All of the students lined up in the middle of the classroom and two students in the middle held force scales. Two reporters stood facing them so that they could observe the scales. Each side pulled their line in opposite directions, and the observers reported seeing the scales move in equal and opposite directions. We can infer that the earth is pulling on the moon and the moon is pulling on the earth (and the sun is pulling on the earth and the earth is pulling on the sun) in an equal and opposite direction.