Today I heard about a neat video Stephen Morris, a prof at the University of Toronto, put together. The idea is that a domino can knock over another domino that is 50% taller than itself. You can use this to build a kind of domino chain reaction where each domino knocks over a larger, subsequent, domino. The initial domino is only 5 mm tall, but after 13 dominos knocks over a massive domino nearly 1 m tall.

That hallway in the physics building at UofT brings back memories.