Editing Barometer (section)

=== Evangelista Torricelli ===
[[File:Evangelista Torricelli by Lorenzo Lippi (circa 1647, Galleria Silvano Lodi & Due).jpg|thumb|202x202px|Evangelista Torricelli]]
Evangelista Torricelli, who was Galileo's amanuensis for the last three months of his life, interpreted the results of the experiments in a novel way. He proposed that the weight of the atmosphere, not an attracting force of the vacuum, held the water in the tube. In a letter to [[Michelangelo Ricci]] in 1644 concerning the experiments, he wrote:

<blockquote>Many have said that a vacuum does not exist, others that it does exist in spite of the repugnance of nature and with difficulty; I know of no one who has said that it exists without difficulty and without a resistance from nature. I argued thus: If there can be found a manifest cause from which the resistance can be derived which is felt if we try to make a vacuum, it seems to me foolish to try to attribute to vacuum those operations which follow evidently from some other cause; and so by making some very easy calculations, I found that the cause assigned by me (that is, the weight of the atmosphere) ought by itself alone to offer a greater resistance than it does when we try to produce a vacuum.<ref>{{cite web|url=http://web.lemoyne.edu/~giunta/torr.html |title=Torricelli's letter to Michelangelo Ricci |publisher=Web.lemoyne.edu |access-date=2010-02-04}}</ref></blockquote>

It was traditionally thought, especially by the [[Aristotelianism|Aristotelians]], that the air did not have weight; that is, that the kilometers of air above the surface of the Earth did not exert any weight on the bodies below it. Even Galileo had accepted the weightlessness of air as a simple truth. Torricelli proposed that rather than an attractive force of the vacuum sucking up water, air did indeed have weight, which pushed on the water, holding up a column of it. He argued that the level that the water stayed at—c. 10.3&nbsp;m above the water surface below—was reflective of the force of the air's weight pushing on the water in the basin, setting a limit for how far down the water level could sink in a tall, closed, water-filled tube. He viewed the barometer as a balance—an instrument for measurement—as opposed to merely an instrument for creating a vacuum, and since he was the first to view it this way, he is traditionally considered the inventor of the barometer, in the sense in which we now use the term.<ref name="History of the Barometer"/>

==== Torricelli's mercury barometer ====
[[File:Torricelli.jpg|thumb|239x239px|Torricelli's mercury in glass tube experiment]]
Because of rumors circulating in Torricelli's gossipy Italian neighborhood, which included that he was engaged in some form of sorcery or witchcraft, Torricelli realized he had to keep his experiment secret to avoid the risk of being arrested. He needed to use a liquid that was heavier than water, and from his previous association and suggestions by Galileo, he deduced that by using [[Mercury (element)|mercury]], a shorter tube could be used. With mercury, which is about 14 times denser than water, a tube only 80&nbsp;cm was now needed, not 10.5&nbsp;m.<ref>{{cite web|url=http://www.barometer.ws/history.html |title=Brief History of the Barometer |publisher=Barometer.ws |access-date=2010-02-04| archive-url= https://web.archive.org/web/20100114144734/http://www.barometer.ws/history.html| archive-date= 14 January 2010 | url-status= live}}</ref> Furthermore, Torricelli demonstrated that atmospheric pressure could support a column of mercury approximately 30 inches high.<ref>{{Cite journal |title=1944JRASC..38...41K Page 49 |url=https://articles.adsabs.harvard.edu//full/1944JRASC..38...41K/0000049.000.html |access-date=2025-03-07 |journal=Journal of the Royal Astronomical Society of Canada|bibcode=1944JRASC..38...41K |last1=Knowles Middleton |first1=W. E. |date=1944 |volume=38 |page=41 }}</ref>