英語翻譯
So far our study of planetary orbits has been restricted to two-body central forces.However,the solar system is not a two-body system because the planets exert gravitational forces on one another.Although the interplanetary forces are small in magnitude in comparison to the gravitational force of the Sun,they can produce measurable effects.For example,the existence of Neptune was conjectured on the basis of a discrepancy between the experimentally measured orbit of Uranus and the predicted orbit calculated from the known forces.