From 1543, when Copernicus published the heliocentric model in his book on the revolutions of the celestial spheres, until 1609, our best theory of the solar system was that planets revolved around the Sun. Crucially, while Kepler contradicted Copernicus with respect to the shape of the planets' trajectories, he kept Copernicus' idea that the planets revolve around the Sun in the first place. And this thing we call knowledge grow? Is our knowledge of how reality works increasing? Are we really understanding ever more of the world as our admittedly conjectural theories rise and fall over the centuries?