Answer:
Comet's orbit.
Explanation:
Edmond Halley and Alexis Clairaut were one of those Newtonian who helped to validate the results of Isaac Newton.
They correctly explained Comet' motion and how planets gravitational force affect them.
But using Newton's idea of Mathematics and Gravity, they have made two important discoveries:
1. Why celestial bodies have different colors.
2. They were able to find the Comet's orbit and prediction(year) of its return.
