Virtual Hyperspace

Imagine that you want to travel to a distant star, some 10 lightyears away, and then come back to earth.

Let's assume that you have a spaceship capable of accelerating at 100 gee. Let's also assume that you can handle the acceleration. You'd spend half the journey (5 ly) accelerating, and half deccelerating at the same speed. Your 10 lightyear journey would be over in 50 days of shipboard time. You'd be 50 days older, while, back on earth, about 10.01 years would have passed. Let's assume that you then spend ten days at your destination, get in your ship, and return to earth using the same velocity envelope.

When you arrived back on earth, everyone you'd left behind would be 20.07 years older. You'd be 110 days older.

If, however, you could arrive back at earth only 110 days after you'd left- thereby synchronizing your perceived passage of time to the rest frame, you'd effectively be making the trip instantaneously (minus 50 days per leg). I'll explain how a little later. You'd be engaging in interstellar time stoppage. You'd almost be time traveling. You'd be able to deliver information about a distant place a whole ten years earlier than it could have arrived by radio. As long as you didn't get it there before you left- obviating the need to make the trip, you wouldn't be violating causality. The information would be between 50 and 60 days old from the standpoint of a single universal frame of reference- a reference we'll call "hypertime." If the distance between the two locations was less, then the gap in time would also be less. If you collapsed the distance to zero, you'd collapse the gap to zero (simultaneous time and place)- you'd never actually get information earlier, from the hypertime perspective, than it was actually produced. The only reason causality wouldn't be breached is because you never actually traveled faster than light. Traveling faster than light goes beyond the instantaneous. It is tantamount to traveling back in time.

How to do it though?

Assume that, before we leave, we built an Einstein-Rosen bridge, using matter with negative mass to keep it open, and take one end of the bridge with us. That's a massive assumption, but as long as building such a bridge is possible, then the assumptions that follow are sound.

We take one end of the bridge to a distant planet, some 10 light years away. We now have a wormhole. If we were to travel through the wormhole, we'd appear instantly back on earth. Let's assume, as Stephen Hawking has, that the act of traveling through it causes a feedback cascade that collapses the bridge, making travel across space impossible. Let's say that the most we can hope for is to keep the bridge open at a distance. Being able to travel through a wormhole at all involves a massive assumption that is probably wrong. However, without it, there's no point in continuing.

We spend ten days at our destination, and then we travel home at 100 gee, arriving fifty days later according to the ships clock.

The mobile end of the ER bridge is then reunited, in terms of literal proximity, with the stationary end. The stationary end is now 20.07 years older. The mobile end is 110 days older. By traveling through the bridge at this point, we emerge on the other side a mere 110 days after we left. We travel back in time- but it's not our own time we travel back into because were weren't around. Assuming that going through the bridge is done in a way that doesn't challenge causality, then it might be allowed. On the other hand, if we travel through and then destroy the bridge, which must continue to exist for another twenty years, or otherwise interfere with crossing through it in the future, then we've created a forbidden paradox. Or, let's say that 20 years later, we choose not to go through the bridge to emerge 20 years earlier. Again, a paradox. However, it's conceivable that we could design a system that would insulate us from paradoxes.

For instance, imagine that the ER bridge could not be accessed without being linked with the missing half. Travel and communication through it wouldn't be possible, but the two ends would still age differently. What if the ship were designed in such a way as to make it impossible to leave the ship without traveling through the ER bridge? Or, even better, a design that physically forces you to travel through when the side are connected. If these decisions were made in advance, and insulated from influence, then the spectre of free-will tampering wouldn't have to emerge.

Perhaps what we need is two bridges.

You go through the first to enter the ship at the beginning of the trip. When the ship physically detaches itself, the stationary end closes and the mobile end opens onto a second bridge which is entirely contained on the ship. Ideally, there would be a neutral region between these, but it is also conceivable that no neutral area exists, and that the bridge is effectively continuous with three sections and two areas where it is stretched across cosmic distances- one for each leg of the trip. The occupants live inside the second half of the bridge- the one that isn't being stretched during the first transit. Once they arrive, they leave the ship via the second bridge, opening it onto the distant planet. When they depart, they leave half of the second bridge behind, closing it from within as they depart to prevent it from being destroyed by a paradox-forbidding cascade. This allows the ship to return again to that distant planet with the same benefit of near instantaneous travel. Limited virtual simultaneity is established between the two locations, though this is different from the simultaneity of hypertime.

When they arrive back on earth, we make it so that the only way to exit the ship is via the local bridge, opening it from within. As long as no one who remained on earth can enter the ship by other means and exit via the wormhole, no actual time travel is possible. If we say that time travel is impossible as a basic requirement of the universe, then we could assume that this is prevented by stating that it is simply impossible to do that. Also, that it is impossible to travel through an ER bridge over great distances, and that it is impossible to enter an ER bridge that is not linked locally (same thing, said twice). If we disallow the breakdown of causality, but not the existence of an ER bridge, then this constraint allows for hyperspace-like travel despite never entering into a literal "hyperspace" other than the strange area within the ER bridge itself.

This scenario assumes a very particular type of ER bridge- one with non-trivial length and extradimensional topology not normally required by an ER bridge. In essence, it needs to have regions that extend beyond the point where the stretch is taking place. It needs to be cut off from normal space, and for its contents to be separated from normal space by the wall of the ER bridge, even though, if traveling through the wall of the bridge were possible, they would simply emerge somewhere in deep space (wherever the ship carrying the bridge happened to be located at the time).

To make the proposition even more elegant, we'd have to say that the ship itself either penetrates the wall (by field or substance), or that the ship can travel through the ER bridge, or is, perhaps, constantly within it, or within the neutral area between two bridges. However, penetrating the wall in any way violates the nature of the allowability of the ER bridge (see above). Therefore, the only solution that doesn't leave a starship parked out in space 20 years later is for the ship to travel through the bridge itself. That means that the bridge would have to be moved, ie carried, from within the bridge itself. This is a problem, since the ship needs to be able to interact with external reality in order to move relative to it.

Assuming you could do that, you've got yourself some hyperspace.