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Logicus proposes:I shall now restore the section on impetus dynamics previously deleted by user Deor without any good reason, but for which deletion Deor has provided no valid justification, but rather to the contrary a justification that entails it definitely must be included.(See above) Deor claimed "The article should deal with exactly what its title implies—the spheres, their natures, and their history in human thought — not the theories of impetus or inertia." But to explain again for Deor and the hard of understanding, the theory of impetus deals exactly with the natures of the spheres, namely whether they are animistic or mechanistic, driven by inner animate souls or by angels or by inanimate forces in their natures.
For a 'scholarly' precedent in the inclusion of discussion of the issue of impetus dynamical explanations of the motions of the celestial spheres in discussions of the medieval physics of the spheres, Deor may wish to consult that American author much favoured by McCluskey, Edward Grant, in his 1996 The Foundations of Modern Science in the Middle Ages. Discussion of Buridan’s impetus mechanics of the spheres is included in its section on the physics of the celestial region ‘The Celestial Region: The causes of celestial motion.’ on page 112.-- Logicus ( talk) 16:14, 27 June 2008 (UTC)
Logicus restores Deor deletion: Deor has unjustifiably deleted this restoration on the patently invalid ground it is unsourced, and with the bogus objection of no consensus on the Talk page. If such expressed consensus were required, there would be virtually no articles.-- 158.143.135.0 ( talk) 18:02, 28 June 2008 (UTC)
Logicus's restoration is as follows:
Parisian impetus dynamics and the spheres
In the 14th century the logician and natural philosopher Jean Buridan, Rector of Paris University, subscribed to the Avicennan variant of Aristotelian impetus dynamics according to which impetus is conserved forever in the absence of any resistance to motion, rather than being evanescent and self-decaying as in the Hipparchan variant. In order to dispense with the need for positing continually moving intelligences or souls in the celestial spheres, which he pointed out are not posited by the Bible, Buridan applied the Avicennan self-conserving impetus theory to their endless rotation by extension of a terrestrial example of its application to rotary motion in the form of a rotating millwheel that continues rotating for a long time after the originally propelling hand is withdrawn, driven by the impetus impressed within it.[ref>See p112 of Edward Grant's 1996 The Foundations of Modern Science in the Middle Ages for his account of Buridan's application of impetus dynamics to celestial motion.[/ref>[ref>According to Buridan's theory impetus acts in the same direction or manner in which it was created, and thus a circularly or rotationally created impetus acts circularly thereafter.</ref> Earlier Franciscus de Marchia had given a partial impetus dynamics account of celestial motion in the form of the sphere’s angel continually impressing impetus in its sphere whereby it was moved directly by impetus and only indirectly by its moving angel.[ref>See p112 The Foundations of Modern Science in the Middle Ages Edward Grant 1996</ref>This hybrid mechanico-animistic explanation was necessitated by the fact that de Marchia only subscribed to the Hipparchan-Philoponan impetus theory in which impetus is self-dissipating rather than self-conserving, and thus would not last forever but need constant renewal even in the absence of any resistance to motion.
Buridan wrote on the impetus of the celestial spheres as follows:
However, having discounted the possibility of any resistance due to a contrary inclination to move in any opposite direction and due to any external resistance, Buridan obviously also discounted any inherent resistance to motion in the form of an inclination to rest within the spheres themselves, such as the inertia posited by Averroes and Aquinas. And in fact contrary to that inertial variant of Aristotelian dynamics, according to Buridan "prime matter does not resist motion". But this then raises the question within Aristotelian dynamics of why the motive force of impetus does not therefore move them with infinite speed. The impetus dynamics answer seemed to be that it was a secondary kind of motive force that produced uniform motion rather than infinite speed, just as it seemed Aristotle had supposed the planets' moving souls do, or rather than uniformly accelerated motion like the primary force of gravity did by producing increasing amounts of impetus. -- 158.143.135.0 ( talk) 18:04, 28 June 2008 (UTC)
I have restored the pre 4 May paragraph 2 because subsequent edits have introduced error and confusion. See my critical comments on the subsequent version in square brackets as follows:
"The spheres were said to surround the earth [No, not the heliocentric spheres of Copernicus -- Logicus ( talk) 19:22, 10 July 2009 (UTC)], which was understood to be spherical, stationary, and at the center of the universe.[Not the heliocentric spheres-- Logicus ( talk) 19:22, 10 July 2009 (UTC)] [1] The spheres were typically in this order up from the earth: Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn, and fixed stars. Medieval Christians identified the sphere of stars with the Biblical firmament and sometimes posited an invisible layer of water above the firmament, to accord with Genesis. [1] A tenth sphere [But there were dozens of spheres, not merely ten. -- Logicus ( talk) 19:22, 10 July 2009 (UTC)], inhabited by angels, appeared in some accounts. [1] The order of the lower planets was not universally agreed. Because Venus and Mercury orbit closer to the sun than earth, their positions in the sky are always near the sun.[This is an unintelligible explanation of their bounded elongation-- Logicus ( talk) 19:22, 10 July 2009 (UTC)] The celestial sphere model doesn't explain this phenomenon [Wrong, it did explain their bounded elongation-- Logicus ( talk) 19:22, 10 July 2009 (UTC)], and scholars disagreed on the positions of Mercury and Venus. Plato and his followers ordered them Moon, Sun, Mercury, Venus, and then followed the standard model for the upper spheres. [2] Ptolemy placed both of them beneath the Sun and with Venus beneath Mercury, but noted others placed them both above the Sun, and some even on either side of the Sun, as Alpetragius came to do. "
I've been looking at the literature on this topic lately, and I've found that there appears to be a tendency, especially among historians of science, to treat this topic under the title of Celestial orbs rather than Celestial spheres. It might be worthwhile to change the title of this article; this change would also have the advantage of avoiding confusion with the modern concept of the Celestial sphere.
Before undertaking such a change (which should involve careful editing to achieve consistent terminology within the article as well), I'd like to here comments on this idea. -- SteveMcCluskey ( talk) 20:33, 7 September 2009 (UTC)
The replacement text introduced by McCluskey on 7/09/09is both wrong about the number of spheres and thus about their order, and also loses important informational detail in the original. And the sentence about medieval Christian spherist cosmology is a detail that really belongs to the section on the middle ages.
So I propose to restore an improved version of the original text, but incorporating the Eastwood reference supplied by McCluskey. I move the medieval Christian sentence to the medieval section.
For reference McCluskey's text was as follows:
"In geocentric models the spheres were said to surround the earth, which was understood to be spherical, stationary, and at the center of the universe.[2] The spheres were typically in this order up from the earth: Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn, and fixed stars. Medieval Christians identified the sphere of stars with the Biblical firmament and sometimes posited an invisible layer of water above the firmament, to accord with Genesis.[2] A tenth sphere, inhabited by angels, appeared in some accounts.[2] The order of the lower planets was not universally agreed; Plato and his followers ordered them Moon, Sun, Mercury, Venus, and then followed the standard model for the upper spheres.[3]"
-- Logicus ( talk) 18:08, 9 September 2009 (UTC)
The section on the Renaissance begins with a discussion of the Copernicus's understanding of the physical spheres and ends with their abandonment by Kepler, but the bulk of the section is concerned principally with the positional and geometrical astronomy of the planets. Indicative of this approach are two figures displaying the geoheliocentric models of Paul Wittich and Ursus, neither of which discuss three dimensional, physical planetary spheres. This material might fit better in the article on the Copernican revolution. -- SteveMcCluskey ( talk) 19:43, 7 October 2009 (UTC)
When Newton used the mathematical procedure described in the article to compute the force of the Moon from the center, he was not basing them on the Lunar orb. He imagined that a square circumscribes the circular path of the Moon, and on that basis computed the central force. (Westfall, Never at Rest, pp. 148-50) -- SteveMcCluskey ( talk) 20:08, 7 October 2009 (UTC)
![]() | This is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
Archive 1 | Archive 2 | Archive 3 |
Logicus proposes:I shall now restore the section on impetus dynamics previously deleted by user Deor without any good reason, but for which deletion Deor has provided no valid justification, but rather to the contrary a justification that entails it definitely must be included.(See above) Deor claimed "The article should deal with exactly what its title implies—the spheres, their natures, and their history in human thought — not the theories of impetus or inertia." But to explain again for Deor and the hard of understanding, the theory of impetus deals exactly with the natures of the spheres, namely whether they are animistic or mechanistic, driven by inner animate souls or by angels or by inanimate forces in their natures.
For a 'scholarly' precedent in the inclusion of discussion of the issue of impetus dynamical explanations of the motions of the celestial spheres in discussions of the medieval physics of the spheres, Deor may wish to consult that American author much favoured by McCluskey, Edward Grant, in his 1996 The Foundations of Modern Science in the Middle Ages. Discussion of Buridan’s impetus mechanics of the spheres is included in its section on the physics of the celestial region ‘The Celestial Region: The causes of celestial motion.’ on page 112.-- Logicus ( talk) 16:14, 27 June 2008 (UTC)
Logicus restores Deor deletion: Deor has unjustifiably deleted this restoration on the patently invalid ground it is unsourced, and with the bogus objection of no consensus on the Talk page. If such expressed consensus were required, there would be virtually no articles.-- 158.143.135.0 ( talk) 18:02, 28 June 2008 (UTC)
Logicus's restoration is as follows:
Parisian impetus dynamics and the spheres
In the 14th century the logician and natural philosopher Jean Buridan, Rector of Paris University, subscribed to the Avicennan variant of Aristotelian impetus dynamics according to which impetus is conserved forever in the absence of any resistance to motion, rather than being evanescent and self-decaying as in the Hipparchan variant. In order to dispense with the need for positing continually moving intelligences or souls in the celestial spheres, which he pointed out are not posited by the Bible, Buridan applied the Avicennan self-conserving impetus theory to their endless rotation by extension of a terrestrial example of its application to rotary motion in the form of a rotating millwheel that continues rotating for a long time after the originally propelling hand is withdrawn, driven by the impetus impressed within it.[ref>See p112 of Edward Grant's 1996 The Foundations of Modern Science in the Middle Ages for his account of Buridan's application of impetus dynamics to celestial motion.[/ref>[ref>According to Buridan's theory impetus acts in the same direction or manner in which it was created, and thus a circularly or rotationally created impetus acts circularly thereafter.</ref> Earlier Franciscus de Marchia had given a partial impetus dynamics account of celestial motion in the form of the sphere’s angel continually impressing impetus in its sphere whereby it was moved directly by impetus and only indirectly by its moving angel.[ref>See p112 The Foundations of Modern Science in the Middle Ages Edward Grant 1996</ref>This hybrid mechanico-animistic explanation was necessitated by the fact that de Marchia only subscribed to the Hipparchan-Philoponan impetus theory in which impetus is self-dissipating rather than self-conserving, and thus would not last forever but need constant renewal even in the absence of any resistance to motion.
Buridan wrote on the impetus of the celestial spheres as follows:
However, having discounted the possibility of any resistance due to a contrary inclination to move in any opposite direction and due to any external resistance, Buridan obviously also discounted any inherent resistance to motion in the form of an inclination to rest within the spheres themselves, such as the inertia posited by Averroes and Aquinas. And in fact contrary to that inertial variant of Aristotelian dynamics, according to Buridan "prime matter does not resist motion". But this then raises the question within Aristotelian dynamics of why the motive force of impetus does not therefore move them with infinite speed. The impetus dynamics answer seemed to be that it was a secondary kind of motive force that produced uniform motion rather than infinite speed, just as it seemed Aristotle had supposed the planets' moving souls do, or rather than uniformly accelerated motion like the primary force of gravity did by producing increasing amounts of impetus. -- 158.143.135.0 ( talk) 18:04, 28 June 2008 (UTC)
I have restored the pre 4 May paragraph 2 because subsequent edits have introduced error and confusion. See my critical comments on the subsequent version in square brackets as follows:
"The spheres were said to surround the earth [No, not the heliocentric spheres of Copernicus -- Logicus ( talk) 19:22, 10 July 2009 (UTC)], which was understood to be spherical, stationary, and at the center of the universe.[Not the heliocentric spheres-- Logicus ( talk) 19:22, 10 July 2009 (UTC)] [1] The spheres were typically in this order up from the earth: Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn, and fixed stars. Medieval Christians identified the sphere of stars with the Biblical firmament and sometimes posited an invisible layer of water above the firmament, to accord with Genesis. [1] A tenth sphere [But there were dozens of spheres, not merely ten. -- Logicus ( talk) 19:22, 10 July 2009 (UTC)], inhabited by angels, appeared in some accounts. [1] The order of the lower planets was not universally agreed. Because Venus and Mercury orbit closer to the sun than earth, their positions in the sky are always near the sun.[This is an unintelligible explanation of their bounded elongation-- Logicus ( talk) 19:22, 10 July 2009 (UTC)] The celestial sphere model doesn't explain this phenomenon [Wrong, it did explain their bounded elongation-- Logicus ( talk) 19:22, 10 July 2009 (UTC)], and scholars disagreed on the positions of Mercury and Venus. Plato and his followers ordered them Moon, Sun, Mercury, Venus, and then followed the standard model for the upper spheres. [2] Ptolemy placed both of them beneath the Sun and with Venus beneath Mercury, but noted others placed them both above the Sun, and some even on either side of the Sun, as Alpetragius came to do. "
I've been looking at the literature on this topic lately, and I've found that there appears to be a tendency, especially among historians of science, to treat this topic under the title of Celestial orbs rather than Celestial spheres. It might be worthwhile to change the title of this article; this change would also have the advantage of avoiding confusion with the modern concept of the Celestial sphere.
Before undertaking such a change (which should involve careful editing to achieve consistent terminology within the article as well), I'd like to here comments on this idea. -- SteveMcCluskey ( talk) 20:33, 7 September 2009 (UTC)
The replacement text introduced by McCluskey on 7/09/09is both wrong about the number of spheres and thus about their order, and also loses important informational detail in the original. And the sentence about medieval Christian spherist cosmology is a detail that really belongs to the section on the middle ages.
So I propose to restore an improved version of the original text, but incorporating the Eastwood reference supplied by McCluskey. I move the medieval Christian sentence to the medieval section.
For reference McCluskey's text was as follows:
"In geocentric models the spheres were said to surround the earth, which was understood to be spherical, stationary, and at the center of the universe.[2] The spheres were typically in this order up from the earth: Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn, and fixed stars. Medieval Christians identified the sphere of stars with the Biblical firmament and sometimes posited an invisible layer of water above the firmament, to accord with Genesis.[2] A tenth sphere, inhabited by angels, appeared in some accounts.[2] The order of the lower planets was not universally agreed; Plato and his followers ordered them Moon, Sun, Mercury, Venus, and then followed the standard model for the upper spheres.[3]"
-- Logicus ( talk) 18:08, 9 September 2009 (UTC)
The section on the Renaissance begins with a discussion of the Copernicus's understanding of the physical spheres and ends with their abandonment by Kepler, but the bulk of the section is concerned principally with the positional and geometrical astronomy of the planets. Indicative of this approach are two figures displaying the geoheliocentric models of Paul Wittich and Ursus, neither of which discuss three dimensional, physical planetary spheres. This material might fit better in the article on the Copernican revolution. -- SteveMcCluskey ( talk) 19:43, 7 October 2009 (UTC)
When Newton used the mathematical procedure described in the article to compute the force of the Moon from the center, he was not basing them on the Lunar orb. He imagined that a square circumscribes the circular path of the Moon, and on that basis computed the central force. (Westfall, Never at Rest, pp. 148-50) -- SteveMcCluskey ( talk) 20:08, 7 October 2009 (UTC)