Conservation of angular momentum

I've been reading a lot about black holes recently. Fact: you can use a rotating black hole as a power source (there are various ways to accomplish this). Perhaps in the far-flung future our descendants will be powering their civilisations with black holes. Anyway, I was just now reading about flywheels, which you can use to store and retrieve energy, and I realised this was exactly the same physics (pretty much) as the rotating black holes. Conservation of angular momentum, large and small.

I profoundly regret not studying physics in high school, which means as an SF reader and writer I constantly struggle with concepts I barely grasp. So this was a pretty exciting moment. Now to Khan Academy for some lessons.