The String Around The World

Imagine I had a very long piece of string: long enough to wrap it around the equator of the Earth. And I'll do just that. Yikes — that's about 40,000 kilometers (or 25,000 miles) of string! I will make sure its pulled completely tight and connect both ends to each other: the result is that it lies flat onto the surface.

Now let me extend the string with just one measly meter. Compared to its total length that's not a lot, is it? Once again I pull it tight, but now, with the added meter, it has come off the ground just a tiny bit. Assume that this extra distance (between the string and the Earth's surface) is equally divided and thus the same all around the globe. How much would you guess this distance is? Surely this must be in the order of nanometers or whatnot, right?

Well, no. Turns out, the entire string has now come almost 16 centimeters off the ground.