Daniel Fahrenheit Daniel Fahrenheit was born in the Polish city of Gdansk on the 14 th of May 1686. He was the oldest of five children and only fifteen when his parents both died. The city council put the four younger Fahrenheit children in foster homes. But Daniel Fahrenheit was instead to complete a four year apprenticeship in which he learnt about bookkeeping. After his four years were over he turned to physics and became a glassblower and instrument maker.

In 1701, Fahrenheit spent ten years traveling round Europe, meeting scientists. This encouraged him to follow his interest in natural sciences and he began to study and experiment in that field. In 1724 this led him to Amsterdam where he lectured in chemistry and became a member of the Royal Society. It was there he learned about thermometers and because it was a trade in Amsterdam, Fahrenheit decided to stay, and make this his profession, so he borrowed against his inheritance to take up thermometer making.

When the city fathers of Gdansk found out, they arranged to have Fahrenheit arrested, so until he was the legal age of 24 he had to dodge police. At first he was simply on the run, but he decided to keep traveling through Denmark, Germany, Holland, Sweden and Poland. Florentine thermometer scales varied no two were the same; makers marked the low point on the scale during the coldest day in Florence that year. They marked the high point during the hottest day.

Fahrenheit wanted thermometers to be reproducible during the year and realized the trick wasn't using the coldness or hotness of a particular day or place, but finding materials that changed at certain temperatures. For seven years Fahrenheit worked on an alcohol thermometer scale, based on three points. He chose the freezing point of a certain salt-water mixture for zero, he used the freezing point of water for 32 degrees and body temperature was 96 degrees. Fahrenheit used alcohol for his first few thermometers but after several series of experiments substituted it for mercury because of its rate of expansion, although it is less than that of alcohol, it is more constant. He also found mercury could be used over a much wider temperature range than alcohol. These experiments also led to the discovery that the boiling point of water varied with changes in atmospheric pressure and the phenomenon of the super cooling of water (this means, cooling water to below its normal freezing point without converting it to ice.

) Fahrenheit's thermometers were highly advanced. He used mercury successfully because of his technique for cleaning it, and he introduced the use of cylindrical bulbs instead of spherical ones. However, his detailed technique for making thermometers was not disclosed for 18 years, since it was a trade secret. Among the other instruments which he devised were a constant-weight hydrometer of excellent design and a 'thermo-barometer' for estimating barometric pressure by determining the boiling point of water. In order to reflect the greater sensitivity of his thermometer, Fahrenheit expanded the previous scale so that body heat was 90^0 and a particular ice-salt mixture was 0^0.

On this scale freezing point was 30^0. Fahrenheit later changed the scale to ignore that body temperature was fixed point and the boiling point of water came to 212^0 which meant freezing point was 32^0. This is the Fahrenheit scale that is still in use today. In 1714 Fahrenheit was still only 28 when he startled the world by making a pair of thermometers that both gave the same readings.

Fahrenheit made sense of temperature by seeing temperature scales in abstract terms. He realized that scales could be connected to universal material properties. He built fine thermometers that carried his thoughts into the world. In 1724 he announced his method of making thermometers in the Philosophical Transactions of the Royal Society, On the 16 th of September 1736, Fahrenheit died, he was unmarried and living in the Netherlands, that was where he was buried..