Have you ever stared in awe at a steam locomotive, wondering how it works?
For the umpteenth time, I relived this experience at a museum last weekend. Specifically, I wondered how the intricate mechanism around the engine’s wheels and their elegant swinging motion were driven by pressurized steam.

This gif I found with a simple Google search answered the question more convincingly than anything else I have come across in 33 years, a degree in mechanical engineering notwithstanding. I only wish for every middle-school science teacher to have his students see this.