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| '''Aristotelian Physics''', the [[natural sciences]], are described in the works of the [[Ancient Greek philosophy|Greek philosopher]] [[Aristotle]] (384 BC – 322 BC). In the ''[[Physics (Aristotle)|Physics]]'', Aristotle established general principles of change that govern all natural bodies; both living and inanimate, celestial and terrestrial—including all motion, change in respect to place, change in respect to size or number, qualitative change of any kind, and coming to be and passing away. As [[Martin Heidegger]], one of the foremost philosophers of the twentieth century, once wrote,
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| {{quote|Aristotelian "physics" is different from what we mean today by this word, not only to the extent that it belongs to antiquity whereas the modern physical sciences belong to modernity, rather above all it is different by virtue of the fact that Aristotle's "physics" is philosophy, whereas modern physics is a positive science that presupposes a philosophy.... This book determines the warp and woof of the whole of Western thinking, even at that place where it, as modern thinking, appears to think at odds with ancient thinking. But opposition is invariably {{sic|hide=y|comprised |of}} a decisive, and often even perilous, dependence. Without Aristotle's ''Physics'' there would have been no [[Galileo]].<ref>Martin Heidegger, ''The Principle of Reason'', trans. Reginald Lilly, ([[Indiana University Press]], 1991), 62-[http://books.google.com/books?id=rWDUmlA6M98C&lpg=PP1&pg=PA63#v=onepage&q&f=false 63].</ref>}}
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| To Aristotle, physics was a broad term that includes all nature sciences, such as philosophy of mind, body, sensory experience, memory and biology, and constitutes the foundational thinking underlying [[Corpus Aristotelicum#Physics .28the study of nature.29|many]] of his works.
| | <li>[http://www.hyzhe.net/forum.php?mod=viewthread&tid=863528&fromuid=99069 http://www.hyzhe.net/forum.php?mod=viewthread&tid=863528&fromuid=99069]</li> |
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| == Ancient concepts ==
| | <li>[http://www.iconbeauty.com.hk/forum.php?mod=viewthread&tid=2401374 http://www.iconbeauty.com.hk/forum.php?mod=viewthread&tid=2401374]</li> |
| Some concepts involved in Aristotle's physics are:
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| #'''[[Teleology]]''': Aristotle observes that natural things tend toward definite goals or ends insofar as they are natural. For example, a seed, under normal circumstances, has the goal (telos) of becoming an adult plant.<ref>{{cite book|last=Aristotle|title=Parts of Animals I.1}}</ref> Regularities manifest a rudimentary kind of teleology.
| | <li>[http://verdamilio.net/tonio/spip.php?article1557/ http://verdamilio.net/tonio/spip.php?article1557/]</li> |
| # '''Natural motion''': Terrestrial objects tend toward a different part of the universe according to their composition of the four elements. For example, earth, the heaviest element, tends toward the center of the universe—hence the reason for the Earth being at the center. At the opposite extreme the lightest element, fire, tends upward, away from the center. The relative proportion of the four elements composing an object determines its motion. The elements are not proper ''[[Substance theory|substances]]'' in Aristotelian theory or the modern sense of the word. Refining an arbitrarily pure sample of an element isn't possible; They were [[abstraction]]s; one might consider an arbitrarily pure sample of a terrestrial substance having a large [[ratio]] of one element relative to the others.
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| # '''Terrestrial motion''': Terrestrial objects move [[gravity|downward]] or [[buoyancy|upward]] toward their natural place. Motion from side to side results from the turbulent collision and sliding of the objects as well as transformations between the elements, (generation and corruption).
| | <li>[http://cgi.www5a.biglobe.ne.jp/~eucaly/dialy/bbs/apeboard_plus.cgi?msgnum=30&command=read_message/ http://cgi.www5a.biglobe.ne.jp/~eucaly/dialy/bbs/apeboard_plus.cgi?msgnum=30&command=read_message/]</li> |
| # '''Rectilinear motion''': Ideal terrestrial motion would proceed straight up or straight down at [[Newton's laws of motion#Newton's first law|constant speed]]. Celestial motion is always ideal, it is circular and its speed is constant.
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| # '''Speed, weight and resistance''': The ideal speed of a terrestrial object is [[directly proportional]] to its weight.<!-- gravitational acceleration varies with both masses --> In nature, however, the matter obstructing an object's path is a limiting factor that's [[inversely proportional]] to the [[viscosity]]<!-- a better approximation than "density"? --> of the medium.
| | </ul> |
| # '''Vacuum isn't possible''': [[Vacuum]] doesn't occur, but hypothetically, terrestrial motion in a vacuum would be indefinitely fast.
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| <!-- sync diff -->
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| # '''Continuum''': Aristotle argues against the ''indivisibles'' of [[Democritus]] (which differ considerably from the [[Corpuscularianism|historical]] and the [[Atomic theory|modern]] use of the term ''[[atom]]'').
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| # '''Aether''': The "greater and lesser lights of heaven", (the sun, moon, planets and stars), are embedded in perfectly concentric [[celestial spheres|''crystal'' spheres]] that rotate eternally at fixed rates. Because the spheres never change and ([[meteorite]]s notwithstanding) don't fall down or rise up from the ground, they cannot be composed of the four terrestrial elements. Much as [[Homer]]'s ''[[aether (mythology)|æthere (αἰθήρ)]]'', the "pure air" of [[Mount Olympus]] was the divine counterpart of the air (άήρ, ''aer'') breathed by [[immortality|mortal]]s, the celestial spheres are composed of a special element, eternal and unchanging, with circular natural motion.
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| # '''Terrestrial change''': {{anchor|celestial unchanging}}[[File:Four elements representation.svg|thumb|right|The four terrestrial elements]] Unlike the eternal and unchanging celestial ''[[Aether (classical element)|aether]]'', each of the four terrestrial elements are capable of changing into either of the two elements they share a property with: e.g. the cold and wet (''[[Water (classical element)|water]]'') can transform into the hot and wet (''[[Air (classical element)|air]]'') or the cold and dry (''[[Earth (classical element)|earth]]'') and any apparent change into the hot and dry (''[[Fire (classical element)|fire]]'') is actually a [[Gray code|two step]] process. These properties are predicated of an actual substance relative to the work it's able to do; that of heating or chilling and of desiccating or moistening. The four elements exist ''only'' with regard to this capacity and relative to some potential work. The celestial element is eternal and unchanging, so only the four terrestrial elements account for ''coming to be'' and ''passing away''; also called ''"generation and corruption"'' after the Latin title of Aristotle's [[On Generation and Corruption|''De Generatione et Corruptione'' (Περὶ γενέσεως καὶ φθορᾶς)]].
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| # '''Celestial motion''': The ''crystal spheres'' carrying the sun, moon and stars move eternally with unchanging circular motion. They're composed of solid ''[[Aether (classical element)|aether]]'' and no gaps exist between the spheres. Spheres are embedded within spheres to account for the ''wandering stars'', (i.e. the modern [[planet]]s, which appear to move erratically in comparison to the sun, moon and stars). Later, the belief that all spheres are concentric was forsaken in favor of [[Ptolemy]]'s ''[[deferent and epicycle]]''. Aristotle submits to the calculations of [[astronomer]]s regarding the total number of spheres and various accounts give a number in the neighborhood of 50 spheres. An ''[[unmoved mover]]'' is assumed for each sphere, including a ''[[primum movens|prime mover]]'' for the ''sphere of [[fixed stars]]''.<!-- Zeus had seen far better days... --> The ''unmoved movers'' do not push the spheres (nor could they, they're insubstantial and dimensionless); rather, they're the [[four causes|final cause]] of the motion, meaning they explain it in a way that's similar to the explanation "the soul is moved by beauty". They simply "think about thinking", eternally without change, which is the ''[[Hylomorphism|idea]]'' of [[Metaphysics (Aristotle)|"being ''qua'' being"]] in Aristotle reformulation of [[Theory of Forms|Plato's theory]].
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| While consistent with common human experience, Aristotle's principles were not based on controlled, quantitative experiments, so, while they account for many broad features of nature, they do not describe our universe in the precise, quantitative way we have more recently come to expect from science. Contemporaries of Aristotle like [[Aristarchus of Samos|Aristarchus]] rejected these principles in favor of [[heliocentrism]], but their ideas were not widely accepted. Aristotle's principles were difficult to disprove merely through casual everyday observation, but later development of the [[scientific method]] challenged his views with [[experiment]]s, careful measurement, and more advanced technology such as the [[telescope]] and [[vacuum pump]].
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| === Elements ===
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| According to Aristotle, the [[classical element|elements]] which compose the terrestrial spheres are different from the one that composes the celestial spheres.<ref name="utk">{{Cite web|url=http://csep10.phys.utk.edu/astr161/lect/history/aristotle_dynamics.html|title=Physics of Aristotle vs. The Physics of Galileo|accessdate=6 April 2009| archiveurl= http://web.archive.org/web/20090411072007/http://csep10.phys.utk.edu/astr161/lect/history/aristotle_dynamics.html| archivedate= 11 April 2009 <!--DASHBot-->| deadurl= no}}</ref> He believed that four elements make up everything under the moon (the terrestrial): [[earth (classical element)|earth]], [[air (classical element)|air]], [[fire (classical element)|fire]] and [[water (classical element)|water]].{{Ref_label|A|a|none}}<ref name="edu">{{Cite web|url=http://www.hep.fsu.edu/~wahl/Quarknet/pepperlect/aristogalnewt.pdf|format=PDF|title=www.hep.fsu.edu|accessdate=26 March 2007}}</ref>
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| He also held that the heavens are made of a special, fifth element called "[[Aether (classical element)|aether]]",<ref name="edu" /> which is weightless and "incorruptible" (which is to say, it doesn't change).<ref name="edu" /> Aether is also known by the name "quintessence"—literally, "fifth substance".<ref name="ari">{{Cite web|url=http://aether.lbl.gov/www/classes/p10/aristotle-physics.html|title=Aristotle's physics|accessdate=6 April 2009}}</ref>
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| [[File:Aristotle Physica page 1.png|thumb|left|200px|Page from an 1837 edition of ''Physica'' by the ancient Greek philosopher [[Aristotle]]—a book about a variety of subjects including the [[philosophy]] of nature and some topics within [[physics]]]]
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| He considered heavy substances such as [[iron]] and other metals to consist primarily of the element ''earth'', with a smaller amount of the other three terrestrial elements. Other, lighter objects, he believed, have less earth, relative to the other three elements in their composition.<ref name="ari" />
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| <!-- In modern Physics, [[chemical element]]s, [[chemical substance]]s, [[chemical compound]]s, and [[mixture]]s are... --> | |
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| === Motion ===
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| Aristotle held that each of the four terrestrial (or ''worldly'') elements move toward their ''natural place'', and that this natural motion would proceed unless hindered. For instance, because [[smoke]] is mainly ''air'', it rises toward the sky but not as high as ''fire''.
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| Motion and change are closely related in Aristotelian physics. Motion, according to [[Aristotle]] involve change from [[potentiality]] to [[actuality]].<ref>{{Bodnar, Istvan, "Aristotle's Natural Philosophy", The Stanford Encyclopedia of Philosophy (Spring 2012 Edition), Edward N. Zalta (ed.), URL = <http://plato.stanford.edu/archives/spr2012/entries/aristotle-natphil/>.}}</ref> He gave example of four types of change.
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| Aristotle proposed that the speed of a naturally moving object is directly proportional to its weight and inversely proportional to the density of the medium through which it moves.<ref name="Gindikin1988">{{cite book |first=S.G. |last=Gindikin |year=1988 |title=Tales of Physicists and Mathematicians |publisher=Birkh |isbn=9780817633172 |lccn=87024971 |url=http://books.google.com/books?id=Vhx--jfFN8IC&pg=PA29 |page=29}}</ref> This would make objects of different weights fall to the ground in different times. [[Galileo]] would later contest Aristotle’s point by demonstrating that object of different weights reach the ground in a similar time.<ref>Lindberg, D. (2008) ''The beginnings of western science: The European scientific tradition in philosophical, religious, and institutional context, prehistory to a.d. 1450'' (2nd ed.) [[University of Chicago Press]]</ref>
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| ===Vacuum===
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| A vacuum, or void, is a place free of everything, and Aristotle argued against the possibility. Aristotle believed that the speed of an object's motion is proportional to the force being applied (or the object's weight in the case of natural motion) and inversely proportional to the viscosity of the medium; the more tenuous a medium is, the faster the motion. He reasoned that objects moving in a void, could move indefinitely fast and thus, the objects surrounding a void would immediately fill it before it could actually form.<ref>Land, Helen ''The Order of Nature in Aristotle's Physics: Place and the Elements'' (1998)</ref> In astronomy, [[Void (astronomy)|voids]], such as the [[Local Void]] adjacent to our galaxy, have the opposite effect; off-center bodies are ejected from the void due to the gravity of the material outside, which being the farthest away in a direction towards the center, is also at its weakest.<ref>{{cite journal |author=Tully |author2=Shaya |author3=Karachentsev |author4=Courtois |author5=Kocevski |author6=Rizzi |author7=Peel |year=2008 |title=Our Peculiar Motion Away From the Local Void |journal=The Astrophysical Journal |volume=676 |number=1 |url=http://stacks.iop.org/0004-637X/676/i=1/a=184 |pages=184|bibcode = 2008ApJ...676..184T |doi = 10.1086/527428 |arxiv = 0705.4139 }}</ref>
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| === Natural place ===
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| The Aristotelian explanation of gravity is that all bodies move toward their ''natural place''. For the element ''earth'', that place is the center of the ([[geocentric]]) universe, next comes the natural place of ''water'' (in a concentric shell around that of ''earth''). The natural place of ''air'' is likewise a concentric shell surrounding the place of ''water''. [[Sea level]] is between those two. Finally, the natural place of ''fire'' is higher than that of ''air'' but below the innermost celestial sphere, (the one carrying the Moon). Even at locations well above sea level, such as a mountain top, an object made mostly of the former two elements tends to fall and objects made mostly of the latter two tend to rise.
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| === Place (topos) ===
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| In Book ''Delta'' of his ''Physics'' (IV.5) Aristotle defines topos (place) as the inner two-dimensional surface boundary of the containing body that is in touch with the outer two-dimensional surface of the contained body. This definition was the most dominant until the beginnings of the 17th century, even though it was called into doubt and debated by philosophers since antiquity, as for instance discussed by [[Simplicius]] in his ''Corollaries on place''. The most significant early serious critique to this conception of place was demonstrated geometrically by the 11th century Arab polymath al-Hasan [[Ibn al-Haytham]] ([[Alhazen]]) in his ''Discourse on place''.<ref>{{cite journal|last=El-Bizri|first=Nader|title=In Defence of the Sovereignty of Philosophy: al-Baghdadi's Critique of Ibn al-Haytham's Geometrisation of Place|journal=Arabic Sciences and Philosophy (Cambridge University Press)|year=2007|volume=17|pages=57–80}}</ref>
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| ==Medieval commentary==
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| {{Cite check|section|date=September 2010}}
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| {{Main|Theory of impetus}}
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| The Aristotelian theory of motion came under criticism and/or modification during the [[Middle Ages]]. The first such modification came from [[John Philoponus]] in the 6th century. He partly accepted Aristotle's theory that "continuation of motion depends on continued action of a force," but modified it to include his idea that the hurled body acquires a motive power or inclination for forced movement from the agent producing the initial motion and that this power secures the continuation of such motion. However, he argued that this impressed virtue was temporary; that it was a self-expending inclination, and thus the violent motion produced comes to an end, changing back into natural motion. In the 11th century, the Persian polymath [[Avicenna]], in ''[[The Book of Healing]]'' (1027) was influenced by Philoponus' theory in its rough outline, but took it much further to present the first alternative to the Aristotelian theory. In the [[Avicennism|Avicennan]] theory of motion, the violent inclination he conceived was non-self-consuming, a permanent force whose effect was dissipated only as a result of external agents such as air resistance, making him "the first to conceive such a permanent type of impressed virtue for non-natural motion." Such a self-motion (''mayl'') is "almost the opposite of the Aristotelian conception of violent motion of the projectile type, and it is rather reminiscent of the principle of [[inertia]], i.e., [[Newton's first law of motion]]."<ref>[[Aydin Sayili]] (1987), "Ibn Sīnā and Buridan on the Motion of the Projectile", ''Annals of the New York Academy of Sciences'' '''500''' (1): 477–482 [477]: {{quote|According to Aristotle, continuation of motion depends on continued action of a force. The motion of a hurled body, therefore, requires elucidation. Aristotle maintained that the air of the atmosphere was responsible for the continuation of such motion. John Philoponos of the 6th century rejected this Aristotelian view. He claimed that the hurled body acquires a motive power or an inclination for forced movement from the agent producing the initial motion and that this power or condition and not the ambient medium secures the continuation of such motion. According to Philoponos this impressed virtue was temporary. It was a self-expending inclination, and thus the violent motion thus produced comes to an end and changes into natural motion. Ibn Sina adopted this idea in its rough outline, but the violent inclination as he conceived it was a non-self-consuming one. It was a permanent force whose effect got dissipated only as a result of external agents such as air resistance. He is apparently the first to conceive such a permanent type of impressed virtue for non-natural motion. [...] Indeed, self-motion of the type conceived by Ibn Sina is almost the opposite of the Aristotelian conception of violent motion of the projectile type, and it is rather reminiscent of the principle of inertia, i.e., Newton's first law of motion.}}</ref>
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| The eldest [[Banū Mūsā]] brother, Ja'far Muhammad ibn Mūsā ibn Shākir (800-873), wrote the ''Astral Motion'' and ''The Force of Attraction''. The Persian physicist, [[Ibn al-Haytham]] (965-1039), discussed the theory of attraction between bodies. It seems that he was aware of the [[Magnitude (mathematics)|magnitude]] of [[acceleration]] due to [[gravity]] and he discovered that the heavenly bodies "were accountable to the [[Physical law|laws of physics]]".<ref>Duhem, Pierre (1908, 1969). ''To Save the Phenomena: An Essay on the Idea of Physical theory from Plato to Galileo'', p. 28. University of Chicago Press, Chicago.</ref> The Persian polymath [[Abū Rayhān al-Bīrūnī]] (973-1048) was the first to realize that [[acceleration]] is connected with non-uniform motion, part of [[Newton's second law of motion]].<ref name=Biruni>{{MacTutor|id=Al-Biruni|title=Al-Biruni}}</ref> During his debate with [[Avicenna]], al-Biruni also criticized the Aristotelian theory of gravity for denying the existence of [[wiktionary:levity|levity]] or gravity in the [[celestial sphere]]s and for its notion of [[circular motion]] being an [[Intrinsic and extrinsic properties|innate property]] of the [[Astronomical object|heavenly bodies]].<ref name=Berjak>Rafik Berjak and Muzaffar Iqbal, "Ibn Sina--Al-Biruni correspondence", ''Islam & Science'', June 2003.</ref>
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| In 1121, [[al-Khazini]], in ''The Book of the Balance of Wisdom'', proposed that the gravity and [[gravitational potential energy]] of a body varies depending on its distance from the centre of the Earth.<ref>Mariam Rozhanskaya and I. S. Levinova (1996), "Statics", in Roshdi Rashed, ed., ''[[Encyclopedia of the History of Arabic Science]]'', Vol. 2, p. 614-642 [621-622]. [[Routledge]], London and New York.</ref>{{Failed verification|date=May 2010}} [[Hibat Allah Abu'l-Barakat al-Baghdaadi]] (1080–1165) wrote a critique of Aristotelian physics entitled ''al-Mu'tabar'', where he negated Aristotle's idea that a constant [[force]] produces uniform motion, as he realized that a force applied continuously produces [[acceleration]], a fundamental law of [[classical mechanics]] and an early foreshadowing of [[Newton's second law of motion]].<ref>{{cite encyclopedia
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| | last = [[Shlomo Pines]]
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| | title = Abu'l-Barakāt al-Baghdādī , Hibat Allah
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| | encyclopedia = [[Dictionary of Scientific Biography]]
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| | volume = 1
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| | pages = 26–28
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| | publisher = Charles Scribner's Sons
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| | location = New York
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| | year = 1970 | |
| | isbn = 0-684-10114-9
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| }}
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| <br>([[cf.]] Abel B. Franco (October 2003). "Avempace, Projectile Motion, and Impetus Theory", ''Journal of the History of Ideas'' '''64''' (4), p. 521-546 [528].)</ref> Like Newton, he described acceleration as the rate of change of [[speed]].<ref>A. C. Crombie, ''Augustine to Galileo 2'', p. 67.</ref> | |
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| In the 14th century, [[Jean Buridan]] developed the [[theory of impetus]] as an alternative to the Aristotelian theory of motion. The theory of impetus was a precursor to the concepts of [[inertia]] and [[momentum]] in classical mechanics.<ref>[[Aydin Sayili]] (1987), "Ibn Sīnā and Buridan on the Motion of the Projectile", ''Annals of the New York Academy of Sciences'' '''500''' (1): 477–482</ref> Buridan and [[Albert of Saxony (philosopher)|Albert of Saxony]] also refer to Abu'l-Barakat in explaining that the acceleration of a falling body is a result of its increasing impetus.<ref name=Gutman>{{Cite book|title=Pseudo-Avicenna, Liber Celi Et Mundi: A Critical Edition|first=Oliver|last=Gutman|publisher=[[Brill Publishers]]|year=2003|isbn=90-04-13228-7|page=193|ref=harv|postscript=<!--None-->}}</ref> In the 16th century, [[Al-Birjandi]] discussed the possibility of the [[Earth's rotation]]. In his analysis of what might occur if the Earth were rotating, he developed a hypothesis similar to [[Galileo Galilei]]'s notion of "circular inertia",<ref>{{Harv|Ragep|2001b|pp=63–4}}</ref> which he described in the following [[Experiment|observational test]]:
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| {{quote|"The small or large rock will fall to the Earth along the path of a line that is perpendicular to the plane (''sath'') of the horizon; this is witnessed by experience (''tajriba''). And this perpendicular is away from the tangent point of the Earth’s sphere and the plane of the perceived (''hissi'') horizon. This point moves with the motion of the Earth and thus there will be no difference in place of fall of the two rocks."<ref>{{Harv|Ragep|2001a|pp=152–3}}</ref>}}
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| == Life and death of Aristotelian physics ==
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| [[File:Rembrandt Harmensz. van Rijn 013.jpg|thumb|right|200px| The famous philosopher Aristotle, depicted in a painting by [[Rembrandt Harmensz. van Rijn]]]]
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| The reign of Aristotelian physics lasted for almost two millennia, and provides the earliest known speculative theories of physics. After the work of [[Galileo]], [[Descartes]], and many others, it became generally accepted that Aristotelian physics was not correct or viable.<ref name="ari"/>
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| Despite this, the scholastic science survived well into the seventeenth century, and perhaps even later, until universities amended their curricula.
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| In [[Europe]], [[Aristotle]]'s theory was first convincingly discredited by the work of [[Galileo Galilei]]. Using a [[telescope]], Galileo observed that the moon was not entirely smooth, but had craters and mountains, contradicting the Aristotelian idea of an incorruptible perfectly smooth moon. Galileo also criticized this notion theoretically – a perfectly smooth moon would reflect light unevenly like a shiny [[billiard ball]], so that the edges of the moon's disk would have a different brightness than the point where a tangent plane reflects sunlight directly to the eye. A rough moon reflects in all directions equally, leading to a disk of approximately equal brightness which is what is observed.<ref name=GalileoTwoSystems>Galileo Galilei, ''[[Dialogue Concerning the Two Chief World Systems]]''.</ref> Galileo also observed that [[Jupiter]] has [[Galilean moons|moons]], objects which revolve around a body other than the Earth. He noted the [[planetary phase|phases]] of Venus, convincingly demonstrating that Venus, and by implication Mercury, travels around the sun, not the Earth.
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| According to legend, Galileo dropped balls of various [[Density|densities]] from the [[Leaning Tower of Pisa|Tower of Pisa]] and found that lighter and heavier ones fell at almost the same speed. In fact, he did quantitative experiments with balls rolling down an inclined plane, a form of falling that is slow enough to be measured without advanced instruments.
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| A heavier body falls faster than a lighter one of the same shape in a dense medium like water, and this led Aristotle to speculate that the rate of falling is proportional to the weight and inversely proportional to the density of the medium. From his experience with objects falling in water, he concluded that water is approximately ten times denser than air. By weighing a volume of compressed air, Galileo showed that this overestimates the density of air by a factor of forty.<ref name=GalileoNewSciences>Galileo Galilei, ''[[Two New Sciences]]''.</ref> From his experiments with inclined planes, he concluded that all bodies fall at the same rate neglecting friction.
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| Galileo also advanced a theoretical argument to support his conclusion. He asked if two bodies of different weights and different rates of fall are tied by a string, does the combined system fall faster because it is now more massive, or does the lighter body in its slower fall hold back the heavier body? The only convincing answer is neither: all the systems fall at the same rate.<ref name=GalileoTwoSystems/>
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| Followers of Aristotle were aware that the motion of falling bodies was not uniform, but picked up speed with time. Since time is an abstract quantity, the [[Peripatetic school|peripatetic]]s postulated that the speed was proportional to the distance. Galileo established experimentally that the speed is proportional to the time, but he also gave a theoretical argument that the speed could not possibly be proportional to the distance. In modern terms, if the rate of fall is proportional to the distance, the differential equation for the distance y travelled after time t is
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| :<math> | |
| {dy\over dt} = y
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| </math>
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| with the condition that <math>y(0)=0</math>. Galileo demonstrated that this system would stay at <math>y=0</math> for all time. If a perturbation set the system into motion somehow, the object would pick up speed exponentially in time, not quadratically.<ref name=GalileoNewSciences/>
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| Standing on the surface of the [[moon]] in 1971, [[David Scott]] famously repeated Galileo's experiment by dropping a feather and a hammer from each hand at the same time. In the absence of a substantial [[atmosphere]], the two objects fell and hit the moon's surface at the same time.
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| With his [[Newton's law of universal gravitation|law of universal gravitation]] [[Isaac Newton]] was the first to mathematically codify a correct theory of gravity. In this theory, any mass is attracted to any other mass by a force which decreases as the inverse square of their distance. In 1915, Newton's theory was replaced by [[Albert Einstein]]'s [[General relativity|general theory of relativity]]. See ''[[gravity]]'' for a much more detailed complete discussion.
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| == See also == | |
| Disputed works are marked by *, and ** marks a work generally agreed to be spurious.
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| * (184a) [[Physics (Aristotle)|Physics]] [http://ebooks.adelaide.edu.au/a/aristotle/physics/ (or ''Physica'')]
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| * (268a) [[On the Heavens]] [http://ebooks.adelaide.edu.au/a/aristotle/heavens/ (or ''De Caelo'')]
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| * (314a) [[On Generation and Corruption]] [http://ebooks.adelaide.edu.au/a/aristotle/corruption/ (or ''De Generatione et Corruptione'')]
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| * (338a) [[Meteorology (Aristotle)|Meteorology]] [http://ebooks.adelaide.edu.au/a/aristotle/meteorology/ (or ''Meteorologica'')]
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| * (391a) [[On the Universe]]** (or ''De Mundo'')
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| * (402a) [[On the Soul]] [http://ebooks.adelaide.edu.au/a/aristotle/a8so/ (or ''De Anima'')]
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| * The [[Parva Naturalia]] ("Little Physical Treatises"):
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| ** (436a) [[Sense and Sensibilia (Aristotle)|Sense and Sensibilia]] [http://ebooks.adelaide.edu.au/a/aristotle/sense/ (or ''De Sensu et Sensibilibus'')]
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| ** (449b) [[On Memory]] [http://ebooks.adelaide.edu.au/a/aristotle/memory/ (or ''De Memoria et Reminiscentia'')]
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| ** (453b) [[On Sleep]] [http://ebooks.adelaide.edu.au/a/aristotle/sleep/ (or ''De Somno et Vigilia'')]
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| ** (458a) [[On Dreams]] [http://ebooks.adelaide.edu.au/a/aristotle/dreams/ (or ''De Insomniis'')]
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| ** (462b) [[On Divination in Sleep]] [http://ebooks.adelaide.edu.au/a/aristotle/prophesy/ (or ''De Divinatione per Somnum'')]
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| ** (464b) [[On Length and Shortness of Life]] [http://ebooks.adelaide.edu.au/a/aristotle/life/ (or ''De Longitudine et Brevitate Vitae'')]
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| ** (467b) [[On Youth, Old Age, Life and Death, and Respiration]] [http://ebooks.adelaide.edu.au/a/aristotle/youth/ (or ''De Juventute et Senectute'', ''De Vita et Morte'', ''De Respiratione'')]
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| * (481a) [[On Breath]]** (or ''De Spiritu'')
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| * (486a) [[History of Animals]] [http://etext.virginia.edu/etcbin/toccer-new2?id=AriHian.xml&images=images/modeng&data=/texts/english/modeng/parsed&tag=public&part=all (or ''Historia Animalium'')]
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| * (639a) [[Parts of Animals]] [http://etext.virginia.edu/etcbin/toccer-new2?id=AriPaan.xml&images=images/modeng&data=/texts/english/modeng/parsed&tag=public&part=all (or ''De Partibus Animalium'')]
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| * (698a) [[Movement of Animals]] [http://ebooks.adelaide.edu.au/a/aristotle/motion/ (or ''De Motu Animalium'')]
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| * (704a) [[Progression of Animals]] [http://historyofideas.org/etcbin/toccer-new2?id=AriGait.xml&images=images/modeng&data=/texts/english/modeng/parsed&tag=public&part=all (or ''De Incessu Animalium'')]
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| * (715a) [[Generation of Animals]] [http://etext.virginia.edu/etcbin/toccer-new2?id=AriGene.xml&images=images/modeng&data=/texts/english/modeng/parsed&tag=public&part=all (or ''De Generatione Animalium'')]
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| * (791a) [[On Colors]]** (or ''De Coloribus'')
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| * (800a) [[On Things Heard]]** (or ''De audibilibus'')
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| * (805a) [[Physiognomonics]]** (or ''Physiognomonica'')
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| * (815a) [[On Plants]]** (or ''De Plantis'')
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| * (830a) [[On Marvellous Things Heard]]** [http://www.archive.org/stream/demirabilibusaus00arisrich/demirabilibusaus00arisrich_djvu.txt (or ''De mirabilibus auscultationibus'')]
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| * (847a) [[Mechanics (Aristotle)|Mechanics]]** (or ''Mechanica'')
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| * (859a) [[Problems (Aristotle)|Problems]]* (or ''Problemata'')
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| * (968a) [[On Indivisible Lines]]** (or ''De Lineis Insecabilibus'')
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| * (973a) [[The Situations and Names of Winds]]** (or ''Ventorum Situs'')
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| * (974a) [[On Melissus, Xenophanes, and Gorgias]]**
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| == Notes ==
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| {{Refbegin}}
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| '''a''' {{Note_label|A|a|none}} The term "Earth" does not refer to planet [[Earth]], which is known by modern science to be composed of a large number of [[chemical element]]s. Modern chemical elements are not conceptually similar to Aristotle's elements. The term "Air" does not refer to the breathable [[air]]. The Earth's atmosphere is also made up of many chemical elements.
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| {{Refend}}
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| == References ==
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| {{Reflist|2}}
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| *{{Cite journal
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| |last=Ragep
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| |first=F. Jamil
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| |year=2001a
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| |title=Tusi and Copernicus: The Earth's Motion in Context
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| |journal=Science in Context
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| |volume=14
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| |issue=1–2
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| |pages=145–163
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| |publisher=[[Cambridge University Press]]
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| |ref=harv
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| |postscript=<!--None-->
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| }}
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| *{{Cite journal
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| |last=Ragep
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| |first=F. Jamil
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| |year=2001b
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| |title=Freeing Astronomy from Philosophy: An Aspect of Islamic Influence on Science
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| |journal=Osiris, 2nd Series
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| |volume=16
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| |issue=Science in Theistic Contexts: Cognitive Dimensions
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| |pages=49–64 & 66–71
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| |ref=harv
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| |postscript=<!--None--> | |
| |bibcode = 2001Osir...16...49R
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| |doi=10.1086/649338
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| |last2=Al-Qushji
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| |first2=Ali}}
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| * H. Carteron (1965) "Does Aristotle Have a Mechanics?" in ''Articles on Aristotle 1. Science'' eds. Jonathan Barnes, Malcolm Schofield, Richard Sorabji (London: General Duckworth and Company Limited), 161-174.
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| ==Further reading==
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| * Katalin Martinás, “Aristotelian Thermodynamics,” ''Thermodynamics: history and philosophy: facts, trends, debates'' (Veszprém, Hungary 23–28 July 1990), 285-303.
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| {{DEFAULTSORT:Aristotelian Physics (History of Science)}}
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| [[Category:Aristotle|Physics]]
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| [[Category:History of physics]]
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| [[Category:Natural philosophy]]
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| [[pt:Teoria aristotélica da gravitação]]
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