I did my PhD thesis on PSR J1023+0038, a millisecond pulsar that is at a fascinating point in its evolution. (In fact there have been developments since the thesis was submitted; more about that later.) But during a moment of procrastination, I got involved with a new and fascinating system. The name, unedifying as usual, is PSR J0337+17, and it is unique in that the pulsar has not just one white dwarf companion but two.
In the quest for something better to run our cars on than gasoline, one of the proposals is flywheels. In fact, for a while there were flywheel-powered buses running in Switzerland and Belgium. On one level, it makes a lot of sense: you're storing energy as mechanical motion, and we're pretty good at transmitting mechanical motion from place to place. On another level it scares the living daylights out of me: a car in motion uses tens of kilowatts, so the car must be able to store hundreds of kilowatt-hours. If you let all those loose at once bad things will happen: 100 g of TNT going off releases about a hundred kilowatt-hours. Fortunately it's hard to get gasoline to do this, but a flywheel is just itching to dump all its energy. Batteries are a little scary too, to be honest. But anyway, that's all a digression: I want to talk about some really staggering examples of flywheel energy storage: pulsars and black holes.