Our earth has only one satellte , that is , the moon .Its diameter is only one – quater that appers so big because it is nearer to our planet than other celastrial bodies . It is about 3,84,400 km away from us . Now you can compare the distance of the earth from the sun and that from the moon . The moon moves around the earth in about 27 days . It exactly take the same time to complete one spin . As a result . Only one side of the moon is visible to us on the earth . The moon does not have conditions favourable for life . It has neither water nor air . It has mountains , plains and depression on its surface . These cast shadows on the moon’s surface . Look at the full moon and observe these shadows .