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#260 by meberbs on 04 Sep, 2017 21:55
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What part of "already did the math" did you not understand?I already did the math that demonstrates that this would very much be in ship 1's past. Do you have any specific disputes with that math?
I'll bite. Please provide math that supports this short story:
1. Ship uses A-FTL to (instantly) jump 100 light years away from point X, to point Y
2. At point Y, accelerates to 0.7c (instantly)
3. Ship uses A-FTL to jump (instantly) back from point Y to point X, ends up in its own past.
You claimed that you had read my posts with math from the beginning of the thread.
Here is a link to one that answers basically the same scenario, except with only 10 light years, and allowing 5 weeks travel time instead of instantaneous. Ship 2 in that scenario is exactly equivalent to a ship 1 that accelerates rapidly to match ship 2's speed. Instantaneous travel and larger distance only make the amount of time travel larger.
(Top of the quote is a link back to the full post)Let me break it down with numbers. Define that Ship 1 is at rest in the Earth frame at t= 0, x = 0. At this time ship 1 activates its FTL drive, allowing it to arrive at a location in the earth frame of x = 10 light years, at time t = 5 weeks, (apparent speed of roughly 100 c). ...
Contrary to one of your previous posts where you claimed that I didn't account for length contraction, you can see in that post where I explicitly listed the length contracted distance to Earth.PS. Yes I have read your examples, they are inadequate IMO. Just to point out some error, Observer1 at A sees distance from A to B to be 10ly, Observer2, traveling at relativistic speed of 0.7c passing A towards B would tell its a different distance; and to him, it would be. It is how relativity works. You ignored that completely in your calculations.
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#261 by aceshigh on 05 Sep, 2017 03:08
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This is a great primer for what the Lorentz Transformations are, and what the Speed of Light actually is.
yeah, I also posted these two other videos that specifically talk about superluminal travel... Kamill says he read the whole thread, but I think he skipped these videos
https://www.youtube.com/watch?time_continue=646&v=HUMGc8hEkpc -
#262 by kamill85 on 05 Sep, 2017 11:53
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This is a great primer for what the Lorentz Transformations are, and what the Speed of Light actually is.
yeah, I also posted these two other videos that specifically talk about superluminal travel... Kamill says he read the whole thread, but I think he skipped these videos
https://www.youtube.com/watch?time_continue=646&v=HUMGc8hEkpc
That is because those videos are barely related to the Apparent FTL travel. They are both about "what happens if you travel faster than light through space, and why you cannot". -
#263 by kamill85 on 05 Sep, 2017 12:36
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What part of "already did the math" did you not understand?I already did the math that demonstrates that this would very much be in ship 1's past. Do you have any specific disputes with that math?
I'll bite. Please provide math that supports this short story:
1. Ship uses A-FTL to (instantly) jump 100 light years away from point X, to point Y
2. At point Y, accelerates to 0.7c (instantly)
3. Ship uses A-FTL to jump (instantly) back from point Y to point X, ends up in its own past.
You claimed that you had read my posts with math from the beginning of the thread.
Here is a link to one that answers basically the same scenario, except with only 10 light years, and allowing 5 weeks travel time instead of instantaneous. Ship 2 in that scenario is exactly equivalent to a ship 1 that accelerates rapidly to match ship 2's speed. Instantaneous travel and larger distance only make the amount of time travel larger.
(Top of the quote is a link back to the full post)Let me break it down with numbers. Define that Ship 1 is at rest in the Earth frame at t= 0, x = 0. At this time ship 1 activates its FTL drive, allowing it to arrive at a location in the earth frame of x = 10 light years, at time t = 5 weeks, (apparent speed of roughly 100 c). ...
Contrary to one of your previous posts where you claimed that I didn't account for length contraction, you can see in that post where I explicitly listed the length contracted distance to Earth.PS. Yes I have read your examples, they are inadequate IMO. Just to point out some error, Observer1 at A sees distance from A to B to be 10ly, Observer2, traveling at relativistic speed of 0.7c passing A towards B would tell its a different distance; and to him, it would be. It is how relativity works. You ignored that completely in your calculations.
Like I said earlier, your math is not fully correct. For example, if ship1 and ship2 have same origin at x=0, and ship2 is going at 0.7c, then for ship2 to witness ship1's exit 10 light years away, would mean that in the tim reference of ship1, ship2 would have to have a head start of at least 14 years. So, ship2 leaves x=0 at year t=-14y, arrives at exit point at around t=5weeks. Then, jumps back, and he isnt getting back any of those 14 years, sorry. He still ends up at ship1's relative time of t=5weeks(+[5*timedilation]weeks if we assume its same A-FTL and not instant). So yeah, check all reference frames and you will see your math is wrong. -
#264 by eriblo on 05 Sep, 2017 14:06
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Once again: It does not matter how you travel between two the two points, only that you can be at two places in space "faster than light can travel between them"....
This is a great primer for what the Lorentz Transformations are, and what the Speed of Light actually is.
yeah, I also posted these two other videos that specifically talk about superluminal travel... Kamill says he read the whole thread, but I think he skipped these videos
...
That is because those videos are barely related to the Apparent FTL travel. They are both about "what happens if you travel faster than light through space, and why you cannot"....
Okej, others have already demonstrated the math but I'll do your exercise. Lets assume that the A-FTL drive causes a flash of light when activated for visualization purposes. The numbers are slightly rounded by using a Lorentz factor of 1.4 instead of 1.4003 for 0.7 c.
I'll bite. Please provide math that supports this short story:
1. Ship uses A-FTL to (instantly) jump 100 light years away from point X, to point Y
2. At point Y, accelerates to 0.7c (instantly)
3. Ship uses A-FTL to jump (instantly) back from point Y to point X, ends up in its own past.
Ship jumps from X to Y 100 light years away, sending out a light pulse that will reach Y in 100 years. If it were to jump back immediately the second light pulse would reach X in 100 years as well (and they would pass each other half way). The two events (departure and arrival) are simultaneous in this reference frame.
Instead the ship at Y instantly accelerates to 0.7 c towards X. The distance to X is now contracted to 100/1.4 = 71.4 light years and the light from X will arrive at Y in 100*1.4 = 140 years (as would be shown by the time dilation of a timer left at Y and now traveling at 0.7 c w.r.t. the ship). The light pulse will then have taken 71.4/(1-0.7) = 238 years to cover the distance and was therefore emitted from X 238-140 = 98 years ago in this reference frame. The ship jumps back to X and arrives 98 years after the pulse was sent and 71.4/(1+0.7) = 42 years before the light form its departure from Y arrives at X.
These times are 98/1.4 = 70 years and 42/1.4 = 30 years in the reference frame of X and Y. According to X the ships departs, arrives at Y and departs again instantaneously but returns 70 years in the future on the jump back. Inconvenient but maybe not a problem?
The symmetric scenario is that the ship instead accelerates instantaneously to 0.7 c away from X before making the second jump. The X-Y distance and the time of arrival of the departure light pulse at Y are again 71.4 light years and 140 years in the future. The pulse will now have taken 71.4/(1+0.7) = 42.0 years to cover the distance and must therefore be emitted 140-42= 98 years in the future in this reference frame. The ship jumps back to X and arrives 98 years before the pulse was sent and 71.4/(1-0.7) = 238 years before the light from its departure from Y arrives at X.
These times are 98/1.4 = 70 years and 238/1.4 = 170 years in the reference frame of X and Y. According to X the ships departs, arrives at Y and departs again instantaneously but returns 70 years before it left on the jump back...
Please let me know if I made any errors.
EDIT: Fixed some grammar.
EDIT:Of course I get the directions wrongNever mind
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#265 by meberbs on 05 Sep, 2017 14:11
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Like I said earlier, your math is not fully correct.
You said earlier that I didn't account for length contractino, when i explicitly did.
For example, if ship1 and ship2 have same origin at x=0, and ship2 is going at 0.7c, then for ship2 to witness ship1's exit 10 light years away, would mean that in the tim reference of ship1, ship2 would have to have a head start of at least 14 years.
First, it is irrelevant whether ship 2 started from Earth, or took some other path to end up there and as I stated, the result is the same as if ship 1 rapidly accelerates to 0.7 c after the jump. The "same origin" is simply part of applying the Lorentz transformation. The math is just simpler if you define the origins to be the same event.
Second, time dilation means that it has not been 14 years for ship 2, if ship 2 had originally departed from Earth.So, ship2 leaves x=0 at year t=-14y, arrives at exit point at around t=5weeks.
Those numbers are all in the ship 1 frame, but time and distance for ship 2 need to be measured in the ship 2 frame.Then, jumps back, and he isnt getting back any of those 14 years, sorry.
Not 14 years, if you actually calculate it, you would find the time of Ship1 exiting FTL is t=-483 weeksin its own frame.He still ends up at ship1's relative time of t=5weeks(+[5*timedilation]weeks if we assume its same A-FTL and not instant). So yeah, check all reference frames and you will see your math is wrong.
This is simply untrue because you did not apply the Lorentz transformation, and you are trying to calculate ship 2's behavior in something other than its own rest frame. Since all frames are equal, the ship 2 rest frame is equally valid, and we defined the FTL speed as relative to the ship's own rest frame.
You are the one who needs to learn to do calculations in different frames. -
#266 by meberbs on 05 Sep, 2017 14:59
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Instead the ship at Y instantly accelerates to 0.7 c towards X.
This is the wrong direction of acceleration if you want to setup time travel to the past.
Your calculations attempt to simply use the time dilation and length contraction effects. these are not the full story of relativity, you instead need to use the full Lorentz transformations that have the time dilation and length contraction embedded in them, but also account for movement of the origins of the frames.The distance to X is now contracted to 100/1.4 = 71.4 light years and the light from X will arrive at Y in 100*1.4 = 140 years (as would be shown by the time dilation of a timer left at Y and now traveling at 0.7 c w.r.t. the ship). The light pulse will then have taken 71.4/(1-0.7) = 238 years to cover the distance and was therefore emitted from X 238-140 = 98 years ago in this reference frame.
No, speed of light is the same in every frame, and in this frame the earth is travelling towards the source of the signal, so they will meet in the middle in just 71.4/(1+0.7) = 42 years. Also, since the acceleration happens at the same time and location as the light pulse, the light pulse in this frame was just emitted.The ship jumps back to X and arrives 98 years after the pulse was sent and 71.4/(1+0.7) = 42 years before the light form its departure from Y arrives at X.
Somehow some of your backwards description canceled out, so you got to the arriving 42 years before the light (in the Y frame) answer correctly. Also, you are correct that it arrives at t = 70 years in the X frame, but the calculation of t' = 30 years in the Y frame does not make sense. I think part of the problem is that you never clearly defined the origin of the Y frame. Usually you pick the origin of the 2 frames to be the same event in spacetime (the ship originally departing point X in this case.) With that definition, the time in that frame is the 98 years number. By the construction of the problem, this is the same time in the Y frame as the time in the Y frame at point Y just before the jump. Your calculation of 42/1.4 = 30 is actually the calculation of how many years remaining before the light pulse arrives at X in the X frame as of when the ship arrives back at X.
These times are 98/1.4 = 70 years and 42/1.4 = 30 years in the reference frame of X and Y.According to X the ships departs, arrives at Y and depart again instantaneously but returns 70 years in the future on the jump back. Inconvenient but maybe not a problem?
This is correct, it is the other direction of acceleration that leads to a paradox.Please let me know if I made any errors.
Let me know if you are still confused, and I can try to help. I don't think I did a particularly good job explaining in this post, so I assume you will have questions. -
#267 by eriblo on 05 Sep, 2017 18:18
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You had me confused with the directions there for a while - are you saying I'm correct (boost away to put your FTL origin in the future and back to put it in the past)? I did both to show the difference.Instead the ship at Y instantly accelerates to 0.7 c towards X.
This is the wrong direction of acceleration if you want to setup time travel to the past.
Your calculations attempt to simply use the time dilation and length contraction effects. these are not the full story of relativity, you instead need to use the full Lorentz transformations that have the time dilation and length contraction embedded in them, but also account for movement of the origins of the frames.
I was trying to visualize it a bit more than just boosting coordinates as that has been done in the thread already. As you say, you can do it manually by time dilation and length contraction if you consider the shifting of the origin.
Yes, the speed of light is 1, I'm just being lazy and calculating the time as how far ahead of X the first light pulse has to get divided by the relative speed.The distance to X is now contracted to 100/1.4 = 71.4 light years and the light from X will arrive at Y in 100*1.4 = 140 years (as would be shown by the time dilation of a timer left at Y and now traveling at 0.7 c w.r.t. the ship). The light pulse will then have taken 71.4/(1-0.7) = 238 years to cover the distance and was therefore emitted from X 238-140 = 98 years ago in this reference frame.
No, speed of light is the same in every frame, and in this frame the earth is travelling towards the source of the signal, so they will meet in the middle in just 71.4/(1+0.7) = 42 years. Also, since the acceleration happens at the same time and location as the light pulse, the light pulse in this frame was just emitted.
This is a little confusing - X and Y are two points in space the same reference frame, with the second frame being that of the boosted ship. Yes, I mix and match a bit between the frames here, I guess it doesn't help the clarity...The ship jumps back to X and arrives 98 years after the pulse was sent and 71.4/(1+0.7) = 42 years before the light form its departure from Y arrives at X.
Somehow some of your backwards description canceled out, so you got to the arriving 42 years before the light (in the Y frame) answer correctly. Also, you are correct that it arrives at t = 70 years in the X frame, but the calculation of t' = 30 years in the Y frame does not make sense. I think part of the problem is that you never clearly defined the origin of the Y frame. Usually you pick the origin of the 2 frames to be the same event in spacetime (the ship originally departing point X in this case.) With that definition, the time in that frame is the 98 years number. By the construction of the problem, this is the same time in the Y frame as the time in the Y frame at point Y just before the jump. Your calculation of 42/1.4 = 30 is actually the calculation of how many years remaining before the light pulse arrives at X in the X frame as of when the ship arrives back at X.
These times are 98/1.4 = 70 years and 42/1.4 = 30 years in the reference frame of X and Y.
I'm unsure of whether I'm confused or notAccording to X the ships departs, arrives at Y and depart again instantaneously but returns 70 years in the future on the jump back. Inconvenient but maybe not a problem?
This is correct, it is the other direction of acceleration that leads to a paradox.Please let me know if I made any errors.
Let me know if you are still confused, and I can try to help. I don't think I did a particularly good job explaining in this post, so I assume you will have questions.
If I put the origin at Y=(x,t)=(0 light years, 0 years) I get:
Go from Earth at X=(-100,0) to Y=(0,0), boost to v=+0.7 c (i.e. away from X)
=> You're now at Y'=(0,0) and you left in the future at X'=(-140,98).
Earth is currently at (-71.4,0), go there and boost back
=> You're now at (-100,-70), i.e. same location you started from (Earth) but 70 years before you left.
EDIT: Clarified by starting from Earth.
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#268 by meberbs on 05 Sep, 2017 18:44
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I only went through the math on the accelerate towards point X version, which you correctly concluded does not lead to a paradox.
You had me confused with the directions there for a while - are you saying I'm correct (boost away to put your FTL origin in the future and back to put it in the past)? I did both to show the difference.Instead the ship at Y instantly accelerates to 0.7 c towards X.
This is the wrong direction of acceleration if you want to setup time travel to the past.
Your calculations attempt to simply use the time dilation and length contraction effects. these are not the full story of relativity, you instead need to use the full Lorentz transformations that have the time dilation and length contraction embedded in them, but also account for movement of the origins of the frames.I'm unsure of whether I'm confused or not
Yes, I believe that is all correct. The main errors I saw in your original post were in your description of the time light takes (I can't see a relevant frame where light would be travelling for 238 years, because none of the distances are that large. Looking again, this seems to be due to you flipping the sign on the velocity, treating it as if X was moving away from Y in the setup where X was moving towards Y.) If I put the origin at Y=(x,t)=(0 light years, 0 years) I get:
Go from X=(-100,0) to Y=(0,0), boost to v=+0.7 c (i.e. away from X)
=> You're now at Y'=(0,0) and you left in the future at X'=(-140,98).
Location X' is currently at (-71.4,0), go there and boost back
=> You're now at (-100,-70), i.e. same location you started from but 70 years before you left. -
#269 by RSE on 05 Sep, 2017 18:58
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The underlying question is:
Does the Lorentz Transformation (And Fitzgerald Contraction) actually apply at supraluminal speeds (if such a thing exits)?
I am not voicing an opinion about this, just noting that is what the debate is about.
I will note - if it does, the object would have a negative length, to go along with travelling backwards in time.
Also, what would be perceived inside such a reference frame? How would it be perceived from an external reference frame? -
#270 by aceshigh on 06 Sep, 2017 05:18
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This is a great primer for what the Lorentz Transformations are, and what the Speed of Light actually is.
yeah, I also posted these two other videos that specifically talk about superluminal travel... Kamill says he read the whole thread, but I think he skipped these videos
https://www.youtube.com/watch?time_continue=646&v=HUMGc8hEkpc
That is because those videos are barely related to the Apparent FTL travel. They are both about "what happens if you travel faster than light through space, and why you cannot".
no, there is a third video, which you can only see the link, which uses the example of a WARP DRIVE ship. Link corrected so you can see the video
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#271 by aceshigh on 06 Sep, 2017 05:23
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maybe Miguel Alcubierre, the guy who invented the concept of warp drive (as we think it nowadays), can convince you?
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#272 by KelvinZero on 06 Sep, 2017 06:56
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maybe Miguel Alcubierre, the guy who invented the concept of warp drive (as we think it nowadays), can convince you?
He gives the basic problem near the beginning (the light cone diagrams we have all seen, the problem of simultaneous being different for different observers.)
https://www.youtube.com/watch?v=zj5Jxux4uYk?t=626 (or go to 10:26)
Starts talking about Grandfather paradox here: https://www.youtube.com/watch?v=zj5Jxux4uYk?t=2700 (45:00 minutes)
Doesn't really talk about how to get around it except to say the causality conjecture does not specifically ban FTL, it would just step in and mess up any attempt to create a time machine, perhaps sort of like feedback of a microphone (I think he said something like that in there somewhere). Doesn't really explain what rules it would impose in practice. -
#273 by KelvinZero on 06 Sep, 2017 07:21
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Im keeping out of all the special relativity tutorials
Anyone got an opinion in whether there are conservation issues even if the grandfather paradoxes are avoided?
I brought up a specific case where from one observer's perspective an FTL flight would lead to an overlap, where for a period the FTL vehicle would exist as two instances simultaneously, and the universe would have a bit more mass. Another observer travelling with the opposite velocity observing the same FTL flight would experience a period where the FTL vehicle's mass had vanished from the universe. -
#274 by meberbs on 06 Sep, 2017 07:36
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Im keeping out of all the special relativity tutorials
Local conservation might be violated depending on the details, but I think globally it is potentially okay (with the caveat that general relativity already produces problems with even defining global conservation laws). Spacelike separated events can't effect each other (and to the extent they can because we are assuming FTL, we are barring certain offensive situations) so I don't see this as being a problem. I could be missing something though.Seeing something in 2 places wouldn't be a problem, I believe that already happens with some gravitational lensing. Bringing the 2 versions of an object too close together to exploit there being 2 of them in a certain frame would run afoul of the no causality violation conditions.
Anyone got an opinion in whether there are conservation issues even if the grandfather paradoxes are avoided?
I brought up a specific case where from one observer's perspective an FTL flight would lead to an overlap, where for a period the FTL vehicle would exist as two instances simultaneously, and the universe would have a bit more mass. Another observer travelling with the opposite velocity observing the same FTL flight would experience a period where the FTL vehicle's mass had vanished from the universe. -
#275 by kamill85 on 06 Sep, 2017 09:22
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Like I said earlier, your math is not fully correct.
You said earlier that I didn't account for length contractino, when i explicitly did.
For example, if ship1 and ship2 have same origin at x=0, and ship2 is going at 0.7c, then for ship2 to witness ship1's exit 10 light years away, would mean that in the tim reference of ship1, ship2 would have to have a head start of at least 14 years.
First, it is irrelevant whether ship 2 started from Earth, or took some other path to end up there and as I stated, the result is the same as if ship 1 rapidly accelerates to 0.7 c after the jump. The "same origin" is simply part of applying the Lorentz transformation. The math is just simpler if you define the origins to be the same event.
Second, time dilation means that it has not been 14 years for ship 2, if ship 2 had originally departed from Earth.So, ship2 leaves x=0 at year t=-14y, arrives at exit point at around t=5weeks.
Those numbers are all in the ship 1 frame, but time and distance for ship 2 need to be measured in the ship 2 frame.Then, jumps back, and he isnt getting back any of those 14 years, sorry.
Not 14 years, if you actually calculate it, you would find the time of Ship1 exiting FTL is t=-483 weeksin its own frame.He still ends up at ship1's relative time of t=5weeks(+[5*timedilation]weeks if we assume its same A-FTL and not instant). So yeah, check all reference frames and you will see your math is wrong.
This is simply untrue because you did not apply the Lorentz transformation, and you are trying to calculate ship 2's behavior in something other than its own rest frame. Since all frames are equal, the ship 2 rest frame is equally valid, and we defined the FTL speed as relative to the ship's own rest frame.
You are the one who needs to learn to do calculations in different frames.
I did say "t" isntead of "t' " on purpose, cause if your calculation does not hold up in Ship1's reference, there must be something wrong with it. In Ship1's time reference, Ship2 must have left "x=0" 14 years earlier. Jumping back wont give that time back to Ship2.
Later in this thread RSE fairly noted that Lorentz transformations might not apply for A-FTL. I agree with that, as C is clearly broken, but not in a way that would result in time travels. -
#276 by kamill85 on 06 Sep, 2017 11:29
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(...)
no, there is a third video, which you can only see the link, which uses the example of a WARP DRIVE ship. Link corrected so you can see the video
The video proves nothing but the fact that the math used today to do those calculations is not valid from all reference frames, hence it must be somehow broken. Lets recap, in the end of the video, Matthew transforms the field to a perspective of 0.99c traveler, fine. In that field, he draws a world paths for the Paradox ship that go beyond the causality plane and then back, showing how it could end up on X=0, about 100 years before its departure. This proves just how exactly Lorentz transformation is not applicable in this case, as such travel can only be possible in the eyes of the 0.99c Ship, but not the Paradox ship it self, that still has a clock that ticks forward, as same rate as on Earth (X=0). The issue comes from the fact that in Lorentz transformation, time axis is reversed if speed > c, while this is only the case for speed through space, not with space. That's why in the causality plane going beyond the field and then back can look like rewinding some time, while its not. The diagram supposed to be for an A-FTL travel, while it clearly assumes the time on board the Paradox ship reverses as it goes beyond the causality plane, and it does not (again, it remains in sync with Earth time/tick/ratio).
Let's take a look are Paradox ship reference frame again, it moves along Earth time axis, and no matter where it would go, its clock (same as Earths) would move forward, in sync, hence no matter the destination & way/path back, it would never end up in its past (without actually breaking C speed through space).
Having said that, let's do a small thought experiment. Let's assume, we, here on Earth, have this magical universe remote control device with 2 buttons, button1 freezes entire Universe, however big it is, and for every coordindate within it, assigns a clock, resets it to zero. We have pressed it. Now, button2 gives us access to any clock value from any coordinate in space, relative to the moment we have pressed it here on Earth. With incorrect math, clocks beyond our visible/causally connected Universe would be negative, as they move away at speed > c, (like A-FTL). Good math/transformation should give a positive value, no matter how small for any point in the entire Universe, not matter how small, but it would be > 0. -
#277 by meberbs on 06 Sep, 2017 14:22
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I did say "t" isntead of "t' " on purpose, cause if your calculation does not hold up in Ship1's reference, there must be something wrong with it. In Ship1's time reference, Ship2 must have left "x=0" 14 years earlier. Jumping back wont give that time back to Ship2.
Yes, something is wrong when you get causality violations, but the thing that is wrong is FTL. You can't actually point out a calculation I have done wrong because I did everything correct. The problem is assuming FTL. Meanwhile, you aren't even responding to the objection I already made showing that your statement is fundamentally contradictory to relativityQuote from: meberbsSecond, time dilation means that it has not been 14 years for ship 2, if ship 2 had originally departed from Earth.
Later in this thread RSE fairly noted that Lorentz transformations might not apply for A-FTL. I agree with that, as C is clearly broken, but not in a way that would result in time travels.
Lorentz transformations do apply. They apply to the objects moving in different reference frames, and no reference frame is different than another. RSE was talking about the objects during the jump, but this doesn't matter, all that matters is their coordinates and relative speeds at the beginning and end of the jumps.The video proves nothing but the fact that the math used today to do those calculations is not valid from all reference frames, hence it must be somehow broken.
No, again, you have not shown that the math is inapplicable, you just refuse to even consider that the premise of "FTL exists" can be an incorrect assumption. Relativity is the only theory that consistently explains how physics works in all reference frames, so unless you have an alternative that can also explain all of the experiments confirming relativity, we are stuck with it. Also, you apparently skipped over the video where the person who came up with the modern concept of how to build a warp drive explains that even if it was possible to build such a device, it would violate causality.
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#278 by kamill85 on 06 Sep, 2017 14:53
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I did say "t" isntead of "t' " on purpose, cause if your calculation does not hold up in Ship1's reference, there must be something wrong with it. In Ship1's time reference, Ship2 must have left "x=0" 14 years earlier. Jumping back wont give that time back to Ship2.
Yes, something is wrong when you get causality violations, but the thing that is wrong is FTL. You can't actually point out a calculation I have done wrong because I did everything correct. The problem is assuming FTL. Meanwhile, you aren't even responding to the objection I already made showing that your statement is fundamentally contradictory to relativityQuote from: meberbsSecond, time dilation means that it has not been 14 years for ship 2, if ship 2 had originally departed from Earth.
Later in this thread RSE fairly noted that Lorentz transformations might not apply for A-FTL. I agree with that, as C is clearly broken, but not in a way that would result in time travels.
Lorentz transformations do apply. They apply to the objects moving in different reference frames, and no reference frame is different than another. RSE was talking about the objects during the jump, but this doesn't matter, all that matters is their coordinates and relative speeds at the beginning and end of the jumps.The video proves nothing but the fact that the math used today to do those calculations is not valid from all reference frames, hence it must be somehow broken.
No, again, you have not shown that the math is inapplicable, you just refuse to even consider that the premise of "FTL exists" can be an incorrect assumption. Relativity is the only theory that consistently explains how physics works in all reference frames, so unless you have an alternative that can also explain all of the experiments confirming relativity, we are stuck with it. Also, you apparently skipped over the video where the person who came up with the modern concept of how to build a warp drive explains that even if it was possible to build such a device, it would violate causality.
You cannot apply Lorentz transformation for an object that jumped over space, instead of traveling through it. It will end up in a mess that makes it look like there are paradoxes possible. If you watch the video again, you will see that Matthew first shows how everything looks good from Paradox ship reference, but wrong from 0.99c-ship reference, therefore, Paradox ship ends up in the past? No, what about the first chart, it was all good in Paradox ship reference, he simply doesn't address that anymore. How convenient.
I did not skip the video, I do not agree with the statements within it. Big claim? I do not think so. We can all agree that everything should follow cause and effect from all reference frames, despite how it might look like from there (B before A, etc.), then why do you insist the FTL is the problem, if the supposed "proof" why it'S the problem, is not even consistent from within two reference frames? You cannot disprove something with a broken solution (again, when you transform any distance via Lorentz, it automatically assumes that distance was traveled through space, and in A-FTL case it is simply not true).
PS. To do a proper Lorentz transformation for an A-FTL drive, the distance delta has to be set to 0. So technically, the ship as far the transformation is concerned has never even moved. Then feel free to recalculate. -
#279 by meberbs on 06 Sep, 2017 15:36
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You cannot apply Lorentz transformation for an object that jumped over space, instead of traveling through it. It will end up in a mess that makes it look like there are paradoxes possible. If you watch the video again, you will see that Matthew first shows how everything looks good from Paradox ship reference, but wrong from 0.99c-ship reference, therefore, Paradox ship ends up in the past? No, what about the first chart, it was all good in Paradox ship reference, he simply doesn't address that anymore. How convenient.
You are the one trying to conveniently ignore a reference frame. By only picking one reference frame, you are defining a frame for absolute simultaneity. We know that there is no such thing as absolute simultaneity, and for something to be possible, it has to be consistent in any reference frame. The Lorentz transformations are only being applied to the objects just before/after the FTL jumps, so it does not matter what happens during the jump.I did not skip the video, I do not agree with the statements within it. Big claim? I do not think so.
You are disagreeing with someone recognized as one of the world's experts on general relativity, and the entire basis of your objection is that his statements don't allow FTL. Do you see the inherent arrogance in your statement?We can all agree that everything should follow cause and effect from all reference frames, despite how it might look like from there (B before A, etc.), then why do you insist the FTL is the problem, if the supposed "proof" why it'S the problem, is not even consistent from within two reference frames?
The inconsistency is the proof. It is called proof by contradiction. FTL has never been demonstrated, however, special relativity has countless supporting experiments. You cannot have both while also maintaining causality.You cannot disprove something with a broken solution (again, when you transform any distance via Lorentz, it automatically assumes that distance was traveled through space, and in A-FTL case it is simply not true).
What "distance delta"? That is simply not a defined term. There are spacetime coordinates of different events in different reference frames, and the Lorentz transformations describe how to translate between them. The relevant events are all taken just before or after the FTL jump, and there is no relevance to how an object moved between the events.
PS. To do a proper Lorentz transformation for an A-FTL drive, the distance delta has to be set to 0. So technically, the ship as far the transformation is concerned has never even moved. Then feel free to recalculate.
If I put the origin at Y=(x,t)=(0 light years, 0 years) I get: