In my Warp Drive paper, the warp field effectively negates the effects of SR by changing the length of the ship and the clocks it contains, so that they match the original rest frame where it started from, at all times. In other words, there is no length contraction or time dilation of the accelerated starship. Therefore, the motion of the ship is not relativistic, it's Newtonian. Lorentz transformations do not apply. Again, how can changing the rate of my clock, moving faster or slower, suddenly give me the ability to travel backwards in time, or send a message backwards in time? It doesn't, it can't. The paradox is only there because SR is not applicable, yet everyone insists it is.
Quote from: WarpTech on 07/19/2017 09:42 pmIn my Warp Drive paper, the warp field effectively negates the effects of SR by changing the length of the ship and the clocks it contains, so that they match the original rest frame where it started from, at all times. In other words, there is no length contraction or time dilation of the accelerated starship. Therefore, the motion of the ship is not relativistic, it's Newtonian. Lorentz transformations do not apply. Again, how can changing the rate of my clock, moving faster or slower, suddenly give me the ability to travel backwards in time, or send a message backwards in time? It doesn't, it can't. The paradox is only there because SR is not applicable, yet everyone insists it is.None of what you said changes the scenario I described. When 2 people have a copy of your magic FTL device, what happens when they act out the scenario above?Remember, GR allows CTCs, just all of the solutions can't be implemented for reasons like needing exotic matter with negative mass. You have not shown that you don't generate CTCs.
The scenario you put forth has an assumption built into it. That is, in the frame of ship 2 the distance to Earth is shorter AND this makes a difference when the FTL drive is switched on. In my model, when the FTL is switched on, regardless of how fast ship 2 was going relative to the Earth prior to that. After the switch, the length of the ship and the clocks on board are "tuned" to be the same as that on Earth, at all times, regardless of the FTL speed. So the distance to Earth is not what it was before the FTL was turned on. In the case of ship 2, that distance gets longer in the FTL frame. Lorentz transformations go out the window. In other words, there is no FTL frame where the distance to Earth is shorter.
Another way to avoid the paradox would be a BSG Jump drive. Regardless of how fast the ship is moving, it can instantaneously jump to another point in space and arrive "at rest" at those coordinates. There would be no way to send the ship back in time, because it didn't take any time to get there.
Quote from: KelvinZero on 07/18/2017 08:33 amIm sure I have been on threads discussing this before, I was probably on that one too.. And I think one result was that you can produce a paradox with just a single FTL 'jump'.. If that is true then choosing a single reference frame does not resolve the issue. Maybe someone can confirm that.The difference from earlier threads is that I wanted to concentrate on published solutions or speculations. Someone must have done this.(just googled "resolutions to FTL paradoxes", found various "researchgate.net" papers, but I don't know if they are reputable.. I will probably have a go at reading them to at least see what they claim.. not sure I will understand them well enough to even do that.)It was published in JBIS, Nov. 2015 issue, (didn't come out until Feb. 2016).http://www.jbis.org.uk/paper.php?p=2015.68.347There are no paradoxes here. Another paper I put together earlier also resolved several issues with warp drives.https://www.researchgate.net/publication/251231464_THE_CONTROLLED_REFRACTIVE_INDEX_WARP_DRIVETodd
Im sure I have been on threads discussing this before, I was probably on that one too.. And I think one result was that you can produce a paradox with just a single FTL 'jump'.. If that is true then choosing a single reference frame does not resolve the issue. Maybe someone can confirm that.The difference from earlier threads is that I wanted to concentrate on published solutions or speculations. Someone must have done this.(just googled "resolutions to FTL paradoxes", found various "researchgate.net" papers, but I don't know if they are reputable.. I will probably have a go at reading them to at least see what they claim.. not sure I will understand them well enough to even do that.)
Quote from: WarpTech on 07/20/2017 04:58 amThe scenario you put forth has an assumption built into it. That is, in the frame of ship 2 the distance to Earth is shorter AND this makes a difference when the FTL drive is switched on. In my model, when the FTL is switched on, regardless of how fast ship 2 was going relative to the Earth prior to that. After the switch, the length of the ship and the clocks on board are "tuned" to be the same as that on Earth, at all times, regardless of the FTL speed. So the distance to Earth is not what it was before the FTL was turned on. In the case of ship 2, that distance gets longer in the FTL frame. Lorentz transformations go out the window. In other words, there is no FTL frame where the distance to Earth is shorter.The Earth is 11 light years away in the Earth frame, and around 8 light years away in the ship frame when the ship 2 FTL is switched on. It is utterly nonsensical to say that the ship's reference frame instantly changes to have the same inertial motion as Earth when it turns on. There is nothing special about the Earth frame.All you have done is created a preferred frame for the entire universe which conveniently is the Earth frame. This has no experimental basis in reality, and instead contradicts everything known about relativity and astrodynamics.Quote from: WarpTech on 07/20/2017 04:58 amAnother way to avoid the paradox would be a BSG Jump drive. Regardless of how fast the ship is moving, it can instantaneously jump to another point in space and arrive "at rest" at those coordinates. There would be no way to send the ship back in time, because it didn't take any time to get there.You apparently have never read the first page of any description of relativity. The very first point is that there is no such things as an arbitrary "at rest." No reference frame is special. For an instantaneous jump drive, the ship would just have to accelerate back in the direction it came sufficiently quickly, before reengaging the drive. It accelerating into a different frame would mean that it is now in a frame where the time it departed from is in the future. If all they want is to send a message back in time, it is even easier, just have someone already moving fast at the destination.
As you say the only frame that matters is the frame that the person with the FTL drive is in. Instead of randomly switching from the ship 2 frame to the Earth frame, let ship 2 stay in the ship2 frame and see what happens."at rest with respect to the target coordinates" is nonsensical. The "target coordinates" would be an event in space-time. An event does not have a velocity, and can be described in any arbitrary frame with any velocity.
Quote from: meberbs on 07/20/2017 06:24 pmAs you say the only frame that matters is the frame that the person with the FTL drive is in. Instead of randomly switching from the ship 2 frame to the Earth frame, let ship 2 stay in the ship2 frame and see what happens."at rest with respect to the target coordinates" is nonsensical. The "target coordinates" would be an event in space-time. An event does not have a velocity, and can be described in any arbitrary frame with any velocity.You are far too nit-picky! You just like to argue and be right.If I'm the pilot of ship 2 and I want to be home on time for dinner, I had better have my clock synchronized with my wife's and when I engage my BSG Jump Drive, I want to arrive home, with my ship parked in the garage. Hence, "at rest with respect to the target coordinates" is far from "nonsensical"!
But how do you synchronize the clocks? Personally I think this discussion shows the paradoxes cannot be resolved.
Quote from: Phil Stooke on 07/20/2017 07:28 pmBut how do you synchronize the clocks? Personally I think this discussion shows the paradoxes cannot be resolved."I'm from Earth, I only work in space." It was synchronized before I left the house. Since neither my warp drive nor my jump drive cause time dilation, our clocks remain synchronized until I get home for dinner.
IMO, Lorentz transformations are the cause of the problem, because when using them, moving reference frames are arbitrary and indistinguishable. These are Math assumptions.
Reality, where accelerations are used to change speed, works differently. IMO, changing the rate of my clock does not allow me to send messages backwards in time.
Quote from: WarpTech on 07/20/2017 09:20 pmReality, where accelerations are used to change speed, works differently. IMO, changing the rate of my clock does not allow me to send messages backwards in time.It isn't the changing clock speeds that cause time travel, it is the FTL device. Accelerations to some extent can be handled in special relativity, at least for simple cases including resolving the "twin paradox" which really is just recognizing there are 3 inertial reference frames involved, not 2.
The Alcubierre warp drive had the feature that dtau=dt, the proper time aboard the ship matched the same time as the folks back home. That is the "Goal"! It is what my drive was designed to do. Earth is only preferred, because that is where we come from. It could just as easily be tuned to a different home-clock, but what clock you choose is irrelevant. Time is relative to where you call "home".
Quote from: meberbs on 07/20/2017 09:45 pmQuote from: WarpTech on 07/20/2017 09:20 pmReality, where accelerations are used to change speed, works differently. IMO, changing the rate of my clock does not allow me to send messages backwards in time.It isn't the changing clock speeds that cause time travel, it is the FTL device. Accelerations to some extent can be handled in special relativity, at least for simple cases including resolving the "twin paradox" which really is just recognizing there are 3 inertial reference frames involved, not 2.You keep missing the point. My FTL device works by changing the rate of "my clock" and changing the length of "my ship". This what the warp field generated around my ship does. It compensates for time dilation and length contraction and thereby allows it to travel FTL without any affects of length contraction or time dilation typical of SR. Again, altering the space around my ship does not allow me to send the ship or any signals backwards in time. Your imaginary FTL device may allow it, but the one I wrote about in my paper does not. It's not relativistic, it's Newtonian. dtau=dt on this ship, my proper time matches that of my wife at home, all day, regardless of my speed. That's how FTL is done "right".
...You cannot just wish this problem away, and nothing you have said addresses it. Ship 2 has no reason to have "synchronized" anything with Earth, and is just relaying a message before it continues to move away from Earth/allow Earth to move away from it at 0.7 c. Neither the Earth frame nor the ship2 frame is any more valid, so the behavior of any FTL drive must be the same in both. Also note that there is no reference to what the people on either ship experience because it doesn't matter. (When talking about the ship2 frame, I am referring to a pure inertial frame of some observer initially commoving with ship2.)
Ship 2 is moving at 0.7c and is at the same location in space-time, where ship 1 exits FTL. This is where the two ships are at the same place "at the same time", so this is where the two coordinate systems (primed and unprimed) are coincident at t=t'=0. Earth has already advanced 5 weeks into the future. So at this point, no matter how fast ship 2 goes, it can never get to Earth before ship 1 left.
Quote from: WarpTech on 07/21/2017 02:25 amShip 2 is moving at 0.7c and is at the same location in space-time, where ship 1 exits FTL. This is where the two ships are at the same place "at the same time", so this is where the two coordinate systems (primed and unprimed) are coincident at t=t'=0. Earth has already advanced 5 weeks into the future. So at this point, no matter how fast ship 2 goes, it can never get to Earth before ship 1 left.It is not t=0 in either frame when ship 1 exits FTL. You just effectively introduced 2 new frames without fully defining them, since you also have to redefine where x=0, and then you would find in the new primed frame, ship 1 left more than 9 years in the future from when it arrived. Stick to just the 2 frames, the new ones just differ from the ones I used by straight constants, and if you actually did everything consistently, the net result wouldn't change. According to Ship 2 when ship 1 exits FTL, it is still years before ship 1 had entered FTL, no matter where you choose the origin of this frame.
According to Ship 2 when ship 1 exits FTL, it is still years before ship 1 had entered FTL, no matter where you choose the origin of this frame.
Quote from: meberbs on 07/21/2017 06:25 amQuote from: WarpTech on 07/21/2017 02:25 amShip 2 is moving at 0.7c and is at the same location in space-time, where ship 1 exits FTL. This is where the two ships are at the same place "at the same time", so this is where the two coordinate systems (primed and unprimed) are coincident at t=t'=0. Earth has already advanced 5 weeks into the future. So at this point, no matter how fast ship 2 goes, it can never get to Earth before ship 1 left.It is not t=0 in either frame when ship 1 exits FTL. You just effectively introduced 2 new frames without fully defining them, since you also have to redefine where x=0, and then you would find in the new primed frame, ship 1 left more than 9 years in the future from when it arrived. Stick to just the 2 frames, the new ones just differ from the ones I used by straight constants, and if you actually did everything consistently, the net result wouldn't change. According to Ship 2 when ship 1 exits FTL, it is still years before ship 1 had entered FTL, no matter where you choose the origin of this frame.Correction: Ship 1 entered FTL at t=-5 weeks, and exited FTL at t=0. This EVENT is coincident in both frames. Ship 1 and ship 2 are at the same place, at the same time, t=t'=0. With my FTL warp drive, the clock on ship 1 is the same as the clock on Earth. What you said;QuoteAccording to Ship 2 when ship 1 exits FTL, it is still years before ship 1 had entered FTL, no matter where you choose the origin of this frame.is logically and physically impossible. If this is what the Lorentz transformation is telling you, you're doing something wrong.
The only thing logically impossible is FTL.