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	Models of Planetary Motion -- McConnell
		This motion is uniform in every way--the speed of the yellow object along the circle is uniform, the circle shares a center with the earth, the object sweeps out equal angles in equal times.
		The motion of the green object is perfectly uniform, though it will appear nonuniform to an observer on earth because the earth does not coincide with the center of the motion.
		For Copernicus, the apparent retrograde motion of the planets is a result of the relative speeds of the earth and the planets as observed from the earth:
	faculty.fullerton.edu /cmcconnell/Planets.html (1465 words)

	[No title]
		According to Aristotle, the natural motion of the terrestrial elements w as rectilinear, whereas the natural motion of the celestial element was circular.
		However, his insistence on uniform circular motion for the planets caused his model to be as complicated as Ptolemy's in the sense that it employed upwards of thirty circles (compared to Ptolemy's seventy or so) to reproduce the observed motions of the planets.
		The motion had to be relative to the position of the Sun and concluded that there was one force from the Sun that moved the planets around it, with the planets c loser to the Sun moving faster than the ones farther out.
	www.math.rutgers.edu /courses/436/Honors02/kepler.html (5251 words)

	Astronomy & Astrology - Astronomy, History of
		In ancient times, people imagined that celestial events, especially the planetary motions, were connected with their own fortunes.
		In addition, to account for solar, lunar, and planetary motions, he assumed that inside the star sphere were many interconnected transparent spheres that revolved in various ways.
		Analyses of planetary and stellar spectra have demonstrated that heavenly bodies are composed of the same chemical elements known on earth.
	www.angelfire.com /realm/shades/horoscopes/aastronomyhist.htm (4596 words)

	Lecture 4, Part 2: Planetary Motions (Site not responding. Last check: 2007-10-11)
		The east to west motion is known as retrograde motion.
		Retrograde motion is observed for all the planets.
		Unlike the observed motions of the Sun and Moon, retrograde motion of the planets is difficult to explain in a Geocentric Universe.
	www-astronomy.mps.ohio-state.edu /~monier/Ast161/Unit1/planetary.html (521 words)

	Article: Astrology And Human Life - Rayudu Astrology
		Constant motion of planets and the tremendous impact of their rays on the sensory nerves of the human body is responsible for multi fold changes in human behavior mental make up thought conduct health and everything that matters.
		As the planetary vibrations of varying character are continuously exerting an influence, which is taken up by are sensory nerves with the resulting bodily reactions mental attitudes, and minds.
		It is but common sense to say that the planetary positions of the Sun and the Moon which affect the sea water causing tides are bound to affect all the store of fluids on the surface of the earth or contained in vegetable kingdom or in human beings.
	webpages.charter.net /rayudu/human.htm (4531 words)

	The Tychonian planetary model
		The Tychonian planetary model, conceived by Tycho around 1583, was an unconvincing attempt to reintroduce geocentrism in the Copernican planetary system.
		From the standpoint of apparent planetary motions as seen from Earth, this system is observationally indistinguishable from the Copernican model, yet maintains the fixity of the Earth.
		The latter belief was held by Tycho to the end of his life, largely because he had been unable to detect the annual parallax of the fixed stars predicted by the Copernican model, despite the unprecedented accuracy of the observations carried out with his giant instruments at Uraniborg.
	www.hao.ucar.edu /Public/education/bios/tycho.4.html (227 words)

	Physics Today February 2004 - Hooke and Newton: Divining Planetary Motions
		To appreciate the importance of Hooke's contribution to planetary motion, which he communicated to Newton during a correspondence in the autumn of 1679, one must understand not only Hooke's views, described at length in Gal's book, but also Newton's own knowledge of the subject at the time.
		For example, Hooke reached his views of planetary motion by analyzing the motion of a conical pendulum, as he explained in detail in a 1666 lecture given at the Royal Society of London.
		The theory of planetary motions was not "divined" by Newton, but should be recognized as a remarkable joint scientific achievement of Newton and Hooke.
	www.aip.org /pt/vol-57/iss-2/p13.html (804 words)

	World Almanac for Kids
		He believed that motions in the sky could be explained by the hypothesis that the earth turns on its axis once every 24 hours and, along with the other planets, revolves around the sun.
		To explain the periodic variations in the speed of the sun and moon and the retrogressions of the planets, they postulated that each of these bodies revolved uniformly around a second circle, called an epicycle, the center of which was situated on the first.
		Improved telescopes permitted the scanning of planetary surfaces, the discovery of many faint stars, and the measurement of stellar distances.
	www.worldalmanacforkids.com /explore/space/astronomy.html (4098 words)

	The Planet Mars: A History of Observation and Discovery. Chapter 1: Motions of Mars. University of Arizona Press.
		Unfortunately, uniform motion around simple circles did not account for the complicated movements the Greeks actually observed, and they faced the problem of "saving the phenomena"---showing how the observed movements could be reconciled with their principle of uniform circular motions.
		Since the apparent motion of the Sun---actually a reflection of the Earth's orbital motion---is variable during the year, it is convenient to introduce the concept of the mean Sun, whose position is defined by the average rate of the Sun's annual motion.
		Copernicus referred the planetary motions to the mean Sun rather than to the true Sun, and this forced him to assume that the Earth's orbit had a variable inclination.
	www.uapress.arizona.edu /onlinebks/mars/chap01.htm (4420 words)

	The Galileo Project \| Science \| Ptolemaic System
		Although this construction violated the rule that the Earth was the center of the cosmos and all planetary motions, the displacement was minimal and was considered a slight bending of the rule rather than a violation.
		Thus the annual retrograde motion of the planets (caused, in heliocentric terms by the addition of the Earth's annual motion to the motion of the planet) could roughly be accounted for.
		The excentric and epicycle meant that planetary motions were not exactly centered on the Earth, the center of the cosmos.
	galileo.rice.edu /sci/theories/ptolemaic_system.html (1629 words)

	What Constitutes
		As time progressed and measurements were made of the motions of the planets it became clear that the qualitative model of Pythagoras was unable to predict planetary (or even lunar) motion.
		Again, inaccuracies in the prediction of planetary motions, prompted by the availability of accurate experimental (observational) data thanks to the work of Tycho Brahe, prompted Johann Kepler (1571 - 1630) to finally abandon Plato's requirement for circular motions and propose a model that was both simple and accurate in its predictions.
		By introducing the notion of forces causing motion, and the force of gravity as the cause of planetary motion, he arrived at a satisfactory theory of planetary motion.
	members.tripod.com /w.g.seeley/Q2Q/good.htm (726 words)

	Solar System Sourcebook: Introduction
		In his work of 1543, Copernicus proposed the idea that planetary motions are centered on the Sun rather than o n the Earth, but he retained the description of planetary motions as being a series of superimposed circular motions, mathematically equivalent to the Ptolemaic theory.
		During the 17th century a German mathematician by the name of Johannes Kepler abandoned his forebears' concept of circular motion in favor of an elliptical scheme, in which the motions of the planets describe a simple series of ellipses in which the Sun i s at one of the foci.
		In the 19th century planetary astronomy flourished, thanks to the construction of large telescopes and their syst ematic use for planetary observations.
	library.thinkquest.org /12857/intro.html (1820 words)

	Planetary Motion and the Laws of
		Copernicus found a natural explanation for these features of planetary motion by using a heliocentric model, in which all planets, including the Earth, are orbiting the Sun: Assuming that Mercury and Venus orbit the Sun inside the Earth's orbit (calling them inferior planets, their positions must necessarily be restricted to the vicinity of the Sun.
		He investigated the motion of bodies in free fall, the movements of a pendulum and the acceleration of objects on an inclined plane, finding that the distance they cover increases as the square of the time.
		The consequence of the first law for planetary motion is, that there is no force causing the planets to move along their orbits, but rather a force pulling them out of their straight motion into a closed path, that is a central force.
	www.uni-sw.gwdg.de /~derek/ASTR1020/planetary.html (2350 words)

	Newswise
		A team of planetary scientists and physicists has identified a tiny, unexplained sunward acceleration in the motions of the Pioneer 10, 11 and Ulysses spacecraft.
		The accelerations are so persistent that they could be pointing to some relevant physics that's been overlooked in trying to explain the motions of bodies in the universe.
		This led him to consider how well we understand gravity's influence on normal matter and whether studies of the motions of comets or spacecraft could be used to identify any deviations from the expected influence of gravity.
	www.newswise.com /articles/view/?id=ODDMOVE.LAL (879 words)

	Science 122 Program 11 Kepler’s Laws
		State Kepler's laws of planetary motion and use them to describe the motion of the planets around the sun.
		The planetary motions are describable in geometric terms, even if they were different terms that the ancients thought.
		We saw that Kepler's laws of motion advanced a heliocentric view, but with the planets moving in elliptical rather than circular orbits, with the sun at a focus rather than at the center, sweeping out equal areas in equal times, and having all the same relationship between period and distance.
	honolulu.hawaii.edu /distance/sci122/Programs/p11/p11.html (3739 words)

	Countrybookshop.co.uk - Planetary Motions
		The one thing connecting all of these physical concepts is the desire of the great scientists of the past to understand the motion of the planets of the solar system.
		"Planetary Motions" enables students to understand how the discoveries of the Scientific Revolution affect the way physics is practiced today.
		"Planetary Motions" is an ideal introduction for students studying physics and astronomy and who need to understand the history and nature of the scientific enterprise.
	www.countrybookshop.co.uk /books/index.phtml?whatfor=031333241X (250 words)

	Week 8 Readings (Site not responding. Last check: 2007-10-11)
		The immense globe of the sun, focus of the principal planetary motions, turns on itself in twenty-five and a half days; its surface is covered with an ocean of luminous material whose lively effervescence forms varying spots, often quite numerous and sometimes larger than the earth.
		To obtain an estimate of the probability of such a cause, we remark that the planetary system as it is known today, comprises seven [planets] and fourteen satellites; we have observed the rotation of the sun, of five planets, of the moon, the ring of Saturn and one of his moons.
		In fact, the absolute movement of the molecules of a planet ought then to be in the direction of the motion of its center of gravity; but it does not at all follow that the motion of the rotation of the planets should be in the same direction as that of the orbital motion.....
	eee.uci.edu /clients/bjbecker/ExploringtheCosmos/week8c.html (1870 words)

	Planetary - definition from Biology-Online.org
		Of or pertaining to the planets; as, planetary inhabitants; planetary motions; planetary year.
		Planetary days, the days of the week as shared among the planets known to the ancients, each having its day.
		Planetary nebula, a nebula exhibiting a uniform disk, like that of a planet.
	www.biology-online.org /dictionary/Planetary (145 words)

	International Catholic University: 23.4
		He asked himself: 'If the sun is indeed the origin and source of planetary motions, then how does this fact manifest itself in the motions of the planets themselves?' He found that Mars moves a little faster when it is nearer to the sun and a little slower when it is further from the sun.
		He continued his work on the planetary orbits, and established a relation between the period of the planet and its mean distance from the sun: the square of the former is proportional to the cube of the latter.
		Galileo also studied the motion of projectiles, and found that their trajectories are parabolae, so that the range is a maximum when the angle of elevation of the gun is 45°.
	home.comcast.net /~icuweb/c02304.htm (5549 words)

	ASTR 121, O'CONNELL. Study Guide 4 [Spring 2004]
		Lecture 3 was the motion of the five bright planets.
		These motions are a combination of the effects of observing from a moving platform (as in the motions discussed in Lecture 3) and intrinsic movement of the planets themselves in their orbits around the Sun.
		The general motion of the planets with respect to the stars is eastward in the sky.
	www.astro.virginia.edu /class/oconnell/astr121/guide4-s99.html (1600 words)

	Planetary Motions (Site not responding. Last check: 2007-10-11)
		In their apparent motions across our sky, the planets behave somewhat like the Sun, but their motions are more complex.
		However, some show retrograde motion for short periods of time, as the Earth over takes and passes them in our journey around the Sun.
		Because the planets are all moving in their orbits at the same time we are, their positions in our sky are constantly changing.
	astrosun.tn.cornell.edu /academics/courses/astro201/planet_motions.htm (175 words)

	Planetary Software: Planetary Dreamscapes 1, Planetary Defense, Lucky Days, ...
		Planetary Dreamscapes 1 Featuring eleven amazing scenes to choose from, six musical compositions to set the mood, blazing stars, swirling nebula, and galactic vista await you as we bring you spectacular images from deep space, both real and imagined.
		Planetary Defense is a space strategy game where you take charge of a planets defenses against waves of attacking aliens.
		The calculation of the positions of the satellites of Jupiter, Saturn, and Uranus is done by the various analytic theories given in the Explanatory Supplement to the Astronomial Almanac.
	www.criticalfiles.com /free/planetary (637 words)

	Astronomy@Kirkwood IC: Supplemental Notes--Renaissance Astronomy
		While planetary motions were simplified, Copernicus actually complicated the lives of natural philosophers trying to unravel the mysteries of Earthly dynamics: namely, why we don't feel Earth's rotation and why objects thrown into the air are not left behind by a moving Earth.
		At the time, the most widely accepted theory of motion was the impetus theory—a concept that had been around for 200 years and shared its roots with the teachings of Aristotle.
		Contrary to the impetus theory—in which an object remains in motion only until its impetus was used up, Galileo theorized that an object set in motion would continue in a state of motion forever or until something acted upon it.
	www.avalon.net /~bstuder/added_notes2.html (1636 words)

	Planetary Motions
		By watching the apparent motion, change in distance, and change in phase of these two planets, we can see that many different effects are explained by the one basic idea that all planets orbit the Sun.
		While Venus appears in about the same place in the sky each evening, its motion with respect to the distant stars is quite rapid; we will use a circular all-sky chart.
		Your report should contain an introduction to the problem of planetary motion, a brief section on equipment used, a description of your observations collecting all relevant measurements and plots, and a section describing your conclusions.
	www.ifa.hawaii.edu /~barnes/ASTR110L_F05/planetmotion.html (1221 words)

	systemic
		For a real planetary system orbiting a real star, it can take years for enough confirming observations to be made, and so it’s useful to have as many criteria as possible for evaluating whether a particular fit is a contender.
		In Laplace’s model, the solar system is completely stable, and the inherent predictability of his planetary motions contributed to the concept of a rational determinism, and the idea of a clockwork universe.
		In the Fall of 2002, however, the planetary interpretation for the Gamma Cephei radial velocity variations was revived by Hatzes et al.
	www.oklo.org (12157 words)

	Planetary Motions · Astrological definition of Planetary Motions · Astrology Encyclopedia
		The term is frequently employed in a contradictory manner, in the sense of the reverse of the accustomed motion.
		In Primary Directions the apparent motion of the planets and the House-cusps is clockwise, resulting from the counter-clockwise motion of the Earth's periphery.
		The apparent diurnal motion of the heavens, in consequence of the Earth's axial rotation; the manner in which the fixed stars and the planetary bodies are caused to make one complete revolution in 24 hours, is termed their Rapt Motion, in accordance with the ancient theory of the Primum Mobile (q.v.).
	www.astrologyweekly.com /dictionary/planetary-motions.php (1045 words)

	Spacing of the Planets (PREFACE of the Book) by Alex Scarborough
		His valuable discoveries proved essential in deriving and proving the new "energy fuels" theory of 1973, a concept that seems destined to displace the "fossil fuels" hypothesis before the turn of the century.
		Strangely, the fallacy of the "fossil fuels" theory was the spark that eventually flamed into the discovery of the proposed Fourth Law of Planetary Motion.
		The proposed Fourth Law of Planetary Motion proved to be the final grand piece that ties everything together in the big jigsaw picture puzzle.
	www.outcrybookreview.com /PlanetaryMotion2.htm (651 words)

	Almagest Planetary Model Animations
		this version if you are using Netscape), wherein the motion is on a concentric deferent but is uniform with respect to an offset point (the equant).
		The animation shows that the concentric equant is equivalent to either an eccentre with varying eccentricity or an epicycle with varying radius.
		A comparison of Kepler motion and equant motion (or use this version if you are using Netscape).
	www.csit.fsu.edu /~dduke/models (1052 words)

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