Editing Vacuum (section)

== Historical understanding ==
Historically, there has been much dispute over whether such a thing as a vacuum can exist. Ancient [[Greek philosophy|Greek philosophers]] debated the existence of a vacuum, or void, in the context of [[atomism]], which posited void and atom as the fundamental explanatory elements of physics. [[Lucretius]] argued for the existence of vacuum in the first century BC and [[Hero of Alexandria]] tried unsuccessfully to create an artificial vacuum in the first century AD.<ref name="genz">{{cite book |last=Genz |first=Henning |title=Nothingness: The Science of Empty Space |date=1994 |publisher=Perseus Book Publishing |isbn=978-0-7382-0610-3 |edition= |place=New York |publication-date=1999 |oclc=48836264}}</ref>

Following [[Plato]], however, even the abstract concept of a featureless void faced considerable skepticism: it could not be apprehended by the senses, it could not, itself, provide additional explanatory power beyond the physical volume with which it was commensurate and, by definition, it was quite literally nothing at all, which cannot rightly be said to exist. [[Aristotle]] believed that no void could occur naturally, because the denser surrounding material continuum would immediately fill any incipient rarity that might give rise to a void. In his ''[[Physics (Aristotle)|Physics]]'', book IV, Aristotle offered numerous arguments against the void: for example, that motion through a medium which offered no impediment could continue ''ad infinitum'', there being no reason that something would come to rest anywhere in particular. 

In the medieval [[Muslim world]], the physicist and Islamic scholar [[Al-Farabi]] wrote a treatise rejecting the existence of the vacuum in the 10th century.<ref>{{Citation |url=https://seop.illc.uva.nl/entries/al-farabi/|year=2016|last=Druart|first=Therese-Anne|title=al-Farabi|encyclopedia=[[Stanford Encyclopedia of Philosophy]] |editor-last=Zalta |editor-first=Edward N. |edition= Winter 2021 |access-date= 2022-10-25}}</ref> He concluded that air's volume can expand to fill available space, and therefore the concept of a perfect vacuum was incoherent.<ref>{{Citation |last=McGinnis |first=Jon |title=Arabic and Islamic Natural Philosophy and Natural Science |date=2022 |url=https://plato.stanford.edu/archives/spr2022/entries/arabic-islamic-natural/ |encyclopedia=[[Stanford Encyclopedia of Philosophy]] |editor-last=Zalta |editor-first=Edward N. |edition=Spring 2022 |access-date=2022-08-11}}.</ref> According to [[Ahmad Dallal]], [[Abū Rayhān al-Bīrūnī]] states that "there is no observable evidence that rules out the possibility of vacuum".<ref name=Dallal>{{cite web|first=Ahmad|last=Dallal|date=2001–2002|title=The Interplay of Science and Theology in the Fourteenth-century Kalam|publisher=From Medieval to Modern in the Islamic World, Sawyer Seminar at the [[University of Chicago]]|url=http://humanities.uchicago.edu/orgs/institute/sawyer/archive/islam/dallal.html|access-date=2008-02-02|archive-url=https://web.archive.org/web/20120210094416/http://humanities.uchicago.edu/orgs/institute/sawyer/archive/islam/dallal.html|archive-date=2012-02-10|url-status=dead}}</ref> The [[suction]] [[pump]] was described by Arab engineer [[Al-Jazari]] in the 13th century, and later appeared in Europe from the 15th century.<ref name="Hill2">[[Donald Routledge Hill]], "Mechanical Engineering in the Medieval Near East", ''Scientific American'', May 1991, pp. 64–69 ([[cf.]] [[Donald Routledge Hill]], [http://home.swipnet.se/islam/articles/HistoryofSciences.htm Mechanical Engineering] {{webarchive|url=https://web.archive.org/web/20071225091836/http://home.swipnet.se/islam/articles/HistoryofSciences.htm|date=2007-12-25}}).</ref><ref>[[Donald Routledge Hill]] (1996), ''A History of Engineering in Classical and Medieval Times'', [[Routledge]], pp. 143, 150–152.</ref>

European [[scholasticism|scholars]] such as [[Roger Bacon]], [[Blasius of Parma]] and [[Walter Burley]] in the 13th and 14th century focused considerable attention on issues concerning the concept of a vacuum. The commonly held view that nature abhorred a vacuum was called ''[[horror vacui (physics)|horror vacui]]''. There was even speculation that even God could not create a vacuum if he wanted and the 1277 [[Paris condemnations]] of [[Bishop]] [[Étienne Tempier]], which required there to be no restrictions on the powers of God, led to the conclusion that God could create a vacuum if he so wished.<ref name="Barrow">{{cite book |last=Barrow |first=John D. |url=https://archive.org/details/bookofnothingvac0000barr |title=The Book of Nothing: Vacuums, Voids, and the Latest Ideas about the Origins of the Universe |date=2000 |publisher=Pantheon Books |isbn=978-0-09-928845-9 |edition=1st American |location=New York |oclc=46600561 |author-link=John D. Barrow |url-access=registration}}</ref> From the 14th century onward increasingly departed from the Aristotelian perspective, scholars widely acknowledged that a [[supernatural]] void exists beyond the confines of the cosmos itself by the 17th century. This idea, influenced by [[Stoic physics]], helped to segregate natural and theological concerns.<ref name="Barrow2002">{{cite book |first=J.D. |last=Barrow |date=2002 |title=The Book of Nothing: Vacuums, Voids, and the Latest Ideas About the Origins of the Universe |series=Vintage Series |publisher=Vintage |isbn=978-0-375-72609-5 |lccn=00058894 |url=https://books.google.com/books?id=sU_K0wbBeugC&pg=PA77 |pages=71–72, 77}}</ref>

Almost two thousand years after Plato, [[René Descartes]] also proposed a geometrically based alternative theory of atomism, without the problematic nothing–everything [[dichotomy]] of void and atom. Although Descartes agreed with the contemporary position, that a vacuum does not occur in nature, the success of his [[Cartesian coordinate system|namesake coordinate system]] and more implicitly, the spatial–corporeal component of his metaphysics would come to define the philosophically modern notion of empty space as a quantified extension of volume. By the ancient definition however, directional information and magnitude were conceptually distinct.{{citation needed|date=August 2024}}

[[File:Baro 0.png|thumb|100px|left|[[Evangelista Torricelli|Torricelli]]'s [[mercury (element)|mercury]] [[barometer]] produced one of the first sustained vacuums in a laboratory.]]

Medieval [[thought experiment]]s into the idea of a vacuum considered whether a vacuum was present, if only for an instant, between two flat plates when they were rapidly separated.<ref name=grant>{{cite book
 | title = Much ado about nothing: theories of space and vacuum from the Middle Ages to the scientific revolution
 | author = Grant, Edward
 | publisher = Cambridge University Press
 | date = 1981
 | isbn = 978-0-521-22983-8
 | url = https://books.google.com/books?id=SidBQyFmgpsC
 }}</ref> There was much discussion of whether the air moved in quickly enough as the plates were separated, or, as [[Walter Burley]] postulated, whether a 'celestial agent' prevented the vacuum arising. [[Jean Buridan]] reported in the 14th century that teams of ten horses could not pull open [[bellows]] when the port was sealed.<ref name="genz" />

[[File:Crookes tube two views.jpg|right|thumb|The [[Crookes tube]], used to discover and study [[cathode ray]]s, was an evolution of the [[Geissler tube]].]]

The 17th century saw the first attempts to quantify measurements of partial vacuum.<ref>{{cite web |url=http://www.denmark.com.au/en/Worlds+Largest+Barometer/default.htm |title=The World's Largest Barometer |access-date=2008-04-30 |url-status=dead |archive-url=https://web.archive.org/web/20080417093648/http://www.denmark.com.au/en/Worlds%2BLargest%2BBarometer/default.htm |archive-date=2008-04-17 }}</ref> [[Evangelista Torricelli]]'s [[Mercury (element)|mercury]] [[barometer]] of 1643 and [[Blaise Pascal]]'s experiments both demonstrated a partial vacuum.

In 1654, [[Otto von Guericke]] invented the first [[vacuum pump]]<ref>{{Cite web |title=Otto von Guericke {{!}} Prussian physicist, engineer, and philosopher {{!}} Britannica |url=https://www.britannica.com/biography/Otto-von-Guericke |access-date=2022-08-11 |website=www.britannica.com |language=en}}</ref> and conducted his famous [[Magdeburg hemispheres]] experiment, showing that, owing to atmospheric pressure outside the hemispheres, teams of horses could not separate two hemispheres from which the air had been partially evacuated. [[Robert Boyle]] improved Guericke's design and with the help of [[Robert Hooke]] further developed vacuum pump technology. Thereafter, research into the partial vacuum lapsed until 1850 when [[August Toepler]] invented the [[Toepler pump]] and in 1855 when [[Heinrich Geissler]] invented the mercury displacement pump, achieving a partial vacuum of about 10&nbsp;Pa (0.1&nbsp;[[Torr]]). A number of electrical properties become observable at this vacuum level, which renewed interest in further research.

While outer space provides the most rarefied example of a naturally occurring partial vacuum, the heavens were originally thought to be seamlessly filled by a rigid indestructible material called [[aether (classical element)|aether]]. Borrowing somewhat from the [[pneuma]] of [[Stoic physics]], aether came to be regarded as the rarefied air from which it took its name, (see [[Aether (mythology)]]). Early theories of light posited a ubiquitous terrestrial and celestial medium through which light propagated. Additionally, the concept informed [[Isaac Newton]]'s explanations of both [[refraction]] and of radiant heat.<ref>[[Robert Hogarth Patterson]], ''Essays in History and Art 10'', 1862.</ref> 19th century experiments into this [[luminiferous aether]] attempted to detect a minute drag on the Earth's orbit. While the Earth does, in fact, move through a relatively dense medium in comparison to that of interstellar space, the drag is so minuscule that it could not be detected. In 1912, [[astronomer]] [[William Henry Pickering|Henry Pickering]] commented: "While the interstellar absorbing medium may be simply the ether, [it] is characteristic of a gas, and free gaseous molecules are certainly there".<ref>{{cite journal | last1 = Pickering | first1 = W.H. | date =1912 | title = Solar system, the motion of the, relatively to the interstellar absorbing medium | journal = [[Monthly Notices of the Royal Astronomical Society]] | volume = 72 | issue = 9 |bibcode=1912MNRAS..72..740P | page = 740 | doi=10.1093/mnras/72.9.740| url = https://zenodo.org/record/1431891 | doi-access = free }}</ref> Thereafter, however, luminiferous aether was discarded.

Later, in 1930, [[Paul Dirac]] proposed a model of the vacuum as an infinite sea of particles possessing negative energy, called the [[Dirac sea]]. This theory helped refine the predictions of his earlier formulated [[Dirac equation]], and successfully predicted the existence of the [[positron]], confirmed two years later. [[Werner Heisenberg]]'s [[uncertainty principle]], formulated in 1927, predicted a fundamental limit within which instantaneous position and [[momentum]], or energy and time can be measured. This far reaching consequences also threatened whether the "emptiness" of space between particles exists.