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The Chronology Protection Conjecture is an entire bundle of rough theorems, counterexamples and conjectures. Hawking's original paper on the topic hinges on two main arguments : That compactly generated closed timelike curves (aka "a time machine", roughly) will violate the energy conditions. That a Cauchy horizon (the part of spacetime where the time ...

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The movie "Prince of Darkness" used the idea of tachion transmissions as a means by which 'information' (in this case a radio transmission) could be streamed into the past.

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If you want to make a flat space theory for a topologically trivial manifold you can do it in the standard ways if your metric was very very close to the Minkowski metric. Yours is not. So for instance you aren't going to be able to ignore higher order terms in $h$ since in one of the $y$ directions your $h$ blows up. You can still compute an $h$ field by ...

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Let's say there are two twins. One on the ground and one moving through the atmosphere at 1,000,000 m/s which is a few thousand times greater than 1,000 km/h. The moving twin does this for 100 years, or about 3 billion seconds, then returns to the ground to compare clocks. The moving twin will have a clock that ticked more slowly by around 16,600 seconds. ...

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Here is the most prominent example I know: The Russian astronaut Sergej Awdejew was in orbit for a total of 748 days (traveling at approximately 17000 miles per hour). Therefore he has time travelled a whopping 0,02 seconds into the future!

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We know that the theory of cosmic censorship prevents singularities from existing without an event horizon that hides them from the Universe. Actually, we don't. Don't forget that cosmic censorship is just a hypothesis. It isn't a rigorous well-tested theory like General relativity. See this on the Wikipedia Cosmic censorship article: "The hypothesis ...

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