What is the significance of the second focus of elliptical orbits of planets in our Solar System?
I just watched a PBS show on planetary motion and Kepler’s Laws and had a couple of questions. According to Kepler’s first law, the planets travel on an elliptical path with the Sun located at one of the two foci. Is there any significance to the other focus? I would think the gravitional pull of the Sun would contribute to the elliptical path, and that some other gravitional pull from the second focus would result in the elliptical orbit. Actually, both the Sun and the planets move around each other with their center of mass lying at the focus of the elliptical orbits. However, since the Sun contains 99.9% of the mass of the solar system, the center of mass is located almost at the Sun and so it looks like the planets are going around the Sun. There is no real significance to the foci of the elliptical orbits. The same laws that govern the orbits of planets around the Sun also govern the motion of binary stars and in that case since the masses of the two stars may be roughly equal, th
