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Science

Ways To Travel Faster Than Light Without Violating Relativity 226

StartsWithABang writes: It's one of the cardinal laws of physics and the underlying principle of Einstein's relativity itself: the fact that there's a universal speed limit to the motion of anything through space and time, the speed of light, or c. Light itself will always move at this speed (as well as certain other phenomena, like the force of gravity), while anything with mass — like all known particles of matter and antimatter — will always move slower than that. But if you want something to travel faster-than-light, you aren't, as you might think, relegated to the realm of science fiction. There are real, physical phenomena that do exactly this, and yet are perfectly consistent with relativity.
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Ways To Travel Faster Than Light Without Violating Relativity

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  • by catmistake ( 814204 ) on Thursday May 28, 2015 @06:33AM (#49789481) Journal
    Nothing can go as fast as light. Slower or faster, sure, but not c.
    • by catmistake ( 814204 ) on Thursday May 28, 2015 @06:40AM (#49789507) Journal

      Relativity requires that nothing can move through space faster than light.

      Relativity requres that nothing can move through space as fast as light (c). Nothing with mass moving slower than c can reach c by moving faster, due to increase in mass and infinite energy required to reach c, and nothing moving faster than light can slow down to c, for the same reasons. The quote from teh article is at best misleading and at worst, false.

      • we have no technology remotely capable of this, but:

        1. a quantum entangled version of yourself moves away from you (at "normal" speed, less than c)

        2. say... many light years away (i know, i said we have no technology remotely capable of this, bear with me here, just a thought experiment)

        3. the "copy" of you can't violate c, but at the last moment, one version of you interacts with its surroundings, collapsing you to that single copy. such that you have achieved instantaneous transportation across light years of distances

        doesn't that happen faster than c?

        • by catmistake ( 814204 ) on Thursday May 28, 2015 @07:10AM (#49789667) Journal

          You're at a very straight, very long beach. Imagine parallel waves striking the shore at a vanishingly slight angle. The point that the wave meets the shore moves along as the intersection of wave and beach occurs. As the waves get closer and closer to parallel with the beach, but not quite parallel, eventually that intersection point will be moving much faster than c.

          But the interesection point between waves and shore doesn't have mass, isn't really a "thing" that's moving.

        • This would appear to run into the problem that quantum entanglement can't transfer anything FTL.

          Also, when two particles are quantum entangled, they need to be kept from undergoing any changes that would break entanglement. Make another human body, quantum entangle it somehow, and how long is that entanglement going to last during normal living? I'm not real happy about being kept in stasis for five hundred years so the quantum entanglement doesn't collapse earlier.

          • yes, agreed. the idea of keeping anything larger than an atom entangled for anything longer than a second over any distance over an inch seems like a colossal almost impossible task with today's technology

            i was only doing a thought experiment

            in the realm of way out there then: i wonder if you could entangle a number of "copies" of yourself: dozens, hundreds, millions

            you just sort of disperse throughout the universe (not interacting with anything, i know, basically impossible by today's standards)

            but in an i

      • by sycodon ( 149926 )

        What it really forbids is the transfer of information or objects through space at a speed greater than that of light in a vacuum.

        What was the point of all this? Did anyone ever express an interest in FTL that did not include information or objects?

        I want the last 5 minutes back please.

      • Relativity requres that nothing can move through space as fast as light (c).

        Not correct - light moves through space as fast as light. Nothing can move faster.

        nothing moving faster than light can slow down to c

        Actually it is stronger than that - nothing moving faster than 'c' should exist because of causality. If something moving faster that 'c' exists then then some inertial frames it will be propagating backwards in time. We could then use whatever it is to communicate with the past and set up all sorts of nasty temporal paradoxes.

        • Relativity requres that nothing can move through space as fast as light (c).

          Not correct - light moves through space as fast as light. Nothing can move faster.

          I've seen rumors that did....

        • by TopherC ( 412335 )

          I think you've stated the main argument about stuff moving faster than c. But more abstractly, consider two events that are separated in both space and time, A and B. Let's say A happens first and "causes" B. Maybe A is "someone throws a ball" and B is "someone catches it." Or perhaps A and B could be sending and receiving a communication. In any case if B is outside of the light cone of A, meaning that light or anything slower could not travel from event A to event B, then there is a reference frame in whi

          • by dak664 ( 1992350 )

            Yes, the direction of the time axis is as observer-dependent as is the rotation of spatial axes. In Cartesian geometry the distance (dx, dy, dz) between points depends on the choice of coordinate system, but the length of that 3-vector is always the same (compared to the distance between some reference pair of points)

            Similarly in space-time it is only the length of the 4-vector between events A and B that can have any physical meaning. This length can be positive, negative, or zero. A positive length means

      • by goombah99 ( 560566 ) on Thursday May 28, 2015 @09:18AM (#49790579)

        It's very easy to travel 100 light years in less than 100 years. Thus for all intents and purposes, one can travel distances at faster than the speed of light. The theory of relativity does not prevent this. You can without violating any laws accelerate a rocket ship at a comfortable 1g for as long as your fuel holds out. You will not get more massive. It will not take increasing amounts of fuel to maintain the 1g acceleration. If you accelerate for 1 year at 1g then you will know that you covering the distance to your destination at faster than the speed of light.

        What is true about relativity is this: and OUTSIDE observer will see you traveling at less than the speed of light. But from your perspective you can travel across galaxies in your lifespan with ease. So for all intents and purposes, you can go faster than the speed of light provided we everything from your point of view (which is all that matters). We define speed as the distance to your destination measured in an inertia frame, divided by the time it takes you to get there, all measurements from your perspective.

        the way reletivity is taught totally confuses people on this point: A HUMAN COULD EASILY TRAVEL ANYPLACE IN THE MILYWAY WITHIN THEIR LIFETIME WITH EXISTING TECHNOLOGY, except for the part about bringing your own fuel. we just don't know how to bring enough fuel to maintain a 1g acceleration for 50 years. This is why these new reactionless EM drives that NASA and others are toying with are really interesting. No doubt they are bullshit since they seem to defy newtons laws, but if it turns out they work.... see you on on the other side of the galaxy baby.

        • by Lumpy ( 12016 )

          Or the pesky part that at relativistic speeds hydrogen atoms rip through the ship as if it was tinfoil.

        • by firewrought ( 36952 ) on Thursday May 28, 2015 @10:04AM (#49790975)

          except for the part about bringing your own fuel

          And the part about obliterating your spacecraft by colliding with interstellar dust at super-high relative velocities. The speed limit for arriving in one piece is way lower than c.

        • by PPH ( 736903 )

          Thus for all intents and purposes, one can travel distances at faster than the speed of light. The theory of relativity does not prevent this.

          Except for the little problem of Lorentz contraction [wikipedia.org]. As you move faster and faster, to a fixed observer you are getting shorter and shorter in the direction of travel. The other side of this is that to you, fixed distances get longer and longer. So that star that was 100 ly away when you were on earth starts to get farther and farther away as you accelerate toward it.

          • by sconeu ( 64226 )

            Bzzzt!!! Thank you for playing. Here's your lovely parting gift.

            Let's rephrase... as an outside observer sees you go faster you get compressed to THEM.

            From your frame of reference, the outside world is going faster and is compressed, so the distance to the star that is 100 ly away gets compressed by the gamma coefficient.

            • by PPH ( 736903 )

              so the distance to the star that is 100 ly away gets compressed by the gamma coefficient.

              So, at .99c, what I saw as 100 ly standing still becomes 10 ly and I cover that in 10.1 years (my time). I just traveled at 9.9c (as I measure it).

              I just traveled faster than light. Not the light coming out of my headlights. But in terms of distance divided by time (my time).

              • by kqs ( 1038910 )

                In your terms, you travelled 10 ly in 10.1 years.

                In terms of someone else (not moving that fast), you moved 100 ly in 101 years.

                So you only moved faster than light if you use your time with someone else's distance. I mean, you can divide anything by anything else, but that doesn't mean the resulting number means anything. :-)

                • sure it does: you can travel 100 light years in less than 100 years. that's the only thing that is meaningful. Arguing about whether you can go faster than light is not meaningful.

                • And likewise you can make anything relative to anything else and make it seem like that comparison is somehow more important.

                  The important point is that to an independent "observer" and to YOUR OWN measurements as taken BEFORE the trip, you travelled faster than the speed of light.

                  THAT, my friend, is what counts here for practical purposes.

                  What you are suggesting (practically speaking) is metaphorically akin to taking a velocity reading of your own body while seated on a supersonic jet and concluding you ar
          • Wrong. But you illustrate perfectly what I meant when I said the way relativity is taught confuses people. You are actually a member of the vast majority of people that think you can't travel to a destination in less time than it would take light. You can!

      • > Relativity requres (sic) that nothing can move through space as fast as light (c)

        That is not entirely accurate.

        Worm holes allow you to travel between points A and B; the Euclidian distance which means your effective velocity was/is significantly faster then 'c'.

        --
        First Contact is coming 2024. Are you ready for a new paradigm?

    • Nothing can go as fast as light. Slower or faster, sure, but not c.

      Light goes as fast as light.

      More specifically, you can't send MATTER, ENERGY, or INFORMATION faster than the speed of light IN VACUUM.

      The fact that there are "things" that travel faster than light (such as phase velocities) is well known; in these neither the matter nor the energy travels faster than light, and they don't carry information.

      If you could, either relativity is wrong, or you can use this to make a time machine to access the past.

      • "If you could, either relativity is wrong, or you can use this to make a time machine to access the past."

        Well, relativity is most certainly 'wrong', in the sense that there is more to the universe that it does not cover. Of course, that's not really wrong, any more than Newton was wrong. Newton was not attempting to model relativistic effects, and Einstein was not attempting to model string theory.

        And luckily, we are not made out of light, so the speed of light has little to do with a machine designed to a

        • Sorry; if special relativity holds, FTL travel is equivalent to time travel.

          Let's assume two spaceships pass each other at a speed giving a contraction factor of 2, and attune their ansibles. You're on one spaceship, and I'm on another.

          Now, I knock my water glass into the main computer an hour later. This is bad. I send you a message saying that I did that, and ask you to repeat it. You receive it at the same time as I send it - but how is that measured? If I perceive you as receiving it at the sa

          • "ansibles"

            Hey, I love thought experiments and speculation as much as the next guy, but that is a fictional device without even an idea as to how it would work.

            I'm also not sure what a contraction factor of 2 means, I assume you mean Lorentz contraction, but I don't know what 'speed' that would be. It really doesn't matter though, for the thought experiment of 2 FTL ships passing; anything over c will do. And I assure you I would never try to dis' special relativity.

            Two ships pass each other, let's say each

        • "If you could, either relativity is wrong, or you can use this to make a time machine to access the past."

          Well, relativity is most certainly 'wrong', in the sense that there is more to the universe that it does not cover.

          Saying "there are things it doesn't cover" is not the same as saying "it's wrong."

          Of course, that's not really wrong, any more than Newton was wrong. Newton was not attempting to model relativistic effects, and Einstein was not attempting to model string theory. And luckily, we are not made out of light, so the speed of light has little to do with

          The phrase "speed of light" is historical usage. An equally accurate phrase would be the universal conversion factor from units of space (meters) to units of time (seconds). It doesn't apply just to light, it is a universal constant that applies to pretty much everything in the universe, not just light. Most particularly, it applies to gravity.

          a machine designed to alter a local region's gravitational constant,

          If you alter the gravitational potential, the gravitational time dilation will me

    • "Yeah, but WORMHOLES!!"--which to me sounds an awful lot like the secular version of "Yeah, but MAGIC!!"

    • Nothing can go as fast as light. Slower or faster, sure, but not c.

      Every massless thing not only can, but must, go at c. That's the very reason light does.

  • Medium.com Alert! (Score:5, Informative)

    by weilawei ( 897823 ) on Thursday May 28, 2015 @06:35AM (#49789493)

    Danger Will Robinson, Danger! This article doesn't actually provide what its title claims. Clickbait, pure and unadulterated. Plus, it's not even that informative. All stuff we see in Slashdot comments any time anyone mentions FTL travel.

    • Re:Medium.com Alert! (Score:5, Informative)

      by sectokia ( 3999401 ) on Thursday May 28, 2015 @06:41AM (#49789511)
      Terrible click bait, doesn't mention a single way to go faster than light. Most nerds would already know all of this.
      • by dmatos ( 232892 )

        With a bit of creative interpretation, it does. For example, you could mimic the beta-decay electrons in nuclear piles:

        1. Start out traveling at almost c.
        2. Slam into a medium with a refractive index > 1.

        For a brief period of time, while your body is being vaporized by the impact, and before Cherenkov radiation robs you of your kinetic energy, you will be traveling faster than light.

    • Yeah by the standards of this article sound waves travel faster than light, at least if you're talking about their speed when passing through a sheet of tin.

    • by account_deleted ( 4530225 ) on Thursday May 28, 2015 @06:56AM (#49789585)
      Comment removed based on user account deletion
      • This means we've already got a plentiful source of fuel to go faster than light: Politicians! I *knew* there had to be some reason we have them.

    • Since when do we get all these medium.com articles? Nowadays I just skip the story when I see it's from their website. Did an editor cofound it or something?
    • Much better is the KentuckyFC guy who scours arxiv.org for interesting NEW physics ideas, discoveries, and speculations. https://medium.com/the-physics... [medium.com] Some of his stories were posted on slashdot in the past, but it seems this StartsWithABang guy has replaced him. So now I just go there directly.
  • Light speed (Score:5, Informative)

    by ArcadeMan ( 2766669 ) on Thursday May 28, 2015 @06:42AM (#49789521)

    The fact that there's a universal speed limit to the motion of anything through space and time, the speed of light, or c. Light itself will always move at this speed.

    Except, you know, cases where we slowed down light itself. By a lot [slashdot.org].

    • One way is to note that the immutable speed of light only applies to light in a vacuum. When light travels through a material, its effective speed is reduced.

      Burn! /Michael Kelso

  • TL;DR (Score:5, Informative)

    by Lord Duran ( 834815 ) on Thursday May 28, 2015 @06:48AM (#49789543)

    You can go faster than light goes in certain materials because then it travels slower than c. If you do that, badass things happen [wikipedia.org].

    That said, the article is pretty well written IMHO, so if you've never heard of this before, go ahead and read it.

  • Article's summary (Score:5, Informative)

    by m.alessandrini ( 1587467 ) on Thursday May 28, 2015 @06:52AM (#49789567)
    Light goes slower than c in any medium different from vacuum. Some objects can go faster than light in that medium (but not faster than c of course).
    • Re: (Score:3, Interesting)

      by Anonymous Coward

      And even then, light in a vacuum goes slower than the actual speed of light.

      The truest speed of light can't be attained in nature due to the fact that the vacuum is not, in fact, a true vacuum. There are virtual particles popping in and out of existence constantly, which light interacts with.
      Creating 2 casimir plates to create a true vacuum would give you the true speed. What that speed may be is not known since, as far as I know, nobody has made such an experiment. But it is theorized to not be that big

  • Don't bother reading (Score:5, Informative)

    by gsslay ( 807818 ) on Thursday May 28, 2015 @06:54AM (#49789571)

    The whole thing hinges on the phrase in the first paragraph; "depending on what you mean by a "thing", "faster-than-light", and "travel""

    If you want to play around with semantics and definitions, then you've got an article. Otherwise, nothing new here. Speed of light unchallenged.

    • by Anonymous Coward on Thursday May 28, 2015 @07:12AM (#49789673)

      The whole thing hinges on the phrase in the first paragraph; "depending on what you mean by a "thing", "faster-than-light", and "travel""

      If you want to play around with semantics and definitions, then you've got an article. Otherwise, nothing new here. Speed of light unchallenged.

      Yeah ... came here, read the article, want my money back.

      What a complete waste of time this article was!

      Did you know that if you try to send a photon through a solid wooden door, it won't ever make it ... however if you shout at the door, the sounds will be heard softly on the other side? In this case of "breaking the light speed barrier" our calculations show that not only are your vocal sound waves traveling faster than the speed of light but since light never got through the door and time still marches on, you are approaching a speed infinitely faster than the speed of light!

      Mind blown? Or are you just angry that I got you to read that horseshit?

    • by sootman ( 158191 )

      In that case, I've banged a lot of chicks, depending on what you mean by "banged", "a lot", and "chicks".

  • not true. light moves at c in a vacuum. light can be slowed down, even stopped. so no, light does not always move at c...
  • Poorly written article and misleading summary. Basically the article says you can "travel faster than the speed of light" without violating relativity...but neglects to mention which "speed of light" you're beating. Light speed is different in depending upon what medium -- or lack thereof -- it's traveling through. It's possible to slow light down to the point where you can walk faster than that speed of light. But you're not violating relativity by doing so because you're moving through a different med

  • by ArcadeMan ( 2766669 ) on Thursday May 28, 2015 @07:03AM (#49789625)

    And time itself is also quite complex. Here's a quote from someone who explains time:

    "People assume that time is a strict progression of cause to effect, but *actually* from a non-linear, non-subjective viewpoint - it's more like a big ball of wibbly wobbly... time-y wimey... stuff." - The Doctor.

  • by Anonymous Coward

    "All Ethan, all the time. Now lets go to Ethan for the forecast"

    "Thank you Ethan, today will be mostly medium.com with some light links to other sites"

    "Well that's the weather, now over to Ethan for the business"

    "Well Ethan, Dice Holding have announced a shocking drop in profits after letting once popular Slashdot.com devolve into a medium.com link aggregator. Sharholders are angry, but DHI spokesperson Ethan Siegel insists the firm is making all the right moves, and it's purely market forces outside there

  • 1. Nothing can travel faster than light in a vacuum.

    2. Some things can travel faster than light in a medium (when it is always slower by some factor).

    Unfortunately the later is just an exploration of a pedantic nature and would never lead to any meaningful definition of FTL travel. it's like saying an ant is faster than a car but only when the car is stationary or moving extremely slowly (duh).

    What was interesting about the article however was the part about cosmic expansion, even though again it does not p

  • This article is more of an opinion piece than anything else, lacking any evidence of faster than light travel in a vacuum. Light that moves through expanding space is not moving faster than c. It's simply being moved with space itself. The article reads like it was written by someone that normally covers the police beat and now is appearing amazed by science. Click-bait headlines bring in ad dollars though.
  • The article says that things don't actually go faster than c. It is possible in a certain medium (example of water) for things (like electrons) to go faster than light does, but not faster than c.

    Not even information can go faster than c, because we haven't discovered quantum entanglement to work that way.

    The end. A dumb article; not worth reading.

  • by GlobalEcho ( 26240 ) on Thursday May 28, 2015 @10:23AM (#49791219)
    Just-in-time optimized code goes faster than c.

    :-)
  • They are just hypothetical at right now... but if they do exist, they will have mass and travel faster than the speed of light. They do not violate the theory of relativity because they always travel faster than c.... they do not start at speeds less than c and accelerate to or beyond the speed of light.
    • Tachyons are nasty negative mass states; really just weird mathematical solutions. You would expect the Spanish inquisition more than the observation of a tachyon anytime soon.

  • This article was a total dissapointment. So things can technically go faster than light when light is slowed through a medium. BFD. This has nothing to do with FTL travel.

  • There may be a way (Score:4, Interesting)

    by PPH ( 736903 ) on Thursday May 28, 2015 @10:52AM (#49791475)

    But I'm not sure TFA deals with it. Nothing can travel faster than c in a vacuum. Light travels at c (in a vacuum). However, light cannot escape from inside a black hole. This isn't due to classical speed limits, but the way space time curves near the black hole's event horizon.

    However, gravity can escape a black hole. Otherwise, how would they exist and grow? So gravity is not constrained by the same space-time curvature as light. Therefore, over long distances, the curvature of space time (even a slight effect caused by the masses of nearby galaxies) would cause the vacuum velocities of gravity to excced that of light. Or, to put another way, the path through space time for light is slightly longer than that for gravity. So gravity gets there first.

    Hint: Think about this effect as an alternative to dark matter/energy.

  • by AdamHaun ( 43173 ) on Thursday May 28, 2015 @11:06AM (#49791651) Journal

    For a more thorough and slightly more technical approach to the same subject, check out the Usenet Physics FAQ's article "Is Faster-Than-Light Travel or Communication Possible?" [ucr.edu]. Here's the conclusion:

    To begin with, it is rather difficult to define exactly what is really meant by FTL travel and FTL communication. Many things such as shadows can go FTL, but not in a useful way that can carry information.

    There are several serious possibilities for real FTL which have been proposed in the scientific literature, but these always come with technical difficulties.

    The Heisenberg Uncertainty Principle tends to stop the use of apparent FTL quantum effects for sending information or matter.

    In general relativity there are potential means of FTL travel, but they may be impossible to make work. It is thought highly unlikely that engineers will be building space ships with FTL drives in the foreseeable future, if ever, but it is curious that theoretical physics as we presently understand it seems to leave the door open to the possibility.

    FTL travel of the sort science fiction writers would like is almost certainly impossible. For physicists the interesting question is "why is it impossible and what can we learn from that?"

  • Even Einstein himself said it was a theory and he might be wrong...... Just like any 'laws' of nature aren't set in stone, they are 'laws' created by humans to help us puny humans understand what's going on, at least what we believe is going on...
    Let's not forget, scientists a long time ago said the world was flat, and if you said otherwise you were a heritic... Now we know better...

Every nonzero finite dimensional inner product space has an orthonormal basis. It makes sense, when you don't think about it.

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