- The curve traced by a fixed point on a closed convex curve as that
curve rolls without slipping along a second curve.
- A gambling game in which the players bet on which slot of a rotating
disk a small ball will come to rest in. On August 18, 1913, on an unbiased
roulette wheel at Monte Carlo, evens came up 26 times in a row. The
probability of this occurring is 1 in 136,823,184.