I am pretty sure number 4 is your answer
This is because the gravitational force on a object is directed to its mass. Since the moon has a lesser mass that the Earth, its gravitational pull is weaker. As a result objects weigh less on the moon.
The classical astronomers concluded that heavens were made up of a sphere, because heavens were thought to be perfect and spheres (circles) are a perfect shape. It was Plato who argued that geometrical figures were spheres and everyone agreed to him. It was also believed that the perfect motion of spheres was a uniform circular rotation.