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Retrograde motion is apparent (obvious) in the night skies and even prehistoric people were able to observe this "irregularity". Retrograde motion is documented even in prehistoric-dated carvings, in caves. This motion was a natural phenomenon to them, anyway, rather than an irregularity.

The "evening star" is followed pretty fast (in terms of days) by a "morning star". That's Venus what looks like during its retrograde motion. It's very typical and it happens for long periods of time (in terms of years) during approximately the same solar-calendar day of a season, every 8 years (the "ninth-year" cycle). Setting an example, Venus is going (to be) retrograde in the early spring in (the 21st century: 2001, 2009,) 2017, 2025, 2033, 2041, 2049,... That's inevitable and plain to see, for earth-dwellers! Venus is going to be retrograde in late autumn this year (2010) and this will happen again in 2018, 2026, 2034, 2042, and so on ...

Philosophers and scientists at a later time tried to explain and decipher this phenomenon and proposed some models, like the Epicycles (proposed by Ptolemy). At last, the introduction of the telescope unclouded this mystery, anyway. (Believe me, it has been an experience for me to look for the first time at the four major satellites of Jupiter through a telescope. No human unaided eye can be thus penetrating (magnifying) like a telescope does.)

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What two planets that retrograde motion around the sun?

Mercury and Venus are the two planets that retrograde motion around the sun.


What is the planet that rotates by retrograde motion?

Actually, 3 planets rotate in a retrograde motion, which, by the way, means that they rotate East to West, or in a counterclockwise motion. Most planets rotate in a clockwise direction, or West to East. The three planets that rotate in a retrograde motion are Venus, Uranus and Pluto.venus


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Venus and Uranus have retrograde rotation.There are other meanings of retrograde motion, but retrograde rotation fits the question best.


What is retrograde motion as applied to a planet?

The "apparent" reverse or backwards motion of a planet as observed from Earth. The innermost planets appear to have a retrograde motion when viewed from Earth.


Which planet rotates by retrograde motion?

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The observed retrograde motion of planets led ptolemy to add blank to Aristotles system?

The observed retrograde motion of planets led Ptolemy to add epicycles to Aristotle's system. Epicycles were small circles that planets moved in on their larger circular orbits around Earth in order to explain the appearances of retrograde motion.


Which planet rotate in retrograde motion?

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Did Galileo's observations confirm the validity of retrograde motion of the planets?

No, Ptolemy did.


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.


What planets are retrograde?

As of October 2021, the outer planets Uranus, Neptune, and Pluto are retrograde. Retrograde motion is an apparent backward motion of a planet as seen from Earth, and it can affect us by prompting introspection and reevaluation in the areas of life governed by the planet.


What do the planets do to incur retrograde motion?

The planets don't have to "do anything" to "go into" retrograde motion. The retrograde motion, the "moving backward" that planets do as we watch them cross the night sky over the weeks, is due to the nature of the orbit of a planet and to our view of that orbit from earth.


What is the name given to the phenomenon in which the apparent motion of the planets sometimes reverses?

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