What is Faster than light: Definition and 244 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. Marcarious Thomas

    B Faster Than Light Travel: Exploring the Possibilities of Spacetime Curvature

    Based on the current understanding of general relativity, it is possible that curving spacetime in the back of a spacecraft would allow for faster-than-light travel. In general relativity, the curvature of spacetime is determined by the universe's distribution of matter and energy. If a...
  2. U

    B Where am I wrong in this travelling faster than light Idea I've had?

    Dear Anyone. Please be nice and let me down gently, I know more about tapdancing than physics and I can't tapdance! It's just... Kept reading nothing could go faster than light, in a vacuum (space.) So I Googled 'why' and discovered it's because things get heavier and heavier as they get...
  3. A

    I Speed faster than light speed in a medium

    hello everyone I read this text in physics book: "Another example is the so-called Cerenkov radiation, which consists of light waves emitted by charged particles that move through a medium with a speed greater than the phase speed of light in that medium. The blue glow of the water that often...
  4. Delta2

    I Entanglement and FTL signaling in professional scientific literature

    According to professional scientific literature and to our best understanding, are there any suggestions that entanglement might imply some sort of faster than light signaling between the entangled particles? I know that according to relativity nothing can travel faster than light, but what...
  5. M

    If you are moving in a ship at FTL, could a pilot react at FTL?

    Faster than light travel is most likely impossible (at least in this dimension) BUT hypothetically I was thinking back to Star Wars: The Force Awakens. At the near-end of the movie, Han Solo, Rey, Chewbacca, Finn and BB-8 get through Starkiller Base's shield by exploiting a loophole. The shield...
  6. SvenDahlhaus

    Is there really nothing faster than light?

    Homework Statement:: Einsteins Theorie Relevant Equations:: Theorie Hi. My name is Sven Dahlhaus. I'm from Germany and just got my high school diploma. Nevertheless, I am a big fan of theoretical physics. There is a question that bothers me a lot. According to Einstein's theory, nothing can...
  7. K

    I Information traveling faster than light? (thought experiment)

    Let us consider a hypothetical scenario, where we are able to translate any mass at a constant speed of 10m/s w.r.t to a given frame of reference. For simplicity, we are going to assume that the object is at rest initially. Case 1 - Now, consider 2 points A and B at a distance of 10m, and our...
  8. B

    B Did the Big Bang expand faster than light?

    I read that our telescopes pointing in any direction show light coming from the early days of the Big Bang (like 13.7 billion years ago). So did the expansion of the Big Bang to "fill" the universe happen faster than the speed of light?
  9. G

    A Can Data Travel Faster Than Light Computation?

    Hi bear with me I have a conundrum I want to ask you. If data traveled many times the speed of light could the results of decrypted cypher message be computed quicker than any system we currently have? For instance if we sent a burst of data at many times the speed of light across the solar...
  10. richengle

    Can Light Travel Faster Than the Speed of Light in Glass?

    i made a simulation of waves in glass and in air. my simulation has led me to believe that if light begins in glass, it can travel to the air, and then move much faster, and then go back into the glass at a point further down. Could this happen in real life? here is the video of my...
  11. danielhaish

    B Why can't energy or information go faster than light?

    as I read here http://www.bbc.com/earth/story/20160429-the-real-reasons-nothing-can-ever-go-faster-than-light#:~:text=But%20light%20is%20made%20up,when%20particles%20like%20electrons%20cannot%3F&text=The%20natural%20energy%20they%20possess,are%20already%20at%20top%20speed. things with mass...
  12. ramim

    B Is it possible to see the history of space if it expands faster than light?

    I was wondering if it would be possible to see the history of space if one was to stand at the edge of the universe as it expanded faster than the speed of light. If the universe was to be expanding faster than the speed of light right now, and I was able to somehow go there and keep up with it...
  13. L

    Faster than light thought experiment

    Hi :) I just had a (most likely totaly unoriginal) thought and thought I should try to ask someone who's thinkings on physics are somewhat more refined than mine. So after thinking twice about private messaging Mr Tyson and Mr Cox :) I decided to google 'physics forum'. So here I am with my...
  14. M

    I Is this explanation of "space itself expanding" correct?

    Hi, I always used to struggle with the concept of "space itself expanding" (didn't Einstein say that the aether did not exist?) until one day an idea struck me that seemed to explain it all, without any need for complicated math. After talking about it with others, I got some great feedback...
  15. M

    I Faster Than Light Particle: Could it Create the Universe?

    I've wondered what would happen to a particle if it could break through the 186,000 miles/second speed barrier and go faster than light. Would it go say 186,001 miles/second or would it go infinitely fast. I know Einsteins Special Relativity prohibits this but I have just wondered. Now if this...
  16. RosutoTakeshi

    B How many times faster than light is this?

    Ok so I'm having trouble understanding how to calculate this If an object is moving so fast that it would take... "Hours for light to catch up to it" .. how fast would it have to be moving? Let's say it would take 2 hours for light to catch up to it. What kind of speed are we looking at...
  17. D

    B Does dark matter travel faster than light?

    Summary: Dark matter, the elusive mass that makes up most of the universe, doesn’t interact with light. Is this because it travels faster than light itself? I have been working on the maths and the theory for several months now in order to discover the nature of dark matter. By rearranging and...
  18. A

    What do you think of this FTL/time travel engine?

    So, I have this idea for the FTL engine for artistic purposes and I wanted to ask if anybody could point out it's flaws. I would greatly appreciate if you were willing to discuss them further. It is just a rough summary, so if you want me to disclose more details, ask away. The idea is as...
  19. F

    B Did anyone actually see the space moving faster than light?

    I keep hearing in these Science Channel programs that the reason why the Big Bang banged (instead of immediately collapsing into a black hole) is that when it banged it made space to expand faster than the speed of light. I'm always puzzled on how sure and certain the speakers look in these...
  20. B

    I Info traveling faster than light, and quantum entanglement

    OK, going to ask a question that I sort of know is going to be shot down but at the moment I can't make sense of this. If I send a machine/robot with a particle that is quantum entangled with another particle that is left on earth. When one particle is blue the other is red. The machine also...
  21. M

    B Layman question about faster than light communication

    Okay, first of all so I'm in no way educated in the concepts and especially the notation of quantum physics; my knowledge is confined to a very simple superficial understanding. However, if someone could educate me about why faster than light communication is impossible in the scenario I'm...
  22. G

    B Can an observer perceive he is traveling faster than light?

    I have seen thought problems with an observer on a train or in a station, etc., but I have not seen ones with the observer traveling at relativistic speeds. It seems to me that at sufficient speed he would observe himself exceeding the speed of light due to the slowing of time. This seems like...
  23. N

    I What time structure supports info moving backward in time?

    This of course is speculative, but IF faster-than-light travel (or wormhole tunneling or some other exotic means) was found to be able to communicate information from the future to the present, what would that indicate about the structure of time? Some might argue that indicates a block-type of...
  24. K

    B Exactly why FTLC is impossible with entangled photons?

    It’s written almost all physics books and courses that entangled photons can’t be used for faster than light communication. The question about used entangled photons to communicate faster than light has been discussed before, but I didn’t get exactly why faster than light communication with...
  25. ISamson

    Faster than light: Instantaneous lever

    Hello. I have been thinking on faster than light things. I thought about: chemical engines, lasers, wormholes... All that kind of cool, advanced physics. But, I stumbled on faster than light mechanical actions. I thought about a lever: first class, if you wish, if you apply a force to one side...
  26. Richie Smash

    B Faster than Light and wormholes

    If the concept of a wormhole is like folding a piece of space-time like a piece of paper, for near instantaneous travel faster than light, what is keeping us back right now? I am aware that it's really complicated and far beyond my scope of understanding right now, however I am fascinated by...
  27. C

    B Why doesn't this FTL communication scheme work?

    If Alice and Bob had a large number of particles entangled together (with state of either 0 or 1), could Alice send information by breaking the entanglement of particles with state of 1 (by flipping the state for example) so that Bob measures 50% of particles to be in the state opposite of 0...
  28. S

    I Traveling at a speed faster than light

    Imagine yourself to be bat. You can't see anything. You don't have eyes. All you can do is echolocate, using ultrasound. Now imagine something is moving away from you faster than the speed of sound. Can you locate it ? Can you perceive its existence ? If the answer is yes, how ? If no , then...
  29. J

    B Send Information Faster than Light: Point A to B

    We have two points A and B, separated by 10 light years away. WE have an iron tube conecting the two points, so this tube its 10 light years long. We are at point A and want to communicate with B, we have two options: -move slightly the iron tube---> instantly the observer at B will receive...
  30. I

    Faster than light communication

    Imagine a small cylinder with a dot at the top. Rotating the cylinder 1 degree clockwise of 0 degrees could signify a 1; and 1 degree anticlockwise of 0 degrees a zero. 0 degrees would be a space. Someone rotating one end of the cylinder would cause the other end of the cylinder to rotate...
  31. ThunderLight

    Faster than Light... Superluminal Group Velocity

    If general relativity in the formal sense constrains all velocities to the speed of light as a maximum, how would superluminal group velocities exceeding speeds of light (at their superpositions) be evaluated in mainstream physics? Would this be a case of General Relativity and Physics...
  32. mpolo

    Can electrons move faster than Light?

    I just read this article and it sounds like they are claiming that there are electron currents moving 6 times the speed of light? Am I understanding this correctly. The article title is "Faster-Than-Light Pulsar Phenomena"http://www.universetoday.com/49646/faster-than-light-pulsar-phenomena/
  33. M

    I Why would we need faster than light travel?

    This is something I often read in news on established websites, and countless times more in different forums. It goes something like this: someone says that in order for us to be able to do something, we would have to reach distant galaxies. To which someone replies "Yeah, but unfortunately...
  34. wolram

    B Does information travel faster than light

    https://www.sciencedaily.com/releases/2012/10/121028142217.htm Usable or not this seems to be a spooky statement can this 10000 be falsified?. Experiments have already shown that if you want to invoke signals to explain things, the signals would have to be traveling faster than light -- more...
  35. MiLara

    B Information traveling faster than light

    I know there is a modern paradigm that states that nothing, including information, can travel faster than the speed of light. (With exception to quantum entanglement, but I'm not going to pretend like I know the exact details of that subject). Thought experiment. Imagine there are a series...
  36. conquest

    I Theoretical problem with an empty seat going faster than light

    Hi everyone, Recently I randomly thought of a thought experiment of something going faster than light, along the lines of a shadow or some other "non-information carrying object". In this case it would be an empty seat. The idea is to take 800 million and one chairs of half a meter breadth...
  37. EricjamesCADstudent

    B What Einstein said on faster than light travel

    Hi, I'm a CAD student, writing a research paper for my English Comp. class on interstellar travel. I wan't to quote Einstein but can't find were he stated this exactly: Because space and time are relative, the faster you move through space the slower you move through time relative to someone...
  38. newjerseyrunner

    What would you see traveling faster than light?

    In my universe, the laws of physics are exactly the same, except we've figured out how to create an Alcubierre drive (we discovered how to create negative energy density, how is done through handwaving.) So, with that assumption, what would you actually see while traveling in a warp bubble like...
  39. pinochet

    Will this travel faster than light

    if i throw a ball of matter forward in space will it travel faster than light given enough time and space with nothing what so ever to stop it i.e Newtons first law of motion in effect.i figured it should becuase it will have a force to give it a constant acceleration(change in velocity).my...
  40. M

    I Do Distant Planets Move Faster Than Light Seen From Earth?

    From the observation point of Earth, you can say that the sky "moves" while the Earth is still. From this point, an observer on Earth would see a distant galaxy travel a circumference millions of light years lomg around the Earth in only a day - resulting in a velocity faster than light. Special...
  41. Tap Banister

    IF you could travel faster than light, would time cease or

    Greetings everyone, I asked my professor about this, recently. I had always heard that if you could gain the impossible amount of energy necessary to run beyond the speed of light, you would travel backwards in time. But he however, told me something that I have never heard before. He said...
  42. J

    Communication faster than light or where is my mistake?

    Hello, here is some reasoning how I got possibility to communicate faster than light. Likely somewhere are mistakes, but I can not find them by myself. Let's consider very simple setup with observers Alice, Bob and a source of entangled photons in-between of them like so...
  43. Seanra

    I My lecturer says "Special relativity is absolutely wrong"

    Hi guys In an assignment I wrote for university I was penalised for claiming that FTL neutrinos would violate special relativity. Below is the relevant part of my assignment and the response from my lecturer. Could somebody please explain what he could mean by that because as far as I can...
  44. C

    B Faster than light communication via entanglement?

    So quantum entanglement acts faster than light but it's not technically communication and not actually transferring "information"? Can someone explain this to me?
  45. Fraser MacDonald

    Faster than light travel in a vacuum chamber

    If an object is in a large vacuum chamber and is dropped, what is to stop it from accelerating to the point that it passes the speed of light, because there would be no air resistance to stop it from constantly accelerating?
  46. Cobalt101

    Faster than light travel implications

    A couple of questions around faster than light travel. 1. I don't understand why this implies traveling back in time (as is sometimes suggested). For example : A tachyon traveling at 150% c travels between Point A and Point B and back again. While it will arrive at Point B before it is...
  47. A AM ARYA

    I How can the universe expand faster than light?

    According to the theory of relativity the speed of light is the cosmic speed limit which means(I think) nothing can go faster than the speed of light.Then how universe can expand faster than light itself?
  48. pixel

    Faster than light - under what circumstances?

    Let’s say I am on the earth’s surface and observing a galaxy at a distance of d=10 billion light years away. In the course of one day, I will have observed the galaxy to move 2*pi*d in my frame of reference. Of course, this is >> c. Now it will be argued that the Earth is rotating so I am not...
  49. Jim Hasty

    Quantum Communication: Instant Transmission of Messages?

    Quantum Communication. All systems described by quantum mechanics can display so-called entanglement, for example, the spin of one electron cannot be known in advance of a measurement yet will be perfectly correlated with the other, even if it is in a distant location. This has recently been...
  50. M

    Can the Graviton be faster than light?

    Hello everyone, I was thinking of the 4 forces and in particular of the gravity force. We know that black holes and their gravity force can bend light and light gets lost on black holes. How can the ipothetic particle of the graviton interact with the photon? I thought that if the interaction...