One answer considered especially useful by astronomers is the barycentre, the point where the masses of the Sun, the planets and all bodies in the system balance out. Imagine placing those masses on a huge platform supported by a single pin; slide the platform until you find the place where it remains perfectly balanced on the pin, and that is the barycentre. Now generalise your intuition to three dimensions. The barycentre is important because the equations of gravitation guarantee that it remains still while all bodies move in their orbits subject to their mutual attraction. Because the Sun is so massive, the barycentre lies relatively
