Seeing this topic, I remembered an interesting question.

Suppose there is an iron ball, and the circumference of its great circle is arbitrary. Suppose it is one meter, make a ring with a circumference of 2 meters (that is, the circumference of the iron ball+1 meter) and evenly surround the iron ball; The equatorial circle of the earth is 40000 kilometers. Suppose a circle of 40000 km+1 m is evenly placed over the equator.

Is the gap between the iron ball and the ring larger (length gauge) or the gap between the earth and the ring larger?

Based on life experience, many people must think that the former is big and the latter is insignificant, but it is not. The two gaps are the same.