icekatze wrote:hi hi
No... it doesn't matter what perspective you are looking at it from. Massless particles and waves travel at c regardless of the motion of the source or the inertial frame of reference of the observer. The thing that changes between reference frames is not the speed of light but the passage of time. Simultaneity is observer dependent.
There is a painfully simple way to break causality with this method. All you need is two of these spacecraft. Using Bernard's star as an example:
• Spacecraft 1 leaves Sol, and from the frame of reference of the traveler, arrives at Bernard's Star instantly. Bernard's star is roughly 5.980 light years away from Sol.
• Bernard's star is traveling at roughly 142.7 km/s relative to Sol. A time dilation factor (y) of about 1.001135. y = 1 / Sqrt [ 1- (v2 / c2) ]
• Spacecraft 1 sends a message to Spacecraft 2. Spacecraft 2 is in orbit around Bernard's Star, at a similar relative velocity with the star compared to Sol.
• Spacecraft 2 travels back to Sol instantly, and arrives almost 2.48 days before Spacecraft 1 left. ((1.001135 * 5.980) - 5.980 = a difference of .0067873 years.)
The difference lessens depending on the speed that you travel, but increases with the distance you travel. And either way you slice it, if you go faster than light towards another object, from any reference frame, you can break causality.
(It is my understanding of expansion that the various parts of the universe in the early split seconds doesn't actually violate relativity due to the stretched nature of spacetime. And even though the velocity of receding galaxies is not real motion, it still has a very real effect on the waves traveling between them. As is shown with the red-shifting of photons. And because the recession is only moving away, not towards anything else, it further supports Consistency Protection. ie, a deterministic past.)
((Edit: They can also get up to incredible real velocity by falling towards a gravity well, then warping directly away and falling back down again. Repeating that process over an over, while picking up more velocity each time. Something that makes the time dilation factor even greater, and makes it a potential planet destroyer.))
Aha, now I see what you're getting at. Here's the thing about ALL warp drives: they depend upon general relativity, not special relativity. Special relativity applies to flat spacetime (Minkowski spacetime), but when one
warps spacetime, general relativity is used. General relativity solves this conondrum through the use of something called
closed causal loops, and actually allows for the existence of such systems. Whether or not they
actually exist would depend on a theory of quantum gravity. Which we do not have. Alcubierre himself solved the matter in his original paper by causally disconnecting the interior of the bubble from the warp field. It may very well be impossible, however I still see no problem in trying to find out exactly why. Why would it be a sham to measure spacetime oscillations?
Now to answer your two examples:
1) You would need to match Barnard's Star's velocity BEFORE you engage the drive. At lest that's my understanding of it.
2)Once activated, it is my understanding that the bubble would carry the craft in the direction it was already heading. If one falls toward the gravity well, and engaged the drive, it would carry him further inside the well, not outside. One cannot jump back, or so it seems.
EDIT: And still no one seems interested in quantum vacuum plasma thrusters, which is a far more exciting and proven technology
.