The experiment of Torricelli, the discoverer of the "first" barometer in history

"Wind is generated by the temperature difference and air density difference between two areas on the earth." This is the first scientific description of wind by humans. The person who said this was Torricelli, the inventor of the mercury barometer.

We have mentioned before that Galileo did not complete the experiment during his lifetime. Subsequently, his students performed this experiment, and his student was Torricelli.

In 1644, Galileo's students Evangelista Torricelli and Vincenzo Viviani conducted this experiment. They chose mercury (which is 13.5 times denser than water). They filled a glass tube about one meter long with mercury, plugged the open end, placed it upside down in a mercury-containing plate, and then removed the plug. At this time, mercury begins to flow from the tube into the plate, but when the mercury level in the tube drops to only 760 mm higher than the mercury level in the plate, the mercury stops flowing out of the tube and remains at this height. This is how the first "barometer" was made. The modern mercury barometer is not essentially different from it.

So what keeps the mercury column at a certain height? Vivani proposed that this was due to the weight of the atmosphere pressing down on the liquid in the dish. This is a revolutionary idea, because according to Aristotle's concept, air has no weight, it just occupies its own inherent range outside the earth ball.

But now people are beginning to understand that a 10-meter-high water column or a 760-mm-high mercury column provides a measure of the weight of the atmosphere. That is to say, the weight of this water column or mercury column is equal to the cross-section The same height is the weight of a column of air from sea level to the top of the atmosphere. If air has finite weight, the atmosphere must have finite height. In this way, if the density is the same at all heights of the atmosphere, the height of the atmosphere will be exactly about 8 kilometers.

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