Celsius (more precisely, a degree Celsius), sometimes called centigrade, is a
0 degrees (°) Celsius is the
Since 1948, this unit has been called Celsius. Centigrade was the name of the unit before the change. Centi meaning 1/100, and grade being a scale.
In 1742, Anders Celsius (1701–1744) made a “reversed” version of the modern Celsius temperature scale. In this scale, zero was the boiling point of water and 100 was the melting point of ice. In his paper Observations of two persistent degrees on a thermometer, he wrote about his experiments. He showed that the melting point of ice was basically unaffected by air pressure. Ice would turn into water at the same temperature, whether it was at sea level or on a mountain. This was not the case for the boiling point of water. It would boil easier with less pressure (on a mountain). He decided that zero on his temperature scale (water’s boiling point) would be set at the standard
In 1744, the year Anders Celsius died, the famous Swedish botanist
The first known document reporting temperatures in this modern “forward” Celsius scale is the paper Hortus Upsaliensis dated 16 December 1745 that Linnaeus wrote to a student of his, Samuel Nauclér. In it, Linnaeus reported the temperatures inside the orangery at the Botanical Garden of Uppsala University:
For the next 204 years, the scientific and thermometry communities worldwide called this scale the “centigrade scale.” Temperatures on the centigrade scale were often reported as “degrees” or “degrees centigrade.” The symbol for temperature values on this scale was °C (in several formats over the years). Because the name “centigrade” was also the Spanish and French language name for a unit of angular measurement (one-hundredth of a right angle) and had a similar meaning in other languages, the term “centesimal degree” was used when very precise, clear language was required for international communication, such as by the
There were three reasons for the decision in 1948 to use the word Celsius:
It would take nearly two decades however, for school textbooks to change from centigrade to Celsius, and many people today still use the old name.