> This is not an assumption, there is no circular reasoning. Of course it is an assumption. A star moving across the sky is not a proof by any means. > And we

> This is not an assumption, there is no circular reasoning. Of course it is an assumption. A star moving across the sky is not a proof by any means. > And we observe different parallaxes for different stars, meaning that stars are not all on the same distance from earth. No, we don't measure different parallaxes for different stars. We measure different trajectories for different stars across our night sky and then, using the assumption that Earth rotates and that it is on an orbit around the sun, we conclude that there must be a parallax effect involved in the observed trajectory of the star which we can then use to estimate its distance to us. > So, this way you prove that the earth moves and stars have different parallaxes and are not all attached to a crystal sphere. I don't see a problem here. To see that what you're referring to as "proof" is no proof at all, consider that Ptolemy's epicycles (i.e. the elaborate version of the crystal spheres) are just a Fourier series and can therefore be used to describe any periodic movement across the sky. (Without you having to know anything about whether Earth rotates or not.) For a very impressive example see https://m.youtube.com/watch?v=QVuU2YCwHjw https://m.youtube.com/watch?v=QVuU2YCwHjw .