But the idea of "causal entropy" goes further, suggesting that a given physical system not only maximises the entropy within its current conditions, but that it reaches a state that will allow it more entropy - in a real sense, more options - in the future.

BBC: Entropy law linked to intelligence, say researchers

Physicists call these causal loop paradoxes, and they affront our desire for the universe to be a rational and ordered system.

CNN: Time travel: Can it really be done?