Who invented thermometer?

The invention of the thermometer was a gradual process involving several scientists over different periods. Here are the key figures and their contributions:

Galileo Galilei

Galileo Galilei is often credited with the invention of the thermoscope, a precursor to the thermometer, in 1593. His device used water and indicated temperature differences but did not have a numerical scale135.

Santorio Santorio

In 1612, Santorio Santorio, an Italian scientist, added a numerical scale to the thermoscope, effectively creating the first thermometer. His instrument was an air thermometer with a scale, although its accuracy was limited due to the effects of varying air pressure234.

Ferdinand II of Tuscany

In 1654, Ferdinand II, the Grand Duke of Tuscany, developed the first sealed liquid-in-glass thermometer using alcohol. This design was more familiar to modern thermometers but still lacked accuracy and a standardized scale24.

Daniel Gabriel Fahrenheit

Fahrenheit made significant contributions in 1709 and 1714. He developed the first mercury thermometer, which was more accurate and reliable than its predecessors. He also created the Fahrenheit scale, which divided the freezing and boiling points of water into 180 degrees234.

Olaus Rømer

Although not directly credited with inventing the thermometer, Olaus Rømer introduced the concept of calibrating a scale using the freezing and boiling points of water in 1701. His work influenced later temperature scales3.

Anders Celsius

In 1742, Anders Celsius developed the Celsius scale, which divided the freezing and boiling points of water into 100 degrees. Initially, he set 100 degrees as the freezing point and 0 degrees as the boiling point, but this was later inverted by Jean-Pierre Christin to the scale we use today234.

The development of the thermometer was thus a collaborative effort over several centuries, with each scientist building upon the work of their predecessors.