Aristotelian theory of gravity: Difference between revisions
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The Aristotelian theory of gravity was first criticized and/or modified by [[John Philoponus]] and later by [[Islamic science|Muslim physicists]] during the [[Middle Ages]]. [[Ja'far Muhammad ibn Mūsā ibn Shākir]] (800-873) of the [[Banū Mūsā]] wrote the ''Astral Motion'' and ''The Force of Attraction'', where he discovered that there was a [[force]] of [[Gravitation|attraction]] between [[Astronomical object|heavenly bodies]],<ref>K. A. Waheed (1978). ''Islam and The Origins of Modern Science'', p. 27. Islamic Publication Ltd., Lahore.</ref> foreshadowing [[Newton's law of universal gravitation]].<ref>[[Robert Briffault]] (1938). ''The Making of Humanity'', p. 191.</ref> |
The Aristotelian theory of gravity was first criticized and/or modified by [[John Philoponus]] and later by [[Islamic science|Muslim physicists]] during the [[Middle Ages]]. [[Ja'far Muhammad ibn Mūsā ibn Shākir]] (800-873) of the [[Banū Mūsā]] wrote the ''Astral Motion'' and ''The Force of Attraction'', where he discovered that there was a [[force]] of [[Gravitation|attraction]] between [[Astronomical object|heavenly bodies]],<ref>K. A. Waheed (1978). ''Islam and The Origins of Modern Science'', p. 27. Islamic Publication Ltd., Lahore.</ref> foreshadowing [[Newton's law of universal gravitation]].<ref>[[Robert Briffault]] (1938). ''The Making of Humanity'', p. 191.</ref> |
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[[Ibn al-Haytham]] (965-1039) also discussed the theory of attraction between [[mass]]es, and 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> [[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> |
[[Ibn al-Haytham]] (965-1039) also discussed the theory of attraction between [[mass]]es, and 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> [[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> He 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> [[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 |
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> [[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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Revision as of 01:48, 27 January 2008
 | It has been suggested that this article be merged into Aristotelian physics and Talk:Aristotelian theory of gravity. (Discuss) Proposed since June 2007. |
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The Aristotelian theory of gravity was a theory that stated that all bodies move towards their natural place. For some objects, Aristotle claimed the natural place to be the center of the earth, wherefore they fall towards it. For other objects, the natural place is the heavenly spheres, wherefore gases, steam for example, move away from the centre of the earth and towards heaven and to the moon. The speed of this motion was thought to be proportional to the mass of the object.
Medieval criticisms
The Aristotelian theory of gravity was first criticized and/or modified by John Philoponus and later by Muslim physicists during the Middle Ages. Ja'far Muhammad ibn Mūsā ibn Shākir (800-873) of the Banū Mūsā wrote the Astral Motion and The Force of Attraction, where he discovered that there was a force of attraction between heavenly bodies,[1] foreshadowing Newton's law of universal gravitation.[2]
Ibn al-Haytham (965-1039) also discussed the theory of attraction between masses, and it seems that he was aware of the magnitude of acceleration due to gravity and he discovered that the heavenly bodies "were accountable to the laws of physics".[3] 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.[4] He also criticized the Aristotelian theory of gravity for denying the existence of levity or gravity in the celestial spheres and for its notion of circular motion being an innate property of the heavenly bodies.[5]
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.[6] 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.[7] Like Newton, he described acceleration as the rate of change of velocity.[8]
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",[9] which he described in the following observational test:
"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."[10]
Modern criticisms
Aristotle's theory was discredited by the work of Galileo Galilei in Europe. According to legend, Galileo dropped balls of various densities from the 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.
Aristotle's confusions can be traced to the fact that he did not believe that motion could be described without a surrounding medium. He believed that motion through a perfect vacuum would be infinitely rapid, a point of view which led him to the famous conclusion that nature abhors a vacuum, that a vacuum is physically impossible. He couldn't treat air resistance as a complicating factor, because in his philosophy the medium was an equal partner in the motion. A heavier body falls faster than a lighter one of the same shape in a dense medium like water, and this led him to speculate that the rate of falling is proportional to the mass 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 a thousand.
On the surface of the moon, David Scott famously repeated Galileo's supposed 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.
With his law of universal gravitation Isaac Newton was the first to mathematically codify the newer theory of gravity according to which any mass, not only the Earth, is attracted to other masses by a function of their mass and the inverse square of their distance.
In 1915, Newton's theory was modified by Albert Einstein, who developed a new picture of gravitation, in the framework of his general theory of relativity. See gravity for a much more detailed complete discussion.
Notes
- ^ K. A. Waheed (1978). Islam and The Origins of Modern Science, p. 27. Islamic Publication Ltd., Lahore.
- ^ Robert Briffault (1938). The Making of Humanity, p. 191.
- ^ 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.
- ^ O'Connor, John J.; Robertson, Edmund F., "Al-Biruni", MacTutor History of Mathematics Archive, University of St Andrews
- ^ Rafik Berjak and Muzaffar Iqbal, "Ibn Sina--Al-Biruni correspondence", Islam & Science, June 2003.
- ^ 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.
- ^ Shlomo Pines (1970). "Abu'l-Barakāt al-Baghdādī , Hibat Allah". Dictionary of Scientific Biography. Vol. 1. New York: Charles Scribner's Sons. pp. 26–28. ISBN 0684101149.
(cf. Abel B. Franco (October 2003). "Avempace, Projectile Motion, and Impetus Theory", Journal of the History of Ideas 64 (4), p. 521-546 [528].) - ^ A. C. Crombie, Augustine to Galileo 2, p. 67.
- ^ (Ragep 2001b, pp. 63–4)
- ^ (Ragep 2001a, pp. 152–3)