# What planets have epicycles?

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The theory was based upon the idea that those that appeared to move the slowest must be farthest away from Earth. The problem is that the epicycle containing Mercury, the epicycle containing Venus, and the Sun all orbited around the Earth in one year!26‏/10‏/2015

1 in Ptolemaic astronomy : a circle in which a planet moves and which has a center that is itself carried around at the same time on the circumference of a larger circle. 2 : a process going on within a larger one.

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Ensuite, What is epicyclic model?

In mathematics: Applied geometry. Apollonius introduced an alternative “epicyclic” model, in which the planet turns about a point that itself orbits in a circle (the “deferent”) centred at or near Earth. As Apollonius knew, his epicyclic model is geometrically equivalent to an eccentric.

Par ailleurs What does epicyclic motion mean?

An epicyclic gear train (also known as planetary gear) consists of two gears mounted so that the center of one gear revolves around the center of the other. The planet and sun gears mesh so that their pitch circles roll without slip. A point on the pitch circle of the planet gear traces an epicycloid curve.

De plus, Why did Ptolemy introduce the concept of epicycles?

In order to preserve the geocentric cosmology of the time and to account for retrograde motion of Mars, Ptolemy had to make a model of planetary motion that invoked the use of epicycles. An epicycle is basically a little “wheel” that orbits on a bigger wheel.

Why did Ptolemy use epicycles?

In order to preserve the geocentric cosmology of the time and to account for retrograde motion of Mars, Ptolemy had to make a model of planetary motion that invoked the use of epicycles. An epicycle is basically a little “wheel” that orbits on a bigger wheel.

## 38 Questions en relation trouvés

### What is Epicycle model?

In the Hipparchian, Ptolemaic, and Copernican systems of astronomy, the epicycle (from Ancient Greek: ἐπίκυκλος, literally upon the circle, meaning circle moving on another circle) was a geometric model used to explain the variations in speed and direction of the apparent motion of the Moon, Sun, and planets.

### Did Copernicus use epicycles?

While Copernicus’ system does not need epicycles to produce retrograde motion, because of his insistance on uniform circular motion he still had to use them in order to get his model to make accurate predictions (i.e., to “preserve appearances”), particularly to reproduce the non-uniform speeds of the planets.

### Why were epicycles necessary in Ptolemy’s model of the universe?

In an earth-centric model of the universe, epicycles were orbits within orbits used to explain discrepancies between expected and observed planetary movement, including the appearance of planets slowing down, speeding up, and moving backward. Placing the sun in the middle of the universe did not correct this problem.

### What objections did Copernicus have to Ptolemy’s system?

Copernicus rejected the Ptolemaic theory basically because he found it too contrived, reasoning that there had to be a simpler hypothesis which could explain everything to his satisfaction. This sentiment had already been expressed in a remark attributed to Alfonso X (1221-1284), the King of Castille and Leon.

Johannes Kepler

### What is the meaning of Epicycle?

epicycle in American English 1. a circle whose center moves along the circumference of another, larger circle. term used to describe planetary motions in the Ptolemaic system. 2. Geometry.

### What was Ptolemy’s objection?

Scientific Objections to Copernicus: For instance: The heliocentric solar system requires the Earth to rotate on its axis once per day which means that you, at this moment have a speed of about 1 000 mi/hr (= 25 000 mi/24 hr).

### What is the difference between the epicycle and deferent?

is that epicycle is (astronomy) a small circle whose centre is on the circumference of a larger circle; in ptolemaic astronomy it was seen as the basis of revolution of the “seven planets”, given a fixed central earth while deferent is (obsolete) that which carries or conveys.

Ptolemy

### Does Copernicus model use epicycles If yes why are they necessary explain?

Copernicus had two main reasons for asserting that the Sun was the center of our solar system. He knew that this could be explained instead by having the Earth also moving around the Sun. The true motion of the planets around the Sun is not uniform circular motion, so Copernicus’ model still needed to have epicycles.

### What theory did Copernicus disprove?

By placing the sun at the center, Copernicus’s idea overturned the ideas devised by the second-century astronomer Ptolemy. In Ptolemy’s theory the sun and planets orbited the Earth, which was regarded as the orthodox model across the Christian world.

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