I have been wondering, what makes a rival? In particular, what sets up college rivals? Is it just age of the instution and geographic location? Why is it Ohio State and Michigan or Berkeley and Stanford or Harvard and Yale? While geography is a component, I think it also the recognition of the similarity between the two places. In a parallel universe, things could be switched and everyone would think it perfectly natural to be in the other place. The people, on average, who attend the rivals, while they deny it, have some fundamental similarities and in other settings are perfectly happy to be friends.