Anders Celsius (1701-1744) is famous for his temperature scale.

At his home in Uppsala, Sweden, Celsius stuck thermometers in thawing snow during all winter months, in various kinds of weather, and at many different barometric pressures to find the melting point of ice. Celsius used the freezing and boiling points of water as the reference points for his scale.

• Following the structure of the simpler metric system, he defined 100 degrees as the freezing point of water and 0 degrees as the boiling point of water.
• Later it was inverted so that large numbers were hotter and low numbers were colder.
• Since the prefix, centi, means one hundredth, the degrees were known as centigrades.
• Today's Celsius scale is the inverted form of Celsius' original design.

Since the metric system was declared as the international standard in 1954-1960, scientists no longer use the Fahrenheit temperature scale or the name "centigrades."

On the Celsius scale: Absolute zero is –273°C. Normal body temperature is 37°C. Water (at sea level air pressure) freezes at 0°C. Water (at sea level air pressure) boils at 100°C.

The Kelvin scale is an absolute temperature scale based on the Celsius scale. We can convert Celsius to Fahrenheit or Celsius to Kelvin.