Ptolemy and Copernicus both used epicycles and were pretty bad as sand alone theories. Copernicus certainly did NOT disprove Ptolemy. Tycho's hypothesis of a fixed Earth with planets orbiting the Sun and the Sun orbiting the Earth shows that a fixed Earth description was consistent with the observations at the time.
On the other hand, the joint work of Galileo and Kepler *did* undermine Ptolemy's system. Kepler showed how to avoid epicycles and Galileo provided observations that directly contradicted Ptolemy's views. It was still possible to have a variant of Tycho's system, but it was no longer possible to have the old Ptolemaic system.
It should also be noted that the 'physics' that supported the Ptolemaic system was also undermined by Galileo's observations. Because of this, the traditional arguments for a fixed Earth were invalidated and a replacement was found. The final nail was Newton's discovery of his laws of motion and his law of universal gravity. This gave a much simpler description that was also much more accurate that either the Ptolemaic or the Copernican system. It even surpassed the system of Kepler by adding in additional corrections *that were motivated* by the theory as opposed to being ad hoc add ons.
On the other hand, the joint work of Galileo and Kepler *did* undermine Ptolemy's system. Kepler showed how to avoid epicycles and Galileo provided observations that directly contradicted Ptolemy's views. It was still possible to have a variant of Tycho's system, but it was no longer possible to have the old Ptolemaic system.
It should also be noted that the 'physics' that supported the Ptolemaic system was also undermined by Galileo's observations. Because of this, the traditional arguments for a fixed Earth were invalidated and a replacement was found. The final nail was Newton's discovery of his laws of motion and his law of universal gravity. This gave a much simpler description that was also much more accurate that either the Ptolemaic or the Copernican system. It even surpassed the system of Kepler by adding in additional corrections *that were motivated* by the theory as opposed to being ad hoc add ons.
