Planets interaction

Yes, for the Earth to orbit the Sun, it is under the influence of many other factors, say the gravitational force of the Moon, the other planets in the Solar system.

However, the Sun contains over 99% of mass of the Solar system. Therefore, we say most of the materials in the Solar system are gathered in the Sun. Therefore, compare to the influence of the Sun, the influence of the gravitational force of the other planets to the Earth are relatively small, we can even neglect it.

We simply consider the Sun and the Earth, that's sufficient.

We use Newton's law of gravitation, that's quite a good calculation.

F = GMm / r2


One special case, for Neptune and Uranus, as Uranus is relatively large, and the Sun are far away from Neptune, therefore the influence of the orbit of Neptune around the Sun by Uranus is quite significant.