# extracting energy from cosmological expansion

This question is a more concrete reincarnation of an old question about energy conservation in GR.

Are there mechanisms to extract energy from the cosmic rate of expansion? putting some extremely long ropes across the universe and extract work from their increase of separation?

assuming this is possible ( i don't see why it would not ), what form would take the back-reaction force? in all physics, every time you extract work from some system by some force, this system will exert a force back. Can we slow down cosmic expansion by variations of these mechanisms?

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When you tie the masses together you're locally changing the spacetime curvature. Assuming an FLRW metric with $\Omega = 0$, if you prevent masses from moving with spacetime you'll make your local region overdense and the area around it underdense.