I'm going to ask this here because you guys are a pretty smart bunch.
I confess to knowing almost nothing about engines. I was wondering why you disconnect the spark plug when you work on a lawnmower, like changing the blade? Is it true you can spontaneously start it by turning the shaft? Is is sort of like in the old WWI movies, where they start the old fighter planes by having a ground crew man give the prop a spin manually?
I'm serious. I'm pretty smart with guns, reloading, casting, etc. I just never was into engines.