Of moons and planets

Something fascinating from an “amateur analysis” of the moon’s orbit — the sort of thing I’m sure a lot of people wish they did but never do.

In other words, the Sun exerts more than twice as much gravitational force on the Moon as the Earth does. Asimov argued that this means the Moon is really orbiting the Sun, with some perturbation by the Earth, and that’s why the Moon’s path looks like a slightly wobbly circle around the Sun.

We might look upon the Moon, then, as neither a true satellite of the Earth, nor captured one, but as a planet, in its own right, moving about the Sun, in careful step with the Earth. To be sure, from within the Earth-Moon system, the simplest way of picturing the situation is to have the Moon revolve about the Earth; but if you were to draw a picture of the orbits of the Earth and Moon about the Sun, exactly to scale, you would see that the Moon’s orbit is everywhere concave toward the Sun. It is always “falling” toward the Sun.

P.S. the link to the Asimov book is here.