A skeleton walks down empty Main Street. Suddenly he sees another skeleton carrying a gravestone. "Hey, what are you doing?” the other skeleton answers "Just strolling", "Why do have the gravestone, buddy?", "Because I always want to have some ID”.
Why do these 2 relationships differ so much: the orbital relationship between the earth and sun and that of a tether ball and it's pole?.......
.......that of the sun and earth is a no strings attatched relationship and the other is not!