A Step Closer To The Alcubierre Drive!

[Wahgineer]

What some guys don't seem to understand is how the FTL drive works. It works by sealing itself in a bubble of negative energy. It then manipulates the bubble to twist space-time around it. Now for the confusing part: the ship itself doesn't accelerate. Instead, the bubble carries the space time it is sitting on and rides the gravity 'wave' that the entire setup is resting on. The bubble moves forward, which causes the 'dip' in front to be pushed and the 'bump' in back to be pulled. The process repeats, causing the ship to move along at FTL speeds without accelerating. The reason the ship doesn't accelerate is because the space time it is resting on is being carried along with it, completely sealed of from the universe. This is how the drive 'cheats': by using the fabric of the universe to move itself, therefore not breaking any of Einsteins theoretical 'laws' (remember, people, it's called the theory of relativity, not the law of relativity.)

[SargeRho]

(remember, people, it's called the theory of relativity, not the law of relativity.)

You do realise that a Theory is superior to a Law in science, right?

[Wahgineer]

What?

Last time I checked, a theory is an idea with a lot of supporting evidence but is still unproven, were as a law was more or less a fact. I fail to see how unproven ideas that may someday be found to be completely false are superior to actual facts.

[N_las]

What?

Last time I checked, a theory is an idea with a lot of supporting evidence but is still unproven, were as a law was more or less a fact. I fail to see how unproven ideas that may someday be found to be completely false are superior to actual facts.

Last time I checked, a law was part of a theory.

Newtons first, second and third law are the part of a theory (Classical mechanics)

E = mc² is a law, and it is part of a theory (Relativity)

The uncertainty principle is a law, and it is part of a theory (Quantum mechanics)

[magnemoe]

Reposted from like a month and a half ago:

Here's something I wrote up somewhere else, I'll repost it here with some modifications:

Anyway, please consider the above thought experiment, and you will see why FTL communication would violate the very foundations of the universe and reality.

Thanks, it explained the paradox. However would you not get the same issue if you stopped the train just after the beams is reflected.

Neither traveling by 1-10% of light-speed or doing an million g braking burn is theoretical impossible, and I'm not sure if its needed for this test, all you need to do is to cause different conditions for the return signal as the stationary observer see it while its not changed for the on-board one.

[-Velocity-]

What some guys don't seem to understand is how the FTL drive works. It works by sealing itself in a bubble of negative energy. It then manipulates the bubble to twist space-time around it. Now for the confusing part: the ship itself doesn't accelerate. Instead, the bubble carries the space time it is sitting on and rides the gravity 'wave' that the entire setup is resting on. The bubble moves forward, which causes the 'dip' in front to be pushed and the 'bump' in back to be pulled. The process repeats, causing the ship to move along at FTL speeds without accelerating. The reason the ship doesn't accelerate is because the space time it is resting on is being carried along with it, completely sealed of from the universe. This is how the drive 'cheats': by using the fabric of the universe to move itself, therefore not breaking any of Einsteins theoretical 'laws' (remember, people, it's called the theory of relativity, not the law of relativity.)

Did you even read the thought experiment? If a warp drive lets you get a signal or ship or anything that contains information from point A to point B faster than the speed of light, THAT IS A CAUSALITY VIOLATION no matter how you try to frame it, and it will lead to impossible stuff like I describe in the thought experiment I posted.

The fact is, Relativity is not a complete description of the universe. Because we think we found a loophole in it that allows us to go faster than light does not mean that we actually found a loophole in the universe.

FTL travel/communication is prohibited by two separate things-

1) It takes infinite energy to accelerate to the speed of light

2) If you communicate faster than the speed of light, you set up causality violations, independent observers observe different things, impossible scenarios, etc.

Point 1) is what warp drives "find a work-around" for. They do not accelerate at all. Obviously. I knew that when I first read about them in the mid 90's. It's written in EVERY SINGLE article and paper about them, and that part of them is not in contention here. If you've heard of warp drives at all, you KNOW they don't accelerate, so please don't bring that up here as some sort of "trump card". Because it is NOT-

Point 2) is not codified in Relativity, per say- at least, as far as I know, Relativity prevents Point 2) only in so much that it says Point 1), and it implies that Point 1) ensures Point 2). However, Point 2) is required to keep reality from... well, existing. We don't have a complete picture of physics yet, but it seems certain that Point 2) will be part of it when or if we do. If you violate causality, if you have two separate observers in the same universe observing different versions of reality... that is CLEARLY impossible.

And don't get hung up on "observers", thinking I am implying an observer is an actual thinking, breathing, observing thing. They are not. A hydrogen molecule in interstellar space is an observer. A neutrino is an observer. Heck, everything is an observer. The very nature of reality would break down if FTL communication was possible.

Edited October 10, 2013 by |Velocity|

[Awaras]

What?

Last time I checked, a theory is an idea with a lot of supporting evidence but is still unproven, were as a law was more or less a fact. I fail to see how unproven ideas that may someday be found to be completely false are superior to actual facts.

From Wikipedia:

A scientific theory is a well-substantiated explanation of some aspect of the natural world, based on knowledge that has been repeatedly confirmed through observation and experimentation. Scientists create scientific theories from hypotheses that have been corroborated through the scientific method, then gather evidence to test their accuracy. As with all forms of scientific knowledge, scientific theories are inductive in nature and aim for predictive and explanatory force.

The strength of a scientific theory is related to the diversity of phenomena it can explain, which is measured by its ability to make falsifiable predictions with respect to those phenomena. Theories are improved as more evidence is gathered, so that accuracy in prediction improves over time. Scientists use theories as a foundation to gain further scientific knowledge, as well as to accomplish goals such as inventing technology or curing disease.

Scientific theories are the most reliable, rigorous, and comprehensive form of scientific knowledge. This is significantly different from the word "theory" in common usage, which implies that something is unsubstantiated or speculative.

[-Velocity-]

Thanks, it explained the paradox. However would you not get the same issue if you stopped the train just after the beams is reflected.

Can you explain this?

Yes, you would still have the same problem.

The whole point is that there is no such thing as simultaneity, and different observers can observe spatially-separated events occurring in different orders. If the train stops the instant the beams are reflected, there is still a mis-match between the two observer's observations using the instantaneous communicator experimental set-up.

Now, if you have the train stop, it is no longer an inertial reference frame, it is an accelerating reference frame. You have to use different parts of Relativity that I am not very familiar with to predict how light will behave. Rest assured though, in the original set-up, using just light beams and no impossible devices, the two observers still agree on the same events taking place.

Edited October 10, 2013 by |Velocity|

[SargeRho]

Last time I checked, a theory is an idea with a lot of supporting evidence but is still unproven,

You must have checked badly then. A theory is proven beyond reasonable doubt. An unproven theory is a hypothesis. Laws form a part of theories.

What I don't understand: Why does faster than light communication prose a paradox problem? Two events happening simultaneously will do so wether or not you observe them in that instance, or a year later, and even if you could transmit information that would prevent that from happening faster than the speed of light...it wouldn't actually have any effect, right? Oh damn you Einstein, stop blending my brain xD

Edited October 10, 2013 by SargeRho

[ThirdHorseman]

2) If you communicate faster than the speed of light, you set up causality violations, independent observers observe different things, impossible scenarios, etc.

And note that the causality issue prevents not just warp drive, but ANY FTL system (wormholes, hyperspace and interdimensional travel, etc).

However, note that you can still have FTL travel without having causality issues. It is quite possible for me to jump into my FTL ship, fly to Alpha Centauri, and land without causing any temporal paradox or closed timelike curve. You have to setup complex situations to cause such things, and yes FTL communication (whether by FTL signals or travel) can cause such situations.

But it's quite possible that any attempt to break causality using FTL travel would be hindered by the Novikov self-consistency conjecture. So if you are just flying around at 2C then good for you. But if you try to setup the thought experiment detailed above, something would stop you. One of the mirrors break. One of the instantaneous communication devices triggers even though it didn't receive a signal. There is a zero probability that any incident that might cause a causality break will happen.

So you can have FTL travel, as long as you don't use the resulting FTL communication to break the universe. The universe will do something to you to stop you...

Edited October 10, 2013 by ThirdHorseman
TAGS

[Technical Ben]

From Wikipedia: [some stuff on Scientific Theory]

Top trumps:

http://en.wikipedia.org/wiki/Scientific_law

A scientific law is a statement based on repeated experimental observations that describes some aspect of the world. A scientific law always applies under the same conditions, and implies that there is a causal relationship involving its elements.

Emphasis mine. Laws always apply, theories do not. Laws do not change, theories do. Thus, laws outweigh theories in all instances. I'll be happy to consider any error in that statement if you can find one. Thanks.

[magnemoe]

Can you explain this?

Yes, you would still have the same problem.

The whole point is that there is no such thing as simultaneity, and different observers can observe spatially-separated events occurring in different orders. If the train stops the instant the beams are reflected, there is still a mis-match between the two observer's observations using the instantaneous communicator experimental set-up.

Now, if you have the train stop, it is no longer an inertial reference frame, it is an accelerating reference frame. You have to use different parts of Relativity that I am not very familiar with to predict how light will behave. Rest assured though, in the original set-up, using just light beams and no impossible devices, the two observers still agree on the same events taking place.

Explained how this could cause an causality problem.

However the instant communication item here is just an gadget used to break causality, the FTL effect was not use to anything else than to find that an beam reach a wall before another from one point of view, replace it with something else like two shutter who only opens for the beam at some set times and would would interrupt the slow beam from the observers point of view while both would pass for the one in the car.

The key is that the stationary observer see something different than the one in the car, both are right however some action from the observation would have different outcome like an bomb exploding in one setting but not the other.

[qeveren]

A scientific law is basically just a set of observations that have been repeated enough times to find the consistent rule to them. They're a 'what' to a theory's 'how'.

[Fractal_UK]

A scientific law is basically just a set of observations that have been repeated enough times to find the consistent rule to them. They're a 'what' to a theory's 'how'.

Yep and he could have read that for himself if he'd carried on reading the article he posted.

[Wahgineer]

1) It takes infinite energy to accelerate to the speed of light

Only if you yourself are accelerating. The FTL drive uses space time to move space time, not accelerate itself. Like in the Star Trek movie from 2009: Scotty: "It never occurred to me that space was the thing that was moving!"

This implies that the ships aren't physically accelerating themselves, that in fact, space time is doing all of the work. And when you get to the point where you're sealing yourself off from the rest of the universe, then using that 'sealer' to twist the fabric of the universe itself, I'm not so sure that the theory of relativity applies. Also, the theory of relativity was meant to disprove quantum mechanics, which exists, which also allows for the existence of warp drives. So much for that.

[-Velocity-]

Only if you yourself are accelerating. The FTL drive uses space time to move space time, not accelerate itself. Like in the Star Trek movie from 2009: Scotty: "It never occurred to me that space was the thing that was moving!"

This implies that the ships aren't physically accelerating themselves, that in fact, space time is doing all of the work. And when you get to the point where you're sealing yourself off from the rest of the universe, then using that 'sealer' to twist the fabric of the universe itself, I'm not so sure that the theory of relativity applies. Also, the theory of relativity was meant to disprove quantum mechanics, which exists, which also allows for the existence of warp drives. So much for that.

I sincerely hope you're trying to troll, because otherwise-

because if you're NOT trying to troll, yes, your failure is pretty epic... please read the post you quoted of mine, starting at the paragraph after the single line you quoted.

Edited October 11, 2013 by |Velocity|

[K^2]

FTL travel/communication is prohibited by two separate things-

1) It takes infinite energy to accelerate to the speed of light

2) If you communicate faster than the speed of light, you set up causality violations, independent observers observe different things, impossible scenarios, etc.

Point 1) is what warp drives "find a work-around" for. They do not accelerate at all. Obviously. I knew that when I first read about them in the mid 90's. It's written in EVERY SINGLE article and paper about them, and that part of them is not in contention here. If you've heard of warp drives at all, you KNOW they don't accelerate, so please don't bring that up here as some sort of "trump card". Because it is NOT-

Point 2) is not codified in Relativity, per say- at least, as far as I know, Relativity prevents Point 2) only in so much that it says Point 1), and it implies that Point 1) ensures Point 2). However, Point 2) is required to keep reality from... well, existing. We don't have a complete picture of physics yet, but it seems certain that Point 2) will be part of it when or if we do. If you violate causality, if you have two separate observers in the same universe observing different versions of reality... that is CLEARLY impossible.

No. Both of these points are related to locality. And locality is, well, local. That means causality is also local. Events have to be properly casually related only in the immediate neighborhood. Which is good, because all action is local as well, meaning that the entire system is self-consistent.

Global causality violations are entirely possible, and they only appear paradoxical because we are not used to dealing with it. So long as the reality is described by a field theory of some sort, and it is, global causality is entirely optional. If we have local causality, and we do, things are fine.

There is absolutely nothing in physics that prohibits faster than light travel or communication. There are things that make it very difficult. It is entirely possible that warp drive is impossible to achieve. But there are configurations of masses that allow for faster than light travel. They are entirely physical, and if they do not exist, it is entirely by chance. This means that whatever else we say about feasibility of FTL travel, whatever laws we use to describe reality have to account for it being possible.

[-Velocity-]

No. Both of these points are related to locality. And locality is, well, local. That means causality is also local. Events have to be properly casually related only in the immediate neighborhood. Which is good, because all action is local as well, meaning that the entire system is self-consistent.

Global causality violations are entirely possible, and they only appear paradoxical because we are not used to dealing with it. So long as the reality is described by a field theory of some sort, and it is, global causality is entirely optional. If we have local causality, and we do, things are fine.

There is absolutely nothing in physics that prohibits faster than light travel or communication. There are things that make it very difficult. It is entirely possible that warp drive is impossible to achieve. But there are configurations of masses that allow for faster than light travel. They are entirely physical, and if they do not exist, it is entirely by chance. This means that whatever else we say about feasibility of FTL travel, whatever laws we use to describe reality have to account for it being possible.

Can you cite a source? And how you reconcile that warp drives would be capable of producing the kind of impossible scenarios I describe in the thought experiment I give? It's a local causality violation, maybe even something worse than that (two observers who are in the same universe observe drastically different experimental outcomes), this problem being caused by sending signals faster than light between two causally connected regions.

[rkman]

Top trumps:

http://en.wikipedia.org/wiki/Scientific_law

Laws always apply, theories do not.

Laws always apply under the same conditions - eg Newton's laws do not apply at relativistic speeds (nor do they apply if you look really really closely at what happens at non-relativistic speed).

The theory of relativity also always applies under the same conditions.

In the end Newton's laws are just a bunch of formulas describing how reality behaves within certain constraints, and so is the theory of relativity.

[Mr. Scruffy]

Reposted from like a month and a half ago:

Here's something I wrote up somewhere else, I'll repost it here with some modifications:

[...]

Anyway, please consider the above thought experiment, and you will see why FTL communication would violate the very foundations of the universe and reality.

I appreciate your efforts and i think i learned something. Also, i dont wanna come off as someone stating that warp-drives and such were possible. But, i think i once saw on TV (and it seemed creditable - this wasnt some cheap station or entertainment show) that they did have a very shortrange but still instantanious transmission set up via ´tunneling´.

As i understand it, that effect occurs when you force something through an ever narrowing tunnel, which it has to pass, but at some point cant anymore. At that point it ´jumps´ - instantaniously to a new location, which seems to be determined by a probability-curve favoring proximity. So, for long-range communication, the signal would rely heavily on relays, re-emitting to signal, as to not have it lose its strength.

I think i have also read something like this in a computer magazine back in 1986, in an article discussing super-computers of the future.

...if that effect could be converted to bigger sized objects somehow, facilitating humans to travel faster than light, it would be sort of ironic, as you could not predict your location (with certainty and precision) after the flight.

You (or someone else?) mentioned that the speed of light is sort of a misnomer and it should be called the speed causality instead. But maybe reality is shaped by more than a 4D-causaulity. I mean: If there really is no reason why a FTL-particle ends up in a specific location, if it cannot be predicted by any means within your spacetime - is its movement a matter of causuality?

[Technical Ben]

Laws always apply under the same conditions - eg Newton's laws do not apply at relativistic speeds (nor do they apply if you look really really closely at what happens at non-relativistic speed).

The theory of relativity also always applies under the same conditions.

In the end Newton's laws are just a bunch of formulas describing how reality behaves within certain constraints, and so is the theory of relativity.

Do you mean the Theory of the Laws of motion or the Laws of relativity? Your mixing terms there, and I'm not sure if you mean they are both the same, or each is different. Either both are a law, or both are a theory. Or are both laws and theories the same thing? Both comment on observations that continue to be observed true (laws) and calculations for predicting them (theories). The calculations can be erroneous and imperfect, as we do not have perfect information. The laws (observations) are perfect, assuming the universe/reality has the information in the first place.

So, observations always outweigh theories. Or is there something lacking in an observation that a theory can correct for?

[magnemoe]

Can you cite a source? And how you reconcile that warp drives would be capable of producing the kind of impossible scenarios I describe in the thought experiment I give? It's a local causality violation, maybe even something worse than that (two observers who are in the same universe observe drastically different experimental outcomes), this problem being caused by sending signals faster than light between two causally connected regions.

Problem with your paradox is that it would be possible to generate in multiple ways without faster than light. Like returning timestamps and not simply reflecting the light will also show that the light arrived at different time for one observer.

Warp drives would have multiple other problems, even if something is theoretical possible it does not say its practical, it might be easier to getting up to 0.9c.

[-Velocity-]

Problem with your paradox is that it would be possible to generate in multiple ways without faster than light. Like returning timestamps and not simply reflecting the light will also show that the light arrived at different time for one observer.

??? Returning timestamps?! Think about it. This does not change the experiment. The timestamps are transmitted to the center of the flatbed car at the speed of light, so the experiment is exactly the same as if you reflected the beams. The clocks can also only be synchronized from a single frame of reference. So if you synchronize the clocks from the perspective of the observer at rest with the flatbed car, the clocks will not by synchronized from the perspective of the observer on the ground. This is why it's nonsensical to say things like "the light you see from the Andromeda galaxy actually left it when humans were just beginning to evolve on Earth"- it's assuming that clocks in the Andromeda galaxy are synchronized with clocks on Earth. Maybe from ONE frame of reference, yes, but from all the other frames of reference, NO.

There is no problem with my paradox; there is only a problem if you try to transmit information faster than light- faster than the speed of causality.

Edited October 13, 2013 by |Velocity|

[-Velocity-]

BTW, this is what happens if c is ever exceeded-

[magnemoe]

??? Returning timestamps?! Think about it. This does not change the experiment. The timestamps are transmitted to the center of the flatbed car at the speed of light, so the experiment is exactly the same as if you reflected the beams. The clocks can also only be synchronized from a single frame of reference. So if you synchronize the clocks from the perspective of the observer at rest with the flatbed car, the clocks will not by synchronized from the perspective of the observer on the ground. This is why it's nonsensical to say things like "the light you see from the Andromeda galaxy actually left it when humans were just beginning to evolve on Earth"- it's assuming that clocks in the Andromeda galaxy are synchronized with clocks on Earth. Maybe from ONE frame of reference, yes, but from all the other frames of reference, NO.

There is no problem with my paradox; there is only a problem if you try to transmit information faster than light- faster than the speed of causality.

Lets break this down: the paradox is that an stationary observer and an observer who is moving see two different things because of relativity effects. The two realities is both true so any follow up action will also be true. In your example the paradox was caused by faster than light travel who is an easy way to generate this.

However I claim you could cause the effect in other ways: In this case get two different results as light moves in the direction of travel or opposite.

If you take two clocks who are synchronized and placed at the front and back of the flatbed before you start moving they will still be moving at the same speed, attach sensors and transmitters who return an time stamp then the beams hit, then both signals return they are stored then compared, if the timestamps are diferent the beams are turned off.

Now for the on board observer both beams hit the sensors at the same time, and the same time is returned so the beam stays on, the time the timestamp signal uses on the return is not important here.

The stationary observer see one beam hit before the other, just as before, he should wherefore get two different timestamps and see the beams turn off because of this.

You might do this simpler. The beams will get an doppler frequency shift because of the flatbeds movement from the stationary observer viewpoint but not from the onboard one.

Yes the frequencies swap around at the mirrors but its still different frequencies who hit the central receiver from the point of the stationary observer and different frequencies trigger the bomb.

----

And it makes perfect sense to say that the light from Andromeda left then humans started to evolve, this does not require synchronized clocks, only an accuracy of some hundred thousand years.

---

No I'm no expert on relativity, however I have a feeling you draw the conclusions too far.