Not quite so long ago, the scientist Bohr was trying to understand the nature of matter. He hypothesized that atoms were made up of descrete subatomic particles. One of these were electrons, which orbited a nucleus. The Bohr model of the atom is the model that the non-scientists in the room know. More here & here.
The trick is both guys were wrong. Sure, in both cases the hypothesis had some support from observation. But an electron is not a ball bearing spinning around a center. Here's a bit from Wikipedia that matches my limited knowledge of physics:
According to quantum mechanics, electrons can be represented by wavefunctions, from which a calculated probabilistic electron density can be determined. The orbital of each electron in an atom can be described by a wavefunction. Based on the Heisenberg uncertainty principle, the exact momentum and position of the actual electron cannot be simultaneously determined. This is a limitation which, in this instance, simply states that the more accurately we know a particle's position, the less accurately we can know its momentum, and vice versa.The curious thing is that Bohr's model is/was very helpful. It furthered human understanding of the natural world, while Ptolemy's was not helpful. It hindered movement toward the more accurate description of the natural world. Was there a fundamental difference in their methods?