We used a ping pong ball tied to a string to model a planet and its orbit. We changed the size of the string so it was a smaller or larger orbit and then timed how long the orbit would take.   We had to consider which variables we had to keep the same to make the test fair and we also thought about why scientists repeat tests. We will now look closely at our results to determine if we can prove that the further the planet from the Sun, the longer the orbit time.