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. T

    Nothing can travel faster than light

    Is that a completely correct statement? I had a discussion with a co-worker the other day (while checking out a customer at a local grocery store lol) about the statement above. I firmly made the argument that nothing can travel faster than light with the exception of inflation and...
  2. M

    Amazing Experiment: Faster Than Light?

    Take a long stick, let's say close to infinity, meaning infinity-0.000001, and ignore all the classical physics acting upon this stick, mount this stick on a rotation bar on Earth and let it expand into the univers, now install a sensor at each point along this stick, and a person at the end of...
  3. A

    How Can Spacecraft Travel Faster Than Light?

    Lets just pretend we have a spaceship traveling in the vacuum of space with no friction from space dust whatsoever. It accelerates at a meager 10m/s. Eventually in millions of years it will near the speed of light. If nothing can go faster than the speed of light than what prevents said...
  4. F

    Faster than light / compress space

    ok, I've heard a theory that it may be possible to compress space in front of a "ship" travel through, or, "over" this compressed space, the result being the ship traveling several light years in minutes. i know bending/stretching of space is proven, is compressing space also proven or just...
  5. M

    Gravity Goes Faster Than Light?

    I would have added this post to the other thread on Gravity, but I thought this was too theoretical of a segway, so it needed its own thread. But, if gravity fields transmit instantaneously, then wouldn't it be a way of transmitting information faster than light? (Say, a sort of gravity...
  6. M

    Faster than light travel proved sort off

    I was laying in bed and a thought came to me. I am sure this has been explored already so I wanted to know what the answer was as my physics is limited as I study biochemistry. I have a feeling this is related closely to general relativity, but again maybe someone could clear this up for me...
  7. M

    How can space be created faster than light during inflation?

    I have a question that bothers me. well, i have a lot of question that bother me. But for now, i will share only one. When inflation began after the big bang, the amount of space that was created exceeded the speed of light. How was that possible?
  8. G

    Is there a possibility of particles faster than light?

    Why do we take photons as the reference and say they are the fastest? Could anyone prove that there isn't a particle that is slightly faster than photons? For example one could probable redo all the relativity argument with that faster particle (gravitons or anything)? Then light would...
  9. J

    Is Faster than Light travel impossible?

    Or is it just that it can't be observed? This is a question that has been on my mind for some time, so i thought it worth asking here. Imagine the following scenario: Two spacecraft travel towards each other. Each travels at 0.6C relative to their point of origin (the points of origin being...
  10. U

    Faster than Light Travel Side Effects

    I was doing research on faster than light travel and a question popped into my head: what would be the side effects of faster than light speed travel? Any ideas?
  11. U

    Is Faster than Light Travel Possible?

    I was doing research on fastaer than light travel, and I came across a chart that said that said that a starship can only travel ten times the speed of light until it occupies all points in space. (I understand that this is fiction, and is only possible in theory but I am still intreasted in...
  12. L

    Faster than light time travel through controlled, spatial distortion

    I have recently heard of a theory that states that faster than light time travel is possible by disrupting the fabric of space-time using tachyons, to create a makeshift wave behind a future spacecraft of some sort. It states that by doing this, one creates a bubble around the spacecraft ...
  13. B

    Faster than light Information Possible?

    Ok my question has to do with a thought experiment which seems to allow faster than light transfer of information. I'm sure there is a problem with it...I just can't seem to figure out what that problem is...so I thought you guys could help. First you build a sort of telegraph system that...
  14. D

    Is it realy true that nothing can travel faster than light? if so, why?

    How do the movement of a particle relate to the speed of light
  15. Y

    Confusion with faster than light

    Confusion with "faster than light" Okay first off hi, this is my first post on these boards, let me clear a few things up here, I'm a bit of a laywoman when it comes to all of this so please go easy on me. I've been into Physics for a couple of years now as a bit of light reading to keep my...
  16. A

    Can We Travel Faster Than Light?

    I know that relativity doesn't permits a motion at speed of light or fast, as the Lorentz factor becomes infinite and we get absurd results, but what about wormholes or something, say wrap drive and what about http://en.wikipedia.org/wiki/Alcubierre_drive" and tachyons. Also I've heard that...
  17. camilus

    Universe expanding faster than light

    I read it is possible for the universe to be expanding faster than the speed of light. What would be the implications of this?
  18. R

    Idea for light speed or possibly faster than light speed travel?

    So the other day while I was folding up some laundry I had this idea pop into my head. Now I'm not an expert or anything and I dropped out of physics in high school, but I do think quantum physics are interesting like most people. I figure this would probably be the best place to post this due...
  19. R

    Why is faster than light travel so bizarrely 'addressed'

    Hello everyone, The topic of superluminal flight has intrigued me for decades but coming from an engineering background and not a strong physics background (although I have studied physics), I am finding the notions about how to possibly achieve such a system quite difficult to accept. In...
  20. S

    Two Spaceships, .90c - Why No Faster Than Light?

    You have 2 identical spaceships, each that can go .90 the speed of light relative to Earth. One spaceship tows the other, and once reaching the maximal speed (.90c relative to earth), the second ship that is currently being towed, is released, which then proceeds to accelerate toward its...
  21. T

    Is Energy Transmitted Faster than Light through Electro-Weak Fields?

    I understand that in our universe, the speed of light represents a limit which objects of mass cannot reach. I also understand that at sufficiently high energies, the electromagnetic force becomes unified with the weak force to make the electro-weak force. Now my question is, is energy...
  22. N

    Is Faster than Light Travel Possible for Objects with Less Mass than a Proton?

    Please correct me if I'm wrong, but as far as I know: 1. Photons have no mass at rest, but gain mass as they accelerate, like all objects (although it is an extremely small amount). 2. Light is composed of Photons traveling in waves. 3. It is theoretically impossible for an object to...
  23. L

    Can objects moving faster than light exist in special relativity?

    Hello, I am really curious about special relativity but don't have a strong background in maths or theoretical physics. would be very greatful if you could help me with this scenario; XYZ are objects in space Y explodes violently, sending X and Z away from Y in opposite directions at C / 2...
  24. N

    SR is that nothing can move faster than light

    Can somebody explain my error to me? 1. The base of SR is that nothing can move faster than light, c + v == c, c - v = c 2 The next step many authors do is proving non-existance of simultaneity by on observer at the platform versus one in a fast train. Flash from the front, to...
  25. T

    Can magnetic field expand faster than light?

    When I was reading abuth EM oscilators, a question suddenly ran through my mind: “Is there a frequency, when the speed of a colapsing/forming magnetic field would exceed the speed of light?“ Einstain said that nothing can go faster than light. Well, ok, but if the magnetic field (generated...
  26. F

    Are there particle's or masses that travel faster than light?

    if it were possible to send a message or travel at speed's higher than light what would happen? i know that at the speed of light time would stop.but beyond...?
  27. R

    Faster than light speed Comunications?

    Hello, I'm newbie to physics and relativity and I wish to know more. I've had a question for 5 years and nobody has been able to give me a clear answer. Here it goes! Suppose there were 2 astronauts in space one in front of the other. There is a distance of one light year between them...
  28. D

    Scientist makes radio waves travel faster than light

    Link: http://www.santafenewmexican.com/HealthandScience/LANL_scientist_makes_radio_waves_travel_faster_than_light Is this true ? Can radio waves or light really be send faster than light using a rapidly spinning magnetic field ? Sorry if there already was a thread about this, I couldn't...
  29. A

    Vector drive - faster than light?

    If a spaceship is traveling at 90% the speed of light on the X axis. And it is also traveling 90% the speed of light on the Y axis. What is its velocity?
  30. P

    Exploring the Possibility of Traveling Faster Than Light

    I know that with todays knowledge, nothing can travel faster than light and nothing with mass can travel at the speed of light. I say with todays knowledge because physics is a living science which changes as new discoveries are made. Some of Einsteins findings overturned Newtonian physics...
  31. M

    Light cones in faster than light travel

    Looking for clarification: FTL travel is said to imply signals moving backwards in time for some inertial frames. Is this because in certain cases, depending on how much greater than light speed one is able to achieve, someone can signal someone else's "past light cone" in the graphical sense...
  32. S

    Rotating a laser beam faster than light?

    This is probably just nuts but let's say you switch on a laser, point it to the sky and leave it on for billions of years until the beam has traveled billions of light years. Then you rotate the laser 360 degrees in let's say 1 RPM. Does the laser spot that is now billions of light years away...
  33. N

    Is Faster-than-Light Travel Possible with Constant Acceleration?

    While SR states one can never measure a velocity greater than C, for all practical purposes one can travel 'faster than light'. Here is what I mean. . . Lets assume I have a Spaceship with the means of constantly accelerating at 1G. The fact that this is technologically unfeasible is...
  34. D

    Are they moving faster than light?

    I have heard and read that some galaxies are receding at speeds even faster than light's, is that true? If they are, then would this not contradict the very well accepted speed limit = 300,000 km/s? Note: the question asked by a non physicist/astronomer/cosmologist.
  35. J

    Electron Beam Speed in TV Picture Tubes: Explaining Special Relativity

    It is possible for the electron beam in a a television picture tube to move across the screen at a speed faster than the speed of light. Why does this not contradict special relativity?
  36. M

    Can information travel faster than light?

    Let's say there's a stick, and two persons are holding the extremities: Person A ----------stick---------- Person B Both are pulling the stick with equal forces. At a certain moment, Person B releases it and instantly Person A knows it becase he can now pull the stick to himself. Why...
  37. X

    Is Faster Than Light Travel Possible?

    The Light Speed has been proved to be around 300.000Km per second. So, Before continuing to expose my real thread, i need to know if it is really impossible to an object to travel faster than Light Speed.
  38. marcus

    Faster than light expansion speeds are standard

    We need a stickythread that makes this point. Prominently so it catches newcomers' attention. Otherwise questions about it keep coming up. If anyone wants to try saying this in an especially clear way, please go ahead. Everybody I can think of has made this point----the mods, the professional...
  39. D

    Negative Rest Mass: Faster than Light?

    Theoretically, if an object were to have negative rest mass, would it travel faster than light?
  40. A

    Can information travel faster than light?

    Theory of Relativity says nothing can exceed the speed of light. My question is: Can any information be made to travel faster than 'c'? suppose, i have a light torch of very high intensity which can be rotated on an axis(its stand). the light is made to fall on a wall(extending for millions...
  41. B

    Exploring Plasma Waves: Faster than Light?

    Hi, I'm studying plasma waves now, and we have talked about waves in class that have phase velocities faster than the speed of light. For example, some of the waves from the Appleton-Hartree dispersion relation have this characteristic. I asked my professor about it and he said that is...
  42. M

    Can Anything Travel Faster Than Light - Explained Simply

    Well, it's an interesting thought, but one that I can't quite believe, or maybe more I can't understand how, something can travel faster than light? I've read this wikipedia, and although a few people don't trust what is written on wikipedia, I have heard of it before. Could anyone explain...
  43. J

    Information traveling faster than light?

    If I am correct, information cannot travel faster than the speed of light? So, let's say a rod, longer than the distance light can travel in a second was constructed in space. It is rigid and firm, and not bendable. At one end, is a button, and when the rod is tilted, it presses this button...
  44. I

    Is light actually faster than light?

    I just read an article that was released 2 years ago about something that some of you may have heard about and maybe even posted threads about at some point but I have to throw this out there because I really want to learn more about it. Researchers from EPFL claim to have made light travel...
  45. D

    Nothing can travel faster than light

    A question has been in my head for some time and I have yet to find an answer when I researched it. I know that nothing can travel faster than light, but WHY? All observers, no matter what speed they are traveling to or from the source of light, see the light as coming at them at 670...
  46. I

    I have devised away to travel Faster Than Light

    this came to me in a dream state meditaion a few days ago everything from light to sound to time all travel along some line and travel all at different speeds. but if you are able to cause mulitple fission explosion for a brief moment everything around that implossion will be sucked inward...
  47. J

    Cheating a faster than light signal.

    A spin zero particle decays into a pair of spin 1/2 particles, each particle in a superposition state of up and down. The pair of particles head off in two opposite directions. One of them enters an apparatus that will collapse its wave function and decide the life and death of a cat based on...
  48. U

    Why cant forces travel faster than light speed?

    Why can't "forces" travel faster than light speed? As always, I'll start with a disclaimer that I know next to nothing about physics, just that I have an interest in the subject (actually, relativity kinda scares the hell out of me for some odd reason). Anyways, I am reading through this...
  49. vincentm

    Can Sound Travel Faster Than Light?

    http://www.livescience.com/technology/070112_ftl_sound.html"
  50. I

    Im not too clever, but faster than light?

    im not too clever, but "faster than light?" Hi, I have no real background in physics, but got to thinking of something. -------------------------------------------- Let’s say light travels at around 670,616,629.384 miles per hour Then let's say I have a imaginary rod 134123326 miles...
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