Why does the moon stay in orbit around the earth instead of falling into orbit round the sun?
The distance ratio of 1/243,000, versus 1/93,000,000 miles is the reason that the mutual attraction of the earth-moon system keeps them together. Gravitational attraction if governed by the inverse-squares law. As a result, distance is a greater factor than the huge mass of the sun in this case. Both objects follow a wobbling course around the sun alternately catching up with each other and then falling behind. The ‘orbit’ of the two is actually the path of the center of gravity of the combined system. The paths of the two bodies look a little like two snakes climbing a tree, with the moon making bigger deflections because of its lower mass.The moon’s orbit looks like a circle, (more or less), around the earth because we are on one of the objects involved in the combined motion.
