Blaise Pascal Warning: You are not logged in. Your IP address will be publicly visible if you make any edits. If you log in or create an account, your edits will be attributed to your username, along with other benefits.Anti-spam check. Do not fill this in! ==Physics== [[File:Pascal's Barrel.png|thumb|An illustration of the (apocryphal) [[Pascal's barrel]] experiment]] Pascal contributed to several fields in physics, most notably the fields of fluid mechanics and pressure. In honour of his scientific contributions, the name ''Pascal'' has been given to the [[pascal (unit)|SI unit of pressure]] and [[Pascal's law]] (an important principle of hydrostatics). He introduced a primitive form of [[roulette]] and the roulette wheel in his search for a [[perpetual motion]] machine.<ref> [[Massachusetts Institute of Technology|MIT]], [https://web.archive.org/web/20030827232844/http://web.mit.edu/invent/iow/pascal.html "Inventor of the Week Archive: Pascal : Mechanical Calculator"], May 2003. "Pascal worked on many versions of the devices, leading to his attempt to create a perpetual motion machine. He has been credited with introducing the roulette machine, which was a by-product of these experiments."</ref> ===Fluid dynamics=== His work in the fields of [[hydrodynamics]] and [[hydrostatics]] centered on the principles of [[hydraulic fluid]]s. His inventions include the [[hydraulic press]] (using hydraulic pressure to multiply force) and the [[syringe]]. He proved that hydrostatic pressure depends not on the weight of the fluid but on the elevation difference. He demonstrated this principle by attaching a thin tube to a barrel full of water and filling the tube with water up to the level of the third floor of a building. This caused the barrel to leak, in what became known as [[Pascal's barrel]] experiment. ===Vacuum=== By 1647, Pascal had learned of [[Evangelista Torricelli]]'s experimentation with [[barometer]]s. Having replicated an experiment that involved placing a tube filled with mercury upside down in a bowl of mercury, Pascal questioned what force kept some mercury in the tube and what filled the space above the mercury in the tube. At the time, most scientists including [[Descartes]] believed in a plenum, i. e. some invisible matter filled all of space, rather than a [[vacuum]]. "[[Nature abhors a vacuum]]." This was based on the Aristotelian notion that everything in motion was a substance, moved by another substance.<ref>Aristotle, ''Physics'', VII, 1.</ref> Furthermore, light passed through the glass tube, suggesting a substance such as [[Luminiferous aether|aether]] rather than vacuum filled the space. Following more experimentation in this vein, in 1647 Pascal produced ''Experiences nouvelles touchant le vide'' ("New experiments with the vacuum"), which detailed basic rules describing to what degree various liquids could be supported by [[air pressure]]. It also provided reasons why it was indeed a vacuum above the column of liquid in a barometer tube. This work was followed by ''Récit de la grande expérience de l'équilibre des liqueurs'' ("Account of the great experiment on equilibrium in liquids") published in 1648. === First atmospheric pressure vs. altitude experiment === [[File:Puy de Dôme near Clermont-Ferrand in Auvergne in France.jpg|thumb|Puy de Dôme]] [[File:Florin Périer measuring the mercury level in a Torricelli barometer near the top of the Puy de Dôme.jpg|alt=Florin Périer measuring the mercury level in a Torricelli barometer near the top of the Puy de Dôme|thumb|Florin Périer on the Puy de Dôme]] The [[Torricellian vacuum]] found that air pressure is equal to the weight of 30 inches of mercury. If air has a finite weight, Earth's atmosphere must have a maximum height. Pascal reasoned that if true, air pressure on a high mountain must be less than at a lower altitude. He lived near the [[Puy de Dôme]] mountain, {{convert|4790|ft}} tall, but his health was poor so could not climb it.<ref name="ley196606">{{Cite magazine |last=Ley |first=Willy |date=June 1966 |title=The Re-Designed Solar System |department=For Your Information |url=https://archive.org/stream/Galaxy_v24n05_1966-06#page/n93/mode/2up |magazine=Galaxy Science Fiction |pages=94–106 }}</ref> On 19 September 1648, after many months of Pascal's friendly but insistent prodding, [[Florin Périer]], husband of Pascal's elder sister Gilberte, was finally able to carry out the fact-finding mission vital to Pascal's theory. The account, written by Périer, reads: {{blockquote|The weather was chancy last Saturday...[but] around five o'clock that morning...the Puy-de-Dôme was visible...so I decided to give it a try. Several important people of the city of [[Clermont-Ferrand|Clermont]] had asked me to let them know when I would make the ascent...I was delighted to have them with me in this great work... ...at eight o'clock we met in the gardens of the Minim Fathers, which has the lowest elevation in town....First I poured 16 pounds of [[Mercury (element)|quicksilver]]...into a vessel...then took several glass tubes...each four feet long and [[Hermetic seal|hermetically sealed]] at one end and opened at the other...then placed them in the vessel [of quicksilver]...I found the quick silver stood at 26" and {{frac|3|1|2}} lines above the quicksilver in the vessel...I repeated the experiment two more times while standing in the same spot...[they] produced the same result each time... I attached one of the tubes to the vessel and marked the height of the quicksilver and...asked Father Chastin, one of the Minim Brothers...to watch if any changes should occur through the day...Taking the other tube and a portion of the quick silver...I walked to the top of Puy-de-Dôme, about 500 [[fathoms]] higher than the monastery, where upon experiment...found that the quicksilver reached a height of only 23" and 2 lines...I repeated the experiment five times with care...each at different points on the summit...found the same height of quicksilver...in each case...<ref>Périer to Pascal, 22 September 1648, Pascal, Blaise. ''Oeuvres complètes''. (Paris: Seuil, 1960), 2:682.</ref>}} Pascal replicated the experiment in Paris by carrying a barometer up to the top of the bell tower at the church of [[Saint-Jacques Tower|Saint-Jacques-de-la-Boucherie]], a height of about 50 metres. The mercury dropped two lines. He found with both experiments that an ascent of 7 fathoms lowers the mercury by half a line.{{NoteTag|1=1 ligne = 2.256 mm, and 1 toise = 1.949 m. Mercury density is 13.534 g/cm3. So by Pascal's numbers, the density of air is about 1.1 kg/m^3.}} Note: Pascal used [[Units of measurement in France before the French Revolution#Length|''pouce'' and ''ligne'']] for "inch" and "line", and ''[[toise]]'' for "fathom".<ref>{{Cite journal |last=Rougier |first=Louis |date=2010-10-01 |title=– Chapitre XI – La Grande expérience de l'équilibre des liqueurs |url=https://journals.openedition.org/philosophiascientiae/189 |journal=Philosophia Scientiæ. Travaux d'histoire et de philosophie des sciences |language=fr |issue=14–2 |pages=196–206 |doi=10.4000/philosophiascientiae.189 |issn=1281-2463 |doi-access=free |access-date=5 July 2023 |archive-date=5 July 2023 |archive-url=https://web.archive.org/web/20230705204756/https://journals.openedition.org/philosophiascientiae/189 |url-status=live }}</ref> In a reply to [[Étienne Noël]], who believed in the plenum, Pascal wrote, echoing contemporary notions of science and [[falsifiability]]: "In order to show that a hypothesis is evident, it does not suffice that all the phenomena follow from it; instead, if it leads to something contrary to a single one of the phenomena, that suffices to establish its falsity."<ref>''Pour faire qu'une hypothèse soit évidente, il ne suffit pas que tous les phénomènes s'en ensuivent, au lieu que, s'il s'ensuit quelque chose de contraire à un seul des phénomènes, cela suffit pour assurer de sa fausseté'', in ''Les Lettres de Blaise Pascal: Accompagnées de Lettres de ses Correspondants Publiées'', ed. Maurice Beaufreton, 6th edition (Paris: G. Crès, 1922), 25–26, available at http://gallica.bnf.fr {{Webarchive|url=https://web.archive.org/web/20161218172021/http://gallica.bnf.fr/ |date=18 December 2016 }} and translated in Saul Fisher, ''Pierre Gassendi's Philosophy and Science: Atomism for Empiricists'' Brill's Studies in Intellectual History 131 (Leiden: E. J. Brill, 2005), 126 n.7</ref> [[Blaise Pascal Chair]]s are given to outstanding international scientists to conduct their research in the [[Île-de-France (region)|Ile de France]] region.<ref>{{cite web|title=Chaires Blaise Pascal|url=http://www.chaires-blaise-pascal.org/uk/index.html|url-status=dead|archive-url=https://web.archive.org/web/20090613064029/http://www.chaires-blaise-pascal.org/uk/index.html|archive-date=13 June 2009|access-date=16 August 2009|publisher=Chaires Blaise Pascal}}</ref> Summary: Please note that all contributions to Christianpedia may be edited, altered, or removed by other contributors. 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