Light, bending space enough to make it actually swirl around?
I don't claim to have the necessary understanding of general theory of relativity when it comes to field equations, but I always thought that relative energy didn't have actual effect on space-time curvature*, and since photons are nothing but relative energy I kinda have my doubts on this interpretation... since the photons have no possible rest stage, they can be considered as pure kinetic energy in the same regard that when objects with a rest mass go faster and faster, they do not collapse into black holes no matter how fast they go.
Although I'm not sure how a continuous beam of light would affect space-time, since it could be viewed as a bar of static energy density... but on the other hand it's still made of photons.
It kinda boils down to the question whether photons just move according to space's curvature along the geodetic straight line, or do they in their part affect the space-time. My intuition would be to say no, they don't affect the curvature of space and time and they just go along, but intuiton is worth nothing in physics. It'd be interesting to see other opinions of that guy's interpretations, but I can't really bother to go and search for them.
The idea about achieving seemingly faster than light movement while moving at sublight speeds in local space-time sounds very plausible - in fact the universe is kinda doing it all the time, that's the reason why the night sky is not as bright as sun - but in that case it's the expansion of the universe which at some point starts making distance between objects and us faster than light can travel, which creates an event horizon of kinds. But interpreting how it would affect time for the object/photon sent into twirling space is a whole another can of worm(hole)s in itself.
For example, if we take an observation point A on geostationary orbit around a black hole, and assume that they send a photon on an interesting trajectory around the black hole, into the swirling space so that it will eventually return to point A, it still won't return to point A before it was sent. It still travels the only path it can at velocity c. The fact that the space around the black hole is so twisted that even catholic priests would be strained by it (into several kilometres long molecular spaghetti threads before being overheated into plasma) doesn't really change the fact that time doesn't go backwards, it only goes forward - although it can stop like it does in event horizon of black holes, from the outside that is.
Even if you take an observation point B opposite to point A and send a photon from A to B so that it travels through swirling time-space close to the event horizon... it will still be the fastest way to contact B from A's location. The fact that the photon's relative velocity in regard to both A and B during it's trip is something else than c due to the fact that the space-time in between moves to some direction doesn't really affect the observers one way or another.
At least that's my interpretation of the matter...
So what gives? I think that probably the only way to time travel is some kind of stasis system which either stops or slows entropia changes in a system, or truly stops or slows the flow of time by stretching time-space. This would cause the effect of traveling to the future, although it would be impossible to get back.
Perhaps the hypothetically most intriguing while physically even remotely plausible time travel method is a combination of a wormhole and a stasis field. The other end of the wormhole would be put into a true stasis field, which would slow the time flow on that end, while the other end would remain put at arbitrary location in normal time flow. This would after some time create a time difference between the ends of the wormhole while being connected to each other, so hypothetically it would then be possible to move from one end to the other.
It would then even be possible to travel from the future into the time when the wormhole was created. But seeing how getting anything of any importance through a wormhole (not to mention making a stable wormhole in the first place) is purely academic question, even this possibility kinda loses it's appeal.
*actually my vague understanding is that relative energy does affect the energy tensor calculations, but in some point of co-ordinate transformations the relative forms of energy will drop out of the equations when it comes to calculationg mass interactions like gravity, or somesuch smart stuff. Don't ask more, I can't answer...
