As can be verified by direct observation, the moon is always moving continually eastward. Since it makes a complete revolution around the earth from new moon back to new moon again in a little less than thirty days, it passes over about twelve degrees a day (360° divided by 30), on the average, or one-half a degree an hour, which is about the angular extent of its own diameter. Therefore every hour the moon moves eastward a distance equal to its own diameter. This is of course only approximate as the moon moves more rapidly in some parts of its orbit than in others.