Sep 16, 2020 · Ptolemy's epicyclic, geocentric model, in use until the Renaissance, was very accurate in terms of predicting the positions of planets and the times of eclipses. What it couldn't account for were things like the correlations between apparent size and phase of Venus, or to properly account for the variation in brightness of the planets.

Sep 28, 2022 · As Rory Alsop points out, the heliocentric model is correct, while the geocentric one is not. Contrary to what Paul Garrett mentions, though, NASA’s model is not geocentric, even though it does allow geocentric coordinates to be determined. I have recently translated Ptolemy’s Almagest to French, including some animations.

May 23, 2023 · The key point is that Venus always goes in a tiny little circle in front of the Sun, in the geocentric model. This was a necessity as they always saw that Venus was close to the Sun, in the morning or after sunset. So when Galileo saw a "full Venus" (implying it was behind the sun) - that broke the model. Here is an illustration:

$\begingroup$ Well, at a simple level, in a geocentric model you're assuming that the frame of the earth is an inertial frame, so using classical dynamics F = ma. But in that frame F doesn't equal ma, there are centrifugal and coriolis forces. The heliocentric model describes that frame as non-inertial, accounting for the extra terms in the ...

Nov 19, 2024 · Ptolemy didn't know. The geocentric model gives the astronomer little ability to measure extraterrestrial distances, as the Earth doesn't move. The baseline for parallax measurements is thus limited by how far one can travel on the Earth. The only body for which this was feasible using ancient methods was the Moon.

Feb 1, 2015 · In the historic geocentric models, and in particular in the Ptolemaic model, the earth is immobile in the centre of the cosmos, and the sphere of the fixed stars rotates around it once a day, carrying the sun, moon and planets with it.

Apr 14, 2014 · The heliocentric model is historically thought first by Aristarchus. He eventually gave up on the idea due to not being able to give evidence for a concept called stellar parallax: If earth orbits the sun then we should see the closer stars shift in relation to the other stars (strong evidence for this didn't come until Galileo).

Apr 29, 2023 · For various reasons, Ptolemy desired to use an epicyclic model. This model allowed him the flexibility to describe a wide range of motions. Ptolemy had inherited a model of the moon's motion from Hipparchus. This had a single epicycle and was quite accurate near full moon and new moon, but not sufficiently accurate at half moon.

May 21, 2015 · Some of them are stand-ins for the foci of an ellipse in a model made out of perfect circles. And the Sun was actually not the center of the Copernican model, a point near the Sun was. According to Copernicus the Sun was just a decoration which randomly happened to hang around near the center.

It is a kinematic, not a dynamic model. It describes the motion of the planets but does not give any reason for that motion. This is also the case for Kepler's and Copernicus model. But Newton's model, on the other hand, describes planetary motion in terms of forces. Now you can do Newtonian mechanics in any coordinate system.