4 ms·

Nothing you just said contradicts my statement, which was, "there are frames of reference in which that information arrived at the destination before it left th

Nothing you just said contradicts my statement, which was, "there are frames of reference in which that information arrived at the destination before it left the origin." I suspect that you don't know anything at all about Special Relativity, in which case, there's not much more I can tell you except to go educate yourself.

teamonkey 14y ago
Special Relativity only applies to cases where there is uniform relative movement in two or more inertial frames of reference. That is not the case with this theory - the relative movement is clearly not uniform and although I've not read the paper I'm certain that the time warp provides a non-inertial frame. TL;DR - ignore Special Relativity completely, General Relativity is the only thing that applies here.
- nessus42 14y ago
  Special Relativity applies ANY TIME that you transmit information from one point A in an inertial frame to another point B in an inertial frame. If you can use your warp drive to transmit information from A to B, then Special Relativity applies. If you cannot use your warp drive to transmit information from A to B (e.g., from Earth to Mars), then what good is it? (I've mentioned several times in this thread that you might be able to come up with some sort of FTL drive that doesn't violate causality if you put enough constraints on it to make it useless.)
  - teamonkey 14y ago
    > Special Relativity applies ANY TIME that you transmit information from one point A in an inertial frame to another point B in an inertial frame. Not true. It also implies uniformity of space-time in all inertial frames and the space between them. Since the theoretical purpose of the warp drive is to create a non-uniformity by definition SR does not apply.
    - enraged_camel 14y ago
      Yeah, pretty much. I'm actually amazed that so many people (nessus included - as he seems to be the most vocal poster on this thread) do not know this.
    - nessus42 14y ago
      All Special Relativity requires is that space be more or less flat between point A and point B. It doesn't matter if the information travels from A to B through a wormhole and then into another universe and then out the butt of Dumbo, if it ends up at B before light would, then causality has been violated. If, on the other hand, your FTL drive bends up space all around us to be like a giant hyperspace pretzel, (1) we're going to have a lot more problems than just a little violation of causality, and (2) causality still ends up being violated via General Relativity.
      - teamonkey 14y ago
        Causality is a consequence of the physical laws you are currently using, not a law in themselves. It just paints a logical boundary condition around what is possible using the current set of laws that you are using. Compare Newtonian causality where there is only one timeframe everywhere to SR causality with its local timeframes to GR which supports warping of space and time. All different and not interchangable. Wormholes cannot exist in SR, therefore applying SR's brand of causality is equally invalid. Under GR the concept of simultaneity is relaxed: the effect is only limited to the light cone of the cause.
        nessus42 14y ago
        Special Relativity is not invalidated by GR: Special Relativity is a special case of GR that tells us what to expect in inertial frames in a flat space. As long as points A and B are in a flat enough space, then the predictions of Special Relativity about the causal nature of information transmitted between A and B BY ANY MEANS will still be true, even if there are nearby wormholes. If Special Relativity tells us that we can make a closed causal loop via the FTL signals that make it through a wormhole, then GR will not overturn this, no matter how the information made it from A to B. I agree that if the space Between A and B is distorted enough so that the light that travels in open space between A and B is seriously affected by a curvature that extends from A to B, then it is true that you cannot use SR to make your predictions, as the premises of SR are violated. But then GR will predict that causality can be violated anyway. (It's generally easier to find ways to violate causality in GR that SR anyway, since it doesn't require FTL transmissions of information in GR to create causal loops.) I refer you to the FTL faq, since it seems that I am not able to talk sense into people on my own: http://www.physicsguy.com/ftl/html/FTL_part4.html http://www.physicsguy.com/ftl/html/FTL_part4.html
- lmm 14y ago
  We're not applying SR to an observer who warps, just to two observers in inertial frames of reference. Suppose we have guy A and guy B who have clocks. They're on spaceships which are both drifting away from each other (i.e. provide inertial frames) at speed c/root 2; at time t=0 they were in the same place. From SR it should be clear that in A's frame, his clock reads 100 at the same time as B's frame reads 50, while in B's frame, when his clock reads 50 A's clock reads 25. All this should be basic and obvious. So suppose an event happens on A's ship at time tA=100, and he transmits this instantly (or sends a courier C on a warpship) to B at time tA=102, when B's clock reads tB=51. From B's perspective, he's just received a message from A at time tB=51 (which is simultaneous with tA=25.5), which A is not going to send until tA=102 i.e. tB=404. Thus, B perceives a violation of causality. (This becomes very obvious if B can send an insta-message back to A with the same technology; B sends it at time tB=54 which is simultaneous with tA=26, A receives it at tA=26, well before he sent the original message at tA=102)
  - Dylan16807 14y ago
    Sure, B sees things happen in the wrong order, but I will maintain that causality is not actually violated until an effect actually disturbs a cause. In other words, if B sends that message back to A, you have violated causality. If B just sits there and watches events happen out of order, then the causality is obscured but not broken.
    - lmm 14y ago
      Maybe. I can't directly see an event disturbing a cause after the first message, but that doesn't mean there's not a way to make it do so. Of course the cheap answer is that it violates SR (and common sense, given the complete symmetry of the situation) for A to be able to send an insta-message to B but B not able to send an insta-message to A.
      - Dylan16807 14y ago
        Well, either one can send a single message. It's the reply from a different frame that causes trouble. In fact you can have unlimited FTL messages sent in a single reference frame. It's only when you combine multiple FTL reference frames that things get wonky.
bluedanieru 14y ago
This is as good a place to start as any: http://en.wikipedia.org/wiki/Relativity_of_simultaneity http://en.wikipedia.org/wiki/Relativity_of_simultaneity

teamonkey 14y ago

Special Relativity only applies to cases where there is uniform relative movement in two or more inertial frames of reference. That is not the case with this theory - the relative movement is clearly not uniform and although I've not read the paper I'm certain that the time warp provides a non-inertial frame. TL;DR - ignore Special Relativity completely, General Relativity is the only thing that applies here.

nessus42 14y ago
Special Relativity applies ANY TIME that you transmit information from one point A in an inertial frame to another point B in an inertial frame. If you can use your warp drive to transmit information from A to B, then Special Relativity applies. If you cannot use your warp drive to transmit information from A to B (e.g., from Earth to Mars), then what good is it? (I've mentioned several times in this thread that you might be able to come up with some sort of FTL drive that doesn't violate causality if you put enough constraints on it to make it useless.)
- teamonkey 14y ago
  > Special Relativity applies ANY TIME that you transmit information from one point A in an inertial frame to another point B in an inertial frame. Not true. It also implies uniformity of space-time in all inertial frames and the space between them. Since the theoretical purpose of the warp drive is to create a non-uniformity by definition SR does not apply.
  - enraged_camel 14y ago
    Yeah, pretty much. I'm actually amazed that so many people (nessus included - as he seems to be the most vocal poster on this thread) do not know this.
  - nessus42 14y ago
    All Special Relativity requires is that space be more or less flat between point A and point B. It doesn't matter if the information travels from A to B through a wormhole and then into another universe and then out the butt of Dumbo, if it ends up at B before light would, then causality has been violated. If, on the other hand, your FTL drive bends up space all around us to be like a giant hyperspace pretzel, (1) we're going to have a lot more problems than just a little violation of causality, and (2) causality still ends up being violated via General Relativity.
    - teamonkey 14y ago
      Causality is a consequence of the physical laws you are currently using, not a law in themselves. It just paints a logical boundary condition around what is possible using the current set of laws that you are using. Compare Newtonian causality where there is only one timeframe everywhere to SR causality with its local timeframes to GR which supports warping of space and time. All different and not interchangable. Wormholes cannot exist in SR, therefore applying SR's brand of causality is equally invalid. Under GR the concept of simultaneity is relaxed: the effect is only limited to the light cone of the cause.
      - nessus42 14y ago
        Special Relativity is not invalidated by GR: Special Relativity is a special case of GR that tells us what to expect in inertial frames in a flat space. As long as points A and B are in a flat enough space, then the predictions of Special Relativity about the causal nature of information transmitted between A and B BY ANY MEANS will still be true, even if there are nearby wormholes. If Special Relativity tells us that we can make a closed causal loop via the FTL signals that make it through a wormhole, then GR will not overturn this, no matter how the information made it from A to B. I agree that if the space Between A and B is distorted enough so that the light that travels in open space between A and B is seriously affected by a curvature that extends from A to B, then it is true that you cannot use SR to make your predictions, as the premises of SR are violated. But then GR will predict that causality can be violated anyway. (It's generally easier to find ways to violate causality in GR that SR anyway, since it doesn't require FTL transmissions of information in GR to create causal loops.) I refer you to the FTL faq, since it seems that I am not able to talk sense into people on my own: http://www.physicsguy.com/ftl/html/FTL_part4.html http://www.physicsguy.com/ftl/html/FTL_part4.html
lmm 14y ago
We're not applying SR to an observer who warps, just to two observers in inertial frames of reference. Suppose we have guy A and guy B who have clocks. They're on spaceships which are both drifting away from each other (i.e. provide inertial frames) at speed c/root 2; at time t=0 they were in the same place. From SR it should be clear that in A's frame, his clock reads 100 at the same time as B's frame reads 50, while in B's frame, when his clock reads 50 A's clock reads 25. All this should be basic and obvious. So suppose an event happens on A's ship at time tA=100, and he transmits this instantly (or sends a courier C on a warpship) to B at time tA=102, when B's clock reads tB=51. From B's perspective, he's just received a message from A at time tB=51 (which is simultaneous with tA=25.5), which A is not going to send until tA=102 i.e. tB=404. Thus, B perceives a violation of causality. (This becomes very obvious if B can send an insta-message back to A with the same technology; B sends it at time tB=54 which is simultaneous with tA=26, A receives it at tA=26, well before he sent the original message at tA=102)
- Dylan16807 14y ago
  Sure, B sees things happen in the wrong order, but I will maintain that causality is not actually violated until an effect actually disturbs a cause. In other words, if B sends that message back to A, you have violated causality. If B just sits there and watches events happen out of order, then the causality is obscured but not broken.
  - lmm 14y ago
    Maybe. I can't directly see an event disturbing a cause after the first message, but that doesn't mean there's not a way to make it do so. Of course the cheap answer is that it violates SR (and common sense, given the complete symmetry of the situation) for A to be able to send an insta-message to B but B not able to send an insta-message to A.
    - Dylan16807 14y ago
      Well, either one can send a single message. It's the reply from a different frame that causes trouble. In fact you can have unlimited FTL messages sent in a single reference frame. It's only when you combine multiple FTL reference frames that things get wonky.

bluedanieru 14y ago

This is as good a place to start as any: http://en.wikipedia.org/wiki/Relativity_of_simultaneity http://en.wikipedia.org/wiki/Relativity_of_simultaneity