Do you think anything like the warp drives of Star Trek will ever exist?

[Nilof]

      Evidence from both the theoretical and mathematical side seem to indicate that it MAY be possible that some form of transit from one point to another at what would appear to be superluminal velocities may be possible.

      However, the most reasonable theories seem to indicate that while transition from one point to another would take far less time than it would at the velocity of light, they do seem to indicate that they would not, in fact, travel backwards in time, relative to their initial frame of reference.

      It would still take a finite and measurable amount of time, traversing from past to future, (and not in reverse) to make the actual journey.

All incorrect.

If you think there is such evidence, please present it.

Relativity definitely, without a doubt, absolutely says that any form of faster-than-light travel is equivalent to time travel.  That's simply a mathematical consequence of relativity.

In relativity, things that happen simultaneously in one frame of reference happen at different times in another frame of reference.  If something moves faster than light in one inertial frame of reference, then there is another inertial frame of reference in which it moved backward in time.  If physics lets you move backwards in time in any inertial frame of reference, relativity says you can move backwards in any other inertial frame of reference, because relativity says there's nothing special about any particular inertial frame of reference.

This is all high-school level physics.

You can have geometries with spacelike-separated wormholes however, which do not lead to any CTC's. If the wormholes can be moved this leaves the problem that one end can be moved into the future light cone of the other to create a closed timelike curve, but that requires a timelike path from one end to the other meaning that they can "know" that they are in an offending position.

So it would not violate causality if wormholes were only traversable when the ends are spacelike separated. You can build a perfectly consistent theory which satisfies that assumption. This would put strong limits on their actual usefulness for FTL travel and is more complex than just assuming that wormholes can't exist, but it can't quite be ruled out as of now.

I'm not aware of any other self-consistent examples than wormholes however, and these are better described as shortcuts than actual FTL travel.

[meberbs]

      Evidence from both the theoretical and mathematical side seem to indicate that it MAY be possible that some form of transit from one point to another at what would appear to be superluminal velocities may be possible.

      However, the most reasonable theories seem to indicate that while transition from one point to another would take far less time than it would at the velocity of light, they do seem to indicate that they would not, in fact, travel backwards in time, relative to their initial frame of reference.

      It would still take a finite and measurable amount of time, traversing from past to future, (and not in reverse) to make the actual journey.

All incorrect.

If you think there is such evidence, please present it.

Relativity definitely, without a doubt, absolutely says that any form of faster-than-light travel is equivalent to time travel.  That's simply a mathematical consequence of relativity.

In relativity, things that happen simultaneously in one frame of reference happen at different times in another frame of reference.  If something moves faster than light in one inertial frame of reference, then there is another inertial frame of reference in which it moved backward in time.  If physics lets you move backwards in time in any inertial frame of reference, relativity says you can move backwards in any other inertial frame of reference, because relativity says there's nothing special about any particular inertial frame of reference.

This is all high-school level physics.

You can have geometries with spacelike-separated wormholes however, which do not lead to any CTC's. If the wormholes can be moved this leaves the problem that one end can be moved into the future light cone of the other to create a closed timelike curve, but that requires a timelike path from one end to the other meaning that they can "know" that they are in an offending position.

So it would not violate causality if wormholes were only traversable when the ends are spacelike separated. You can build a perfectly consistent theory which satisfies that assumption. This would put strong limits on their actual usefulness for FTL travel and is more complex than just assuming that wormholes can't exist, but it can't quite be ruled out as of now.

I'm not aware of any other self-consistent examples than wormholes however, and these are better described as shortcuts than actual FTL travel.

If you can have one wormhole, then you can have 2. The second wormhole can have a different rest frame, and therefore it would be able to send the output of the first wormhole back next to the  entrance of the first, but in its past.

The second wormhole could be relatively far from the first and still cause this if it went far enough back in time (read: was moving very fast relatively)

[Nilof]

      Evidence from both the theoretical and mathematical side seem to indicate that it MAY be possible that some form of transit from one point to another at what would appear to be superluminal velocities may be possible.

      However, the most reasonable theories seem to indicate that while transition from one point to another would take far less time than it would at the velocity of light, they do seem to indicate that they would not, in fact, travel backwards in time, relative to their initial frame of reference.

      It would still take a finite and measurable amount of time, traversing from past to future, (and not in reverse) to make the actual journey.

All incorrect.

If you think there is such evidence, please present it.

Relativity definitely, without a doubt, absolutely says that any form of faster-than-light travel is equivalent to time travel.  That's simply a mathematical consequence of relativity.

In relativity, things that happen simultaneously in one frame of reference happen at different times in another frame of reference.  If something moves faster than light in one inertial frame of reference, then there is another inertial frame of reference in which it moved backward in time.  If physics lets you move backwards in time in any inertial frame of reference, relativity says you can move backwards in any other inertial frame of reference, because relativity says there's nothing special about any particular inertial frame of reference.

This is all high-school level physics.

You can have geometries with spacelike-separated wormholes however, which do not lead to any CTC's. If the wormholes can be moved this leaves the problem that one end can be moved into the future light cone of the other to create a closed timelike curve, but that requires a timelike path from one end to the other meaning that they can "know" that they are in an offending position.

So it would not violate causality if wormholes were only traversable when the ends are spacelike separated. You can build a perfectly consistent theory which satisfies that assumption. This would put strong limits on their actual usefulness for FTL travel and is more complex than just assuming that wormholes can't exist, but it can't quite be ruled out as of now.

I'm not aware of any other self-consistent examples than wormholes however, and these are better described as shortcuts than actual FTL travel.

If you can have one wormhole, then you can have 2. The second wormhole can have a different rest frame, and therefore it would be able to send the output of the first wormhole back next to the  entrance of the first, but in its past.

The second wormhole could be relatively far from the first and still cause this if it went far enough back in time (read: was moving very fast relatively)

That case is more difficult to analyze, but technically you have the same thing happening there too. For a closed timelike curve to form, it has to go through at least one wormhole. That means that there is a timelike curve going between the wormhole ends, meaning that the wormhole can "know" that it should close up without violating causality. You just happen to have a more complex geometry in that case.

Basic algorithm: are closed timelike curves present? Then you can close one of the wormholes that has one going through it. Repeat until there are no CTC's left.

[Eric Hedman]

The question is kind of irrelevant because there is no way to know if a breakthrough will one day happen.  We may some day think our understanding of physics is complete.  But we will never know for sure.  A good answer to this question may only come when someone figures out how to do it or there are no more questions to ask about physics.  I kind of don't want to be around when there are no more questions to ask.  I don't think anyone has to worry about that for a very long time.

[JasonAW3]

      Evidence from both the theoretical and mathematical side seem to indicate that it MAY be possible that some form of transit from one point to another at what would appear to be superluminal velocities may be possible.

      However, the most reasonable theories seem to indicate that while transition from one point to another would take far less time than it would at the velocity of light, they do seem to indicate that they would not, in fact, travel backwards in time, relative to their initial frame of reference.

      It would still take a finite and measurable amount of time, traversing from past to future, (and not in reverse) to make the actual journey.

All incorrect.

If you think there is such evidence, please present it.

Relativity definitely, without a doubt, absolutely says that any form of faster-than-light travel is equivalent to time travel.  That's simply a mathematical consequence of relativity.

In relativity, things that happen simultaneously in one frame of reference happen at different times in another frame of reference.  If something moves faster than light in one inertial frame of reference, then there is another inertial frame of reference in which it moved backward in time.  If physics lets you move backwards in time in any inertial frame of reference, relativity says you can move backwards in any other inertial frame of reference, because relativity says there's nothing special about any particular inertial frame of reference.

This is all high-school level physics.

The Alcuierre Drive theory, is a spacial distortion drive that, while never actually moving the craft generating the field effect needed, never ACTUALLY exceeds the velocity of light, as it is the space that the craft occupies itself, that is actually shifted at effectively, super luminal velocities.

      As such, time would pass at the same rate for the craft in question, (assuming it was not accelerated initially at a significant fraction of the velocity of light, prior to the activation of said field effect) as it would for it's initial frame of reference.  This is implicit to the actual function of this spatial distortion.

       As a new theory about time and space being more fully connected,  in that the expansion of space seems to be tied to the forward progression of time, such time like loops would be impossible.  This does not actually rule out different forms of spatial travel at "effectively" velocities faster than the velocity of light, but it does eliminate the possibility of going backwards in time.  At least on THIS timeline, if one accepts the "Many Worlds" theory of cosmology. Or "Brane" theory, or Supersymmetric Superstring theory, or any of a dozen other partial Unified Field Theories.

     Overall, at present, we cannot say for certain whether or not such a drive IS possible, nor can we state unequivocally that such a thing is impossible.

      I for one do feel much like you do, that reverse progression of time is not possible, as that eliminate the very concepts of free will and chaos mathematics, as it would indicate that all things would be mutable in our reality, as any travel into the past would directly affect the present in some form, no matter how minute that effect might be.

      Your argument of simultaneous forward and reverse progression of time, should the EFFECTIVE velocity of light be exceeded, tends to indicate a similar reasoning to that which was used when it was supposed that exceeding the speed of sound was impossible.  Effectively, one would suppose that ANY travel at ANY velocity, should cause a similar, no matter how minute, simultaneous forwards and reverse transit of time.

      The problem here is that we are discussing inertial frames versus relative frames.   As has been demonstrated in recent orbital experiments, (as well as with GPS satellite timing) travel through space itself, does dilate time.  However; if it is space itself being accelerated or distorted in a fashion that effectively exceeds the velocity of light, all inertial frames remain consistent with each other as does the relative frame of the craft being translated along the spatial distortion, and time dilation is no longer a factor.

       There are other effects, such as quantum tunnelling, that likewise seem to defy physics, even through the apparent velocity of light.

      Wisdom is knowing that you don't know everything. In this, I will admit, that I don't know nearly enough to properly judge whether or not methods of travel that appear to exceed the velocity of lights are possible, but I do know that most times that someone said something was impossible, someone came along and proved the opposite.

      I guess, in the end, it all depends on your frame of reference.

[MATTBLAK]

Some light reading:

https://www.amazon.com/Physics-Star-Trek-Lawrence-Krauss/dp/0465002048/ref=sr_1_1?s=books&ie=UTF8&qid=1476081290&sr=1-1&keywords=The+Physics+of+Star+Trek

https://www.amazon.com/Physics-Impossible-Scientific-Exploration-Teleportation/dp/0307278824/ref=sr_1_2?s=books&ie=UTF8&qid=1476081290&sr=1-2&keywords=The+Physics+of+Star+Trek

[SICA Design]

Let's talk about very specifically something based on warping spacetime.

Gravity can do this. We've built instruments that rely on this very fact for probing black holes.

There's just one problem: The amount of energy required to get spacetime to budge an inch is ridiculous.

In-fact it takes exactly one-Earth's-mass-full (*C^2) to shrink the 24 thousand mile path around Low Earth Orbit by one inch! 

http://bigthink.com/dr-kakus-universe/scientists-find-einsteins-missing-inch

[cro-magnon gramps]

 I remember a conversation I had with Zorn back in the day, about birds...
He said he didn't believe we would ever fly like birds, it just wasn't possible
that we would ever progress far enough. Zorn had developed the wheel so
we all believed him. Now look where we are. Sure wish he were here now
to see what his invention has led to...

Gramps (btw that's a bit of snark and mixed with a little humour, very little  )

Ps perhaps you would like Lethel's thoughts on Fire???

[nacnud]

I remember a conversation I had with Zorn back in the day, about birds...
He said he didn't believe we would ever fly like birds, it just wasn't possible

This is exactly the problem, but backwards.

You see a bird fly, and you know flight is possible.
You hear the crack of a whip, and know that travel faster than the speed of sound is possible.

It's a hell of a jump from seeing something happen in reality and then reproducing it, to imagining something is possible and doing it.

There have been no observations of superluminal travel, ever. 

[cro-magnon gramps]

I remember a conversation I had with Zorn back in the day, about birds...
He said he didn't believe we would ever fly like birds, it just wasn't possible

This is exactly the problem, but backwards.

You see a bird fly, and you know flight is possible.
You hear the crack of a whip, and know that travel faster than the speed of sound is possible.

It's a hell of a jump from seeing something happen in reality and then reproducing it, to imagining something is possible and doing it.

There have been no observations of superluminal travel, ever.

But you are losing the plot... could my friend see people flying.. could he see the things that might come after... no... there is no way he could see a wheel turning humans into flying beings...
no more than we can see what the next 100 years might bring... we are on the brink of a cliff, and each step into the future makes the past seem ridiculously primitive... we may not see it, but we know it is possible, because we know that the expansion of the Universe happens at greater than the speed of light... Newtonian Physics led to Quantum Physics, and what is the next step, now that we have found Gravity Waves... basing Quantum Physics on a Newtonian view of the final conception of the Universes Physics will get you no where...
  The actual OP question is a mugs game, when you are coming from a primitive concept like Quantum Physics and String Theory... you are asking my friends from 20,000 years ago, to imagine nuclear energy... will it exist... not based on today's understanding of the universe(s), but we are not dealing in today... we are dealing "EVER"... that my friend, is a H-LL of a long time, and there is no way, a person today can confidently say, Neyet, Nix, Nein, No!!! if you or anyone here on NSF has a complete answer than they should proclaim themselves the best at physics and we can close down a lot of useless universities etc... (I'm sure Jim could have been more concise/terse )

[Khadgars]

I remember a conversation I had with Zorn back in the day, about birds...
He said he didn't believe we would ever fly like birds, it just wasn't possible

This is exactly the problem, but backwards.

You see a bird fly, and you know flight is possible.
You hear the crack of a whip, and know that travel faster than the speed of sound is possible.

It's a hell of a jump from seeing something happen in reality and then reproducing it, to imagining something is possible and doing it.

There have been no observations of superluminal travel, ever.

But you are losing the plot... could my friend see people flying.. could he see the things that might come after... no... there is no way he could see a wheel turning humans into flying beings...
no more than we can see what the next 100 years might bring... we are on the brink of a cliff, and each step into the future makes the past seem ridiculously primitive... we may not see it, but we know it is possible, because we know that the expansion of the Universe happens at greater than the speed of light... Newtonian Physics led to Quantum Physics, and what is the next step, now that we have found Gravity Waves... basing Quantum Physics on a Newtonian view of the final conception of the Universes Physics will get you no where...
  The actual OP question is a mugs game, when you are coming from a primitive concept like Quantum Physics and String Theory... you are asking my friends from 20,000 years ago, to imagine nuclear energy... will it exist... not based on today's understanding of the universe(s), but we are not dealing in today... we are dealing "EVER"... that my friend, is a H-LL of a long time, and there is no way, a person today can confidently say, Neyet, Nix, Nein, No!!! if you or anyone here on NSF has a complete answer than they should proclaim themselves the best at physics and we can close down a lot of useless universities etc... (I'm sure Jim could have been more concise/terse )

Nicely put.  However, I think a better way to phrase it is, theoretically now and in the near future, it will not happen.

We cannot speak to what we will know in 20,000 years.

[gospacex]

With current state of our understanding of physics (we know a lot, but also we know that our theories are incomplete), it's impossible to predict whether "warp drives" are possible.

[R7]

My beliefs are irrelevant.
The physics enabling warp drives either have existed since the beginning of time, or do not exist.
Which is it we do not yet know for sure.
So the answer is "TBD".

[Norm38]

It is not clear what rules would prevent time travel into the past being trivial with FTL, and if time travel into the past is acceptable, the theories do not seem to explain how basic paradoxes are resolved. Maybe they are journeying through a multiverse? It is just not explained. It is likely to allow infinitely powerful computation by sending results into the past. Maybe the instant we develop the most miniscule FTL example, sending mere photons, we hit a true technological singularity are are consumed by infinitely evolved electronic superviruses from the future and all history ceases.

How does going faster than light equal going back in time?  If I have a ship that goes 10ly in 10 minutes, it's still 10 minutes later when I get there. Just because I'm watching TV from 2006 doesn't mean I went back in time.  There's no break in causality, no ability to send information into the past. No paradox, entropy is always increasing.
A bubble of spacetime moving around faster than light at no point is doing anything other than moving forward normally in time.

[KelvinZero]

How does going faster than light equal going back in time?

You should probably google for a better reference, since it needs pictures. It is generally accepted by scientists who understand relativity.

I know enough to demonstrate the paradox with an instantaneous communicator. I keep confusing myself when I try to understand why even travelling even 1% faster than c violates causality also, though it has been explained to me a few times.

[Norm38]

Are you referring to stuff like this? https://einstein.stanford.edu/content/relativity/q295.html

I'm referring to "Tachyon A", which is moving FTL, but forward in time. No violation of causality.  Tachyon B and C are thought exercises. "If we can send a tachyon into the past, then causality is violated".  Well sure, but how does that happen?  I can just as easily say "If I build a flux capacitor...."  Just because the math shows a sign change at velocities greater than c doesn't mean it's physically possible.

Regardless, relativity only implies time travel for FTL for objects moving FTL with respect to space-time.  Since that requires infinite energy, it's impossible.  The trappings of sci-fi all exploit a loophole where speeds are not relativistic and causality is not violated.  Even the "ansible" concept, the instantaneous communicator (quantum entanglement) does not violate causality.  Time must elapse for the communicator to move from place to place and information cannot be sent into the past.
If FTL is possible in some fashion, it will be without needing infinite energy, without actually exceeding c in normal space, and no time travel.

I'm just laying that down as what I believe to be fixed law.  If FTL exists, it will exist in such a way that it does not provide for time travel.

[Nilof]

This issue is that Lorentz symmetry leads to relativity of simultaneity. A tachyon that goes forward in time in the reference frame of one observer will go backwards in time from the viewpoint of another. So if you had a transmitter that could emit tachyons going forward in time, you could essentially put the transmitter on a slower than light spacecraft to emit tachyons going backwards in time in your original reference frame.

Meaning that you can't have something directly travel faster than light through normal space without breaking causality. Any proposal to implement FTL without breaking causality must be directly linked to the geometry of spacetime in some way, like wormholes. There would be strong restrictions on what you could actually do, with wormholes immediately closing if the ends end up inside each other's light cones, or Alcubierre warp drives physically not allowing you to exit the bubble at your destination if other Alcubierre drives were used to travel in the opposite direction at the wrong time.

[Patchouli]

Are you referring to stuff like this? https://einstein.stanford.edu/content/relativity/q295.html

I'm referring to "Tachyon A", which is moving FTL, but forward in time. No violation of causality.  Tachyon B and C are thought exercises. "If we can send a tachyon into the past, then causality is violated".  Well sure, but how does that happen?  I can just as easily say "If I build a flux capacitor...."  Just because the math shows a sign change at velocities greater than c doesn't mean it's physically possible.

Regardless, relativity only implies time travel for FTL for objects moving FTL with respect to space-time.  Since that requires infinite energy, it's impossible.  The trappings of sci-fi all exploit a loophole where speeds are not relativistic and causality is not violated.  Even the "ansible" concept, the instantaneous communicator (quantum entanglement) does not violate causality.  Time must elapse for the communicator to move from place to place and information cannot be sent into the past.
If FTL is possible in some fashion, it will be without needing infinite energy, without actually exceeding c in normal space, and no time travel.

I'm just laying that down as what I believe to be fixed law.  If FTL exists, it will exist in such a way that it does not provide for time travel.

The Alcubierre drive doesn't seem cause any causality violations from the view point of the travelers or those at the point of origin or destination.

To a distant observer is may seem to arrive before it left but all you're seeing is light from before it left but of course in reality the ship never meets itself before it left.

For the universe to have matter and energy as uniformly distributed as we observe space may have expanded massively faster than c during the moments after the big bang or c had a different value.

Yes the math could be done to say it could be used for time travel but our mathematical theories of how the universe works probably are not exactly how it works but are simply just the best models we have so far.
Relativity breaks badly on the very small and when trying to describe a black hole.
You get an infinitely dense singularity when describing what goes  inside of a black hole.
Michio Kaku described  the term singularity as we simply do not know the answer.

[KelvinZero]

I think this debate should be moved to the "new physics" forum. 

[FishInferno]

Based on our current understanding of the universe, the answer is no.

I am not going to base the discoveries of tomorrow on the knowledge of today.