On 28 Mar 2019 at 18:30, Kurt Feltenberger wrote: > I don't see any sort of time travel or other paradoxes being created > by how Traveller handles "FTL" travel. Jumpspace isn't normal space, > it's something else, and the drive takes the ship and just enough of > ourspace with it (a bubble, grid, whatever) to maintain reality during > the duration of the jump. For the time spent in J-space, the ship, > its contents, and the "bubble" aren't in this reality. The problem is that the time travel bit is a function of the geometry of *our* spacetime. It doesn't matter *how* you from point A at time T1 to point B at T2 (values for the distance covered and elapsed time vary according to the reference frame of the observer). If the interval (a value that is calculated somewhat like you calculate distance between (X1,Y1,Z1) and (X2,Y2,Z2), but includes the time coordinates and the speed of light) is such that light couldn't have gotten between the two points in spacetime then the relationship between the two events will be seen as time travel in a number of reference frames. That is, for some observers event 1 (the jump entry) will occur *after* event 2 (the jump exit). Doesn't how you get from point (X1,Y1,Z1,T1) to point (X2,Y2,Z2,T2). All that matters is the space time co-ordinates of the two events. On the other hand, time travcel isn't *explictly* forbidden by relativity. It just creates some odd restrictions. FTL strict local casuality relativity Pick any *two*. Casuality is "causes must alway preceed events". Local causality means that it applies to any frame. *Global* casuality allows causes to preceed effects in some frames. (I may have those backwards). and you can swap in "time travel" for "FTL" in the above set of choices. relativity compliant time travel puts some really odd conditions on time travel. Like you can't change the past. But if you don't *know* what happened in the past, then you can do things. Mind you, you may *think* you know what happened but be wrong. :-) This goes clear down to the quantum level. So if you try to shoot Hitler, *something* will prevent it. Because that is the highest probability event. -- Leonard Erickson (aka shadow) shadow at shadowgard dot com
