This is simple exercise with unintuitive result, perhaps old as hell, but still surprising. Suppose we wrap earth with a string along equator, tightly, so that string is touching ground along its whole path. Assume earth is perfect sphere. Length of this string would be calculated as circumference of earth. Now imagine we add 1 meter to the total length of this string. Question is: by how much would this string lift off ground if distance to the ground is kept uniform along whole length of it?