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Old September 19, 2017, 21:37   #6
Pete Mack
Join Date: Apr 2007
Location: Seattle, WA
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Originally Posted by Patashu View Post
Layman, but I think time travel is 'allowed' specifically when it doesn't carry any information back.
Yep. "Phase velocity" is exactly such a phenomenon.
Faster-than-light travel is forbidden because it is equivalent to time travel under the theory of relativity. Time travel is forbidden because it's paradoxical: if it were possible, we'd already know because it would have "already" happened. (The universe would also be hopelessly unstable.) It makes for great humorous SF: see Kage Baker and Charlie Stross. But there's just no chance it's real.
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