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{{short description|Physicist and engineer (1686–1736)}}
{{Use dmy dates|date=September 2025}}
{{Infobox scientist
| name              = Daniel Gabriel Fahrenheit
| image             = Fahrenheit small.jpg
| image_size        = 180px
| birth_date        = 24 May 1686 (14 May [[Old Style and New Style dates|Old Style]])
| birth_place       = [[Danzig]], [[Polish–Lithuanian Commonwealth]]
| death_date        = {{Death date and age|df=yes|1736|9|16|1686|5|24}}
| death_place       = [[The Hague]], [[Dutch Republic]]
| residence         = 
| field             = [[Physics]] ([[thermometry]])
| work_institutions = 
| alma_mater        = 
| known_for         = [[Precision thermometry]]<br />[[Alcohol thermometer]]<br />[[Mercury-in-glass thermometer]]<br />[[Fahrenheit|Fahrenheit scale]]<br />[[Fahrenheit hydrometer]]
| influences        = 
| influenced        = 
| prizes            = 
| footnotes         = 
| signature         = Daniel Gabriel Fahrenheit Signature.svg
}}
'''Daniel Gabriel Fahrenheit''' [[Fellow of the Royal Society|FRS]] (24 May 1686 – 16 September 1736)<ref>{{Cite EB1911|wstitle=Fahrenheit, Gabriel Daniel |volume=10 |page=126}}</ref> was a <!-- Please do not include nationality without a prior discussion on talk page.-->[[physicist]], [[inventor]], and [[scientific instrument]] maker, born in [[Polish–Lithuanian Commonwealth|Poland]] to a family of [[Germans|German]] origin. Fahrenheit significantly improved the design and manufacture of thermometers; his were accurate and consistent enough that different observers, each with their own Fahrenheit thermometers, could reliably compare [[temperature]] measurements with each other.<ref>{{Cite journal |last=Dorsey |first=N. Ernest |title=Title of the Article |journal=Journal of the Washington Academy of Sciences |volume=36 |issue=[issue number] |date=15 November 1946 |page=363}}</ref> Fahrenheit is also credited with producing the first successful [[mercury-in-glass thermometer]]s, which were more accurate than the [[Alcohol thermometer|spirit-filled thermometers]] of his time and of a generally superior design. The popularity of his thermometers also led to the widespread adoption of his [[Fahrenheit|Fahrenheit scale]], with which they were provided.<ref name="Grigull, Ulrich 1966 pp. 9">Grigull, Ulrich (1966). ''Fahrenheit, a Pioneer of Exact Thermometry''. (The Proceedings of the 8th International Heat Transfer Conference, San Francisco, 1966, Vol. 1, pp. 9–18.)</ref>

== Biography ==
=== Early life ===
[[File:Fahrenheit's birthplace in Gdansk 20250619 080724.jpg|left|thumb|upright|Fahrenheit's birthplace in [[Gdańsk]]]]
Fahrenheit was born in Danzig (Gdańsk), then in the [[Polish–Lithuanian Commonwealth]]. The Fahrenheits were a German [[Hanse]] merchant family who had lived in several [[Hanseatic League|Hanseatic]] cities. Fahrenheit's great-grandfather had lived in [[Rostock]], and research suggests that the Fahrenheit family originated in [[Hildesheim]].<ref>{{cite book |author=Kant, Horst |title=G. D. Fahrenheit / R. -A. F. de Réaumur / A. Celsius |year=1984 |publisher=B. G. Teubner |url=https://books.google.com/books?id=XYKtGQAACAAJ |access-date=14 June 2008}}</ref> Daniel's grandfather moved from [[Kneiphof]] in [[Königsberg]] (then in the [[Duchy of Prussia]]) to Danzig and settled there as a merchant in 1650. His son, Daniel Fahrenheit (the father of Daniel Gabriel), married Concordia Schumann, the daughter of a well-known Danzig business family. Daniel was the eldest of the five Fahrenheit children (two sons, three daughters) who survived childhood. His sister, Virginia Elisabeth Fahrenheit, married Benjamin Krüger and was the mother of Benjamin Ephraim Krüger, a clergyman and playwright.<ref>See the [http://www.g-gruppen.net/danzigforedt.htm#a2 Fahrenheit and Krueger genealogies].</ref>

As a young adult, Fahrenheit "showed a particular desire for studying," and was scheduled to enroll in the [[Academic Gymnasium Danzig|Danzig Gymnasium]].<ref name="momber" />{{rp|111}} But on 14 August 1701, his parents died after eating poisonous mushrooms.<ref>{{cite journal |last1=Meyer |first1=F.A. |title=Daniel Gabriel Fahrenheit aus Danzig |journal=Westpreussen Jahrbuch |date=1952 |issue=1951–1952 |pages=138–141}}</ref> Fahrenheit, along with two brothers and sisters, was placed under guardianship. In 1702, Fahrenheit's guardians enrolled him in a bookkeeping course and sent him to a four-year merchant trade apprenticeship in [[Amsterdam]].<ref name="star" />{{rp|1}}

Upon completing his apprenticeship, Fahrenheit ran off<ref name="momber" />{{rp|111}} and began a period of travel through the [[Holy Roman Empire]], Sweden, and Denmark in 1707. At the request of his guardians, a warrant was issued for his arrest with the intention of placing him into the service of the Dutch East India company.<ref name="star" />{{rp|3–4}}

===Work with thermometers, Fahrenheit  scale===
By around 1706, Fahrenheit was manufacturing and shipping barometers and spirit-filled thermometers using the Florentine temperature scale.<ref name="momber">{{cite journal |last1=Momber |first1=Alfred |title=Daniel Gabriel Fahrenheit.; sein Leben und Wirken |journal=Schriften der Naturforschenden Gesellschaft in Danzig |date=1890 |volume=7 |issue=J }}</ref>{{rp|116}} In 1708, Fahrenheit met with the mayor of Copenhagen and astronomer, [[Ole Rømer]], and was introduced to [[Rømer scale|Rømer's temperature scale]] and his methods for making thermometers. Rømer told Fahrenheit that demand for accurate thermometers was high.<ref name="star" />{{rp|4}} The visit inspired Fahrenheit to try to improve his own offerings.<ref name="middleton">* {{cite book |author=Middleton, W. E. Knowles |title=A History of the Thermometer and its Use in Meteorology |year=1966 |location=Baltimore, Maryland |publisher=Johns Hopkins Press}}{{rp|71}}</ref> Perhaps not coincidentally, Fahrenheit's arrest warrant was dropped around the time of his meeting with Rømer.<ref name="star" />{{rp|3–4}}

In 1709, Fahrenheit returned to Danzig and took observations using his barometers and thermometers, traveled more in 1710 and returned to Danzig in 1711 to settle his parents' estate. After additional travel to Königsberg and Mitau in 1711, he returned to Danzig in 1712 and stayed there for two years. During this period he worked on solving technical problems with his thermometers.<ref name="star" />{{rp|4–5}}

Fahrenheit began experimenting with mercury thermometers in 1713.<ref name="star" />{{rp|26}} Also by this time, Fahrenheit was using a modified version of Rømer's scale for his thermometers which would later evolve into his own [[Fahrenheit scale]]. In 1714, Fahrenheit left Danzig for Berlin and Dresden to work closely with the glass-blowers there.<ref name="star" />{{rp|5}} In that year [[Christian Wolff (philosopher)|Christian Wolff]] wrote about Fahrenheit's thermometers in a journal after receiving a pair of his alcohol-based devices, helping to boost Fahrenheit's reputation in the scientific community.<ref name="middleton" />{{rp|74}}

In addition to his interest in meteorological instruments, Fahrenheit also worked on his ideas for a mercury clock, a [[perpetual motion machine]], and a [[heliostat]] around 1715. He struck up a correspondence with [[Leibniz]] about some of these projects. From the exchange of letters, we learn that Fahrenheit was running out of money while working on his projects and asked Leibniz for help obtaining a paid post so he could continue his work.<ref name="star" />{{rp|5–7}}

In 1717 or 1718, Fahrenheit returned to Amsterdam and began selling barometers, [[areometer]]s, and his mercury and alcohol-based thermometers commercially.<ref name="star" />{{rp|8}} By 1721, Fahrenheit had perfected the process of crafting and standardizing his thermometers.<ref name="star" />{{rp|24}} The superiority of his mercury thermometers over alcohol-based thermometers made them very popular, leading to the widespread adoption of his Fahrenheit scale, the measurement system he developed and used for his thermometers.<ref name="Grigull, Ulrich 1966 pp. 9"/>

===Later life and controversy ===
Fahrenheit spent the remainder of his life in Amsterdam. From 1718 onward, he lectured in chemistry in Amsterdam. He visited England in 1724 and was elected a [[Fellow of the Royal Society]] on 5 May.<ref>{{Cite web |url=http://www2.royalsociety.org/DServe/dserve.exe?dsqIni=Dserve.ini&dsqApp=Archive&dsqCmd=Show.tcl&dsqDb=Persons&dsqPos=0&dsqSearch=((text)%3D'fahrenheit') |title=The Royal Society Archive catalogue |access-date=26 November 2010 |archive-url=https://web.archive.org/web/20111127053001/http://www2.royalsociety.org/DServe/dserve.exe?dsqIni=Dserve.ini&dsqApp=Archive&dsqCmd=Show.tcl&dsqDb=Persons&dsqPos=0&dsqSearch=((text)%3D'fahrenheit') |archive-date=27 November 2011 |url-status=dead }}</ref> In that year, he published five papers in [[Latin]] for the Royal Society's scientific journal, ''[[Philosophical Transactions of the Royal Society|Philosophical Transactions]]'', on various topics. In his second paper, "Experimenta et observationes de congelatione aquæ in vacuo factæ", he provides a description of his thermometers and the reference points he used for calibrating them. For two centuries, this document was the only description of Fahrenheit's process for making thermometers.<ref name="middleton" />{{rp|75}} In the 20th century, [[Ernst Cohen]] uncovered correspondences between Fahrenheit and [[Herman Boerhaave]] which cast considerable doubt on the veracity of Fahrenheit's article explaining the reference points for his scale and that, in fact, Fahrenheit's scale was largely derived from Rømer's scale. In his book, ''The History of the Thermometer and Its Use in Meteorology'', W. E. Knowles Middleton writes,
{{Blockquote
|text=I believe that much of the confusion [over the Fahrenheit scale] has resulted from believing that [Fahrenheit] meant exactly what he said [in his Royal Society article], and discounting the natural tendency of an instrumentmaker to wish to conceal his processes, or at least to obfuscate his readers.<ref name="middleton" />{{rp|75}}
|author=W. E. Knowles Middleton
|title=''The History of the Thermometer and Its Use in Meteorology''
}}

From August 1736 to his death, Fahrenheit stayed in the house of Johannes Frisleven at [[Het Plein|Plein Square]] in The Hague in connection with an application for a [[patent]] at the [[States of Holland and West Friesland]]. At the beginning of September, he became ill and on the 7th his health had deteriorated to such an extent that he had [[notary]] Willem Ruijsbroek come to draw up his will. On the 11th, the notary came by again to make some changes. Five days after that, Fahrenheit died at the age of fifty. Four days later, he received the fourth-class funeral of one who is classified as [[destitute]], in the [[Kloosterkerk, The Hague|Kloosterkerk]] in The Hague (the Cloister or Monastery Church).<ref name="star">Star, Pieter van der: [https://books.google.com/books?id=1-z0asXiafcC&pg=PA13 Daniel Gabriel Fahrenheit's Letters to Leibniz and Boerhaave]. Rodopi Publishers, Amsterdam 1983.</ref><ref>{{cite web | url=http://www.kloosterkerk.nl/bezoek-de-kerk/en/ | title= The Kloosterkerk | publisher=The Kloosterkerk | access-date=16 September 2017}}</ref><ref>Zuiden, D.S. van: [https://resolver.kb.nl/resolve?urn=MMKB16:001954001:00183 Het Testament en de Inboedel van Daniel Gabriel Fahrenheit], in: "Oud-Holland", pp. 123-130, Binger Publishers, Amsterdam 1913</ref>[[File:House where Gabriel Fahrenheit died in 1736, at Plein square, The Hague; img01.jpg|thumb|upright|House where Gabriel Fahrenheit died in 1736, at Plein square, The Hague]]

== Fahrenheit scale ==
{{main|Fahrenheit}}
According to Fahrenheit's 1724 article,<ref name="ftempsc"/><ref>Fahrenheit describes, in Latin, these numerical choices in the following paper: {{cite journal |author=Fahrenheit, D. G. |title=Experimenta et Observationes de Congelatione aquae in vacuo factae |journal=Philosophical Transactions of the Royal Society |volume=33 |pages=78–84 |year=1724 |doi=10.1098/rstl.1724.0016 |issue=381–391 |doi-access=free }}</ref> he determined his scale by reference to three fixed points of [[temperature]].  The lowest temperature was achieved by preparing a [[frigorific mixture]] of [[ice]], water, and a salt ("[[ammonium chloride]] or even sea salt"), and waiting for the [[eutectic system]] to reach [[equilibrium temperature]].  The thermometer then was placed into the mixture and the liquid in the thermometer allowed to descend to its lowest point.  The thermometer's reading there was taken as {{not a typo|0&nbsp;°F}}.  The second reference point was selected as the reading of the thermometer when it was placed in still water when ice was just forming on the surface.<ref name="why32">{{cite web|url=http://www.physlink.com/Education/AskExperts/ae64.cfm?CFID=21412834&CFTOKEN=55577927 |title=Why does the Fahrenheit scale use 32 degrees as a freezing point? |access-date=9 May 2008 |last=Heath |first=Jonathan |publisher=PhysLink}}</ref> This was assigned as {{not a typo|30&nbsp;°F}}. The third calibration point, taken as {{not a typo|90&nbsp;°F}}, was selected as the thermometer's reading when the instrument was placed under the arm or in the mouth.<ref name="Burdge2014">{{cite book|last=Burdge|first=Julia|title=Chemistry: Atoms First|url=https://books.google.com/books?id=2XVzCgAAQBAJ&pg=PA11|access-date=16 September 2017|date=10 January 2014|publisher=McGraw-Hill|isbn=9780077646479|page=11}}</ref>

Fahrenheit came up with the idea that mercury boils around 300 degrees on this [[temperature scale]]. Work by others showed that water boils about 180 degrees above its freezing point.  The Fahrenheit scale later was redefined to make the freezing-to-boiling interval exactly 180 degrees,<ref name="ftempsc">{{cite web|url=http://www.sizes.com/units/temperature_Fahrenheit.htm |title=Fahrenheit temperature scale |access-date=9 May 2008 |date=10 December 2006 |publisher=Sizes, Inc}}</ref> a convenient value as 180 is a [[highly composite number]], meaning that it is evenly divisible into many fractions. It is because of the scale's redefinition that normal mean body temperature today is taken as 98.6 degrees,<ref>{{cite journal |doi=10.1001/jama.1992.03490120092034 |title=A Critical Appraisal of 98.6°F, the Upper Limit of the Normal Body Temperature, and Other Legacies of Carl Reinhold August Wunderlich |year=1992 |last1=MacKowiak |first1=Philip A. |journal=JAMA: The Journal of the American Medical Association |volume=268 |issue=12 |pages=1578–80 |pmid=1302471}}</ref> whereas it was 96 degrees on Fahrenheit's original scale.<ref>{{cite journal |last1=Elert |first1=Glenn |title=Temperature of a Healthy Human (Body Temperature) |url=http://hypertextbook.com/facts/1997/LenaWong.shtml |access-date=4 December 2008 |doi=10.1046/j.1471-6712.2002.00069.x |year=2002 |journal=Scandinavian Journal of Caring Sciences |volume=16 |pages=122–8 |pmid=12000664 |last2=Forsberg |first2=C |last3=Wahren |first3=LK |issue=2|url-access=subscription }}</ref>

The [[Fahrenheit|Fahrenheit scale]] was the primary temperature standard for climatic, industrial and medical purposes in English-speaking countries until the 1970s. The British Meteorological Office officially adopted "Centigrade" — the [[Celsius|Celsius scale]] — as standard in 1963 but continued using Fahrenheit for public broadcasts into the 1980s. It is presently mostly replaced by the Celsius scale long used in the rest of the world, apart from the United States, where temperatures and weather reports are still broadcast in Fahrenheit.<ref>{{cite web |url= https://www.livescience.com/39916-fahrenheit.html |title= Fahrenheit: Facts, History & Conversion Formulas |first= Kim Ann |last= Zimmermann |website= [[Live Science]] |date= 24 September 2013 |access-date= 16 September 2017}}</ref>

==See also==
* [[Fahrenheit hydrometer]]
* [[List of people from Gdańsk|People from Gdańsk (Danzig)]]
* [[Anders Celsius]]
* [[Lord Kelvin]]

==References==
{{Reflist}}

==Further reading==
* {{cite book |author=Bolton, Henry Carrington |author-link=Henry Carrington Bolton|title=Evolution of the Thermometer, 1592–1743 |year=1900 |publisher=The Chemical Publishing Company |location=Easton, Pennsylvania |pages=[https://archive.org/details/evolutionthermo01boltgoog/page/n76 66]–79 |url=https://archive.org/details/evolutionthermo01boltgoog}}
* {{cite journal |author=Fahrenheit, D. G. |title=Experimenta circa gradum caloris liquorum nonnullorum ebullientium instituta (Experiments done on the degree of heat of a few boiling liquids) |journal=Philosophical Transactions of the Royal Society |volume=33 |issue=381 |pages=1–3 |year=1724 |url=http://web.lemoyne.edu/~giunta/fahrenheit.html |doi=10.1098/rstl.1724.0002|doi-access=free }}
* {{cite journal |author=Fahrenheit, D. G. |title=Experimenta et Observationes de Congelatione aquae in vacuo factae |journal=Philosophical Transactions of the Royal Society |volume=33 |pages=78–84 |year=1724 |doi=10.1098/rstl.1724.0016 |issue=381–391|url=https://zenodo.org/record/1432206 |doi-access=free }} (Latin)
* {{NDB|4|746|747|Daniel Gabriel Fahrenheit|Klemm, Friedrich}}
* {{Cite news|pmid=775856|last=Kops|first=J|publication-date=Feb 1976|year=1976|title=Who was G.D. Fahrenheit? |volume=26 |issue=2 |periodical=Zdravotnická Pracovnice|pages=118–19}} (Czech)
* {{Cite ADB|6|535|535|Fahrenheit, Gabriel Daniel|Lommel|ADB:Fahrenheit, Daniel Gabriel}}
* {{NDB|4|746|747|Daniel Gabriel Fahrenheit|Friedrich Klemm}}
* {{cite book |author=Middleton, W. E. Knowles |title=A History of the Thermometer and its Use in Meteorology |year=1966 |location=Baltimore, Maryland |publisher=Johns Hopkins Press}}
* {{cite news|pmid=3543477|last=Sorokina|first=T S|publication-date=Oct 1986|year=1986|title=Creators of medical thermometry (on the 300th anniversary of the birth of Gabriel Daniel Fahrenheit—24 May 1686 and on the 350th anniversary of the death of Santorio Santorio—22 February 1636)|volume=64|issue=10|periodical=Klinicheskaia Meditsina|pages=147–51}} (Russian)
* {{cite book |title=Fahrenheit's Letters to Leibniz and Boerhaave |editor=Van Der Star, P. |publisher=Editions Rodopi |year=1984}}

==External links==
{{Commons category|Daniel Gabriel Fahrenheit}}
* Letter from Daniel Gabriel Fahrenheit ([http://www.alvin-portal.org/alvin/resultList.jsf?aq=%5B%5B%7B%22COL%22%3A%22uub_linnaeus_correspondence%22%7D%5D%5D&sortString=relevance_sort_desc&aqe=%5B%5D&af=%5B%5D&searchType=EXTENDED&noOfRows=10&dswid=-9963 scan]) to [[Carl Linnaeus]], 7 May 1736 n.s., [http://linnaeus.c18.net/Letters/display_txt.php?id_letter=L0112] {{in lang|de}}
* {{cite EB9 |wstitle = Gabriel Daniel Fahrenheit |volume= VIII | page=847 |short=1 }}
* {{cite web |title=Why isn't 0°F the lowest possible temperature for a salt/ice/water mixture? |author=Senese, Fred |year=2005 |url=http://antoine.frostburg.edu/chem/senese/101/solutions/faq/zero-fahrenheit.shtml}}
*[http://rstl.royalsocietypublishing.org/search?fulltext=fahrenheit&submit=yes&x=17&y=7 Fahrenheit's papers in the Royal Society Publishing] {{in lang|la}}

{{Scientists whose names are used as non SI units}}
{{Authority control}}

{{DEFAULTSORT:Fahrenheit, Daniel Gabriel}}
[[Category:1686 births]]
[[Category:1736 deaths]]
[[Category:Immigrants to the Dutch Republic]]
[[Category:Fellows of the Royal Society]]
[[Category:17th-century people from the Polish–Lithuanian Commonwealth]]
[[Category:Scientists from Gdańsk]]
[[Category:Creators of temperature scales]]