Imagine we have 2 coins. The radius of the larger coin is 3 times the radius of the smaller coin.
We roll the smaller coin all the way around the edge of the larger coin, without it slipping:

The question is, how many times will the smaller coin rotate as it rolls around the edge of the larger coin?
The result might not be quite what you expect, and in this article, we will look at a couple of explanations why. In addition, we will explore how this paradox relates to astronomy!