Daniel Gabriel Fahrenheit FRS (24 May 1686 – 16 September 1736) was a physicist, inventor, and maker of scientific tools. He was born in Poland to a family of German origin, although he lived most of his life in the Dutch Republic. Fahrenheit improved the design and production of thermometers; his thermometers were so accurate and consistent that different people could compare temperature measurements reliably. Fahrenheit is also credited with creating the first successful thermometers that used mercury inside glass. These thermometers were more accurate than the spirit-filled thermometers of his time and had a better overall design. The popularity of his thermometers led to the widespread use of the Fahrenheit scale, which these thermometers used.
Biography
Daniel Gabriel Fahrenheit was born in Danzig, which is now known as Gdańsk, in the Polish–Lithuanian Commonwealth. The Fahrenheits were a German Hanse merchant family who lived in several cities in the Hanseatic League. Fahrenheit’s great-grandfather lived in Rostock, and research suggests the family originally came from Hildesheim. Daniel’s grandfather moved from Kneiphof in Königsberg (then in the Duchy of Prussia) to Danzig in 1650 and settled there as a merchant. His son, Daniel Fahrenheit (the father of Daniel Gabriel), married Concordia Schumann, the daughter of a well-known Danzig business family. Daniel was the oldest of the five Fahrenheit children (two sons and 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.
As a young adult, Fahrenheit showed a strong interest in studying and was scheduled to enroll in the Danzig Gymnasium. However, on August 14, 1701, his parents died after eating poisonous mushrooms. Fahrenheit, along with two brothers and sisters, was placed under the care of guardians. In 1702, his guardians enrolled him in a bookkeeping class and sent him to a four-year apprenticeship in Amsterdam, where he learned about merchant trade.
After completing his apprenticeship, Fahrenheit ran away and began traveling 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 goal of placing him in the service of the Dutch East India Company.
By around 1706, Fahrenheit was making and shipping barometers and thermometers filled with alcohol using the Florentine temperature scale. In 1708, he met the mayor of Copenhagen and astronomer Ole Rømer, who introduced him to Rømer’s temperature scale and methods for making thermometers. Rømer told Fahrenheit that demand for accurate thermometers was high. This meeting inspired Fahrenheit to improve his own designs. Around the same time, the warrant for his arrest was canceled.
In 1709, Fahrenheit returned to Danzig and used his barometers and thermometers to take observations. He traveled more in 1710 and returned to Danzig in 1711 to settle his parents’ estate. After additional trips to Königsberg and Mitau in 1711, he returned to Danzig in 1712 and stayed there for two years. During this time, he worked on solving technical problems with his thermometers.
Fahrenheit began experimenting with mercury thermometers in 1713. By this time, he was using a version of Rømer’s scale for his thermometers, which later became his own Fahrenheit scale. In 1714, Fahrenheit left Danzig for Berlin and Dresden to work with glassblowers. That year, Christian Wolff wrote about Fahrenheit’s thermometers in a journal after receiving a pair of his alcohol-based devices, which helped raise his reputation in the scientific community.
In addition to his work with meteorological instruments, Fahrenheit also explored ideas for a mercury clock, a perpetual motion machine, and a heliostat around 1715. He corresponded with Leibniz about these projects. From their letters, it is clear that Fahrenheit was struggling financially and asked Leibniz for help finding a paid position to continue his work.
In 1717 or 1718, Fahrenheit returned to Amsterdam and began selling barometers, areometers, and his mercury and alcohol-based thermometers commercially. By 1721, he had perfected the process of making and standardizing his thermometers. His mercury thermometers became more popular than alcohol-based ones, leading to the widespread use of his Fahrenheit scale.
Fahrenheit spent the rest of his life in Amsterdam. From 1718 onward, he taught chemistry there. He visited England in 1724 and was elected a Fellow of the Royal Society on May 5. That year, he published five papers in Latin for the Royal Society’s scientific journal, Philosophical Transactions, on various topics. In his second paper, Experimenta et observationes de congelatione aquæ in vacuo factæ, he described his thermometers and the reference points he used for calibrating them. For two centuries, this document was the only record of Fahrenheit’s process for making thermometers. In the 20th century, Ernst Cohen discovered letters between Fahrenheit and Herman Boerhaave that cast doubt on the accuracy of Fahrenheit’s explanation of his scale’s reference points, suggesting his scale was largely based on Rømer’s.
From August 1736 until his death, Fahrenheit stayed in the home of Johannes Frisleven at Plein Square in The Hague while applying for a patent in the States of Holland and West Friesland. In early September, he became ill, and by September 7, his health had worsened to the point that he asked notary Willem Ruijsbroek to draft his will. Ruijsbroek returned on September 11 to make changes to the will. Five days later, Fahrenheit died at the age of 50. Four days after his death, he received a simple funeral, as he was considered destitute, in the Kloosterkerk (Cloister or Monastery Church) in The Hague.
Fahrenheit scale
In 1724, Fahrenheit created his temperature scale using three fixed points. The lowest temperature was measured by mixing ice, water, and salt (such as ammonium chloride or sea salt) until the mixture reached a stable, very cold temperature. A thermometer was placed in the mixture, and the lowest temperature it reached was recorded as 0 °F. The second point was the temperature of water just as ice began to form on its surface, which was set to 30 °F. The third point was the temperature of a thermometer placed under a person’s arm or in their mouth, which was set to 90 °F.
Fahrenheit believed that mercury boils at about 300 °F on his scale. Later research showed that water boils 180 degrees above its freezing point. The Fahrenheit scale was later changed so that the range between freezing and boiling water was exactly 180 degrees. This was useful because 180 is a number that can be divided evenly into many smaller numbers. Because of this change, the average human body temperature is now recorded as 98.6 °F, whereas it was 96 °F on Fahrenheit’s original scale.
The Fahrenheit scale was the main way to measure temperature for weather, industry, and medicine in English-speaking countries until the 1970s. In 1963, the British Meteorological Office officially switched to the Celsius scale (also called "Centigrade") but continued using Fahrenheit in public weather reports until the 1980s. Today, most countries use the Celsius scale, except the United States, where temperatures and weather reports are still given in Fahrenheit.