Newton was certainly not the first person to see an apple fall from a tree. He may, however, have been the first to imagine the apple and the Moon to be one and the same. To Newton, the Moon was merely a much larger apple very much further from the Earth. It is the tangential velocity of the Moon that prevents it from getting any closer to the Earth and the gravitational force that holds it in orbit. Newton thought of a gravitational force of attraction between the Earth and the apple before realizing that the force is between any two masses. This led to a revolution in science and thought. This chapter mixes some classic problems with some new twists.