Two decades after Fahrenheit published his findings, Swedish astronomer Anders Celsius grew tired of measuring heat against unstable chemical solutions. Working at the Uppsala Astronomical Observatory in 1742, Celsius sought an objective standard based entirely on astronomical and planetary constants that any scientist on Earth could recreate with nothing more than pure water and barometric observation.
Celsius recognized that phase transitions offered absolute consistency. At mean sea-level pressure of 1013.25 millibars, ice melts at one unyielding mark, and steam boils at another. Celsius divided the space between those events into 100 equal parts, naming it the centigrade scale from the Latin centum (hundred) and gradus (step).
In his original 1742 paper, Celsius actually assigned 0 to the boiling point of water and 100 to the freezing point to avoid negative temperatures during brutal Swedish winters. Immediately after his death in 1744, botanist Carl Linnaeus and manufacturer Daniel Ekström flipped the scale into the orientation used worldwide: zero for freezing, one hundred for boiling.
