What are epicycles, deferents, eccentrics, equants, etc. ? In this passage Aquinus is summarising Eudoxus' theory of planetary motions as described by Aristotle in Metaphysics XII The theory of deferents and epicycle was developed by Hipparchus some centuries after Aristotle, and further developed by Ptolemy
What happened in astronomy between Hipparchus and Ptolemy? Hipparchus applied Apollonius's epicycle eccenter construction to the motion of the Sun and the Moon, but not to the planets There are speculations about epicyclic gears for planets in the Antikyt
astronomy - History of Science and Mathematics Stack Exchange the alignment of the radii of the (second) epicycles for outer parents and the deferents of inner planets with the Earth-Sun line, and the equivalence of the outer epicycle and inner different radii with the Earth-Sun distance
astronomy - Did the Ptolemaic system have rotating center of the . . . 2 I've come across this diagram of the Ptolemaic model Am I understanding correctly that this means that all the planets' deferents rotate around a point which next to Earth, while Venus' deferent rotates around an epicycle rotating around the same point Is that correct?
mathematics - When were vectors invented? - History of Science and . . . A striking example is the famous theorem of Apollonius, about "equivalence of excentric and epicycle" Motion on epicycle means that a point moves on a circle around the center (E), while the planet moves on another circle (of smaller radius) around this point
Did Archimedes use epicycles in his planetarium? There is no historical evidence relating Archimedes to epicycle theory The story of the recently found object in Olbia which is presumably a piece of a toothwheel from Archimedes "planetarium" is strange All information about this object found on the Internet comes from a single person who is an engineer, and who wrote a book about it
How critical were Tycho Brahe’s accurate observations? I am speculating about the value of Tycho Brahe’s - for his time - accurate observations and Kepler’s calculations Might it have been possible for Kepler to formulate his laws based on Ptolemy’s s
astronomy - History of Science and Mathematics Stack Exchange Some sources (modern sources, and Kepler himself) claim that in his Geo-Heliocentric (Tychonic) model, Tycho Brahe saw that the orbs of the Sun and Mars intersect, and this was one of the reasons w