How exactly was the Celsius scale originally defined?

Celsius temperature scale, also called centigrade temperature scale, scale based on 0° for the freezing point of water and 100° for the boiling point of water. read more

Celsius A, 1742, Observationer om tw¨anne best¨andiga Grader p°a en Thermometer Kongl. Svenska Vetenskapsacademiens Handlingar 3 171–80. It’s a little hard to get your hands on. I myself can’t read Swedish. Edit: Celsius didn’t invent the Celsius scale but liked using a Centigrade scale. Centigrade only means divided by 100. read more

Celsius is credited with being the first astronomer to analyze the changes in the Earth’s magnetic field, and he developed measuring tools to assess the brightness of stars. Celsius performed diligent experiments to develop his scale, although he originally had 0 as the boiling point and 100 as the freezing point. read more

This definition also precisely relates the Celsius scale to the Kelvin scale, which defines the SI base unit of thermodynamic temperature with symbol K. Absolute zero, the lowest temperature possible, is defined as being exactly 0 K and −273.15 °C. read more