Roman ring

A Roman ring is, in theoretical physics, a wormhole configuration in which for each individual wormhole, the time difference that occurs through its "mouths" is such that it might not allow formation of a closed curve of time type or closed temporal curve (CTC). If these wormholes and their respective "mouths" are arranged in the proper configuration, the CTC may have the possibility of forming again. For example, a wormhole formed between Earth and Moon whose farthest end would be 0.5 seconds in the past would not violate the principle of causality, since the information sent to that end through the hole of worm and returned through normal space, would arrive at Earth 0.5 seconds later (-0.5 + 1 = 0.5) from which it would have been transmitted. But an additional wormhole in the opposite direction would allow the information to be back on Earth 1 second before it was transmitted.

Semi-classical gravity-based approximations have been described in order to incorporate quantum effects into general relativity, but such approximations seem to show that the chronology protection conjecture, postulated by physicist Stephen Hawking, fails to time to prevent the formation of this type of rings. However, some experts like Matt Visser argue that there is reason to believe that such approaches are unreliable in this context, and that a more complete theory of quantum gravity will probably keep the conjecture of chronological protection intact. A wormhole without CTC. A Roman ring with two wormholes. A Roman ring with four wormholes.

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