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How was Ptolemy's idea of retrograde different from Copernicus' idea of retrograde motion?
Wiki User
∙ 9y ago
We now understand that all the planets travel round the Sun, and a planet's retrograde motion happens as the Earth overtakes the other planet in its orbit. That was also Copernicus's view although we now use Kepler's theory, but on this point the two models are in agreement.
In Ptolemy's model the Earth is stationary in the centre, and the planets move on circles and epicycles, explained as follows.
Using Mars as an example and assuming the orbits of Earth and Mars are circular for simplicity, the Earth is at the centre and there is then a circle (or deferent) round it with a radius of 1.524 units. The epicycle is a smaller circle whose centre travels round the deferent in 687 days. The epicycle has a radius of 1.000 units and Mars travels round this in 365¼ days.
That was Ptolemy's geometric construction to explain the motion of Mars, and the retrograde motion happens when Mars on its epicycle moves close to the Earth.
Wiki User
∙ 9y ago
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What does a planet do when in retrograde motion?
Nothing special. The idea of "retrograde motion" is a trick of perspective; nothing actually goes "retrograde". Here's how it works. We usually talk about Mars when referring to "retrograde" motion, but it happens (to a lesser extent) to all of the outer planets. All the planets orbit the Sun in the same direction (counterclockwise as seen from high above the Earth's north pole). Nothing ever turns and goes the other way. Closer-in planets orbit faster than further-out planets. When Mars goes retrograde, what is really happening is that the Earth is about to overtake Mars in our respective orbits, and move ahead of it. Mars is moving more slowly, and as the Earth passes Mars, Mars SEEMS TO move backwards. It's just as if you were jogging on an inner lane on the track and you pass somebody in an outer lane. The other jogger isn't moving backwards; it just seems that way because you are moving faster, and getting ahead of him.
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What is the difference between oscillating and rotational motion?
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How did Copernicus explain the retrograde motions of the planets?
All the models explain retrograde motion because it is such an obvious phenomenon. In Copernicus's model an outer planet goes into retrograde motion when the inner planet overtakes it so that it appears from the inner planet to be going backwards along the ecliptic.
Why did the model of the universe proposed by Copernicus gain support after its publication?
It was a more elegant explanation of retrograde motion.
The apparent westward movement of a planet is known as?
retrograde motion
Which two planets have Retrograde motion?
Venus and Uranus have retrograde rotation.There are other meanings of retrograde motion, but retrograde rotation fits the question best.
Major advantage of Copernicus' Sun-centered model over the Ptolemaic model?
It offered more natural explanation for the apparent retrograde motion of planets in our sky.
Copernicus ideas that supported his ideas about the sun being at the centre of the Solar System?
he was a polish priest scientist stated retrograde motion occured whenever earth passes around another plant gained acceptance from people had a much simpliar way to explain retrograde motion than Ptolemy
Was retrograde motion a theory?
Retrograde motion describes something by definition. It is not and has never been a theory.
What is the difference between prograde and retrograde?
Prograde motion is a counter-clockwise motion or west to east, retrograde motion is clockwise motion or east to west.
What actors and actresses appeared in Retrograde Motion - 2013?
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When a superior planet is in the middle of its retrograde motion what planetary configuration is it in?
Superior planets are in opposition when in the middle of their retrograde motion.
According to copernicus the retrograde motion for mars must occur?
at opposition when the earth overtakes mars and passes between mars and the sun
Why was retrograde motion important in astronomy?
Retrograde motion important in astronomy because it helped to explain that the planets revolved around the Sun. Retrograde motion is the ability of some objects to rotate in a direction that is opposite what is expected.
