Time dilation occurs at speeds far less than the speed of light. For instance GPS satellites and jet planes experience measurable time dilation.

I am very curious about the time effects of such a drive. Does the ability to warp space using such a device necessarily include the ability to warp time? Is it possible, within a frame of reference, to locally reverse the arrow of time and thereby reverse entropy within that pocket?

>A beam of light inside the warp bubble will still travel faster than the ship, for instance.

But that beam of light seen from outside the bubble will appear to travel faster than the speed of light.

Sure, but I think (?) the original question was asking about time dilation in the massive sense: i.e., you go on a round trip to some distant point in space and return, and it's only been a few days for you, but a few hundred or thousand years have passed on Earth. That sort of time dilation.

That sort won't occur with an Alcubierre ship. It's my understanding that the ship isn't actually moving at all inside the bubble -- or, if it is, it's moving extremely slowly.

For instance, assuming the 'string' was made of a tough alloy, would it snap and the coin remain where it was at that time, would the ship be dragged back to where the coin is, or can the question not yet be answered by science?

I ask because, presumably, if the coin can exit and be fine, this could be the basis for some kind of inter galaxy bus, no need to slow down the bus, merely drive your spaceship off the bus and exit the bubble when at your destination.

One of the problems with this approach that has been explored in other papers is that even if you have a warp drive and even if you have actually gotten a ship into it and even if you've managed to point it in the direction you want to go, the collision of the interstellar medium with your warp field tears it apart quite violently and the warp field "collapses". And unlike when they "collapse" on Star Trek and the only manifestation is a polite electronic "whirring" noise, being in a collapsing real warp field is a death sentence, with tidal forces on par with black hole gravitational fields.

Bear in mind, this article only addresses one of the many fundamental challenges to the Alcubierre drive: the energy requirements. Typically, the energy requirement has been considered the primary challenge to the feasibility of the device. But it's not the only one. Science hasn't completely worked out what would happen inside the bubble, or what happens to particles of matter interacting with the bubble at its leading edge. I've heard at least one speculation that the bubble would fill up with Hawking radiation and pretty much roast everyone alive inside it, like a big, interstellar dutch oven.

Another issue is the stability of the bubble itself. Again, the article doesn't really address this issue. But it's a pretty big one.