Imagine you would have to put a rope around the moon. Since the moon is 1,738,000 metres in diameter, this is a hard task.
Finally you have managed to get the rope around the moon but... it is one meter short.
You decide to dig a groove all around the moon, so that the shorter rope suffices. How deep must this groove be?
(Assume the Moon to be a perfect sphere.)
If you set up the equation with variables instead of numbers, you will notice that the circumference of the moon cancels itself out. The answer would be the same if you asked it about the earth, the sun or the entire galaxy!
Interesting observation
