Daniel Gabriel Fahrenheit (born May 24, 1686 in Danzig, Poland-Lithuania, and died September 16, 1736 in The Hague, Netherlands) was a German physicist who developed the temperature scale that bears his name.
Gabriel Fahrenheit was born in 1686 in what was then the Republic of the Two Nations to German parents. His father was from a family of merchants in the Hanseatic League who lived in many of its cities. His family seems to have originated in Hildesheim according to historical research, but his great-grandfather came from Rostock. His grandfather moved from Kneiphof, Königsberg, to Danzig in 1650 and his father, also named Daniel, married Concordia Schumann, the daughter of a well-known businessman in the city. They had five children of whom Gabriel Daniel was the eldest.
At the age of 15, Fahrenheit lost his parents, who died accidentally on August 14, 1701 as a result of ingesting poisonous mushrooms. While his four siblings were placed in foster homes, he started as an apprentice to a merchant in Danzig who sent him to Amsterdam. In 1704, he began to develop a passion for natural sciences and discovered Florentine thermometers. His intention was to manufacture physics devices and market them, but experimentation gradually diverted him to a scientific life. When his boss finally learns that Fahrenheit is neglecting his learning, he threatens to have him arrested.
At the request of the authorities in Danzig, he was to be taken on board a ship of the Dutch East India Company, but he escaped and went to Berlin, Halle, Leipzig, Dresden, Copenhagen and to his home town. He met several personalities during this journey, including : Ole Rømer who built an ethanol thermometer in 1702, Christian Wolff and Gottfried Wilhelm Leibniz. He did not return to Holland until he came of age, at the age of twenty-four.
In 1709, Fahrenheit took up the method of Rømer of the alcohol thermometer whose calibration uses two fixed points: the temperature of fusion of the ice and that of the human body. In 1714, he became a glass blower and made meteorological instruments: barometers, altimeters and thermometers. In 1715, he corresponded with and befriended Nicolas Leyde about the use of a clock to determine longitude at sea, a very important problem for maritime navigation which was the subject of a competition organized by the British Admiralty.
He moved to The Hague (Holland) in 1717 for the rest of his life, but also taught chemistry in Amsterdam from 1718. In 1721, Fahrenheit discovered the writings on mathematics and experimentation of Willem Jacob ”s Gravesande, of whom he became a friend. Together they made a heliostat with mirrors, a device to follow the course of the sun. He also maintained an important correspondence with several other scientists of the time. He developed the mercury thermometer which he described in 1724, as well as the method used to calibrate it, in the “Philosophical Transactions” of the Royal Society of London. He mentions that mercury has a higher coefficient of thermal expansion than alcohol, that it is easy to clean and more visible, but above all that its boiling point is very high. Fahrenheit also describes a temperature scale, the Fahrenheit (°F) scale, which he developed. During a visit to England the same year, he was elected Fellow of the Royal Society for his work.
Fahrenheit also developed an improved hydrometer to measure the density of a liquid and a thermo-barometer to estimate atmospheric pressure using the boiling temperature of water and a hygrometer. Shortly before his death, he patented a machine for pumping water from polders to increase the area of cultivable land.
He will never marry. He died in The Hague in 1736. He is buried in the cloister cemetery of Kloosterkerk. After his death, several manufacturers produced mercury Fahrenheit thermometers, a device that became widely used.
The asteroid (7536) Fahrenheit is named in his honor.
The Fahrenheit scale was widely used in Europe until the French Revolution. It was gradually replaced by the Celsius scale but is still often used in English-speaking countries, mainly in the United States where it is the official scale.
Daniel Gabriel Fahrenheit decided to define his scale by two reference temperatures:
He first divided this interval into twelve units before changing his mind and subdividing each of these units into eight degrees. The difference between the two reference temperatures is then fixed at 12 × 8, or 96 degrees (°F). It should be noted that Fahrenheit never used the boiling point of water as a high fixed point, because it varies with atmospheric pressure.
Fahrenheit observed that, in his scale, water freezes at normal atmospheric pressure (1,013.25 hPa) at 32 degrees and boils at 212 degrees, a difference of 180 degrees. To obtain a temperature in degrees Fahrenheit, we multiply the temperature in degrees Celsius by 1.8 and add thirty-two.
His technique made it possible to make all thermometers comparable, previously they were not calibrated.
Marie-Nicolas Bouillet and Alexis Chassang (dir.), “Gabriel Fahrenheit” in Dictionnaire universel d”histoire et de géographie, 1878 (read on Wikisource)