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ptolemy
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∙ 11y ago
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What are epicycles?
an epicycle is a system where things rotate around a fixed point.
Which planets' motions were described with epicycles in the Ptolemaic system?
All the known planets
Purpose of using epicycles and deferents to explain the motion of the planets in the night sky was to account?
retrograde motion
What was the purpose of the epicycle in the Ptolemaic model?
Epicycles helped account for the apparent motion of the other planets in the geocentric model.
How do planets move according to the geocentric model of the universe?
A Geocentric model of the solar system would be where the Earth was at the centre of the system, while the sun and planets revolved around the Earth. We now know this not to be true, since the sun is at the centre of the solar system (Heliocentric).
Who created the idea of epicycles?
copernicus
What did ptolemy invent?
geocentric model & epicycles
Who belived that the planets move in epicycles?
Ptolemy.
Was the geocentric model of Ptolemy based on epicycles and deferents?
Yes it was, because the Greeks believed that the planets must follow the perfect shape, the circle. We now know the planets travel in ellipses, but in those days Ptolemy allowed for that by introducing the idea of epicycles. An epicycle is a small circle whose centre travels round a bigger circle, and the planet travels round the epicycle. A circle and an epicycle is a very accurate model of an ellipse provided the eccentricity factor is small, as it is for most of the planets, which is why it took over 1400 years for this concept to be questioned. A further complication was that the Greeks believed the Earth was at the centre. We now know that the Sun is at the centre, but Ptolemy's model had to allow for the observed effects by introducing extra epicycles. For the inner planets these 'spurious' eipcycles were very large. In the end the Ptolemaic model was very complicated, with 40-50 epicycles altogether.
What are the small circles or rotations of an object called?
epicycles
What were epicycles used to describe?
The retrograde motion of planets
What was ptolemy theory on planets?
The astronomical system of Ptolemy, in which the earth is at the center of the universe with the sun, moon, planets, and stars revolving about it in circular orbits.Ptolemaic system Ptolemy believed that Earth was at the center of the universe and that the Sun and planets orbited Earth (with the planets also moving in smaller circles called epicycles). In this system, the centers of Mercury's and Venus's epicycles always lie on the line shown in the diagram between the Earth and the Sun.
What are epicycles?
an epicycle is a system where things rotate around a fixed point.
Why do planets look like they are moving backwards as we view them from earth?
Their called epicycles
Which planets' motions were described with epicycles in the Ptolemaic system?
All the known planets
The observed retrograde motion of planets led ptolemy to add blank to Aristotles system?
Epicycles
Purpose of using epicycles and deferents to explain the motion of the planets in the night sky was to account?
retrograde motion
