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From what I learned watching Brian Greene's "Fabric of the Cosmos" episode on Nova, if you look at spacetime like a loaf of bread, then each 'slice' depends on your relative speed compared to another point in the loaf. This I have no problem with, but it really got confusing when he mentioned that an observer billions of light years away would see an older image of Earth if he traveled away from it. Upon seeing this my mind immediately asked the question, does that mean time travel BACK in time is possible, or does it simply mean the light traveling from Earth to the observer is older.

To simplify, if an exotic means of travel existed, where you could instantly warp 10 billion light years without breaking the speed of light limit (via a wormhole or whatever), would you then end up 200 years in the past if you stepped through the wormhole after traveling away from Earth, and 200 years in the future after traveling towards Earth? (You'll know what I mean if you have seen that episode, where the alien's 'slice' in spacetime is relative towards a distant past Earth slice when he's traveling away from Earth, but when he's traveling towards Earth his slice is connected with a future Earth).

How I understand spacetime is that it always moves forward, but at different speeds depending on gravitational force and relative speed, so traveling back in time should never be possible (it just moves forward at different speeds, but there's always a NOW, you've just aged at different speeds depending on where you are in the Universe). But the scenario depicted in Greene's show seemed to imply otherwise.

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# Spacetime 'loaf' according to Fabric of the Cosmos

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