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.)

How can the circumference not matter? The posted solution creates 1 meter of rope...from nothing... giving you a C of 100 cm :( Yes the formula is correct, but only if you are starting from zero, that's why it would work with a globe as well. Unfortunately we're not starting from zero, we're starting with an existing C of app. 5,467,574 meters. We need to reduce this C by 1 meter in order for the rope to fit, right? So...wouldn't you just divide 1M by the C to get the groove?

Posted by John Ryder on 2002-05-08 07:11:38