Galileo Galiliei...Invention of the thermoneter

What is a Thermometer?
Thermometers measure temperature, by using materials that change in some way when they are heated or cooled. In a mercury or alcohol thermometer the liquid expands as it is heated and contracts when it is cooled, so the length of the liquid column is longer or shorter depending on the temperature. Modern thermometers are calibrated in standard temperature units such as Fahrenheit or Celsius.

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Early History
The first thermometers were called thermoscopes and while several inventors invented a version of the thermoscope at the same time, Italian inventor Santorio Santorio was the first inventor to put a numerical scale on the instrument. Galileo Galilei invented a rudimentary water thermometer in 1593 which, for the first time, allowed temperature variations to be measured. In 1714, Gabriel Fahrenheit invented the first mercury thermometer, the modern thermometer. Thermometer
At the start of the seventeenth century there was no way to quantify heat.
Santorio Santorio
Santorio invented several instruments, a wind gauge, a water current meter, the "pulsilogium," and a thermoscope, a precursor to the thermometer. Santorio was the first to apply a numerical scale to his thermoscope, which later evolved into the thermometer.