Einstein's neighbor at Princeton, Kurt Gödel, perhaps the greatest mathematical logician of the past 500 years, found a new solution to Einstein's own equations which allowed for time travel.
The 'river of time' now had whirlpools in which time could wrap itself into a circle. Gödel's solution was quite ingenious: It postulated a universe filled with time that flowed like a rotating fluid. Anyone walking along the direction of rotation would find oneself back at the starting point, but backwards in time!
in 1963, Roy Kerr, a New Zealand mathematician, found a solution of Einstein's equations for a rotating black hole, which had bizarre properties. The black hole would not collapse to a point (as previously thought) but into a spinning ring (of neutrons). The ring would be circulating so rapidly that centrifugal force would keep the ring from collapsing under gravity.
Anyone walking through the ring would not die, but could pass through the ring into an alternate universe.
In the quantum theory, we can have multiple states of any object. For example, an electron can exist simultaneously in different orbits (a fact which is responsible for giving us the laws of chemistry). Similarly, Schrödinger's famous cat can exist simultaneously in two possible states: dead and alive. So by going back in time and altering the past, we merely create a parallel universe. So we are changing someone ELSE's past by saving, for example, Abraham Lincoln from being assassinated at the Ford Theater, but our Lincoln is still dead. In this way, the river of time forks into two separate rivers.
Because of the enormous amount of work done by theoretical physicists within the last five years or so, Hawking has since changed his mind, and now believes that time travel is possible (although not necessarily practical).
Wheeler has argued that because there is no such thing as time in the singularity, when BKL tidal gravity forces peak, space gives way to "Quantum foam"
The previously provided references by Loren, Adjoint are not in respect to trans-event horizon luminous velocity physics for WormHoles and Black Holes, but rather for accretion disk flux.
If transluminous physics were impossible then the cerenkov effect u > v(w) would violate Lorentz Invariance, and as a result, the cerenkov effect would be theoretically impossible.
Loren is correct that cosmic obsevations are limited by |v| < c, however physics and Superstring Theories are not necessarily limited by |v| < c, but rather by |u| > v(w).
Proof that space-time fabric is a medium for luminous velocity is from the curved space-time effects on photon vectors resulting in the 'lensing effect'.
Space-Time medium luminous velocity
B, p are not constant or new constant for |v| < c
v(w) = \sqrt{ \frac{ B}{p}}
Universal Vacuum:
B, p are constant for |v| = c
v(w) = \sqrt{ \frac{ B}{p}} = \frac{1}{ \sqrt{ \mu_o \epsilon_o}} = c
Space-Time Fabric Medium:
B = \frac{ 1}{ \epsilon_o}
p = \mu_o
B, p are not constant or new constant for |v| > c
v(w) = \sqrt{ \frac{ B}{p}} \geq c
v(w) - Space-Time medium luminous velocity.
B - Space-Time Bulk Modulus.
p - Space-Time fabric density.
Reference:
http://www.pbs.org/wnet/hawking/mysteries/html/kaku1-1.html
http://dnausers.d-n-a.net/dnetGOjg/Black/Holes.htm
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