English: Motion of a Ball on a Non-rotating oblate spheroid, On the image the brown ellipse represent a planet, a bit rust-coloured, no water on it, an oblate spheroid in shape and non-rotating (Of course this is strictly hypothetical, for a real celestial body that is non-rotating is drawn to a near-perfect sphere by its self-gravitation.) This image shows this planet with on the North pole a convex bowl. It is effectively a bowl, because wherever a ball is placed, it will roll towards the pole. The pole is the point of lowest gravitational potential of the bowl, the point closest to the center of gravity. Illustration for w:Talk:Coriolis effect page