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. D

    Big Bang Theory: Can Universe Expand Faster than Light?

    Let me preface this by saying that I know very little about astronomy, but this is a question that has been bugging me for quite a while. I've tried looking it up online and in books, but I can't find it directly addressed anwhere. My question is that if the universe began with a single...
  2. M

    Objects faster than light because space is expanding

    I have seen the argument many times that objects can travel faster than the speed of light because space is expanding. Now, what I understand from SR and GR is that no object with mass can travel at or above the speed of light. So how can this be? Moderator: feel free to move this to...
  3. E

    How to travel faster than light - why wont this work?

    what if the size of our main spaceship was unlimited. Let's say our spaceship is the size of our solar system. Reach the highest speed possible without breaking any laws of physics. Lets say -- 90% the speed of light. Now fly a smaller spaceship INSIDE the main ship as fast as you can...
  4. G

    Here's the way to go faster than light

    Sorry but was necessary to write an appariscent title to make you read. ---- We know it's impossible to reach light because the mass of the object moveing grows exponentially by the icreasing of speed ---- But, what happends in a gravitational field? the acceleration we wold get doesn't...
  5. N

    Can someone appear to be moving faster than light?

    If you have two people moving at opposite directions at nearly the speed of light, 9/10 for example, how would the other person appear to them? Would they seem to be moving faster than light?
  6. R

    Faster than light communication and signals moving backwards in time

    Hi, Can someone help explain why something that has the ability to move faster than c can potentially send a signal backwards in time - thus ruling out superluminal travel. If a 'superluminal' ray starts out at t=0 then even if it does travel faster than light, any information it...
  7. D

    Method and Apparatus For Transmitting Signals Faster than Light? (Based on EPR/QM)

    Method and Apparatus For Transmitting Signals Faster than Light?? (Based on EPR/QM) Method and Apparatus For Transmitting Signals Faster than Light?? (Based on EPR/QM) Does the following apparatus make sense? Please discuss and let me know where the logic or science is falling short, if...
  8. A

    Can Sound Actually be Faster Than Light?

    considering the speed of sound is determined based on environment isn't it possible for there to be an environment that makes speed of sound faster than the speed of light ? if this is true and possible this means that sound has the potential to be fastest in the universe keyword being potential
  9. P

    Maximizing Photon Energy: Measuring Electron's Energy Potential

    Yet another faster than light question... So I was thinking the other day: an electron experiences a significant energy gain and as a result a photon is jetted. This is how the photon is created, no? Ok then, I asked myself: is there a way to measure the energy level of the electron prior to...
  10. S

    Galaxies recede faster than light

    This is my first post on this message board. So if this message does not represent itself the way I am trying to express it, I apologize in advance. Based on an article in Scientific American March 2005 addition, it stated that galaxies recede faster than light. "The recession of a galaxy...
  11. O

    Space Ships faster than light.

    Dear Michio Kaku. I wanted to ask a question about traveling in space with a space ship. If a spacecraft emits a dense electron field around itself extended out to space in all directions from the craft, Wouldn't this electron force field (Electrons themselves) allow the material of the...
  12. G

    Faster Than Light Communication/Transportation Not Possible?

    Because if it is then it could cause problems with causality. Or is it possible but our "laws" are still incomplete?
  13. M

    Can a rigid object transmit a signal faster than the speed of light?

    If I push a rigid object at one end, the whole rod should move instantaneously. Would this mean that a signal has been transmitted from the end which is pushed to the the far end faster than the speed of light?
  14. S

    Mandel & Faster than Light Communication ?

    In Mandel et Al's most famous experiment (Fig 6 at ‎[URL]http://student.science.nus.edu.sg/~g0203645/Atomic%20Molecular%20and%20Optical%20Physics/Quantum%20effects%20in%20one-photon%20and%20two-‎photon%20interference.pdf) the signal beams from two coherent downconverters are ‎observed to...
  15. R

    Faster than light communication

    Hi, I just found this on archive: physics/0306073 [abs, pdf] : Title: Information Field and Superluminal Communication Authors: V.P.Oleinik Comments: 14 pages, pdf Subj-class: General Physics Has anyone heard of this and do you think it is a valid claim?
  16. R

    Are There String Theory-Based Methods for Achieving Faster-Than-Light Travel?

    You are all probably familiar with the theoretical work of Alcubierre, Krasnikov, Thorne etc in the field of Wormholes and warp drives. Anyone know of any string theory based FTL drives?
  17. M

    What happens if you go faster than light?

    Let's say you are in water where light travels at a speed of \frac{c}{n_w} where n_w = 1.5 and you travel faster than this speed - what happens? What do you see?
  18. E

    I know how to travel faster than light :\

    I travel at .9c for 1 second. From a stationary frame of reference, only 0.316 seconds has passed for me. So from there frame of reference, I traveled 269813212 meters in only 0.316 seconds or 2.8c or 280% the speed of light. I know that you cannot literally travel faster than light itself...
  19. Reshma

    Faster than light in a material medium?

    Velocity of light changes when it passes through a material medium. IS it possible for a particle(e. g. an electron) to travel faster than light in THAT medium? IF so, can someone give me some examples or experiments documenting this?
  20. A

    Faster than light communication?

    I was thinking of something: Say we have pairs of entangled photons. Say we send these through a polarization filter. We can call the output "ones". Now, we separate the pairs into two streams (through two optic cables). We store one member of the pair (without measuring it) and send the...
  21. D

    Tachyon is said to travel faster than light

    The tachyon is said to travel faster than light because it has a negative squared mass. -How is it possible to have a negative squared mass? Is there a lot more too it? Thanks
  22. C

    Is gravitation faster than light?

    As far as I read, gravitation or better: gravitational waves expand with c. However, particles like photons which are moving along with c are subject to the curvature of space. Regarding a black hole, light cannot escape with c but gravitation can. Is gravitation thus faster than c? Carsten
  23. Y

    Faster than light communication

    Say I have a solid rod of steel and I push one end, does the other end move near instantaneously? As an extreme, say I had a solid rod extending from two space stations very far apart, if I pushed the rod perfectly perpendicular to the face of the rod, would the time difference between when I...
  24. A

    Is Faster-Than-Light Travel Possible Through Alcubierre's Theory of Warp Drive?

    out of curiosity, who thinks we'll ever be able to travel faster than light (either directly or through higher dimensional shortcuts) ?
  25. M

    Faster than Light? Exploring X-Ray Reflection

    Faster than c! hi I read that the refractive index(n) for X-rays in meterials are less than 1(very little less than 1). I got confused ..I am using X-ray reflection at the moment. But I am not convinced by the fact that n<1 means faster than c(velocity of light in vacuum or in air)! hope...
  26. Gara

    Faster Than Light Theory #759310

    Okay, I'm proberly very wrong on many things of the following, also, I know no theory can be good with too many IF's, but here goes. IF, some how, we made a portable gravity well of some kind. IF this gravity well was strong enough to make the pull of 1000 G's, over the entire ship. IF...
  27. M

    Faster than light theory #759309

    faster than light theory #759309... imagine a propeller from a helicopter...we know that the part of the blade farthest form the pivot point moves faster than the section nearest to the pivot point... so in theory, if we could get the section nearset to the pivot point to move close to the...
  28. Z

    Back in time by going faster than light?

    Well, I guess I should introduce myself first. I'm 15, and in Canada. It's pretty hard to find answers to questions that relate to physics at this age, over the summer, so I've turned here. =) Okay, I've been interested in physics for quite some time, and I've always wondered... I've been...
  29. J

    Can particles traveling near the speed of light create a time reversal effect?

    According to Einstein nothing can move faster than c. But whereas c is constant in all frames of reference, the speed of massive objects is defined relative to other massive objects. So when we say nothing can go faster than c, we surely mean nothing can go faster than c relative to another...
  30. R

    Particles traveling faster than light

    i'm new to this forum and the physics world. please don't laugh if inqure about subjects that seem ignorant to you. what does eveyone think about particles travling faster than light, inwhich the minimum speed is just above the speed of light and the maximum is just below double the speed of...
  31. Whitestar

    Sonoluminescence - The Key To Faster Than Light Travel?

    A few years ago I was in contact with a physicist by the name of Ray Fleming. He had a theory regarding sonoluminescence being the key to faster than light travel. Here is a direct quote from him on the possibility of a ship traveling faster than light with sonoluminescence: "In order to...
  32. R

    Can Gravity Escape a Black Hole Faster Than Light?

    Take two objects like the Earth and the sun. Before light can reach the Earth from the sun the distance between them would need to be defined. Gravity is what defines this distance, right? So gravity would have to get here first before the light did. The only way this happens is that the speed...
  33. B

    I find a way to go faster than light

    Ok you can't go as fast as light. How about two rockets going at 75% of the speed of light in opposite direction? then an observer in one rocket will see the other rocket going faster than light.
  34. P

    Can a Strong Cable Connect Planets Faster Than the Speed of Light?

    My friends had asked me a question which I thought was rather troubling and provoking. The problem is that is actually seems to violate the law that states that nothing travels faster than the speed of light. Their question was: Suppose two planets (planet A and planet B) which are one...
  35. K

    Faster than light by a long way

    If you take the equation for the radius of the event horizon of a black hole and imagine that the mass of a proton is made from lots of tiny masses that form a mini black hole, and that the charge of the proton is made from mini charges that also form a black hole then: G M/ 3 C^ 2 = K Q /...
  36. R

    Why Can't Anything Travel Faster Than Light?

    hello, I've always been wondering why do people say that nothing can travel faster than light? is it because we just don't have anything to push to a speed faster than light or is it actually impossible??
  37. C

    Is it possible to communicate faster than light according to Bohm's theory?

    Can someone help me to understand exactly what Bohm did to indicate the possiblity of faster than light communication. Bohm did something to the akin of splitting a particle and than changing the direction of one half of the particle and the other half responded so quickly that light would not...
  38. R

    Faster than light speed - No conflict between classical and relativistic motion

    Assume that c is the maximum velocity of electromagnetic radiation in an inertial frame of reference centred upon the source of the elecromagnetic radiation. Assign an interface (boundary layer) between adjacent inertial frames of reference such that the velocity of the electromagnetic...
  39. T

    Going Faster Than Light: Can It Be Achieved?

    I heard a few things about going faster then c. But how would it really be achieved? I don't mean like tachyons or anything, maybe likejust before light reaches the event horizon it accelorates to beyond te speed? Is it possible at all? Some comments please, I am curious and interested :biggrin:
  40. R

    Faster than Light: 2D Photon Field?

    When a Photon travels at C, it is transversing a Three dimensional domain. In a Electromagnetic Domain, there are usually only two degree's of freedom, this translates to a Two-Dimensional Domain, do Photons travel through a reduced dimensional field at a 'Faster than light'? (when compared to...
  41. C

    Can Electricity Enable Faster-Than-Light Travel?

    I just had a conundrum.we could travel faster than light so easy and its been there the whole time.electricity!when you use metal to bridge a positive and a negative magnetic field what happens.you induce a current.whats that.electron instantaniously accelerate to light with no inertia.light...
  42. S

    Bohm's faster than light information travel experiment

    [SOLVED] Bohm's faster than light information travel experiment can anyone please give me a somewhat detailed account as to the experiment Bohm performed which dealt with splitting a particle (i think) and changing the direction of part of the particle which made the other part that was no...
  43. C

    Anti gravity travels faster than light.

    If a mass has gravity and pulls on spacetime.spacetime is charged with the same type of energy that gravity comes from.gravity seems to pull energy in faster than light but its not confirmed.but what about anti gravity.if matter can pull energy that fast,what happens when anti gravity hits...
  44. M

    A question about supposed faster than light movements.

    A question about supposed "faster than light" movements. I'm having a real problem understanding when people talk about the universe's expanding faster than the speed of light. Isn't that impossible? Also, I have heard that a black hole's gravitational pull works at a speed faster than that of...
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