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Superluminal spacecraft: impossible?

  1. Jan 23, 2004 #1
    Einstein asserted that the mass would have become infinite and/or created a black hole. But then came Alcubierre in 1994 who said it might be possible by contracting space in front of the ship and expanding space behind. They said this would violate laws of energy conservation, but the physicist Van Den Broeck theorized a way around this. So the solution may lie with Mr.Broeck. I haven't researched him at all; have any of you? Aside from that, do you think it will ever be possible for humans or any other species? Will we be capable of creating technology some day that can tamper with the sacred laws of gravity, quantum mechanics, relativity, energy, etc. that will allow us to explore some portion of our galaxy or beyond? This is an important question, because if the answer is no, then it could mean that the end of the human frontier.
  2. jcsd
  3. Jan 23, 2004 #2


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    The laws of nature are what they are, and there is no way around them. Physics theories today are the best known approximation to the laws of nature, and current theory says things will always travel less than the speed of light. It is possible that in the future someone will be able to show a better theory that will allow faster than light speed, but as far as we know today, it just isn't so.

  4. Jan 23, 2004 #3
    Of course less than a century ago faster-than-sound travel was held by many scientists to be impossible... I wouldn't be too quick to give anything that label, especially when any possibly solution most likley deals with levels of technology we do not yet possess- and we know our technology (and our knowledge of science) is far fram perfect.

    Personally I think it is possible in the same way that I would have thought flight was possible before it was developed; I would reserve any ultimate judgement. Instead of speculating on if things are possible, we need to research and try to find a way to make possible that which we desire/need. Only then will we have any idea of someting's possibility...
  5. Jan 24, 2004 #4


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    WRONG. Bullets have been traveling faster than the speed of sound for longer than that. But you are referring to the "sound barrier." Very, very common misunderstanding: the sound barrier was an engineering barrier, not a theoretical/scientific one. Scientists knew it was possible for objects to travel faster than the speed of sound, engineers didn't know if they could make it work for a plane. Its not the same as the speed of light barrier.

    The inability to travel faster than light has nothing to do with technology.
    I'm sorry, but thats because you don't understand why flight was known to be possible while travel faster than C is known(theorized) to be impossible.

    As for the contracting space idea, its a case of having your cake but not being able to eat it. By reducing the distance you have to travel, you can reduce the time it takes to get there without traveling faster than c. But here's the problem: the field that warps space has to propagate the full distance at C. So a star 4.5 light years away can be gotten to in a day only if you started setting up the field (with you inside it) 4.5 years ago. So you still have to pack more than just a lunch.
    Possible, but extremely unlikely. As I'm sure you know, the further our knowledge advances, the lower the error between what we think the answers are and what they actually are. We're so close with relativity that the chances of that big of an error existing is extremely small (if not nonexistant).
    Last edited: Jan 24, 2004
  6. Jan 24, 2004 #5
    All massive bodies in space-time seem to be constrained to move at C. This is not to say that we can move at *superluminal velocities in space. Relative speeds in space can be seen as simply objects moving in space-time at the same speed but in different directions.

    Superluminal velocities would require a change in this constant space-time speed. I would say that from this perspective that moving at sub-luminal speeds (in space-time) would be as difficult as moving at superluminal speeds. To move faster than light through space would require changing the magnitude of an objects space-time speed. That has to be difficult; maybe impossible.

    *edit: nor can we move at relative speeds equal to c in space.
    Last edited: Jan 24, 2004
  7. Jan 24, 2004 #6
    My point was that there have been numerous times in the past when things were considered impossible, but later we found a way to do it. We recently developed flight for the first time- we even more recently learned how to harness nuclear energy. We are just now uncovering the complexities of string theory, M-theory, and the like. We can hardly say, at this point in time, that there is ANYTHING we can rule out as impossible. For a species that's only recently gained flight (relatively recently), has only recently gained spaceflight, has only recently cloned an adult animal, has never set foot on another planet, has only recently developed any sort of quantum mechanics, and who only recently has developed relativity itself... I think it's extremely illogical to be walking around saying "Well we're so advanced now we've almost learned the deepest complexities of science. We're 99.9% sure that this thing is impossible." That's like a bronze age guy claiming that he has the most advanced weapon that will ever be made; there's always a chance that he coudl be right but it isn't smart of him to assume that. He should strive to make better things and not concern himself with what's possible and what's impossible.

    And to Jimmy:

    Yeah... Pretty interesting stuff. (Yes, it's pathetic that I have a couple lines to say to you and two trillion characters or so for the other thing... oh well :P)
  8. Jan 24, 2004 #7
    I agree that we need to be careful about what we say is impossible. We should be equally cautious about what we say is possible as well.

    A way may be found to go faster than light but I don't see it happening for a very long time. I could be wrong though. A discovery in the near future could make it possible.

    :P to you too, lol!
  9. Jan 24, 2004 #8


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    Name one since the start of science in the 1500s where a theoretical barrier has been broken.

    ALL of your examples so far have been about technology, not scientific theory.
  10. Jan 24, 2004 #9
    The reason we should never give up hope is because technology does have a way of playing with hard knowledge. Our theories of relativity and of c may never change, but the invention of planes didn't change the law of gravity. There have been experiments where gravity can be shown to fluctuate using superconductors-I know little about this though. My point is that technological innovation and experimentation have a way of complementing scientific knowledge and vice versa. The absoluteness of c surely can't apply to all matter in all its forms under all imaginable circumstances. Also, we are learning that this universe isn't one that takes kindly to the idea of absolutes. It could be that we have a lot more dots to connect and a lot more gray areas to fill in with regards to c.
  11. Jan 24, 2004 #10
    The simple fact is that physics as we know it today tells us faster than light travel is impossible. It's also unlikely that new theories of physics will change that fact, since for those new theories to work they will have to be able to duplicate the results of the old theories.

    Of course, it's possible that new physics will show us FTL travel is possible. But physics is not like technology. We can't say "lets develop physics that lets us travel faster than light". Physics is developed to reflect the real world, and it may very well be that FTL travel is impossible.

    As for the references to technology overcoming barriers set by physics...it hasn't happened yet. All of the developments referenced in this thread (heavier than air flight, faster than sound travel, nuclear power) were developed specifically because the laws of physics said they were possible. People who said flight was impossible did so because they didn't understand the physics.

    And I don't give up hope. I would love to see FTL travel. But I'm not going to let wishful thinking cloud my judgement. As it stands now, FTL travel may be possible some day in the future. But it's unlikely. And it's very unlikely it will be developed anytime in the near future.
  12. Jan 24, 2004 #11
    Ironically, if it is indeed impossible than that would support the idea that there is intelligent alien life-perhaps an abundance of it. And conversely, the fact that we haven't been visited by aliens would support the idea that FTL travel is impossible.

    Meaning that we have reason to believe there is alien life, but that we will never make contact with them.

  13. Jan 24, 2004 #12
    FTL travel isn't required for interstellar travel. Yes, it would make it a lot easier (and faster), but real exploration is always hard.
  14. Jan 24, 2004 #13
    FTL potential is interesting.
    Like one might think of the concept of "infinity", I suppose it tickles the imagination on wondering why there is ANY speed limit. Should not speed also be potentially infinite, especially with regards to massless propagation?

    Apparently not, as not a single thread of evidence has ever shown FTL.

    I wonder, though, about this: If a police radar gun is hard-programmed to detect speeds up to, say 200mph, what would a car travelling at 280mph read on that gun? 200mph, of course.
    Is it possible that our current technology is simply "unable-to-be-designed" to indicate FTL?
  15. Jan 24, 2004 #14
    A valid point.

    Though technology can only be as good as the physics it is based on.
  16. Jan 24, 2004 #15
    If we can't measure something, what good is its existance? There is no rule that superliminal particles cannot exist. But there is no mechanism that would allow us to interact with them, so for all intents and purposes they do not exist.
  17. Jan 24, 2004 #16
    Maybe we have reached the limits of our current physics.

    If superliminal particles do exist as part of the fabric of the universe, their existance may be of paramount importance to our very existance.
  18. Jan 24, 2004 #17
    If we can't measure them, they can't affect us. So they can't possibly be important (to us).
  19. Jan 24, 2004 #18
    Even if there is a speed limit, there are ways around that (wormholes and such). Something I find particularly interesting is that several versions of string theory (perhaps M theory as well, I'm not too familiar with it unfortunately) set space and/or location as a property of the strings- meaning that if we could find a way to influence a string in the correct way it's location property would change, instantly transporting it to another location.

    Perhaps there's something we could do with entangled particles. The point is there are numerous possibilities- If the speed limit really is C, who says we need to travel using speed?

    People used to think there was no way to find out what Protons and Neutrons were made of- but it was done. Prior to that people thought we couldn't split an atom- but it was done. Prior to that people didn't think atoms were splitable even in principle.

    There was some question as to whether faster-than-sound land travel was possible a while back, wasn't there? People didn't used to think we could ever make a useful computer smaller than a large room- but we did it. Superconductors weren't always around. We've built motors smaller than the head of a pen. True alot of this was technology, not science, but technology has a tendency to "get around" science's laws without actually breaking them.

    But really, this entire conversation is pointless. What we need to be doing is developing FTL, not discussing whether or not its possible- if we find after a long time of dedicated resources that it IS impossible, or at least that it is utterly useless to be studying it at our current level of understanding, then we can let it go. But the question to ask is never "Is it possible?" but rather "How can we do it?".
  20. Jan 24, 2004 #19
    I agree Sikz. At least I agree there could be ways around it. Within the context of the Theories of Relativity and 4d space-time, C is the limit. Nothing is moving faster or slower than C; light or matter. So we have to look for other possibilities involving other dimensions and String Theory is the best bet right now.

    Interesting comment about not using speed. Maybe we could slow down and let things come to us? Just a crazy thought. :smile:
  21. Jan 24, 2004 #20
    To achieve FLT, assuming it is possible, we need to first understand what the speed of light is.

    What are the mechanics behind the natural speed of light that ensures that its velocity is constant (in a vacuum).
    A common belief is that there is a medium (Aether) through which it travels. That medium has a natural property which governs the velocity at which energy/photons can travel.

    To achieve FLT you either have to effect this medium is some manner so as to alter this natural property, or alternatively, avoid the medium completely.

    Taking a leaf out of popular science fiction, the idea of sub-space communications.

    If you can't go through it, go under it.
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