As we know in order the earth to make this elliptical movement around the sun it needs two foci as we know from the first law of Kepler. The first foci is the sun. So my question is what is the other foci?
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The second focus is... a point in space. An orbit (by Kepler's laws) is not symmetric between the two foci, but the planet travels faster when near the sun (equal area swept out in equal times) and slower when far from the sun. No similar relation holds with respect to the second focus.
An ellipse is a kind of generalized circle, generated by not one central point and a rule, but by two points and a rule. An orbit, while having the ellipse shape, also has a time-dependent planet position, and only the shape, not the orbit, respects that second focus.
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