On 19 October 2014 06:48, John Clark <johnkcl...@gmail.com> wrote: > On Sat, Oct 18, 2014 at 1:22 AM, Bruno Marchal <marc...@ulb.ac.be> wrote: > >> >> > Gödel shows that there are solution of Einstein's equation of >> gravitation with closed timelike curves, making them consistent. >> > > But only if you assume that the Universe is rotating, and experimental > evidence proves that it is not. And only if you assume that Einstein's > General Theory of Relativity is 100% correct, and we know it can't be, it's > the best theory of gravity we have but it can't be the final word because > it doesn't take Quantum Mechanics into account. > That isn't quite true. Several GR based time machines have been proposed - Tipler cylinders and wormholes, at least, as well as a Godel universe. And none of these require GR to be 100% correct, merely correct on the scale involved (the only place anyone is (99%) sure GR breaks down is within something like the Planck length from where there would, according to GR, be a singularity - but at least some GR based time machines don't involve singularities).
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