Rush's Law: Why You Can't Get Pepper Out of Pepper Shakers

One of my minor hobbies is swapping the caps on salt-and-pepper shakers in restaurants. Convention places the small holes on pepper shakers and the large on salt. This is backwards, of course.

Salt crystals are all about the same size. If any will fit through the holes, they all will. Ground pepper particles range from dust to chunks. If any of the particles of pepper are larger than the holes in the cap, the shaker will eventually be filled with particles to large for the holes.

Each time the restaurant workers fill the pepper shakers, the percentage of too-large particles increases. Eventually that percentage approaches 100. When it does, no one bothers to fill the shakers because they are always full. This is Rush's Law.