Fahrenheit was born in 1686 in Gdańsk, Poland. The Fahrenheits were a merchant family who had moved around Europe, Fahrenheit's great-grandfather had lived in Rostock, and research suggests that the Fahrenheit family originated in Hildesheim. Daniel's grandfather moved from Kneiphof (in Königsberg) to Danzig and settled there as a merchant in 1650. By widespread trading, he became the richest man in eastern Prussia. His son, Daniel Fahrenheit (the father of the subject of this article), married Concordia (widowed name, Runge), daughter of the well-known Danzig business family of Schumann. Daniel Gabriel was the eldest of the five Fahrenheit children (two sons, three daughters) who survived childhood.
When his parents died in 1702 from accidentally having eaten poisonous mushrooms, sixteen-year-old Gabriel Daniel Fahrenheit began training as a merchant in Amsterdam. However, his interest in natural science caused him to take up studies and experimentation in that field. From 1707 onwards, he traveled to Berlin, Halle, Leipzig, Dresden, Kopenhagen, and also to his hometown. During that time, Fahrenheit met or was in contact with Ole Rømer, Christian Wolff, and Gottfried Leibniz. In 1717, Fahrenheit settled in The Hague with the trade of glassblowing, making barometers, altimeters, and thermometers. From 1718 onwards, he gave lectures in chemistry in Amsterdam. In 1724, he visited England and became a member of the Royal Society. (On this occasion, he signed himself as "Polonus", indicating that he was born a Polish subject.) Fahrenheit died in The Hague and was buried there at the Kloosterkerk (Cloister Church).
According to Fahrenheit's 1724 article, 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 ammonium chloride, a salt, and waiting for it to reach equilibrium. The alcohol or mercury thermometer was placed into the mixture and the liquid in the thermometer allowed to descend to its lowest point. The reading on the thermometer was taken as 0 °F. The second reference point was selected as the reading of the thermometer when it was placed in still water as ice is just forming on the surface. This was taken as 32 °F. The third calibration point, taken as 96 °F, was selected as the thermometer's reading when the instrument was placed under the arm or in the mouth.
Fahrenheit noted that mercury boils around 600 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. It is because of the scale's redefinition that normal body temperature today is taken as 98.6 degrees, whereas it was 96 degrees on Fahrenheit's original scale.
Until the switch to the Celsius scale, the Fahrenheit one was widely used in Europe. It is still used for everyday temperature measurements by the general population in the United States and, less so, in the UK.