> Anders Sandberg.
> Is it just me, or are everyone implicitly assuming it will work?
That's an old idea.
J. Richard Gott of Princeton proposed (Phys. Rev. Lett., 4 March 1991) that
two parallel cosmic strings, passing each other in opposite directions,
would so warp the fabric of spacetime as to create closed timelike curves
(CTC's), trajectories along which physical particles, although moving at
less-than-light speeds, could go backwards in time.
Now, a pair of articles in the 20 January 1992 issue of Physical Review
Letters raise reservations to Gott's scheme. In one article, Sean M.
Carroll, Edward Farhi (617-253-4871), and Alan H. Guth of MIT and Harvard
assert that in an open universe, one in which expansion continues
indefinitely, there is *not enough mass* to build such a time machine. They
note that it may be possible if the universe were closed. In the other
paper, Stanley Deser (Brandeis), Roman W. Jackiw (MIT), and Gerard 't Hooft
(Utrecht) argue that CTC's cannot be generated by physical, timelike
sources.
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