# Fahrenheit

Celsius TC = (TF − 32) ÷ 1.8 TF = (TC × 9/5) + 32 TK = (TF + 459.67) ÷ 1.8 TF = (TK × 9/5) − 459.67 TR = TF + 459.67 TF = TR − 459.67 Additional conversion formulas

Fahrenheit is a temperature scale named after the German-Dutch physicist Daniel Gabriel Fahrenheit (1686–1736), who proposed it in 1724.

In this scale, the melting point of water is 32 degrees Fahrenheit (written “32 °F”), and the boiling point is 212 degrees, placing the boiling and melting points of water exactly 180 degrees apart. On the Celsius scale, the melting and boiling points of water are exactly 100 degrees apart, thus the unit of this scale, a degree Fahrenheit, is 59 of a degree Celsius. The Fahrenheit scale coincides with the Celsius scale at -40 °F, which is the same temperature as -40 °C.

Absolute zero is −459.67 °F. The Rankine temperature scale was invented to use degrees the same size as Fahrenheit degrees, so 0 °R would be absolute zero, namely −459.67 °F.

## History

There are a few competing versions of the story of how Fahrenheit came to devise his temperature scale. According to Fahrenheit himself in an article he wrote in 1724 [1] he determined three fixed points of temperature. The zero point is determined by placing the thermometer in a mixture of ice, water, and ammonium chloride (or sea salt) and letting the liquid (alcohol or mercury) descend to its lowest point. The second point is the 32nd degree found by mixing ice and water without the salts. He named this the "freezing point", stating that a thin layer of ice covered the water at this measurement. His third point, the 96th degree, was the level of the liquid in the thermometer when held in the mouth or under the armpit. Fahrenheit noted that, using this scale, mercury boils at around 600 degrees.

Other theories are similar in nature. One states that Fahrenheit established the zero (0 °F) and 96 °F points on his scale by recording the lowest outdoor temperatures he could measure, and his own body temperature. He took the lowest temperature which he measured in the harsh winter of 1708 through 1709 in his hometown of Danzig (now Gdańsk, Poland) (−17.8 °C) as his zero point. (He was later able to reach this temperature under laboratory conditions using a mixture of ice, ammonium chloride and water.)

A variant of this version is that the mixture of ice, salt, and water registered the lowest temp temperature Fahrenheit could attain in the lab, so he used that for his zero point, using his body temperature as 96 °F. [2]

Fahrenheit wanted to avoid the negative temperatures that the Rømer scale had produced in everyday use. He fixed his own body temperature as 96 °F. (As noted below, the scale has since been re-calibrated so that normal body temperature is closer to 98.6 °F). He then divided his scale into twelve sections, and subsequently each of these into 8 equal subdivisions, producing a scale of 96 degrees. Fahrenheit noted that his scale placed the melting point of water at 32 °F and the boiling point at 212 °F, a neat 180 degrees apart.

Another story holds that Fahrenheit established the zero of his scale (0 °F) as the temperature at which an equal mixture of ice and salt melts (some say he took that fixed mixture of ice and salt that produced the lowest temperature); and ninety-six degrees as the temperature of blood (he initially used horse blood to calibrate his scale). Initially, his scale only contained 12 equal subdivisions, but later he subdivided each division into 8 equal degrees ending up with 96.

A fourth well-known version of the story, as described in the popular physics television series The Mechanical Universe, holds that Fahrenheit simply adopted Rømer’s scale, at which water freezes at 7.5 degrees, and multiplied each value by 4 in order to eliminate the fractions and increase the granularity of the scale (giving 30 and 240 degrees). He then re-calibrated his scale between the melting point of water and normal human body temperature (which he took to be 96 degrees); the melting point of ice was adjusted to 32 degrees so that 64 intervals would separate the two, allowing him to mark degree lines on his instruments by simply bisecting the interval six times (since 64 is 2 to the sixth power).

A fifth version maintains that Fahrenheit based 0 degrees on an estimate of the temperature at which someone would freeze to death, and 100 degrees on the temperature at which someone would die of heat exhaustion, therefore making 0 to 100 the livable range for human beings. This, however, is arguable because the human body has been known to survive at temperatures above and below these thresholds.

A sixth version maintains that Fahrenheit marked the melting point of ice, normal human body temperature, and the boiling point of water. He then divided the span from melting to boiling into 180 degrees. Setting the normal human body temperature as 96 resulted in the freezing point and boiling point being 32 and 212, respectively.

A seventh version maintains that the coldest temperature he could achieve in the lab was designated with 0 degrees, and the melting point of butter was 100 degrees.[3]

His measurements were not entirely accurate; by his original scale, the actual melting and boiling points would have been noticeably different from 32 °F and 212 °F. Some time after his death, it was decided to recalibrate the scale with 32 °F and 212 °F as the exact melting and boiling points of plain water. That change was made to easily convert from Celsius to Fahrenheit and vice versa, with a simple formula. This change also explains why the body temperature once taken as 96 °F by Fahrenheit is today taken by many as 98.6 °F (it is a direct conversion of 37 °C), although giving the value as 98 °F would be more accurate.

## Usage

The Fahrenheit scale was the primary temperature standard for climatic, industrial and medical purposes in most English-speaking countries until the 1960s. In the late 1960s and 1970s, the Celsius (formerly Centigrade) scale was phased in by governments as part of the standardizing process of metrication. In the United States and perhaps a few other countries (such as Belize[4]) the Fahrenheit system continues to be the accepted standard for non-scientific use. Most other countries have adopted Celsius as the primary scale in all use. Fahrenheit is sometimes used by older generations in English speaking countries, especially for measurement of higher temperatures.

## The special Unicode °F character

The Fahrenheit symbol has its own Unicode character: U+2109. This is a compatibility character encoded for roundtrip compatibility with legacy CJK encodings (which included it to conform to layout in square ideographic character cells) and vertical layout. Use of compatibility characters is discouraged by the Unicode Consortium. The ordinary degree sign (U+00B0) followed by the Latin letter F is thus the preferred way of writing the symbol for degrees Fahrenheit.

## References

Celsius is, or relates to, the Celsius temperature scale (previously known as the centigrade scale). The degree Celsius (symbol: °C) can refer to a specific temperature on the Celsius scale
The kelvin (symbol: K) is a unit increment of temperature and is one of the seven SI base units. The Kelvin scale is a thermodynamic (absolute) temperature scale where absolute zero — the coldest possible temperature — is zero kelvins
Rankine is a thermodynamic (absolute) temperature scale named after the Scottish engineer and physicist William John Macquorn Rankine, who proposed it in 1859.

The symbol is °R (or °Ra if necessary to distinguish it from the Rømer and Réaumur scales).

## Kelvin

Kelvin
Celsius [C] = [K] − 273.15 [K] = [C] + 273.15
Fahrenheit [F] = [K] 9/5 − 459.67 [K] = ([F] + 459.67) 5/9
Rankine [Ra] = [K] 9/5 [K] = [Ra] 5/9
Raumur [R] = ([K] − 273.15) 4/5 [K] = [R] 5/4 + 273.15
Newton [N] = ([K] − 273.
trillion fold).]]

Temperature is a physical property of a system that underlies the common notions of hot and cold; something that is hotter generally has the greater temperature. Temperature is one of the principal parameters of thermodynamics.
physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena spanning all length scales: from the sub-atomic particles from which all ordinary matter is made (particle physics) to the behavior of the material Universe as a whole
Daniel Gabriel Fahrenheit (24 May 1686 – 16 September 1736) was a German physicist and engineer who worked most of his life in the Dutch Republic. The °F Fahrenheit scale of temperature is named after him.
The melting point of a crystalline solid is the temperature range at which it changes state from solid to liquid. Although the phrase would suggest a specific temperature and is commonly and incorrectly used as such in most textbooks and literature, most crystalline compounds
Water is a common chemical substance that is essential to all known forms of life.[1] In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor.
boiling point of a liquid is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid.[1][2][3][4]
Celsius is, or relates to, the Celsius temperature scale (previously known as the centigrade scale). The degree Celsius (symbol: °C) can refer to a specific temperature on the Celsius scale
units of measurement have played a crucial role in human endeavour from early ages up to this day. Disparate systems of measurement used to be very common. Now there is a global standard, the International System (SI) of units, the modern form of the metric system.
Absolute zero describes a theoretical system that neither emits nor absorbs energy. The Absolute zero temperature is known to be (–273.15 °C).
Rankine is a thermodynamic (absolute) temperature scale named after the Scottish engineer and physicist William John Macquorn Rankine, who proposed it in 1859.

The symbol is °R (or °Ra if necessary to distinguish it from the Rømer and Réaumur scales).
Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when temperature surrounding is very different. This process is one aspect of homeostasis: a dynamic state of stability between an animal's internal environment and its
Motto
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ICE may refer to:
• Internal combustion engine, a fuel engine
• In case of emergency, the emergency contact program created after the 7 July 2005 London Bombings
• International Cometary Explorer, a former spacecraft
• Integrated Collaboration Environment

Ammonium chloride (NH4Cl) (also Sal Ammoniac, salmiac, nushadir salt, zalmiak, sal armagnac, sal armoniac, salmiakki, salmiak and salt armoniack
Rømer is a disused temperature scale named after the Danish astronomer Ole Christensen Rømer, who proposed it in 1701.

In this scale, the zero was initially set using freezing brine. The boiling point of water was defined as 60 degrees.
Normal human body temperature is a concept that depends on the place in the body at which the measurement is made. The value of 36.8 °C ±0.7 °C, or 98.2 °F ±1.3 °F. is the common oral measurement.
ICE may refer to:
• Internal combustion engine, a fuel engine
• In case of emergency, the emergency contact program created after the 7 July 2005 London Bombings
• International Cometary Explorer, a former spacecraft
• Integrated Collaboration Environment

For sodium in the diet, see salt.

Sodium chloride, also known as common salt, table salt, or halite, is a chemical compound with the formula NaCl.
The Mechanical Universe... And Beyond, is a 52-part telecourse filmed at the California Institute of Technology, funded by the Annenberg/CPBProject, and produced by Caltech and INTELECOM Intelligent Telecommunications (a non-profit consortium of California community
Ole Christensen Rømer [o(ː)lə ˈʁœːˀmɐ] (25 September 1644, Århus – 19 September 1710, Copenhagen) was a Danish astronomer who in 1676 made the first quantitative measurements of the
Celsius is, or relates to, the Celsius temperature scale (previously known as the centigrade scale). The degree Celsius (symbol: °C) can refer to a specific temperature on the Celsius scale
Metrication (or metrification) refers to the introduction of the SI metric system as the international standard for physical measurements—a long-term series of independent and systematic conversions from the various separate local systems of weights and measures.
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