Ptolemy

Ptolemy used circles and epicycles for his model.

The basic orbit is a large circle, the deferent. Then there is a smaller circle called an epicycle with its centre going round the deferent, and the planet travels round that epicycle. That is the simplified model that accounts for planets that are, as we now understand, going round the Sun in circular orbits (in a simplified view).

The epicycle is there to allow for the fact that, as we now know, the Sun is at the centre. Ptolemy's aim was to model the planets' positions as seen, and his model does that quite accurately.

Take Venus's orbit, with Venus going round in 225 days compared to the Earth's 365 days. In Ptolemy's model the Earth is fixed, so Venus's deferent is a circle with the centre of the epicycle going round every 365 days. The deferent has a radius of 1.000, let's say, and then the epicycle has a radius of 0.723, a little smaller, with Venus travelling round the epicycle in 225 days. It's a good model of what actually happens, and this is the model that was used in planetariums until the days of computers. We now now that if the Earth's orbit has a mean radius of 1, then Venus's orbit has a radius of 0.723.

Fred Hoyle the astronomer pointed out that the deferent and the epicycle are interchangeable without making any difference to the model (because, he said, addition of complex numbers is commutative) . But by convention the largest one always seems to be called the deferent.

Ptolemy's model represents the movement of Venus fairly accurately and the question of whether the Earth or the Sun was at the centre was not properly answered until discoveries of the law of gravity and the laws of motion, which was well after the times of Copernicus, Tycho, Galileo and Kepler. Then it was realised that the Sun must be at the centre because it is so much more massive.

Ptolemy's theory was in fact more complex than explained in this article, and it also allows for what we now call the eccentricity and the inclination of each orbit.

All the constellations were fixed to a crystal sphere that rotates at a slightly different rate from the Sun's rotation rate. So while the Sun goes round 365 times in a year, the sphere of the constellations go round 366 times.

Alexander’s Empire was divided into thirds, approximately, giving Egypt to Ptolemy, Palestine and Greece to Antigionus and Persian to Seleucus.

The Ptolemaic kingdom lasted from 305 BC to 30 BC. The first king of the Ptolemy dyansty of Greek kings of Egyipt was Ptolemy I. The Last one was Celopatra VI. The Romans took over in 30 BC.

Ptolemy 2 Philadelphus was the most beneficent. The Ptolemies in general, while not all kind to the Jews, didn't actively try to stamp out Judaism. That was attempted by the Seleucid king Antiochus Epiphanes.

Ptolemy was the famous Alexandrian responsible for the most popular map printed from movable type in the fifteenth century. The Ptolemy's world map is a map of the known world to Hellenistic society written in c. 150.

The similarity is that both theories used a system of circles and epicycles to explain how the planets move around. Copernicus's theory (1543) used a similar number of epicycles, but many of them were smaller so that the paths followed by the planets were geometrically simpler.

The difference was that Copernicus placed the Sun at the centre rather than the Earth as the ancient theory had done.

Another theory was later produced by Kepler (1609), which used Copernicus's idea of having the Sun at the centre, but Kepler used elliptical orbits for the planets. This new model fitted observational measurements better, but it was not until many years later after the discovery of the law of gravity and the laws of motion (1687) that it was possible to pick out Kepler's theory as the correct one that is still in use today.

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.

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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.

By "main" theory I presume you mean Big Bang Cosmology.

You can evaluate it by repeating the following tests, all of which have been repeated thousands of times:

1) See how well Hubble's Law holds.

2) Calculate the age of our Universe with Hubble's Law.

3) Check for isotropic radiation from space, with a spectrum identical to a black body with temp 3 K.

4) Look for white dwarf stars older than the age you computed in (2).

5) Examine the ratio of long lived isotopes to their decay products, and see if any decays show radioactivity occuring for longer than the age you computed in (2).

6) Check the ratio of hydrogen to deuterium to helium to lithium in all parts of our Universe, and compare these ratio to that predicted by Big Bang Cosmology.

7) Search for nearby quasars. If the "recent" (ie, the last three billion years or so) Universe is pretty much the same as the older Universe, then there should be as many quasars nearby as there are ones far away.

As you can probably guess, all of these tests show that our Universe has been expanding from an immensely more dense and hot state since about 13.7 billion years ago. As of 2012, no observation exists that is in contradiction to that statement.

They were very incorect, and this was proven.

The earth revolved around the sun 1403 times between 140-1543.

were based on the idea of a SE

There were fourteen Ptolomy kings. Ptolomy Caesar, who actually was Ptolomy XV , never made it. Cleopatra did make him co-ruler with her, but she held all the power.

Euclid is said to have told told King Ptolemy that.

Um... Ptolemy. Hence the name (the adjectival form is usually spelled "Ptolemaic", though).

You're more generous than I am if you call him a "scientist," though.

Copernicus' view was that the sun was the centre of the solar system. He believed everything revolved around the sun in circular orbits. Ptolmey on the other hand placed a static Earth at the centre with the planets and the sun orbiting the earth.
Copernicus thought that the solar system revolved around the sun and not the Earth.

Aristarchus came up with the heliocentric model of the solar system about the same time that Aristotle developed the geocentric model. But since it was OBVIOUS that the Sun went around the Earth, the geocentric model prevailed for about 1800 years before Copernicus realized that the math worked better if the Sun was at the center.

Ptolemy's view of the universe placed the sun, the other solar system planets, and the stars inside a huge rotating sphere centered a point in space close to the earth.

Aristotle came first, followed by Ptolemy, then Copernicus and Galileo. Other important players in the story after them were Tycho Brahe, Johannes Kepler and Isaac Newton.

We do not know because we have not found any of his writings yet.

Shortly before Copernicus died he figured that the Earth was notthecenter of things, but the Sun was. This theory is still used today.

He worked out this this theory from detailed observations of the orbit of Mars.

Both Models Show That Celestial Objects Have Circular Paths