Lesson Plan #30 http://www.phy6.org/stargaze/Lgravity.htm . This lesson re-derives Newton's result, that if the force of gravity decreases like the square of the distance from the center of attraction, the same force that causes objects on the Earth"s surface to fall can also be responsible for the motion of the Moon. ... This lesson plan supplements: "Newton's Theory of Universal Gravitation," section #20 http://www.phy6.org/stargaze/Sgravity.htm . ... Starting the lesson: . ...