[MacDorcha]

"An object rotating in space (the outer kind) is technically a perpetual-motion machine (an object in motion will remain in motion; an object at rest will remain at rest; until acted upon by an outside force). However, extracting energy from such an arrangement introduces one or more outside forces. "

then why would a universe slow down to crunch again? it IS losing energy if it's slowing down, otherwise, the Universe would only exoand, being "always in motion." planets arent perpetual motion machines anymore than glass is a solid, it's a very slow moving liquid.

[Junior]

The universe is not losing energy. The energy is being converted into a non-useable form (heat).