Comment by hermitcrab
3 days ago
>If you spin up a wheel in the vacuum of space, it's going to keep spinning forever.
Even interstellar space is not 100% vaccuum. So it will slow from the occasional contact with matter. No doubt it would take a very long time, though.
Right. And also efficiency is about its interaction as part of a system, which is the difference between perpetual motion, and perpetual motion machine.