We find that the moon is about 239,000 miles(384,551 km)away from the earth,and,to within a few thousand miles,its distance always remain the same.Yet a very little observation observation observation shows that the moon is  not standing still.Its distance from the earth remains the same,but its direction continually changes.We find that it is traveling in a circle--or very nearly a circle--round the earth,going completely round once a month,or,more exactly,once every 27 1/3 days.It is our nearest neighbour in space,and like ourselves it is kept tied to the earth by the earth's gravitational pull.(To be continued.)