# Three years of degrees are worth something

## Where does the unit "degree Celsius" and the abbreviation "°" come from?

In the 18th century, a scientist named Anders was doing the research Celsius with temperatures. He lived in Uppsala, a city in Sweden, from 1701 to 1744. He was working on a new thermometer and was looking for a way to compare different temperatures.

So he simply stipulated the following: the temperature at which water starts to boil, i.e. at which it is so hot that it evaporates, he gave the value 100. The temperature at which water freezes to ice, he gave the value 0 He divided the distance between these two extremes into 100 equal parts. Just as Celsius invented it back then, we still use the scale today. He also chose the term "degrees Celsius". The “C” simply stands for the name of the scientist. But where do the term “degree” and the small circle come from?

You don't know for sure. Ptolemy, an astronomer who lived in the 2nd century AD, already used the small circle. But he didn't invent the symbol either, it had been in use for a long time - as a value for part of the circle. In mathematics, a circle is made up of 360 equal parts - it has 360 °. The number "360" probably comes from the fact that in ancient times the year was divided into 12 lunar cycles of 30 days each - a total of 360 days.

The number of days in a year, which was very special for the ancients, was then simply transferred to other areas - such as mathematics. You simply used them to describe a full circle. This could then be divided into different angles: 180 ° is therefore a half circle, 90 ° is a quarter and so on.

Mr. Celsius simply used an already known symbol for a new thing: as a unit for measuring temperatures - the temperature scale has nothing to do with the division into 360. In order to be able to differentiate between a geometric angle and a temperature, there is a small difference in the notation: For temperatures there is always a space after the number (25_ ° C) and in front of the degree symbol, for angles the degree symbol follows the number (25_ ° C) without a space °) - and of course the "C" is also missing.

There are other units commonly used to measure temperatures. One of them is called Fahrenheit and is also named after a scientist: after the German Daniel Gabriel Fahrenheit, who lived from 1686 to 1736. The degree symbol is also used here: 25 ° F. But that's only a cold -3.9 ° C.

And then there is the degree unit Kelvin, named after William Thomson, 1st, the Baron of Kelvin. Zero Kelvin - without degrees - is the lowest temperature that can theoretically be reached. That is -273 degrees Celsius. So water freezes at 273 Kelvin, zero degrees Celsius.