350:: fire, water, air, and earth. Corruptible elements were only contained in the sublunary region and incorruptible elements were in the superlunary region of Aristotle's geocentric model. Aristotle had the notion that celestial orbs must exhibit celestial motion (a perfect circular motion) that goes on for eternity. He also argued that the behavior and property follows strictly to a principle of natural place where the quintessential element moves freely of divine will, while other elements, fire, air, water and earth, are corruptible, subject to change and imperfection. Aristotle's key concepts rely on the nature of the five elements distinguishing the Earth and the Heavens in the astronomical reality, taking Eudoxus's model of separate spheres.
376:. Aristotle emphasized that the speed of the celestial orbs is unchanging, like the heavens, while Eudoxus emphasized that the orbs are in a perfect geometrical shape. Eudoxus's spheres would produce undesirable motions to the lower region of the planets, while Aristotle introduced unrollers between each set of active spheres to counteract the motions of the outer set, or else the outer motions will be transferred to the outer planets. Aristotle would later observe "...the motions of the planets by using the combinations of nested spheres and circular motions in creative ways, but further observations kept undoing their work".
551:
42:
1083:
1107:
1059:
1095:
1071:
305:+23° 30' 05.5". Implied in this position is that it is as projected onto the celestial sphere; any observer at any location looking in that direction would see the "geocentric Moon" in the same place against the stars. For many rough uses (e.g. calculating an approximate phase of the Moon), this position, as seen from the Earth's center, is adequate.
342:' theory, Aristotle had described celestial bodies within the Celestial sphere to be filled with pureness, perfect and quintessence (the fifth element that was known to be divine and purity according to Aristotle). Aristotle deemed the Sun, Moon, planets and the fixed stars to be perfectly concentric spheres in a superlunary region above the
387:
preventing the downward movement from natural causes. Aristotle criticized
Empedocles's model, arguing that all heavy objects go towards the Earth and not the whirl itself coming to Earth. He ridiculed it and claimed that Empedocles's statement was extremely absurd. Anything that defied the motion of
227:
Conversely, observers looking toward the same point on an infinite-radius celestial sphere will be looking along parallel lines, and observers looking toward the same great circle, along parallel planes. On an infinite-radius celestial sphere, all observers see the same things in the same direction.
353:
Numerous discoveries from
Aristotle and Eudoxus (approximately 395 B.C. to 337 B.C.) have sparked differences in both of their models and sharing similar properties simultaneously. Aristotle and Eudoxus claimed two different counts of spheres in the heavens. According to Eudoxus, there were only 27
602:
Observers on other worlds would, of course, see objects in that sky under much the same conditions – as if projected onto a dome. Coordinate systems based on the sky of that world could be constructed. These could be based on the equivalent "ecliptic", poles and equator, although the reasons for
337:
that outlined the natural order and structure of the world. Like other Greek astronomers, Aristotle also thought the "...celestial sphere as the frame of reference for their geometric theories of the motions of the heavenly bodies". With his adoption of
320:
coordinates, that is, as seen from a particular place on the Earth's surface, based on the geocentric position. This greatly abbreviates the amount of detail necessary in such almanacs, as each observer can handle their own specific circumstances.
266:
of any particular observer, and the utility of the celestial sphere is maintained. Individual observers can work out their own small offsets from the mean positions, if necessary. In many cases in astronomy, the offsets are insignificant.
523:
did away with the planetary spheres, but it did not necessarily preclude the existence of a sphere for the fixed stars. The first astronomer of the
European Renaissance to suggest that the stars were distant suns was
532:(1584). This idea was among the charges, albeit not in a prominent position, brought against him by the Inquisition. The idea became mainstream in the later 17th century, especially following the publication of
887:
432:, respectively. As the celestial sphere is considered arbitrary or infinite in radius, all observers see the celestial equator, celestial poles, and ecliptic at the same place against the
515:
in the mid 5th century BC was the first known philosopher to suggest that the stars were "fiery stones" too far away for their heat to be felt. Similar ideas were expressed by
235:) will seem to change position against the distant celestial sphere if the observer moves far enough, say, from one side of planet Earth to the other. This effect, known as
383:
gave an explanation that the motion of the heavens, moving about it at divine (relatively high) speed, puts the Earth in a stationary position due to the
354:
spheres in the heavens, while there are 55 spheres in
Aristotle's model. Eudoxus attempted to construct his model mathematically from a treatise known as
580:
of a sphere, resulting in a mirror image of the constellations as seen from Earth. The oldest surviving example of such an artifact is the globe of the
487:
The ancient Greeks assumed the literal truth of stars attached to a celestial sphere, revolving about the Earth in one day, and a fixed Earth. The
891:
439:
From these bases, directions toward objects in the sky can be quantified by constructing celestial coordinate systems. Similar to geographic
1012:
576:
A celestial sphere can also refer to a physical model of the celestial sphere or celestial globe. Such globes map the constellations on the
766:
U.S. Naval
Observatory Nautical Almanac Office, Nautical Almanac Office; U.K. Hydrographic Office, H.M. Nautical Almanac Office (2008).
765:
1127:
597:
534:
329:
Celestial spheres (or celestial orbs) were envisioned to be perfect and divine entities initially from Greek astronomers such as
1024:
920:
775:
511:
challenge: "By the assumption of what uniform and orderly motions can the apparent motions of the planets be accounted for?"
460:
519:. However, they did not enter mainstream European and Islamic astronomy of the late ancient and medieval period. Copernican
17:
239:, can be represented as a small offset from a mean position. The celestial sphere can be considered to be centered at the
1037:
950:
346:. Aristotle had asserted that these bodies (in the superlunary region) are perfect and cannot be corrupted by any of the
408:
on Earth, when projected onto the celestial sphere, form the bases of the reference systems. These include the Earth's
259:
451:
specifies positions relative to the celestial equator and celestial poles, using right ascension and declination. The
985:
958:
832:
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natural place and the unchanging heavens (including the celestial spheres) was criticized immediately by
Aristotle.
860:
645:
539:
231:
For some objects, this is over-simplified. Objects which are relatively near to the observer (for instance, the
824:
488:
123:
119:
992:
Bibliography (References) for
Knowledge assignment on Celestial Sphere. (APA6 format). Crowe, M. J. (2001).
974:
Merchant Marine officers' handbook: based on the original edition by Edward A. Turpin and
William A. MacEwen
247:, or any other convenient location, and offsets from positions referred to these centers can be calculated.
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710:
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107:
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to celestial objects, it makes no difference if this is actually the case or if it is Earth that is
542:(1686), and by the early 18th century it was the default working assumptions in stellar astronomy.
463:. Besides the equatorial and ecliptic systems, some other celestial coordinate systems, like the
213:
977:
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167:
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positions of objects on the celestial sphere, without the need to calculate the individual
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from each other, will seem to intersect the sphere at a single point, analogous to the
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690:, about the old concept of the celestial sphere to be a material, physical entity.
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models were based, was the first geometric explanation for the "wandering" of the
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or the observer. If centered on the observer, half of the sphere would resemble a
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in the sky without consideration of its linear distance from the observer. The
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For applications requiring precision (e.g. calculating the shadow path of an
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offers no information on their actual distances. All celestial objects seem
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665:
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within it, including that occupied by the observer, can be considered the
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27:
Imaginary sphere of arbitrarily large radius, concentric with the observer
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The celestial sphere can thus be thought of as a kind of astronomical
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628:
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330:
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50:
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444:
429:
420:. At their intersections with the celestial sphere, these form the
279:, and is applied very frequently by astronomers. For instance, the
263:
236:
178:
994:
Theories of the world from antiquity to the
Copernican revolution
492:
409:
309:
964:
972:
MacEwen, William A.; William Hayler; Turpin, Edward A. (1989).
660:
182:
151:
69:
65:
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building a system that way are as much historic as technical.
508:
363:
159:
88:
upon the inner surface of the celestial sphere, which may be
77:
286:
232:
1070:
139:
81:
507:. Eudoxus used 27 concentric spherical solids to answer
138:
are at such remote distances, casual observation of the
1007:
MEASURING THE SKY A Quick Guide to the
Celestial Sphere
285:
for 2010 lists the apparent geocentric position of the
888:"Eudoxus of Cnidus: Astronomy and Homocentric Spheres"
455:
specifies positions relative to the ecliptic (Earth's
1047:
324:
890:. Vignettes of Ancient Mathematics. Archived from
270:
220:will seem to intersect the sphere in a coincident
102:The celestial sphere is a conceptual tool used in
162:underfoot seems to remain still. For purposes of
1119:
467:, are more appropriate for particular purposes.
679:, a type of longer-term motion of distant stars
396:These concepts are important for understanding
391:
316:gives formulae and methods for calculating the
673:, a type of short-term motion of distant stars
730:A Manual of Spherical and Practical Astronomy
708:
368:) and asserted the shape of the hippopede or
177:The celestial sphere can be considered to be
400:, frameworks for measuring the positions of
1025:Interactive Sky Chart – SkyandTelescope.com
584:sculpture, a 2nd-century copy of an older (
768:The Astronomical Almanac for the Year 2010
709:Newcomb, Simon; Holden, Edward S. (1890).
591:
174:while the celestial sphere is stationary.
726:
333:. He composed a set of principles called
939:
908:Early Greek Science: Thales to Aristotle
598:International Celestial Reference System
549:
535:Conversations on the Plurality of Worlds
40:
30:For the ancient cosmological model, see
905:Lloyd, Geoffrey Ernest Richard (1970).
885:
747:
154:with a large but unknown radius, which
14:
1120:
1031:Web Archives (archived 2005-06-13)
1013:General Astronomy/The Celestial Sphere
852:
904:
733:. J.B. Lippincott Co., Philadelphia.
886:Mendell, Henry (16 September 2009).
1009:– Jim Kaler, University of Illinois
951:National Imagery and Mapping Agency
751:A Compendium of Spherical Astronomy
166:, which is concerned only with the
45:Visualization of a celestial sphere
24:
996:. Mineola, NY: Dover Publications.
379:Aside from Aristotle and Eudoxus,
325:Greek history on celestial spheres
118:divides the celestial sphere into
25:
1149:
1000:
856:Practical Astronomy for Engineers
1105:
1093:
1081:
1069:
1057:
1021:– University of Nebraska-Lincoln
946:The American Practical Navigator
876:, art. 2, p. 5, at Google books.
861:E.W. Stephens Publishing Company
491:, on which the Aristotelian and
1128:Astronomical coordinate systems
976:(5th ed.). Cambridge, Md:
898:
879:
715:. Henry Holt and Co., New York.
646:Equinox (celestial coordinates)
540:Bernard Le Bovier de Fontenelle
530:De l'infinito universo et mondi
461:ecliptic longitude and latitude
271:Determining location of objects
846:
837:
825:Johns Hopkins University Press
810:
797:
785:
770:. U.S. Govt. Printing Office.
759:
741:
735:chauvenet spherical astronomy.
720:
702:
404:. Certain reference lines and
158:westward overhead; meanwhile,
129:
68:that has an arbitrarily large
13:
1:
1044:– for every location on Earth
933:
853:Seares, Frederick H. (1909).
545:
99:over the observing location.
805:A Short History of Astronomy
619:Equatorial coordinate system
614:Horizontal coordinate system
449:equatorial coordinate system
398:celestial coordinate systems
392:Celestial coordinate systems
289:on January 1 at 00:00:00.00
7:
727:Chauvenet, William (1900).
606:
10:
1154:
754:. Macmillan Co., New York.
595:
561:
480:
474:
470:
465:galactic coordinate system
453:ecliptic coordinate system
364:
84:can be conceived as being
36:Celestial (disambiguation)
29:
843:Newcomb (1906), p. 92-93.
792:Astronomical Almanac 2010
756:, p. 90, at Google books.
738:, p. 19, at Google books.
503:was thought to carry the
499:. The outermost of these
193:. It also means that all
695:
224:(a "vanishing circle").
821:Reconfiguring the World
748:Newcomb, Simon (1906).
592:Bodies other than Earth
489:Eudoxan planetary model
374:planetary retrogression
978:Cornell Maritime Press
913:W. W. Norton & Co.
559:
424:, the north and south
295:equatorial coordinates
46:
34:. For other uses, see
1019:Rotating Sky Explorer
588:, ca. 120 BCE) work.
553:
481:Further information:
214:graphical perspective
150:onto the inside of a
80:. All objects in the
44:
873:practical astronomy.
803:Arthur Berry (1898)
517:Aristarchus of Samos
483:History of astronomy
372:was associated with
335:Aristotelian physics
282:Astronomical Almanac
204:apart or across the
136:astronomical objects
18:Celestial hemisphere
1133:Spherical astronomy
1029:Library of Congress
941:Bowditch, Nathaniel
869:1909pafe.book.....S
651:Spherical astronomy
554:Celestial globe by
164:spherical astronomy
110:the position of an
104:spherical astronomy
1040:2007-09-13 at the
980:. pp. 46–51.
586:Hellenistic period
560:
402:objects in the sky
348:classical elements
47:
922:978-0-393-00583-7
817:Margaret J. Osler
777:978-0-7077-4082-9
501:"crystal spheres"
497:classical planets
422:celestial equator
340:Eudoxus of Cnidus
185:. This means any
156:appears to rotate
116:celestial equator
90:centered on Earth
32:Celestial spheres
16:(Redirected from
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963:. Archived from
949:. Bethesda, MD:
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911:. New York, NY:
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863:, Columbia, MO.
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671:Stellar parallax
639:Equatorial mount
568:Armillary sphere
477:Cosmic pluralism
434:background stars
367:
366:
344:sublunary sphere
291:Terrestrial Time
144:equally far away
59:celestial sphere
21:
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1042:Wayback Machine
1035:Monthly skymaps
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894:on 16 May 2011.
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634:Polar alignment
609:
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572:Celestial globe
562:Main articles:
548:
485:
479:
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426:celestial poles
394:
385:circular motion
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299:right ascension
273:
216:. All parallel
210:vanishing point
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1001:External links
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967:on 2007-06-24.
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526:Giordano Bruno
475:Main article:
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241:Earth's center
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582:Farnese Atlas
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521:heliocentrism
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1112:Solar System
993:
973:
965:the original
945:
915:p. 84.
907:
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892:the original
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848:
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820:
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799:
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666:Orbital pole
601:
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486:
438:
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378:
355:
352:
328:
317:
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301:6 57 48.86,
280:
274:
260:heliocentric
254:can predict
249:
245:Sun's center
230:
226:
222:great circle
206:Solar System
176:
133:
101:
58:
48:
1100:Outer space
1088:Spaceflight
1015:– Wikibooks
688:Fixed stars
505:fixed stars
318:topocentric
303:declination
252:astronomers
202:millimetres
130:Description
1122:Categories
934:References
782:, p. M3-M4
624:Hour angle
596:See also:
564:Star chart
556:Jost Bürgi
546:Star globe
513:Anaxagoras
428:, and the
381:Empedocles
370:lemniscate
365:Περί Ταχών
256:geocentric
200:, be they
168:directions
74:concentric
55:navigation
1064:Astronomy
807:, page 38
712:Astronomy
683:Firmament
629:Pole star
493:Ptolemaic
459:), using
441:longitude
356:On Speeds
331:Aristotle
277:shorthand
86:projected
51:astronomy
1038:Archived
943:(2002).
827:page 15
794:, sec. D
656:Ecliptic
607:See also
445:latitude
430:ecliptic
264:geometry
237:parallax
195:parallel
179:infinite
172:rotating
146:, as if
134:Because
124:southern
120:northern
63:abstract
1138:Spheres
1050:Portals
1027:at the
865:Bibcode
819:(2010)
717:, p. 14
578:outside
528:in his
509:Plato's
471:History
410:equator
314:Almanac
312:), the
310:eclipse
108:specify
72:and is
984:
957:
919:
831:
774:
661:Zodiac
570:, and
558:(1594)
447:, the
416:, and
406:planes
243:, the
218:planes
191:center
183:radius
152:sphere
112:object
97:screen
70:radius
66:sphere
61:is an
57:, the
1076:Stars
696:Notes
457:orbit
418:orbit
360:Greek
297:, as
293:, in
198:lines
187:point
160:Earth
148:fixed
78:Earth
982:ISBN
955:ISBN
917:ISBN
829:ISBN
772:ISBN
443:and
414:axis
287:Moon
233:Moon
122:and
53:and
538:by
258:or
212:of
181:in
140:sky
106:to
82:sky
76:to
49:In
1124::
953:.
871:.
859:.
823:,
566:,
436:.
412:,
362::
1052::
990:.
925:.
867::
780:.
358:(
38:.
20:)
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