Well yes, but if you introduce the kind of topologies you can get with wormholes, things can take the shorter path through the wormhole, so it "looks like" they are moving faster than light.
Hmm...I am not an expert in GR, but absent some other constraint, lorentz invariance is a local theory, right? Not a global one...
I mean, I send two light beams simultaneously, one directly to you, one off angle to a mirror which reflects and then reaches you too[0]. The direct one reached first because it had a shorter route, they both travel at c...we don't violate lorentz.
I think you're referring to a topology that would allow closed timelike loops which would imply grand father paradox issues? That doesn't violate lorentz which is local and doesn't care about global structure, but it leads to logical inconsistencies (which is global, I think...)? Enlighten me. Again, my expertise is not GR.
[0] If you want to be pedantic, we are both in the same lorentz frame...needs not to be said, but just in case :)
> No. You can't go faster than light. There are no loop holes.
That's what I just said. Your objection is silly.
You're basically saying "Look, if light follows an extrinsically curved geodesic that goes into a black hole it takes 10 minutes to reach the singularity. But if we shoot it straight into the black hole, the math says it only takes 9 minutes. Impossible! That's science fiction! It's going faster than light!"
Information traveling through a wormhole is emphatically not going faster than light. It's just taking a shorter route to get to the other side. You can't necessarily violate causality like this; you can just bring objects closer together.
The mathematics on wormholes is quite solid and appears to admit traversable wormholes in principle. There are many reasons why it might not actually feasible to build or use one, but your objection isn't one of them.
Wormholes are not a shorter path through space time. That's the mistake you're making. The whole topology/folded paper thing you keep mentioning has already been described as science fiction.
There are several resolutions to this complaint. One popular suggestion is that any causality-violating wormholes would cause a feedback loop of virtual particles to accumulate inside the wormhole and destroy it.
> It might be mathematically interesting but that's it
That's exactly what they said about photons and antimatter. Both were discovered mathematically before they were discovered physically. "Oh, this is just a mathematical fluke, this couldn't exist in the real world."
The best physical theory we currently have admits the existence of wormholes. If you have a problem with that, then feel free to try to come up with an alternate physics that explains the world better than we can right now.
Time travel from our perspective is impossible. What people talk about when discussing wormholes affecting things before they've happened are on a quantum level.
Quantum particles decay and change and do stuff to each other and to understand it you need an equation to explain that, but some of those equations require the state of those decayed particles to provide their state to earlier parts of the equation, before they were created through quantum decay or their state determined by waveform collapse. This is sometimes described as time travel but it's not really, time has no relevance at that level of understanding. WE live in space-time and quantum physics is the foundation of that fabric. So the solution doesn't really violate the laws of time, it happens in a place where space and time don't have the same relevance.
If you somehow did create a feedback loop in this situation we'd never know. The concepts of it taking forever or being instantaneously resolved don't apply, because as far as we're concerned we only get the end product. We're not even sure of coherence is a good way of telling how much work has been done in a twisty, strange quantum problem like that.
I mention coherence because at the quantum level it's the only way of knowing which direction everything is happening in. It's not the same as time, but it's a bit more like very very fast entropy at a quantum level.
All of these things come together to give you space-time.
So when we talk about wormholes we're talking about the transmission of information on a quantum level, not a feature of space-time. The space and time parts are only relevant later.
General relativity admits traversable (i.e. macroscopic) wormholes. This is what we're discussing.
> you need an equation to explain that
Which equation? Schroedinger? The SE has time as a variable and doesn't do any of the "time travel" stuff you're talking about, so you must be referring to something else.
> One popular suggestion is that any causality-violating wormholes would cause a feedback loop of virtual particles to accumulate inside the wormhole and destroy it.
I would imagine a more likely solution is, wormholes either can't exist or can't transmit information.
> The best physical theory we currently have admits the existence of wormholes.
Just because the maths says it can exist in one set of equations, doesn't mean it can/does exist in our universe, especially lacking any evidence.
I'm not saying to stop researching the idea, but anyone sensible knows the outcome.
They will not be possible not matter how much you want them to be true. Just because something can exist doesn't mean it's either likely or not crazy.
> wormholes either can't exist or can't transmit information.
This would contradict known physics. Again, please provide a better solution.
> Just because the maths says it can exist in one set of equations
That "one set of equations" is everything we know about the universe.
> but anyone sensible knows the outcome.
You mean like Kip Thorne, Leonard Susskind, Mat Visser, David Deutsch, and any other physicist who's studied wormholes? Because all those people agree that either we're wrong about physics or wormholes are theoretically possible. Causality violation, probably not, but wormholes don't violate causality just by existing.
> They will not be possible not matter how much you want them to be true
I have no strong opinion one way or the other. However, I accept that, based on the best physical theories we have available to us, wormholes are physically viable.
It seems like, for some reason, you really want them to be false. Perhaps it's your sense of "sensibility", which does not appear to be based in fact (unless you know something physicists don't).
My point is, lots of things are still unproven but we know the outcome. This includes in mathematics. Things remain unproven but mathematicians know the outcome.
It might piss the purists off to think like this but tough luck this is how the world works.
You seem happy to throw out causality? but not the faster than light bit. This seems biased.
> You seem happy to throw out causality? but not the faster than light bit.
Nope, going faster than light violates causality. As I have said N times, wormholes do not allow you to go faster than light. I really can't be any clearer on that. What they do is alter the topology of space so that you can create a shorter route between two locations that used to be "far away" in the old topology.
Yes, but if you entering the wormhole at one end and leaving it at the other are events with spacelike separation, then those events have no absolute order, which means that there is at least one frame of reference in which you leave the wormhole before you enter it. That's time-travel, and that raises the possibility of causality violations.
The paper bending, sticking a pencil through explanation
is science fiction.
There is nothing science fiction about a curved 2D surface in a 3D space and travelling to a different location on the 2D surface via the 3rd dimension. I can both demonstrate the 'fiction' on my kitchen table and mathematically describe the system, showing that something seems to have moved from A to B faster-than-light.
It's entirely unclear why you believe this would be impossible if our observable 4D universe is curved and embedded in one or more additional spatial dimensions.
Then what makes a worm-hole special? I always thought it was that a worm-hole made a smaller path between two points than could normally exist in plain space.
It's a hypothetical mechanism for the transmission of information. It's not taking a shortcut, it's just a different mechanism for getting there, in the same way entanglement propagation can't exceed the speed of light.
And that's why this technique is being described as a wormhole - it's a relatively good simulation of one in terms of some of the measurements they want to make and can be used to carry one of the properties we think a wormhole should be able to carry.
Everything moves slower than [the speed of] light.
Unless you are in a scifiction story or a conspiracy theorist who believes in that sort of thing and stuff like perpetual motion machines.