Knowing three orbital positions of a planet’s orbit, Sir Isaac Newton was able to produce an equation that predicted a planet’s motion; i.e., to give its orbital properties: position, orbital diameter, period and orbital velocity. Years later however, Newton and other astronomers discovered that the equation wasn’t particularly accurate. Newton realised that this was because of the multiple gravitational interactions that take place once you introduce a third body:
“And hence it is that the attractive force is found in both bodies. The Sun attracts Jupiter and the other planets, Jupiter attracts its satellites and similarly the satellites act on one another.”