On 13 Sep 2015, at 19:29, John Clark wrote:
On Sun, Sep 13, 2015 Bruno Marchal <marc...@ulb.ac.be> 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.
Gödel shows that Einstein's equation allows circular space-time loop.
He provided a model with rotating universe, but other have shown that
in a non rotating universe a rotating mass, heavy enough, can generate
space time deformation leading to circular time loop.
> 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
showed that an infinitely long,
To simplify the calculus. I think. Not really the time to plunge in GR
right right now.
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.
OK.
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.
Perhaps.
Bruno
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 everything-list+unsubscr...@googlegroups.com.
To post to this group, send email to everything-list@googlegroups.com.
Visit this group at http://groups.google.com/group/everything-list.
For more options, visit https://groups.google.com/d/optout.
http://iridia.ulb.ac.be/~marchal/
--
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 everything-list+unsubscr...@googlegroups.com.
To post to this group, send email to everything-list@googlegroups.com.
Visit this group at http://groups.google.com/group/everything-list.
For more options, visit https://groups.google.com/d/optout.
