Daniel Gabriel Fahrenheit research suggests that the Fahrenheit family originated in Hildesheim. Daniel's grandfather moved from Kneiphof in Königsberg (present-day Kaliningrad) to Danzig and settled there as a merchant in 1650. His son, Daniel Fahrenheit (the father of the subject of this article), married Concordia Schumann, 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 Elizabeth Fahrenheit, married Benjamin Ephraim Krueger of an aristocratic family from Danzig. Daniel Gabriel began training as a merchant in Amsterdam after his parents died on 14 August 1701 from eating
Mercury-in-glass thermometer Nowadays, the triple point of water is used instead of the freezing point (the triple point occurs at 273.16 kelvins (K), 0.01 °C). Before the discovery of the true thermodynamic temperature, the thermometer "defined" the temperature; thermometers made with different materials would define different temperature scales (a coloured alcohol thermometer would give a slightly different reading than a mercury thermometer at, say half-scale). In practice, several materials gave very similar temperatures to each other and, when discovered, to the thermodynamic temperature. One special kind of mercury-in-glass thermometer, called a maximum thermometer, works by having a constriction in the neck close