Naked Science Forum
General Science => General Science => Topic started by: chris on 01/06/2017 09:48:56
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Jack wants to know:
If you went faster than light, which i know is theoretically impossible - but if you could, would you see that light from before and thus see the past?
What do you think?
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We are always observing the past since the speed of light is finite. You cannot reverse causality so going faster than light would not take you into the past. You would see all the photons from the past in rapid succession so that remote objects would approach the present of the traveller heading toward them.
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Jack wants to know:
If you went faster than light, which i know is theoretically impossible - but if you could, would you see that light from before and thus see the past?
What do you think?
Yes.
Jeff - I believe the OP is asking about the seeing the past of the place that they're located, e.g. Earth. While we can see the past of Proxima Centari we can't see the past of Boston.
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If you went faster than light, which i know is theoretically impossible - but if you could, would you see that light from before and thus see the past?
What do you think?
Going faster than light is not possible according to our current theories. No one knows what would happen if we could go faster than light. However, attempting to preserve the Principles of Relativity with v > c would require backwards time travel.
According to Special Relativity all inertial reference frames are treated equally. The Lorentz Time Transformation below is used:
t' = γ (t - v x / c²)
This transformation can be used to transform from one reference frame to another then back again. The important term to consider here is the - v x / c². Not only do clocks in another reference frame moving at v relative to us depend on our time t but they also depend on position x. I see their plane of simultaneity defined with t = 0 as having a slope -v / c² in the x t' plane.
What does this mean? Their plane of simultaneity (what they see as simultaneous) is sloped into our past if they are moving away from us (negative v) and into our future if moving towards us.
If reference frames are truly identical and we send a message instantaneously to another observer at rest relative to us at distance x and they send a signal straight back no backwards time travel occurs. The message is sent round trip instantly. However, if the other observer is moving away their plane of simultaneity is sloped into our past. According to Relativity they would receive our signal along our plane of simultaneity in our "present" and send their instantaneous signal back along their plane of simultaneity and into our past. If reference frames can be treated exactly equal then ANY faster than light transfer of information breaks causality for at least some subset of reference frames.
You can have any of the following two: Relativity, Causality, or Faster than Light travel
Without some form of "background" to the universe the only known thing that preserves the ordering of events is the constant speed of light and nothing exceeding this speed. The only way I know of around this is to have all faster than light travel transferring off of one reference frame (an idea explored by physicist John Bell while struggling with an explanation of how entanglement might work). This would violate Relativity faster than the speed of light but this is fine because we haven't tested Relativity in that domain.
The safest answer is faster than the speed of light is impossible. Many thousands of experiments back this answer. If it is possible strictly using the principles of Relativity would demand backwards time travel otherwise all reference frames could not be treated equally. However, if FTL is possible relativity may be violated faster than c. This wouldn't mean relativity is wrong because it works perfectly in all domains it's been tested. This is why physicists continually try to push the boundaries to test theories. Always be skeptical of theories (only believe them in areas they've been well-tested) and always be even more skeptical of new claims saying they've proven theories wrong.
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Going faster than light is not possible according to our current theories.
That is incorrect. While its not possible to travel at a speed equal to or greater than the speed of light by accelerating a body of finite rest mass, it may be possible to travel from one point in space to another at a rate which would exceed that of light. One example is by using a wormhole (if one can be created that is). Another would be to use the Alcubierre drive aka Alcubierre warp drive . For details please see: https://en.wikipedia.org/wiki/Alcubierre_drive
As for time travel: At MIT they teach a method of time travel which uses two cosmic strings passing by each other. Its also possible by using a wormhole where the mouths are in relative motion.
So while its not yet know whether FTL is possible or not its still far too premature to say that its not possible.
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That is incorrect. While its not possible to travel at a speed equal to or greater than the speed of light by accelerating a body of finite rest mass, it may be possible to travel from one point in space to another at a rate which would exceed that of light. One example is by using a wormhole (if one can be created that is). Another would be to use the Alcubierre drive aka Alcubierre warp drive . For details please see: https://en.wikipedia.org/wiki/Alcubierre_drive
As for time travel: At MIT they teach a method of time travel which uses two cosmic strings passing by each other. Its also possible by using a wormhole where the mouths are in relative motion.
So while its not yet know whether FTL is possible or not its still far too premature to say that its not possible.
Wormholes and warp drives require exotic forms of matter and have multiple issues. Even if they are possible these "FTL" methods would still break causality (unless relativity breaks). These solutions to GR are also technically not "faster than light" as nothing goes faster than light locally in wormholes, cosmic strings, or warp drives. Any "faster than light" loop according to Relativity breaks causality (for some subset of reference frames) even if light speed isn't broken locally and the method is a solution of GR.
Breaking light-speed is theoretically impossible. Bending "spacetime" to effectively move faster than light may be possible.
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Good grief. A proper scientific debate on TNS. Am I in the right forum?
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Jack wants to know:
If you went faster than light, which i know is theoretically impossible - but if you could, would you see that light from before and thus see the past?
What do you think?
If you use the analogy of a jet traveling faster than the speed of sound; say Mach 1.1, the jet gets ahead of its own sound waves, therefore, the present of the jet will appear to occur in the future, in terms of the (sound) signal we observe. If we continue the analogy, the light speed signal, from someone going faster than the speed of light, would appear like a boom or a blast of energy when it reaches us in the future.
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.daviddarling.info%2Fimages%2Fsonic_boom_diagram.jpg&hash=e46cae5cf8344e5464eb59680afa61a1)
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Wormholes and warp drives require exotic forms of matter and have multiple issues.
And as of yet there are no reasons so assume that exotic matter cannot exist.
Even if they are possible these "FTL" methods would still break causality (unless relativity breaks).
And yet there are solutions to Einstein's equations for which it can happen.
These solutions to GR are also technically not "faster than light" as nothing goes faster than light locally in wormholes, cosmic strings, or warp drives.
Yo! dutch! Nobody suggested that they did. :D
The OPs question is about an observer moving from Earth to a point in space r in as short enough time such that the observer arrives at r in time to observe that light signal. This requires a displacement which happens faster than light could reach r, i.e. FTL. That you took that to mean that an object or particle was moving at a speed v > c is beside the point. Then there's the question of the possible existence of tachyons.
Breaking light-speed is theoretically impossible.
That too is incorrect. Tachyons are theoretical particles which travel FTL and play an important part in physics. Its been held that the most famous example of a tachyon is the Higgs boson. In its uncondensed phase, the square of the mass of the Higgs field is negative, and therefore, the associated particle is a tachyon.
See also: https://phys.org/news/2014-12-faster-than-light-particles.html
Folks - dutch is basing his assumptions of two things:
1) a particle with real and finite proper mass cannot be accelerated from a speed less than the speed of light to a speed equal to or greater than the speed of light. That would require infinite energy, which is a meaningless concept.
2) if FTL exists then there's problems with causality
It was long ago hypothesized by George Sudarshan that if particles were created which are already moving FTL then no infinite energy would be necessary.
Problems with causality may not be a problem since the existence of tachyons does not imply the ability to violate causality. Using wormholes etc to move FTL (and I don't mean have a speed v > c) is problematic and not yet resolved.
Speaking as a moderator: The purpose of this forum is to inform visitors of all things that appear in the physics literature and community which includes those which may indeed be proven possible in the future. Please understand and respect that. This doesn't mean not to point out problems with current ideas. Just don't act like certain things have already been proven impossible.
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Many people work under the assumption that space-time has to always remain integrated. But as an intellectual exercise, consider separating the fabric of space-time into separated threads of space and threads of time. In this case, each can act independently. This would allow affects what appears to be being able to travel faster that the speed of light.
If you could move in space; space thread, without restrictions of time, you can be anywhere is zero time. A wormhole could be explain with distance potential, dissociated from time. Such movement is not based on speed, since speed has the units of distance/time, whereas this does not use time. If you assume only space-time, then you would calculate movement faster than light. But if you assume this is pure distance potential, there is no violation of light speed, since this is not formally a velocity.
Proof that time and distance can separate can be seen with force and acceleration. Acceleration has the units of d/t/t or one part distance and two parts time. Which amounts to extra time potential embroidered into space-time.
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Many people work under the assumption that space-time has to always remain integrated.
I don't even know what that means if it were true.
Spacetime is merely a mathematical object called a manifold. The elements of this manifold are called events where an event is a place and a time, i.e. (r, t). There has never been any requirement or assumption that space-time has to always remain integrated. Spacetime is often used in relativity merely as a way to describe what happens in nature. The mathematical object we call spacetime has curvature described by Einstein's field equations. There is a correspondence between the mathematical object and what we observe in nature. That's all.
It must be kept in mind that space and time are physically very different things.
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Breaking light-speed is theoretically impossible.
That too is incorrect. Tachyons are theoretical particles which travel FTL and play an important part in physics. Its been held that the most famous example of a tachyon is the Higgs boson. In its uncondensed phase, the square of the mass of the Higgs field is negative, and therefore, the associated particle is a tachyon.
What? BREAKING LIGHT SPEED! Tachyons (if they exist in non-virtual form) don't break light-speed. They're already moving faster than light. You're misinterpreting and misreading what I said. Breaking light-speed means to transition from sub-light speed to faster than light-speed. This is similar to how breaking the sound barrier means to go from sub-sonic to supersonic. What other possible definition of the word breaking exists? Also were're talking about Jack not tachyons.
2) if FTL exists then there's problems with causality
How do tachyons go in faster than light loops? I CLEARLY stated and described faster than light round trips. I even discussed instantaneous faster than light round trips. If tachyons actually do go in FTL round trips they would break causality IF relativity doesn't break.
These solutions to GR are also technically not "faster than light" as nothing goes faster than light locally in wormholes, cosmic strings, or warp drives.
Yo! dutch! Nobody suggested that they did.
That's what I meant. Maybe you misinterpreted what I was saying and maybe I didn't write that part well enough.
Problems with causality may not be a problem since the existence of tachyons does not imply the ability to violate causality. Using wormholes etc to move FTL (and I don't mean have a speed v > c) is problematic and not yet resolved.
I wrote:
If reference frames are truly identical and we send a message instantaneously to another observer at rest relative to us at distance x and they send a signal straight back no backwards time travel occurs. The message is sent round trip instantly. However, if the other observer is moving away their plane of simultaneity is sloped into our past. According to Relativity they would receive our signal along our plane of simultaneity in our "present" and send their instantaneous signal back along their plane of simultaneity and into our past. If reference frames can be treated exactly equal then ANY faster than light transfer of information breaks causality for at least some subset of reference frames.
I describe round trips in the above from my original comment. Could you at least acknowledge this? I could have put round trip after "faster than light" again in the final sentence (however, read my last paragraph in this comment).
Jack wants to know:
If you went faster than light, which i know is theoretically impossible - but if you could, would you see that light from before and thus see the past?
What do you think?
That you took that to mean that an object or particle was moving at a speed v > c is beside the point. Then there's the question of the possible existence of tachyons.
The original poster was talking about himself or someone else moving faster than light not tachyons. Jack going faster than light from point a to b by any means also means he should have the ability to go from point b back to a FTL. To stipulate this is FTL in an area of roughly flat spacetime like a trip from Earth to Alpha Centauri. Just by Jack going from point a to b faster than light implies that FTL round trips would be possible because a trip from b to a would also be possible breaking causality (or relativity).
Even if they are possible these "FTL" methods would still break causality (unless relativity breaks).
And yet there are solutions to Einstein's equations for which it can happen.
What can happen? Please specify. What faster than light loop doesn't break causality (again if relativity doesn't break)? If I (I am not a tachyon and neither is Jack) can go from point a to b FTL then this implies I (or something else I hand the "baton" off to) should be able to go back FTL. This would violate causality (if relativity isn't violated).
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dutch - It's become cumbersome to keep correcting all the flawed assumptions that you keep making and I don't have the desire to keep correcting you. I'll merely explain to you your misconception that Einstein's field Equations don't allow for time travel this one last time.
There are indeed solutions to Einstein's field equations which allow for time travel. I stated an example above and you chose to ignore it. It was first proposed by Richard Gott. It uses two cosmic strings in relative motion. For details start here:
http://www.dummies.com/education/science/physics/crossing-cosmic-strings-to-allow-time-travel/
In 1991, J. Richard Gott (who, with William Hiscock, solved Einstein’s field equations for cosmic strings in 1985) realized that two cosmic strings could actually allow time travel.
And there are ways around paradoxes of time travel. In fact they've been proposed by Gott as well. One such way has been used by Sci-Fi writers for a long time - Alternate time lines. This invokes the many worlds theory of quantum mechanics. Then there's the notion that all time travel remain self-consistent, i.e., one can visit the past but not change it, as in the Novikov self-consistency principle. The point is that there's nothing known to day which prevents time travel. However that doesn't mean that it won't be proven impossible in the future. Do us and yourself a favor and read more about it before making further erroneous assertions. E.g. start here:
https://en.wikipedia.org/wiki/J._Richard_Gott
And as I explained, OPs don't always know how to frame the question to get the answer that they're looking more. In this case the OP wanted to know about seeing back in time by moving to places which are so far away that one might have to travel FTL to get there. What he didn't appear to know is that there are ways around moving at speeds for which v > c. But that's why he came here. To learn and we have to keep in mind that the OP might not know how to ask a question to get to what he wants to know. You did him a disservice by taking him to mean, for example, moving in a ship which is speeding at v > c. Don't make such assumptions in the future because you're doing the OP a disservice.
Please be careful. While I did place you in my ignore list it doesn't mean that I won't keep an ear open for your assertions. If you insist on posting deceiving comments I will talk to my fellow moderators and perhaps give you a warning. There's a person on the internet named david waite who posts in a manner like yours and he's a bad influence on people trying to learn physics. Try not to be like him.
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I'll merely explain to you your misconception that Einstein's field Equations don't allow for time travel this one last time.
There are indeed solutions to Einstein's field equations which allow for time travel. I stated an example above and you chose to ignore it. It was first proposed by Richard Gott. It uses two cosmic strings in relative motion. For details start here:
http://www.dummies.com/education/science/physics/crossing-cosmic-strings-to-allow-time-travel/
Never disputed this. Where did I ignore what you wrote? What are you writing about???? I did leave GR solutions out of my original comment and I acknowledged it.
And there are ways around paradoxes of time travel. In fact they've been proposed by Gott as well. One such way has been used by Sci-Fi writers for a long time - Alternate time lines. This invokes the many worlds theory of quantum mechanics. Then there's the notion that all time travel remain self-consistent, i.e., one can visit the past but not change it, as in the Novikov self-consistency principle. The point is that there's nothing known to day which prevents time travel. However that doesn't mean that it won't be proven impossible in the future. Do us and yourself a favor and read more about it before making further erroneous assertions. E.g. start here:
https://en.wikipedia.org/wiki/J._Richard_Gott
I never said there weren't. Where did I say there weren't? What are you possibly writing about? This paragraph doesn't relate to anything I wrote whatsoever. I said it would break causality and causality may be broken in nature. Or perhaps relativity breaks FTL instead. We haven't experimented in this domain even with countless attempts to get something moving faster than light (something I also said; this doesn't mean it's not impossible. I said it's probably a safe answer that it's not).
Cause → Effect. If this changes anywhere to Effect → Cause (retro-causality which occurs when time traveling to the past) then general causality breaks. A five-year-old child will understand that a movie rewinding does not look right. A broken coffee cup typically doesn't un-break. Causality reversing is a pretty clear occurrence in nearly all systems. I said the following:
You can have any of the following two: Relativity, Causality, or Faster than Light travel (travel as in people traveling implying the possibility of round trips... writing about hypothetical a person called Jack or objects not tachyons that can't drop to sub-light speeds).
Hume expanded this to a list of eight ways of judging whether two things might be cause and effect. The first three:
1. "The cause and effect must be contiguous in space and time."
2. "The cause must be prior to the effect."
3. "There must be a constant union betwixt the cause and effect. 'Tis chiefly this quality, that constitutes the relation."
https://en.wikipedia.org/wiki/Causality#cite_note-44
Hypothetical superluminal particles called tachyons would have a spacelike trajectory, and thus move backward-in-time according to observers in some reference frames. Despite frequent depiction in science fiction as a method to send messages back in time, theories predicting tachyons do not permit them to interact with normal tardyonic matter in a way that would violate standard causality. Specifically, the Feinberg reinterpretation principle renders impossible construction of a tachyon detector capable of receiving information.[30]
And as I explained, OPs don't always know how to frame the question to get the answer that they're looking more. In this case the OP wanted to know about seeing back in time by moving to places which are so far away that one might have to travel FTL to get there. What he didn't appear to know is that there are ways around moving at speeds for which v > c. But that's why he came here. To learn and we have to keep in mind that the OP might not know how to ask a question to get to what he wants to know. You did him a disservice by taking him to mean, for example, moving in a ship which is speeding at v > c. Don't make such assumptions in the future because you're doing the OP a disservice.
I think this answers it pretty well from my original comment: You can have any of the following two: Relativity, Causality, or Faster than Light travel This statement is commonly used by physicists (do a Google search of phrases similar to this).
Retro-causality occurs when you travel to the past. According to Relativity you wouldn't just see the past with FTL travel you could go there if performing FTL loops. Look into this series:
Problems with causality may not be a problem since the existence of tachyons does not imply the ability to violate causality. Using wormholes etc to move FTL (and I don't mean have a speed v > c) is problematic and not yet resolved.
Where are wormholes not problematic? If relativity is correct then round trip FTL with wormholes violates causality pure and simple. Not yet resolved implies that Relativity doesn't have clear predictions using it's principles but in this case it does.
If you insist on posting deceiving comments I will talk to my fellow moderators and perhaps give you a warning.
What is deceiving? Now you're not just saying I'm wrong but you're attacking my character. I stand my ground when moderators make errors if you and the forum can't accept that then the forum doesn't have integrity. You should keep moderators to the same level of scrutiny.
Also you didn't point out what was wrong in this moderator's comment below in this thread. You CAN reverse causality by taking someone like Jack (Jack is not a tachyon) faster than light IF Relativity is correct.
You cannot reverse causality so going faster than light would not take you into the past. You would see all the photons from the past in rapid succession so that remote objects would approach the present of the traveller heading toward them.
By your very standards your post below is also wrong. According to Relativity going in faster than light loops could have you see the past of Boston and actually be in the past of Boston. You could also go faster than light out to 50 light-years, stop, and look at the past of Boston (see the photons). It's quite bad when moderators are making so many mistakes in succession and can't take criticism.
Jeff - I believe the OP is asking about the seeing the past of the place that they're located, e.g. Earth. While we can see the past of Proxima Centari we can't see the past of Boston.
Please report me. I'd like to see if this forum is worth anyone's time. I think it's important to keep moderators honest and fair. If they aren't honest and fair then I don't want to deal with the forum. I'm not trying to offend but I will defend the what's right.
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Once a photon has left the vicinity of an event the event itself is in the past. To break causality is to undo the event. If the mathematics only work with time travel into the past then the mathematics are wrong.
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Once a photon has left the vicinity of an event the event itself is in the past. To break causality is to undo the event. If the mathematics only work with time travel into the past then the mathematics are wrong.
What do you mean when you say that the event is in the past? Do you mean that the time after the photon is emitted is greater than the time of the event in that frame? I assume so.
To break causality is to undo the event. If the mathematics only work with time travel into the past then the mathematics are wrong.
Not necessarily. It could mean that the theory is incomplete. E.g. we may need to take account the many worlds theory of QM.
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To the first part. Yes. To the second part maybe.
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The parts quoted below are Relativity. Sure you can consider some parallel universe theory where new branches form. This may not have certain time paradoxes such as the Grandfather Paradox. OK. Fine I never said any different. However, this does not change the fact that cause and effect can been seen as backwards by at least some subset of reference frames for faster than light travel. This breaks Einstein's causality conditions (a general causality condition). Even with MWI and parallel universes branching off cause and effect can still be seen as backwards FTL by at least some subset of reference frames. MWI does seem to offer ways out of many time paradoxes but this is a separate issue from breaking the causality condition outlined below. A subset of reference frames can still see "effects causing causes while others see causes causing effects." The ordering of events past to future is lost.
Consequently, the relativistic principle of causality says that the cause must precede its effect according to all inertial observers.
In the theory of general relativity, the concept of causality is generalized in the most straightforward way: the effect must belong to the future light cone of its cause
https://en.wikipedia.org/wiki/Causality_(physics)
In diagram 2 the interval AB is 'time-like'; i.e., there is a frame of reference in which events A and B occur at the same location in space, separated only by occurring at different times. If A precedes B in that frame, then A precedes B in all frames. It is hypothetically possible for matter (or information) to travel from A to B, so there can be a causal relationship (with A the cause and B the effect).
The interval AC in the diagram is 'space-like'; i.e., there is a frame of reference in which events A and C occur simultaneously, separated only in space. There are also frames in which A precedes C (as shown) and frames in which C precedes A. If it were possible for a cause-and-effect relationship to exist between events A and C, then paradoxes of causality would result (I’m adding here – if the Principles of Relativity hold greater than c) . For example, if A was the cause, and C the effect, then there would be frames of reference in which the effect preceded the cause.
https://en.wikipedia.org/wiki/Special_relativity#cite_note-36
Causality is one of the most fundamental and essential notions of physics.[44] Causal efficacy cannot propagate faster than light. Otherwise, reference coordinate systems could be constructed (using the Lorentz transform of special relativity) in which an observer would see an effect precede its cause (i.e. the postulate of causality would be violated) .
https://en.wikipedia.org/wiki/Causality#Physics
Certain reference frames would see cause and effect backwards and if you travel to the past you’d also overwhelmingly likely see the entropy of the universe decreased. "Causal relations" could still be maintained (even if running backwards for many reference frames). A "Causal relationship" (either q ≤ p and/or p ≤ q is true) does not care about maintaining the ordering (past to future) cause and effect it only demands a link between events p and q. It’s different than general causality ( If both p ≤ q and q ≤ p then p = q) where cause precedes effect for ALL frames of reference. If traveling faster than light cause would not precede effect for all reference frames. Perhaps there are no “causes and effects” in nature (no consistent ordering of cause and effect from past to future) but rather only links between events but then general causality would be broken.
https://en.wikipedia.org/wiki/Causality_conditions#Distinguishing
If someone still has issues with this then use the following (but it's a clumsier saying):
You can have any of the following two: Relativity, no time travel to the past, or faster than Light travel.
(Again tachyons are not a Jack or a "You")
Once a photon has left the vicinity of an event the event itself is in the past. To break causality is to undo the event. If the mathematics only work with time travel into the past then the mathematics are wrong.
Don't shoot the messenger. I'm just conveying the conclusions of the Principles of Relativity should FTL occur.
To break causality is to undo the event.
No, according to Stephen Hawking (and others) on the clearest definition I could find (causal condition) breaking causality happens when the following is violated:
If both p ≤ q and q ≤ p then p = q
where ≤ denotes a causal relation (cause ≤ effect) and p and q are events.
This does not mean events are undone as both p and q can still happen. I've seen this definition before and it makes sense. I have severe issues with PmbPhy definition of causation (whatever that is) and nothing I find corroborates it. Sure, he offers some ways to solve some time paradoxes but this doesn't solve the ordering issue. Observers can disagree on the order of events and maintain causality but they cannot disagree on the ordering of cause and effect.
If the mathematics only work with time travel into the past then the mathematics are wrong.
I would personally like to think this is right but your statement isn't true using current theory. Also time travel to the past is only predicted FTL (in anything mentioned in this thread).
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The OP was asking about the consequences of something impossible happening. Sometimes I just like to follow that course of thinking. It can be profitable sometimes.
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Surely, the fastest anything could get anywhere would be instantly.
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That would require infinite speed.
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Surely, the fastest anything could get anywhere would be instantly.
The problem with this statement is that different frames of reference disagree on what "now" is.
The Lorentz Transform is:
t' = γ ( t - v x ) (with c = 1 units)
The above equation allows us to transfer from any one inertial reference frame to another (in flat spacetime).
If I let t = 0 then t' = -γ v x their "now" t' depends on distance x (as viewed by me) and according to me my "now" does not.
However, in order to keep the speed of light constant in a moving reference frame (relative to you) the slope of the "plane of simultaneity" is - γ v. This means clocks are out of sync in reference frames moving with respect to you. These un-synchronized clocks allows the other frame to measure c for the speed of light in all directions. They don't measure a faster light-speed in one direction and slower in the other because their clocks are out of sync when viewed by me. Likewise, they see my clocks out of sync keeping relativity symmetric.
Reference frames do not agree on what "instantaneous" means. IF all inertial reference frames are truly identical (and they appear to be) then ALL these planes of simultaneity are equally valid.
Depending on what v is, instantaneous messages as viewed by another reference frame can appear to move into the future or the past. ANY faster than light message will appear instantaneous to some reference frame and to other reference frames instantaneous may send messages backwards into the past or forward into the future. The "now" plane is sloped with changing v.
There are three options (regardless of MWI):
1) FTL (even if a solution from GR) is impossible and thus it doesn't matter what occurs FTL.
2) FTL only occurs off of one reference frame thus violating Relativity faster than light. Planes of simultaneity appear real for each reference frame for speeds c or less but to FTL messages only one reference frame (or foliation in GR) is real. This could be right because we've never tested anything moving faster than c. This would require a modification to Relativity FTL.
3) There is no agreed upon cause and effect for FTL. This requires time travel to the past (or future) for FTL
You're thinking the second one is correct because you're looking at the problem in a classical way. However, the second one requires some form of preferred frame and no such thing as ever been found. This would mean one frame's simultaneity would be more "right." The Theory of Relativity does not work this way.
No FTL has been seen. Virtual particles go FTL sometimes in Quantum Field Theory but these don't carry causal efficacy and are born out of the uncertainty principle (they aren't "real" particles and often described as a by-product of how we describe quantum fields). Wormholes and warp drives require exotic matter (we don't know if this exist). Time travel to the past also breaks other laws like the conservation of energy. Having a spaceship appear somewhere in the past from the future changes the energy content of the past frame. Even if a parallel universe breaks off this near twin universe would still have more energy appearing in it's past reference frame. However, General Relativity still has solutions possibly allowing time travel to the past. GR also doesn't globally conserve energy (think expansion of the universe).
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1) FTL (even if a solution from GR) is impossible and thus it doesn't matter what occurs FTL.
Nothing in science prevents motion FTL, nothing. Hence the possible existence of tachyons. Don't confuse the fact that no tardyon can be accelerated from v < c to v = or v > c with a particle being created already moving at v > c.
2) FTL only occurs off of one reference frame thus violating Relativity faster than light.
FTL does not violate FTL and never has.
Then there's the notion that we might discover something in the future which defies known science. In fact any reasonable scientist knows that what we understand of science today will change as it always has in he past. Our laws of physics will be updated when we learn new things. Take NASA's EmDrive as an example. It defies the laws of physics.
https://www.forbes.com/sites/briankoberlein/2016/11/19/nasas-physics-defying-em-drive-passes-peer-review/#435aff4a659d
NASA's Physics-Defying EM Drive Passes Peer Review
The reactionless thruster known as the EM Drive has stirred heated debate over the past few years. If successful it could provide a new and powerful method to take our spacecraft to the stars, but it has faced harsh criticism because the drive seems to violate the most fundamental laws of physics. One of the biggest criticisms has been that the work wasn't submitted for peer review, and until that happens it shouldn't be taken seriously. Well, this week that milestone was reached with a peer-reviewed paper. The EM Drive has officially passed peer review.
It's important to note that passing peer review means that experts have found the methodology of the experiments reasonable. It doesn't guarantee that the results are valid, as we've seen with other peer-reviewed research such as BICEP2. But this milestone shouldn't be downplayed either. With this new paper we now have a clear overview of the experimental setup and its results. This is a big step toward determining whether the effect is real or an odd set of secondary effects. That said, what does the research actually say?
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Its also fallacious to assert that the physics community discounts FTL altogether. In fact there was an article in Scientific American some years ago entitled Faster than Light?
Experiments in quantum optics show that two distant events can influence each other faster than any signal could have traveled between them
Even recently there's been notions which appear to indicate that some neutrinos are in fact tachyons. This appeared in the highly respectable science journal Nature
http://www.nature.com/news/neutrino-experiment-replicates-faster-than-light-finding-1.9393
Latest data show the subatomic particles continue to break the speed limit.
Physicists have replicated the finding that the subatomic particles called neutrinos seem to travel faster than light. It is a remarkable confirmation of a stunning result, yet most in the field remain skeptical that the ultimate cosmic speed limit has truly been broken.
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See also:
Superluminal signal velocity by G. Nimtz, Ann. Phys 7 (1998), 7-8, 618-624
Superluminal Tunneling Devices - G¨unter Nimtz, November 2001 - https://cds.cern.ch/record/547324/files/0204043.pdf
Can EPR-correlations be used for the transmission of superluminal signals? by P. Mittelstaedt, Ann. Phys. 7 (1998). 7-8, 710-715
Faster-than-c signals, special relativity, and causality,Annals Phys. 298 (2002) 167-185
https://arxiv.org/abs/gr-qc/0107091
Abstract - Motivated by the recent attention on superluminal phenomena, we investigate the compatibility between faster-than-c propagation and the fundamental principles of relativity and causality. We first argue that special relativity can easily accommodate -- indeed, does not exclude -- faster-than-c signalling at the kinematical level. As far as causality is concerned, it is impossible to make statements of general validity, without specifying at least some features of the tachyonic propagation. We thus focus on the Scharnhorst effect (faster-than-c photon propagation in the Casimir vacuum), which is perhaps the most plausible candidate for a physically sound realization of these phenomena. We demonstrate that in this case the faster-than-c aspects are ``benign'' and constrained in such a manner as to not automatically lead to causality violations.
Note: Ann. Phys. is the journal Annals of Physics
For those of you out there with a serious and open minded desire to learn about the current research being done at NASA by scientists on FTL travel then you should watch the video of one of their lead scientists discuss it at
https://www.nasa.gov/ames/ocs/2014-summer-series/harold-white
He's the scientist who showed that a modified Alcubierre warp drive could work using much less energy
https://en.wikipedia.org/wiki/Alcubierre_drive
In 2012, physicist Harold White and collaborators announced that modifying the geometry of exotic matter could reduce the mass–energy requirements for a macroscopic space ship from the equivalent of the planet Jupiter to that of the Voyager 1 spacecraft (~700 kg) or less, and stated their intent to perform small-scale experiments in constructing warp fields.[7] White proposed changing the shape of the warp bubble from a sphere to a torus. Furthermore, if the intensity of the space warp can be oscillated over time, the energy required is reduced even more.
End story - Contrary to the assertion made by dutch, there are plenty of serious physicists currently working on both FTL communication and FTL travel and thus dutch's claims that its impossible are his and his alone.
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Nothing in science prevents motion FTL, nothing. Hence the possible existence of tachyons. Don't confuse the fact that no tardyon can be accelerated from v < c to v = or v > c with a particle being created already moving at v > c.
There are three options (regardless of MWI):
FTL does not violate FTL and never has.
What does your sentence mean? Your sentence makes no sense. My sentence was saying Relativity could be violated faster than light. This should obviously be interpreted as the Principles of Relativity could be violated FTL. Could there still be a violation to Relativity outside of what we've tested? YES. My sentence makes sense. I'm sorry, I don't understand your sentence or your point.
Then there's the notion that we might discover something in the future which defies known science. In fact any reasonable scientist knows that what we understand of science today will change as it always has in he past. Our laws of physics will be updated when we learn new things. Take NASA's EmDrive as an example. It defies the laws of physics.
I had stated relativity could be violated faster than light as one of the options... I don't get your point. I did have three very different options. I'm not seeing how the EM Drive relates to anything I wrote.
Even recently there's been notions which appear to indicate that some neutrinos are in fact tachyons. This appeared in the highly respectable science journal Nature
I will reply to your Nov 2011 article with my own Mar 2012 article from the same source:
https://www.nature.com/news/neutrinos-not-faster-than-light-1.10249
It's important to remember to replicate experiments multiple times before daring to say current well-tested laws of physics were violated. In the case of your article it was experimental error and the article is outdated. It's not a recent article. I remember the entire physics community watching the results of the first experiment very closely and I remember when they announced the cause of their error...
See also:
Superluminal signal velocity by G. Nimtz, Ann. Phys 7 (1998), 7-8, 618-624
Superluminal Tunneling Devices - G¨unter Nimtz, November 2001 - https://cds.cern.ch/record/547324/files/0204043.pdf
Can EPR-correlations be used for the transmission of superluminal signals? by P. Mittelstaedt, Ann. Phys. 7 (1998). 7-8, 710-715
These are old and from the 1990s and very early 2000s. No one has ever sent information faster than light. In the 90s and early 2000s we didn't know as much about entanglement and quantum tunneling as we do now. For quantum tunneling group, and phase velocities of a wavefunction can go faster than the speed of light but the front velocity never has. This means information isn't moving faster than light. This has been described like train cars leaving a long train moving at speed v. If the train cars uncouple fast enough the center of the train could move forward at such a rate that it moves faster than v. However, the front car was still moving at v and never moved faster than v. We always had a probability of detecting the particle at that more forward position at time t. Entanglement also does not send information FTL but is only a correlation. If information was sent faster than light please provide proof of it. Otherwise it's just speculation.
There is no signal (information) moving faster than light in any quantum mechanical experiment and most physicist don't think its possible (No Communication Theorem). The newest source you provided of the above three is about 16 years old...
https://en.wikipedia.org/wiki/Faster-than-light_communication
https://en.wikipedia.org/wiki/No-communication_theorem
https://en.wikipedia.org/wiki/Wightman_axioms#W3_.28local_commutativity_or_microscopic_causality.29
Faster-than-c signals, special relativity, and causality,Annals Phys. 298 (2002) 167-185
https://arxiv.org/abs/gr-qc/0107091
Quote
Abstract - Motivated by the recent attention on superluminal phenomena, we investigate the compatibility between faster-than-c propagation and the fundamental principles of relativity and causality. We first argue that special relativity can easily accommodate -- indeed, does not exclude -- faster-than-c signalling at the kinematical level. As far as causality is concerned, it is impossible to make statements of general validity, without specifying at least some features of the tachyonic propagation. We thus focus on the Scharnhorst effect (faster-than-c photon propagation in the Casimir vacuum), which is perhaps the most plausible candidate for a physically sound realization of these phenomena. We demonstrate that in this case the faster-than-c aspects are ``benign'' and constrained in such a manner as to not automatically lead to causality violations.
This is hypothetical and way beyond anything we could test (also from 2002). The speed of light would increase by 1 part in 10^36 if we put two plates a micrometer apart. A millionth of a meter is tiny distance and even nano meters or femto meters wouldn't be much better. This is tens of orders of magnitude below anything we could measure. Even if this effect is correct how would Jack move to Alpha Centuri FTL? Even if FTL does occur I gave options...
https://en.wikipedia.org/wiki/Scharnhorst_effect
For those of you out there with a serious and open minded desire to learn about the current research being done at NASA by scientists on FTL travel then you should watch the video of one of their lead scientists discuss it at
https://www.nasa.gov/ames/ocs/2014-summer-series/harold-white
He's the scientist who showed that a modified Alcubierre warp drive could work using much less energy
https://en.wikipedia.org/wiki/Alcubierre_drive
Quote
In 2012, physicist Harold White and collaborators announced that modifying the geometry of exotic matter could reduce the mass–energy requirements for a macroscopic space ship from the equivalent of the planet Jupiter to that of the Voyager 1 spacecraft (~700 kg) or less, and stated their intent to perform small-scale experiments in constructing warp fields.[7] White proposed changing the shape of the warp bubble from a sphere to a torus. Furthermore, if the intensity of the space warp can be oscillated over time, the energy required is reduced even more.
Then we'll wait and see if his speculative theories actually do something in the lab. If they actually have positive results then we'll wait for others to replicate the effects... In any case, we'll see which one of my three options occurs.
My options in simple language:
1) We won't see FTL. I don't care about effects that seem FTL. This is information going FTL.
2) We'll see it and Relativity will be violated. This could happen because we haven't tested relativity FTL. We'd have to add/remove postulates to relativity.
3) We'll see it and Relativity won't be violated leading to at the very least a loss of cause → effect for some. MWI may keep links between events and may prevent certain paradoxes but it still doesn't change this.
thus dutch's claims that its impossible are his and his alone
Again... I gave three options and I've given these three options from the start. Please tell me what other option exists?
Also BTW nothing here you wrote was ever new to me in the least. I only took so long to reply because I said I was going to hold my tongue. However, with your inaccuracies I can't. There isn't much use to a forum that let's moderators mislead this much.
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You don't need to travel faster than light to see the past. Everything you see now is past information, just past by differing amounts of time. If magically one could exceed the speed of light and get beyond the 'now' wave front at the instant of your departure and, say, instantly travel to the surface of neptune with a good telescope, and look back at earth, then the info coming in would be past, and you might be able to observe yourself pondering leaving before you left. AFIK such magic is not known, or if 'known', unproven to be of any practical use.
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Many people work under the assumption that space-time has to always remain integrated.
I don't even know what that means if it were true.
Spacetime is merely a mathematical object called a manifold. The elements of this manifold are called events where an event is a place and a time, i.e. (r, t). There has never been any requirement or assumption that space-time has to always remain integrated. Spacetime is often used in relativity merely as a way to describe what happens in nature. The mathematical object we call spacetime has curvature described by Einstein's field equations. There is a correspondence between the mathematical object and what we observe in nature. That's all.
It must be kept in mind that space and time are physically very different things.
All I did was extrapolate the standard manifold of space-time to allow separated space and separate time, both which can act independently of the other. If we act in time but without the restriction of space, we can be anywhere in zero time. This allows for faster than light affects. Since this is only time, it is not a velocity base affect so it does not violate the speed of light. This extrapolation also allows for other types of affects such as integrated large scale systems where light speed becomes limiting in terms of integration over long distances.
A spiral galaxy that is 100,000 light years across acts like an integrated object. Even though the forces may take thousands of years between objects within the galaxy, the galaxy is not subject to endless randomization in shape. The superstructures of the universe is another application. It is integrated in time, regardless of the huge distances, that should limit its integration using forces limited to light speed. This is governed by time potential and not space-time.
Moving faster than light, using time potential, allows you too see into the future. The objects in the galaxy know where to be, to maintain integration, even before the light speed limited force reaches it. It is where it needs to be ahead of time, allowing it to greet the late signal. Time potential is not a speed, or t is not d/t.