How do you get a geocentric model with ellipses? Venus clearly does not go in an ellipse around the Earth. Did Riccioli just add a bunch of epicycles to the ellipses?
Googling… oh, it was a Tychonic model, where Venus orbits the sun in an ellipse (in agreement with Kepler), but the sun orbits the Earth.
Kepler’s ellipses wiped out the fully geocentric models where all the planets orbit around the Earth, because modeling their orbits around the Earth still required a bunch of epicycles and such, while modeling their orbits around the sun now involved a simple ellipse rather than just slightly fewer epicycles. But it didn’t straightforwardly, on its own wipe out the geoheliocentric/Tychonic models where most planets orbit the sun but the sun orbits the Earth.
How do you get a geocentric model with ellipses? Venus clearly does not go in an ellipse around the Earth. Did Riccioli just add a bunch of epicycles to the ellipses?
Googling… oh, it was a Tychonic model, where Venus orbits the sun in an ellipse (in agreement with Kepler), but the sun orbits the Earth.
Kepler’s ellipses wiped out the fully geocentric models where all the planets orbit around the Earth, because modeling their orbits around the Earth still required a bunch of epicycles and such, while modeling their orbits around the sun now involved a simple ellipse rather than just slightly fewer epicycles. But it didn’t straightforwardly, on its own wipe out the geoheliocentric/Tychonic models where most planets orbit the sun but the sun orbits the Earth.
I mean, that’s not even a different model, that’s just the real thing visualized in a frame of reference centred on the Earth.
Keep in mind that any ellipse can be modelled by 2 epicycles.
Ellipses were a tighter constraint on available epicycle models.
Kepler’s model actually involved hyperbola for comets, which cannot be explained by epicycles.