On Sun, Sep 13, 2015 Bruno Marchal <[email protected]> wrote: > > Gödel was a logician. he constructed a model of the theory GR, just to > show a counter-example to some proposition by Einstein. > >
Godel showed that if the universe were different from the way it is then a time machine would be possible, but it the universe were different from the way it is perpetual motion machines would be possible too. > > > That pure GR leads to close time circle is of some conceptual importance, > especially that you don't need to rotate the universe, it is enough to > rotate a massive cylinder in the universe, > Tipler (not Godel) found a solution in General Relativity that show ed that an *infinitely *long, extremely dense cylinder made of Neutronium (the stuff of Neutron Stars) and spinning at almost the speed of light would be able to tip a light cone enough to act as a time machine and allow you to visit the past, but there are two very important problems : 1) Nobody knows if a cylinder of finite length would also work, the math is too difficult to figure out. 2) The very rapid rotation would cause the cylinder to fly apart. This is much more than just an Engineering difficulty, no known force in Physics would be strong enough to hold the cylinder together, not even the strong nuclear force. So for this to work new Physics would need to be found, which is just another way of saying that as far as we know now it is impossible. John K Clark -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
