What is Ftl: Definition and 174 Discussions

Faster-than-light (also superluminal, FTL or supercausal) communications and travel are the conjectural propagation of information or matter faster than the speed of light.
The special theory of relativity implies that only particles with zero rest mass may travel at the speed of light. Tachyons, particles whose speed exceeds that of light, have been hypothesized, but their existence would violate causality, and the consensus of physicists is that they do not exist. On the other hand, what some physicists refer to as "apparent" or "effective" FTL depends on the hypothesis that unusually distorted regions of spacetime might permit matter to reach distant locations in less time than light could in normal or undistorted spacetime.
According to the current scientific theories, matter is required to travel at slower-than-light (also subluminal or STL) speed with respect to the locally distorted spacetime region. Apparent FTL is not excluded by general relativity; however, any apparent FTL physical plausibility is currently speculative. Examples of apparent FTL proposals are the Alcubierre drive, Krasnikov tubes, the traversable wormholes, and quantum tunneling.

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  1. H

    Exploring the Possibility of FTL Communication with Entangled Particles

    I am puzzled with the following gedankenexperiment. Consider a pair of particles that are sent from x = 0 on different directions +x and -x with entangled position on the y axis. Parallel to the y-axis we locate two double slit plates A and B. They plate A is located at x = -L and the plate B...
  2. E

    Proof that FTL communication quantum protocol is impossible?

    Hi all, I am reading pretty much everywhere that no quantum protocol for faster-than-light communication can exist. Now, clearly neither super-dense coding nor any other quantum protocol I know of can be used for FTL communication - but is there a self-contained proof that no such protocol can...
  3. heusdens

    Bell experiment would somehow prove non-locality and information FTL?

    The famous Bell experiment would somehow proof non-locality and/or traveling of information faster then light. A very simple explenation of the experiment is this: there is a subatomic event that creates a particle pair going opposite directions. The subatomic event determines the possible...
  4. E

    Is it Possible to Beat a Beam of Light and Shake Hands with Yourself?

    As a preface to my question, I am in no way asserting a FTL posibility which violates the posulates of Special Relativity. Throughout several online articles and books that I have been reading, there has been a referance to some sort of warping of spacetime that allows you to, in their words...
  5. S

    Exploring FTL Transport Using Singularities

    i don't know where to put this so feel free to move it: I wolud like to discuss ways of Faster than light transport using singularity based forms. (not in reality, only good ways of doing it) thers always the basic one of: ship> }-----------worm hole----------{ but what about...
  6. L

    Negative Energy and a SciFi ftl

    I know crazy unsupported theories aren't supposed to be posted, but I have been working on some fiction which requires faster than light travel. I have read many other guides to ftl in SciFi, and I had origionally fitted in a form of hyperdrive, which would simply avoid the issue by ignoring the...
  7. A

    Ftl - Heim QT based propulsion models

    http://news.scotsman.com/scitech.cfm?id=16902006 what?
  8. I

    Another Hairbrained FTL Scheme

    Arguments against FTL communication are usually based on causuality arguments, which I tend to agree with. But it seems to me that the 'backwards in time' problem seems to make an assumption that might not always apply, ie that FTL velocity would be relative to C for all observers. Here's...
  9. A

    Why can't Spooky action send FTL information?

    Why can't "Spooky action" send FTL information? I understand that for two entangled particles, that if you observe one it will instantly affect the other. I can even understand how we can't make sense of what was observed without sending a "Hey, I got and 'up' what about you?" But what I...
  10. A

    Exploring Possibilities of No Movement FTL Travel

    I was thinking a while back, after reading something about inflation. if you could build a device that will increse the distance between you and an object(lets say earth), you would be able the change posision faster then sublightspeed motion allows. because you would create distance, of which...
  11. G

    FTL Travel: Will we get there?

    I have heard many suggestions for ways to travel faster than the speed of light. Everything from the more mundane (wormholes) to the extreme (Alcubierre waves), although I suppose it's all exotic when it comes to this field. Getting to the point, however, I would like to hear your opinions of...
  12. E

    Negative Mass: Possibility of FTL Travel?

    Is there any theories or something of that sort, which allows negative mass? Hence, v > c rather than v < c. This seems like the only logical possibility to FTL travel.
  13. G

    Is FTL Travel Within a Light Cone Possible for Time Travel?

    FTL travel in a light cone? I read in several places there there is one condition in GR, that will allow you to travel faster than light, and allow time travel to the past. Can someone explain this further, without getting too mathamatical (Ok, maybe a little math). Thanks in advance :smile:
  14. Arctic Fox

    Is it possible to know the future through a biological mechanism?

    So, if I'm thinking of this correctly... The faster we travel, the slower time progresses for those traveling. We go faster, time for us slows down. Just for ease of example, let's say the travelers are traveling exactly at c. They travel toward a star that is 10LY away - so at c...
  15. B

    Simple ftl setup using Stern-Gerlach

    Hi, I've been reading David Albert's book "Quantum Mechanics and Experience," and it got me thinking about how one could use Stern-Gerlach sorts of measurements on entangled electron pairs (or electron-positron pairs) to transmit a statistical signal from one to the other. Let's say you...
  16. S

    Debate with regards to time and FTL travel

    I figured this might spark some interesting debate with regards to time and FTL travel. First off if you were traveling at or near the speed of light wouldn't your body be stretched out thin like a noodle, so much so, that your stretched pencil shaped blood vessels would have trouble fitting...
  17. M

    FTL Communication-Best Candidate?

    1st Question: Just how firmly established is the idea that, not only can't anything with a non-zero mass be accelerated to C+ speeds, but that *information*, of *any* kind, can not be sent from one point to another in less time than it would take a beam of light to cover the distance in a total...
  18. F

    Quantum Entanglement and FTL Information transfer

    First post. There's something I don't quite understand about quantum entanglement and I'm hoping someone here can put me right. When I first heard about the Aspect experiment, I thought that it had to open the way forward for faster-than-light information transfer as follows: Bob is on...
  19. T

    FTL Gravity wave spatial transmission

    After playing around equations producing velocities greater than C in normal space due to space-time warping i had the theory that if a graviton travels at the speed of light and gravitons are the messenger particles of gravity (assuming that gravitons warp space-time by nature ) that depending...
  20. T

    Unlocking the Mystery of Light: FTL Travel

    Firstly, just a high to everyone, (first post, aye). Now, everyone has been saying that FTL Travel (Faster than Light) and even the speed of light is impossible. (dammit... ) than how is it that light can go at the speed of light. Now, for some touching back on the SOL theory. As you...
  21. J

    Gravity and the Speed of Gravitational Influence

    The Earth has a gravitational pull that attracts things to it correct? If we launced a rocket from Earth and said rocket was traveling from the ground to space at, oh let's say, 100 miles per hour (or kilometers - it really doesn't matter). Given the slow speed of the rocket, it would never...
  22. J

    Is FTL Travel Possible with a Mini Cooper in an Alternate Space Network?

    Special relativity asserts that an object approaching the speed of light would also increase its mass to the point that even an infinite supply of fuel/energy would not be able to push that little go-kart passed the critical limit of C, right - close enough maybe? Why is C the limit? Is it...
  23. S

    FTL Signals and the Paradox of Causality

    This is a pretty basic concept of relativity that used to make sense to me but I have since become a little unclear on the issue. The question is how can one violate the principle of causality simply by broadcasting information that travels faster-than-light?
  24. R

    Can Magnitism Stretch Time and Allow for Faster-Than-Light Travel?

    My woodshop teacher, who is a physics hobbyist, insists that by using magnitism to stretch time, we could travel faster than light. I protested at the idea; but my explanations of how time doesn't matter much when it comes to ftl travel, and the fact that you need infinite energy failed to...
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