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Thermometer with Fahrenheit units on the outer scale and Celsius units on the inner scale
Definition and conversions
Fahrenheit temperature conversion formulae
|
from Fahrenheit |
to Fahrenheit |
| Celsius |
[°C] = ([°F] − 32) × 5⁄9 |
[°F] = [°C] × 9⁄5 + 32 |
| Kelvin |
[K] = ([°F] + 459.67) × 5⁄9 |
[°F] = [K] × 9⁄5 − 459.67 |
| Rankine |
[°R] = [°F] + 459.67 |
[°F] = [°R] − 459.67 |
For temperature intervals rather than specific temperatures,
1 °F = 1 °R = 5⁄9 °C = 5⁄9 K
Comparisons among various temperature scales |
On the Fahrenheit scale, the
freezing point of
water is 32 degrees Fahrenheit (°F) and the
boiling point 212 °F (at
standard atmospheric pressure), placing the boiling and freezing points of water exactly 180 degrees apart.
[3] A degree on the Fahrenheit scale is
1⁄180 of the interval between the freezing point and the boiling point. On the Celsius scale, the freezing and boiling points of water are 100 degrees apart, hence the
unit of this temperature scale.
[3] A temperature interval of 1 degree Fahrenheit is equal to an interval of
5⁄9 degrees Celsius. The Fahrenheit and Celsius scales converge at −40 degrees (i.e.
−40 °F and
−40 °C represent the same temperature).
[3]Absolute zero is
−459.67 °F.
[4] The
Rankine temperature scale was created to use degree intervals the same size as those of the Fahrenheit scale, such that a temperature difference of one degree Rankine
(1 °R) is equal to a difference of
1 °F, except that absolute zero is
0 °R – the same way that the
Kelvin temperature scale matches the Celsius scale, except that absolute zero is
0 K.
History
According to a journal article Fahrenheit wrote in 1724,
[5] he based his scale on three reference points of temperature. The zero point is determined by placing the
thermometer in
brine: he used a mixture of
ice, water, and
ammonium chloride, a salt. This is a
frigorific mixture which automatically stabilizes its temperature at
0 °F. A mixture of ice and water stabilizes, either freezing or melting at 32 °F,
[6] though Fahrenheit did not use this point in defining his temperature scale. The third point, 96 degrees, was the level of the liquid in the thermometer when held in the mouth or under the armpit of his wife. Fahrenheit noted that, using this scale, mercury boils at around 600 degrees.
Later, work by other scientists observed that water boils about 180 degrees higher than the freezing point and decided to redefine the degree slightly to make it exactly 180 degrees higher.
[5] It is for this reason that
normal body temperature is 98.6 on the revised scale (whereas it was 96 on Fahrenheit's original scale).
[7]According to a letter Fahrenheit wrote to his friend
Herman Boerhaave,
[8] his scale was built on the work of
Ole Rømer, whom he had met earlier. In
Rømer’s scale, the two fixed reference points are that
brine also freezes at 0 degrees and water boils at 60 degrees. He observed that, on this scale, water freezes at 7.5 degrees. Fahrenheit multiplied each value by four in order to eliminate fractions and increase the granularity of the scale (resulting in 30 and 240 degrees, respectively).
.^ Any time a guy like this comes along and says, "I told him I had two nephews and one was going to Iraq and one was going to Afghanistan," he’s lying.- Fifty-nine Deceits in Fahrenheit 911, Dave Kopel, Independence Institute 15 September 2009 8:35 UTC www.davekopel.com [Source type: FILTERED WITH BAYES]
^ Any time a guy like this comes along and says, "I told him I had two nephews and one was going to Iraq and one was going to Afghanistan," hes lying.- Fifty-nine Deceits in Fahrenheit 911, Dave Kopel, Independence Institute 9 January 2010 21:21 UTC davekopel.com [Source type: FILTERED WITH BAYES]
[9]Usage
The Fahrenheit scale was the primary temperature standard for climatic, industrial and medical purposes in some English-speaking countries until the 1960s. In the late 1960s and 1970s, the
Celsius (known until 1948 as
centigrade) scale was adopted by most of these countries as part of the standardizing process called
metrication.
Only in the
United States and a few other countries (
Belize[2],
Burma, and
Liberia[10]) does the Fahrenheit system continue to be used, and only for non-scientific use. Most other countries have adopted Celsius as the primary scale in all use, although Fahrenheit continues to be the scale of preference for a minority of people in the United Kingdom, particularly when referring to summer temperatures
[citation needed].
In the U.S., weather forecasts, food cooking and freezing temperatures are commonly in degrees Fahrenheit.
Various reasons are given for the resistance to the Celsius system in the U.S., including the larger size of each degree Celsius (resulting in the need for decimals where integer Fahrenheit degrees were adequate for much technical work), or the lower zero point in the Fahrenheit system which reduces the number of negative signs when measurements such as weather data were averaged.
[11] .^ Like Clarke, most of the political figures in Fahrenheit 9/11 were not filmed by Moore; he used footage which had been shot by news organizations.- Fifty-nine Deceits in Fahrenheit 911, Dave Kopel, Independence Institute 9 January 2010 21:21 UTC davekopel.com [Source type: FILTERED WITH BAYES]
- Fifty-nine Deceits in Fahrenheit 911, Dave Kopel, Independence Institute 15 September 2009 8:35 UTC www.davekopel.com [Source type: FILTERED WITH BAYES]
^ On the other hand, this segment of Fahrenheit omits a very relevant fact which would supply an alternative explanation: Bush served as C.I.A. Director in 1976.- Fifty-nine Deceits in Fahrenheit 911, Dave Kopel, Independence Institute 9 January 2010 21:21 UTC davekopel.com [Source type: FILTERED WITH BAYES]
- Fifty-nine Deceits in Fahrenheit 911, Dave Kopel, Independence Institute 15 September 2009 8:35 UTC www.davekopel.com [Source type: FILTERED WITH BAYES]
^ That Moore ignores Israel in Fahrenheit makes sense, given Moore's stated intention of using the movie to defeat George Bush in November.- Fifty-nine Deceits in Fahrenheit 911, Dave Kopel, Independence Institute 9 January 2010 21:21 UTC davekopel.com [Source type: FILTERED WITH BAYES]
- Fifty-nine Deceits in Fahrenheit 911, Dave Kopel, Independence Institute 15 September 2009 8:35 UTC www.davekopel.com [Source type: FILTERED WITH BAYES]
[12]Representation
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 ("°F") is thus the preferred way of recording the symbol for
degree Fahrenheit.
Temperatures and intervals
As with the
Celsius scale, the same symbol,
°, is used to denote both a point on the temperature scale, with a letter (C, F) indicating which scale is being used (
e.g. "
Gallium melts at
85.5763 °F"), and to denote a difference between temperatures or an uncertainty of temperature (
e.g. "The output of the heat exchanger is hotter by
72 °F" and "Our standard uncertainty is
±5 °F").
See also
References
- ^ "Metric usage and metrication in other countries". http://lamar.colostate.edu/~hillger/internat.htm. Retrieved December 11, 2009.
- ^ a b "Belize Weather Bureau". http://www.hydromet.gov.bz/. Retrieved May 9, 2008.
- ^ a b c Conversion of Temperature
- ^ Temperature Units Converter
- ^ a b "Fahrenheit temperature scale". Sizes, Inc. December 12, 2006. http://www.sizes.com/units/temperature_Fahrenheit.htm. Retrieved May 9, 2008.
- ^ Muller, R.A. (2009). Physics for Future Presidents. pp. 2-5, 2-17. http://physics.berkeley.edu/academics/Courses/physics10/teaching/Physics10/PffP_textbook_F08/PffP-02-heat-F08.pdf. Retrieved 20 February 2010.
- ^ Elert, Glenn (2002). "Temperature of a Healthy Human (Body Temperature)". Scandinavian Journal of Caring Sciences 16: 122. doi:10.1046/j.1471-6712.2002.00069.x. http://hypertextbook.com/facts/LenaWong.shtml. Retrieved 2008.
- ^ Ernst Cohen and W. A. T. Cohen-De Meester. Chemisch Weekblad, volume 33 (1936), pages 374–393, cited and translated in http://www.sizes.com:80/units/temperature_Fahrenheit.htm
- ^ Cecil Adams. "On the Fahrenheit scale, do 0 and 100 have any special significance?". The Straight Dope. http://www.straightdope.com/classics/a4_188.html.
- ^ CIA Factbook: Weights and Measures
- ^ [1] Halsey, Frederick A., Dale, Sanuel S., "The metric fallacy," The American institute of weights and measures, Second Edition, 1919. Pages 165-166, 176-177. Retrieved May 19, 2009
- ^ [2] Information about New Zealand's money and metric measures
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