It is impossible to imagine that it took a century and a half of efforts of many scientists to create such a simple, as it seems to us, device as a thermometer. And it would seem, what is so difficult? A scale with graduations, to which is attached a tube, which is sealed on top and a ball on the bottom, with mercury or alcohol inside. The principle of operation of this item is very simple. When heated, the liquid inside the tube expands, and its level rises, and thus shows the temperature. But the assumption of using the phenomenon of thermal expansion of bodies to measure temperature appeared only at the end of the 16th century. Then the question arises, how was the temperature measured before the invention of the thermometer? Very simple. Ancient scientists judged the temperature by their feelings, that is, by touching the body with their hand, they could judge whether it was cold or hot. Agree
In 1592, Galileo Galilei invented a device called a thermoscope, which made it possible to judge the temperature, but, unfortunately, this was also not a completely objective way. This device consisted of a glass sphere with a glass tube soldered to it, which was not hermetically sealed. As a result, atmospheric pressure acted on the liquid in it, and therefore it was possible to compare the temperature of different bodies at the same time and in the same place. Another drawback was that the device did not have a scale.
The history of the creation of the thermometer in subsequent years is just the history of the improvement of Galileo’s thermoscope. Tinted alcohol, and later mercury, replaced the air. We also ruled out the effect of atmospheric pressure by pumping air out of the tube and sealing its edges. And the most important improvement was the appearance of the scale. And this was the most difficult stage, since each scientist offered his own scale. And only in 1730, the Swedish physicist A. Celsius proposed as reference points the temperature of melting ice (offered by Shtormer) and the boiling point of water, which were respectively 100 ° C and 0 ° C, and divided the interval into equal parts. And here it is! A thermometer was created, which we use to this day.