What is Faster-than-light: Definition and 26 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. M

    Is there any way to send instantaneous signals w/o breaking causality?

    In Star Wars, they move FTL by accessing hyperspace which is a short-cut of sorts or like a wormhole that allows them to travel very fast without breaking causality as they are technically not in this dimension. FTL signals are also sent through this same dimension (called hyperwave...
  2. Giovanni Cambria

    A Is this solution for interstellar travel viable?

    I have in mind a way to enable FTL travel. Is this way viable? In the paper: "Weighing the vacuum with the Archimedes experiment" we can see the dependency of the gravitational repulsion exerted by Casimir Vacuum on the energy between the plates. The force goes as E / c^2. In the papers...
  3. M

    I Length Contraction & FTL Speeds: Are Lower Grades Faster?

    I’m not a physicist but let’s say hypothetically ;we have the Millennium Falcon. It’s FTL hyperdrive can go Class 0.5 past lightspeed. Then we have an X-wing which has a Class 1 past lightspeed drive. This is all from the lore. MF is 0.5 and X Wing is 1 but MF is faster. Anyway even though the...
  4. TerranIV

    I The Possibility of Faster-Than-Light Communication?

    If we were to discover a way to lower the electric and magnetic constants of free space, would this allow faster than light communications? This would probably only be useful for some sort of hyper-fast computers in the future, but I don't see of a physical reason why this wouldn't be feasible...
  5. M

    B Could this FTL idea with a fast moving large mass be possibl

    Could this FTL idea with a fast moving large mass be possible? I have recently come up with a possible way to achieve faster-than-light (FTL) travel by using a high speed singularity or large mass. Background As everyone knows, according to relativity, under normal conditions, it is impossible...
  6. edguy99

    Long-distance correlation, information, and faster-than-light interaction

    [Mentor's note: Split off from https://www.physicsforums.com/threads/an-abstract-long-distance-correlation-experiment.852684/page-6 because this subthread was discussing possible mechanisms behind the phenomenon] My take on these: 1) - not weird at all - you send a photon in one direction...
  7. A

    Exploring Physics: Faster-than-Light Phenomenon

    Hello i love physics and would love to learn more about it. I stumbeld upon a wikipedia page called faster then the speed of light https://en.m.wikipedia.org/wiki/Faster-than-light And if you look at 3.1 it seems to be prooven Could someone with knowledge of the topic explain this to me and...
  8. T

    Exploring the Possibilities of Faster-Than-Light Warp Drives

    Popular Science has been running an article about Sonny White, a prominent engineer at NASA's JSC. White has been attempting to realize a warp drive as theorized by Miguel Alcubierre of UNAM in Mexico. Warp Factor Faster-Than-Light Drive Negative energy, spacetime bubbles...
  9. T

    Are Faster-Than-Light Effects Predicted by Special Relativity?

    I was watching a video of Michio Kaku. He said that when you go faster than light, time goes backwards and objects have negative mass. Does SR really predict such FTL effects?
  10. C

    BREAKING NEWS: Error Undoes Faster-Than-Light Neutrino Results

    It appears that the faster-than-light neutrino results, announced last September by the OPERA collaboration in Italy, was due to a mistake after all. A bad connection between a GPS unit and a computer may be to blame...
  11. H

    CERN's OPERA Experiment: Measuring Faster-Than-Light Speed

    I have been reading and I think I understand what they were doing in CERN (OPERA) when they measured a speed faster than light. But I am not sure so I would like to ask you if I understand this right. As I understand it they "shot" two microwaves. The first one went straight to a "goal" but...
  12. J

    Faster-Than-Light Communication: Exploring Possibilities

    1. Say there are two Earth's and many light years apart. You have a very long pole which is connected to both Earth's. And one guy on Earth 1 starts pushing/tilting the other end forward. So the guy on Earth 2 feels the pole being pushed forward. guy on Earth pushes pole forward in morse...
  13. Mueiz

    How to send a faster-than-light signal (spot Paradox)?

    Suppose you have a source that send a very strong straight beam of light (say laser ) Then you direct the light toward a distant wall with angle 45 degree as show in the drawing below Then if you rotate the source 90 degree in one second, what is the velocity of the visual effect (spot)on...
  14. M

    Faster-than-light newbie question

    i'm on a ship traveling 1mph less than light speed, i decide to run the length of the ship in the direction we're travelling, let's say 10mph running speed. can i do this? or will the light-speed barrier prevent me from moving faster than 1mph? i know relative to the ship I'm moving at...
  15. K

    Why Do Some Theories Suggest Speeds Faster Than Light?

    I was wondering whether it makes sense to talk about "speeds" faster than the speed of light. For example, Wikipedia mentions that the "speed" of quantum entanglement has a minimum lower bound of 10,000 times the speed of light. - http://en.wikipedia.org/wiki/Quantum_entanglement#Concept But...
  16. A

    Faster-than-light communication

    Many seem to be skeptical whether faster-than-light communication is possible. Consider the experiments performed by Alain Aspect where the polarization of one of the entangeled photons force the other to collapse into the opposite axis. http://en.wikipedia.org/wiki/Alain_Aspect The...
  17. T

    Exploring Faster-Than-Light Travel with a Black Hole

    first, I would like to apologize for my lousy english second,I hardly know anything about relativity (well I understand why you can't travel faster than light, and i understand a few concepts,so I get the simplfied big idea , but I don't know the fine stuff of it) me and a friend were discussing...
  18. G

    Exploring the Possibility of Faster-Than-Light Travel at Big Bang

    Is it possible at the start of big bang matter and energy went faster than c?
  19. H

    Exploring the Possibility of Faster-Than-Light Communication

    I have a thought/question that maybe someone with more knowledge than I could explain. From what I understand, nothing can travel faster than the speed of light, basically we cannot even communicate faster than the speed of light. So here is my question, imagine a hypothetical rod that is...
  20. W

    Does violation of Bell's inequality imply faster-than-light communication?

    In a traditional Bell-type experiment, although one set of measurements is correlated with the other set, no communication can be conveyed because each set in itself appears a random sequence. It requires both sets of measurements to reveal action at a distance. What if entangled triplets are...
  21. C

    Relativity and the Laser Beam: Is Faster-Than-Light Travel Possible?

    I saw this awhile ago, I don't remember where though. Supposdly some scientists accelereted the beam of a laser faster then the speed of light, by shooting it through a high density gas. The opinion being that Relativity only states that nothing can go faster then the speed of light in a...
  22. T

    Faster-Than-Light Communication: What's Wrong?

    imagine you have this hugely long rod. like a lightyear long. and there's a button on one side of the rod. you, on the other side, push the rod onto the button (as fast/s;pw as you want), conveying a signal to the other side, and basically sending information faster than light. what's wrong with...
  23. R

    Is Faster-than-light Communication Possible?

    Dear group, recently I have written a paper on the possiblity of sending faster-than-light signals using entangled photons. I have shown it to several people and I have not yet received any feedback on it. I also sent a copy to arxiv.org but it was rejected and no reason was given. I am looking...
  24. G

    Faster-than-light experiments at home?

    Hi, I've been thinking about too quite simple ways to create what I believe to be faster-than-light speeds, and would like to know your opinion. First experiment: 1. Shoot a laser pointer on the moon on a clear night sky. 2. Move the dot through the diameter of the moon. If a person...
  25. Z

    The energy and the faster-than-light motion of the quasar

    The spacetime of the foggoid (for information about foggoid, please see Chapter 6 of the Antigravitation Engine Site) is curved; therefore the foggoid has gravitation. Due to the nature of "whole or none" of antigravitation, the curvature of foggoid is unstable; hence the gravitation of...
  26. D

    Exploring Faster-Than-Light Travel

    Greetings ! Let me see if I got the theoretical idea of FTL right: We take some huge amount of light in front of the spaceship turn it into matter and then back into light and so on - we repeat the process. Seems like SR has no effect here, so we should go FTL ? Live long and prosper.