This is one of those questions that I've always wanted to ask, but felt stupid for it. If we look at celestial mechanics from a relativistic standpoint, considering that all inertial reference frames are equivalent and we may choose any arbitrary reference frame, how is it that we can say that the earth truly revolves around the sun? Of course, it does if we choose the sun as a stationary frame of reference. But what if we choose the earth as our frame of reference (which, being our home, seems like a natural one)? Isn't it then perfectly legitimate to say that the sun goes around the earth? It seems to me that the heliocentrism/geocentrism question simply depends on the reference frame from which the system is viewed.