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I've studied ellipses. I've studied physics. But when it comes down to the elliptical orbits of the planets is where I get confused. Ellipses contain two foci — and in the orbits of our solar system the sun is consistently stated as one of them. Okay. What about the second focus point? Why is it never brought up? And if there is no second focus — then how do we even move in an elliptical orbit?