Ptolemaic model, which would need to be faster to observe retrograde motion from the Earth?

For a planet in the Ptolemaic model, which would need to be faster so that we could observe retrograde motion from Earth:



1. The planet鈥檚 speed in its orbit along the deferent? or

2. Its speed in its orbit about its epicycle?Ptolemaic model, which would need to be faster to observe retrograde motion from the Earth?You need to adjust the epicycle in order make it fit an observation made from earth. See below.



"The epicycle on deferent model is quite flexible. By adjusting the size of the epicycle, Ptolemy could fit his model to the size of the retrograde loops observed in the heavens. By adjusting the rates of rotation, he could adjust the frequency of retrograde motion."