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.)
The required depth of the groove is approximately 15.92 centimeters.
Edited on June 7, 2008, 4:29 pm