comfortable and practical workshop temperature and that it resulted in an integer value on both the Celsius and Fahrenheit scales.

ISO 31-4

ISO 31-4 is the part of international standard ISO 31 that defines names and symbols for quantities and units related to heat. It is superseded by ISO 80000-5.

Its definitions include:

Annex A of ISO 31-4 lists units of heat based on the foot, pound and second and some other units, including the degree Rankine, degree Fahrenheit, British thermal unit and others. Annex B lists conversion factors for three versions of the calorie.


The Kelvin scale is an absolute thermodynamic temperature scale using as its null point absolute zero, the temperature at which all thermal motion ceases in the classical description of thermodynamics. The kelvin (symbol: K) is the base unit of temperature in the International System of Units (SI).

Until 2018, the kelvin was defined as the fraction 1/273.16 of the thermodynamic temperature of the triple point of water (exactly 0.01 °C or 32.018 °F). In other words, it was defined such that the triple point of water is exactly 273.16 K.

On 16 November 2018, a new definition was adopted, in terms of a fixed value of the Boltzmann constant. For legal metrology purposes, the new definition will officially come into force on 20 May 2019 (the 130th anniversary of the Metre Convention).The Kelvin scale is named after the Belfast-born, Glasgow University engineer and physicist William Thomson, 1st Baron Kelvin (1824–1907), who wrote of the need for an "absolute thermometric scale". Unlike the degree Fahrenheit and degree Celsius, the kelvin is not referred to or written as a degree. 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. The definition implies that absolute zero (0 K) is equivalent to −273.15 °C (−459.67 °F).

NGC 40

NGC 40 (also known as the Bow-Tie Nebula and Caldwell 2) is a planetary nebula discovered by William Herschel on November 25, 1788, and is composed of hot gas around a dying star. The star has ejected its outer layer which has left behind a smaller, hot star with a temperature on the surface of about 50,000 degrees Celsius. Radiation from the star causes the shed outer layer to heat to about 10,000 degrees Celsius, and is about one light-year across. About 30,000 years from now, scientists theorize that NGC 40 will fade away, leaving only a white dwarf star approximately the size of Earth.


Ochamchire or Ochamchira (Georgian: ოჩამჩირე, [ɔtʃʰɑmtʃʰire] (listen); Abkhazian: Очамчыра, Ochamchyra; Russian: Очамчира, Ochamchira) is a seaside city on the Black Sea coast of Abkhazia, Georgia. and a centre of the eponymous district.

According to the 1978 population census, Ochamchire had 18,700 residents. After the Georgian-Abkhaz conflict of 1992-93, Ochamchire experienced a significant population decline due to ethnic cleansing of Georgians. Most of the internally displaced persons who were affected by the conflict have yet to return to the city. Ochamchire lies along the left bank of the Ghalidzga River at an elevation of 5 metres (16 feet) above sea level. The city is located 53 kilometres (33 miles) southeast of Sukhumi capital city. Ochamchire's climate is humid subtropical, with mild winters and hot summers. The average annual temperature is 13.6 degrees Celsius. January's average temperature is 4.5 degrees Celsius while the average temperature in July is 23 degrees Celsius. Average annual precipitation is approximately 1,552 mm (61 in).

Ochamchire evolved as a town from a small maritime settlement, which was a scene of fighting between the Russians and Turkish-Abkhaz forces in 1877.The ancient Greek colony of Gyenos (Greek: Γυένος) is supposed to have located near Ochamchire, though the identification cannot be considered as definitive because of doubts as to the actual location and the very poor preservation of the archaeologic site itself.According to Itar Tass, in 2009, Russia planned to construct a new naval base for its Black Sea Fleet (as of 2009 based at Sevastopol) in Ochamchire.The former Georgian Soviet footballer Vitaly Daraselia was from Ochamchire.

Rankine scale

The Rankine scale () is an absolute scale of thermodynamic temperature named after the Glasgow University engineer and physicist William John Macquorn Rankine, who proposed it in 1859. (The Kelvin scale was first proposed in 1848.) It may be used in engineering systems where heat computations are done using degrees Fahrenheit.

The symbol for degrees Rankine is °R (or °Ra if necessary to distinguish it from the Rømer and Réaumur scales). By analogy with kelvin, some authors term the unit rankine, omitting the degree symbol. Zero on both the Kelvin and Rankine scales is absolute zero, but a temperature difference of one Rankine degree is defined as equal to one Fahrenheit degree, rather than the Celsius degree used on the Kelvin scale. Thus, a temperature of 0 K (−273.15 °C; −459.67 °F) is equal to 0 °R, and a temperature of −458.67 °F equal to 1 °R.

The US National Institute of Standards and Technology recommends against using the degree symbol when using Rankine in NIST publications.Some important temperatures relating the Rankine scale to other temperature scales are shown in the table below.

Recurring Saturday Night Live characters and sketches introduced 1998–1999

The following is a list of recurring Saturday Night Live characters and sketches introduced between September 26, 1998, and May 15, 1999, the twenty-fourth season of SNL.


Setcases (Catalan pronunciation: [ˌsɛtˈkazəs, ˌsɛˈkːazəs]; literally meaning "Seven Houses", set "seven" and cases "houses") is a municipality and town in the Pyrenean comarca of Ripollès in Girona, Catalonia, Spain, near the French border. The source for the Ter River is in the mountains just above Setcases. The current mayor is Jaume Busquets i Bartolí.The name Setcases has been documented back to 965, from records of some donations made by Count Sunifred of Besalú in the nearby monastery of Sant Pere de Camprodon.The church contains a Baroque altarpiece dedicated to Saint Michael, which is the only such example of one in all of the Camprodon Valley. Unlike many other relics, it was saved from being burned during the Spanish Civil War.Today, Setcases has most of its economic base in year-round tourism, including hiking in the warmer months (e.g. Ulldeter hiking circuit) and skiing during the winter season with a lift at Vallter 2000.

Vallter 2000 is a very big attraction for tourists from all Spain.

The weather is very cold, specially in winter the temperature can get to about -20 Celsius. In summer the temperature can rise to 20-25 degrees Celsius.


Temperature is a physical quantity expressing hot and cold. It is measured with a thermometer calibrated in one or more temperature scales. The most commonly used scales are the Celsius scale (formerly called centigrade) (denoted °C), Fahrenheit scale (denoted °F), and Kelvin scale (denoted K). The kelvin (the word is spelled with a lower-case k) is the unit of temperature in the International System of Units (SI), in which temperature is one of the seven fundamental base quantities. The Kelvin scale is widely used in science and technology.

Theoretically, the coldest a system can be is when its temperature is absolute zero, at which point the thermal motion in matter would be zero. However, an actual physical system or object can never attain a temperature of absolute zero. Absolute zero is denoted as 0 K on the Kelvin scale, −273.15 °C on the Celsius scale, and −459.67 °F on the Fahrenheit scale.

For an ideal gas, temperature is proportional to the average kinetic energy of the random microscopic motions of the constituent microscopic particles.

Temperature is important in all fields of natural science, including physics, chemistry, Earth science, medicine, and biology, as well as most aspects of daily life.

Uppsala Astronomical Observatory

The Uppsala Astronomical Observatory (UAO), Astronomiska observatoriet i Uppsala) is the oldest astronomical observatory in Sweden. It was founded in 1741, though there was a professorial chair of astronomy at the University of Uppsala from 1593 and the university archives include lecture notes in astronomy from the 1480s.

In the 18th century, Anders Celsius performed his research there and built the first observatory proper in 1741. Celsius got the university consistory to buy a large stone house of medieval origin in central Uppsala, where he had an observatory constructed on the rooftop. Celsius both worked and had his personal living quarters in the house. This observatory remained in use until the new observatory, now known as the "old observatory", was built in 1853. The Celsius house itself still remains as one of few older buildings on a modern shopping street, but the observatory on the roof was demolished in 1857.

In the 19th century Anders Jonas Ångström was keeper of the observatory and conducted his experiments in astronomy, physics and optics there. His son, Knut Ångström, also conducted research on solar radiation at the observatory.

In 2000 the observatory merged with the Institute of Space Physics to form the Department of Astronomy and Space Physics and moved to the Ångström Laboratory. In 2008, another merger resulted in the Department of Physics and Astronomy, Astronomy and Space Physics becoming one of its divisions.

In addition to facilities in Uppsala, the observatory maintains the Kvistaberg Observatory in Sweden and the Uppsala Southern Station at the Siding Spring Observatory in Australia.

Research at the observatory over the years includes stellar parallaxes, stellar statistics, galactic structure, external galaxies, stellar atmospheres and solar system research.

Base units
Derived units
with special names
Other accepted units
See also
Base units
Derived units
with special names
Other accepted units
See also

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