Ye olde history of perpetual motion machines

[KarlS]

@ChaosEngineer

Now, what would be interesting is a perpetual motion machine based on some kind of exotic matter that’s light when it’s lifted up, but becomes heavy when it falls down. Nobody ever builds those.

The Martians in Kurd Lasswitz’ 1897 novel Two Planets had a dynamically adjustable version of that as the basis of much of their technology. Unfortunately the technical detail was rather limited.