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Speed of light

  1. Feb 1, 2004 #1
    Will anything ever go the speed of light? they are testing with muons but have never succeded... mass ads on w/the amount of energy that you are adding to push it that fast any way so will it ever be possible?
  2. jcsd
  3. Feb 1, 2004 #2
    Once in Discovery Channel I've seen that two prof. has successfully done a experiment where they've shown that there are particles that can go beyond the speed of light !!!

    I am not sure how it was....but may be:

    They were experimenting with two particles....when they both are released...after certain time if one's direction is changed....other also changed automatically! and the time other took to change direction proved that they contact with each other beyond the light speed!

    Anyone specilized in this side...can explain more :)
  4. Feb 1, 2004 #3
    Yeah, I heard about that too, but I haven't seen anything official.
  5. Feb 1, 2004 #4


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    You're talking about quantum entanglement -- the EPR effect. It is NOT communication faster than light.

    Nothing has ever been observed going faster than light, and no one expects that we ever will. If we did, it would invalidate pretty all of modern physics.

    - Warren
  6. Feb 1, 2004 #5
    Thanks! Chroot,
    But I'm not familier with this "quantum entanglement -- the EPR effect"

    Isn't it any communication between particles???
  7. Feb 1, 2004 #6
    Well..........It's not the EPR effect but rather a paper authored by Eienstien, Podolsky and Rosen, that tries to explain what Einstein described as " Spooky action at a distance". The papers main thrust was that there are "hidden local variables" at work and not a violation of SRT.

    The main idea of locality is one of a handful of areas of investigation where the accommodation between classical relativity and QM break down. There have been numerous experiments that suggest FTL information exchange ( the entangled pairs of virtual particles) which rely on one of these two conjectures. Either there are unknown forces at the local level or that there is a connection that is FTL between particle pairs.
  8. Feb 1, 2004 #7


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    No information is propagated FTL. The quantum system composed of both particles collapses simultaneously. There is no information transmitted.

    - Warren
  9. Feb 1, 2004 #8
    I have a question about photons. They compose light, right? They are particles with zero mass, no electric charge, and an indefinitely long lifetime, right?

    The thing that seems weird to me is - if they have zero mass, what keeps them from going faster, in fact - how can they even physically exist with 0 mass? It would seem to me that something with 0 mass could be capable of instant speed. Obviously, this is wrong. But why? What keeps light/photons "existing" the way they do?

    Also, doesn't having a set "smallest amount of a physical quantity that can exist independently" seem illogical? (to me, it seems like logic should say you can break something down [that exists] indefinitely.) Obviously I am wrong, but how?
    Last edited: Apr 26, 2004
  10. Feb 1, 2004 #9
    Well, I'm no expert on this, but I think those are essentially correct. The thing about zero mass should be zero rest mass. Photons do have momentum. A subtle distinction, perhaps, but it's an important one. Also, I don't know what you mean by an indefinitely long lifetime. It's not infinitely long; a photon ends when it absorbed. Even if you meant it has an infinitely long half life, that's a bulk property. A free neutron has a half life of about ten minutes on average, but an individual neutron can decay in ten mincroseconds or less or ten millenium or longer. You don't know beforehand. In all cases, the lifespan on any individual particle is indefinate.

    They're going as fast as they can. The structure of space time doesn't allow them to go faster. And why shouldn't they exist without mass? Things exist without charge. As far as I know, the only thing that's absolutely necessary for something to exist is energy, and they have that.

    I'm not sure what you mean by "instant speed." When a photon is emitted from an atom, say, it begins it's existance moving at the speed of light. It has that speed instantly. Particles without mass cannot go slower than that, not even for an instant. I suspect you meant to say "infinite speed," but that concept doesn't make sense in our universe.

    What allows a photon to continue to exist is that it's an oscillating electromagnetic field. You can't have a static electric field without a charge, but the photon is an uncharged particle. So it's electric field decays. But change in an electric field induces a magnetic field. But, you can't have a static magnetic field without a current to anchor it, and you can't have a current without a charged particle, so the magnetic field decays too. And that induces an electric field, which gets us back to where we started. And so on, and so on. The photon is the continual inducement of these fields because the fields cannot be maintained statically. As I understand it, that's why the photon has to be moving, and move it sure does!

    Well, I don't have a problem with that. There's at least as much philosophical problem with breaking things down infinitely, isn't there? Logically, don't you have to get to a point where breaking something down has to chage the essential nature of the substance? For example, you can only divide a glass of water a few dozen times before you have to break down a water molecule into hydrogen and oxygen, and then it's not water any more. At some point, shouldn't the nature of reality itself have to break down, and so, since this can't happen, provide a floor below which you can't go?

    It's an interesting differnce of perspective, though.
  11. Feb 2, 2004 #10

    Umm...Yeah. Light has no mass buddy. its a value oscillation in the electro magnetic field that propagates and behaves in a matter similar to particle, even though it really isn't as anyone aware of the wave-particle duality can tell you. Even if light had mass equivalent to its energyr (as converted by E=mc^2 or m=E/c^2) then its momentum would be extremely insignificant being E/c^2 and thus, no noticable impact would occur.

    Questioning current theories is one thing, but you have to understand them and the observations that pertain to them first. Quite frankly reading your posts make me feel like Nietzsche studying Platonic Philosophy. Your ideas have no real basis in reality, you are, as integral said, making non physical assumptions and thus your ideas have no real physical meaning. Its like saying y=x+1 is the equation of motion of a pendulum, either you have to reinvent mathematics ( or in your case language) or your ideas have no physical meaning.

    As for a more legitimate inquiriy into the theory of light, you should start with an actual observation that disagrees with the current theory, rather than inventing non-real scenarios that disagree the theory, or finding an alternate explanation that gives predictions concurrent with reality and not just your artificail Platonic constructs.
  12. Feb 3, 2004 #11
    Chroot: "No information is propagated FTL. The quantum system composed of both particles collapses simultaneously. There is no information transmitted."

    Well that's an awfully declarative position even tho it is the consensus of the majority of people studying this area of physics.

    There are alternative takes such as GHZ http://www.sciencedaily.com/encyclopedia/GHZ_experiment ( three particle Ex )and Stapps paper on the interpretation of that Ex and others (A Bell-type Theorem Without Hidden Variables. LBNL-49602 ) . Griffith's rebuttal (http://xxx.lanl.gov/abs/quant-ph/9805056 )utilizes Hardy's paradox as an disproof but Stapps reply (http://www.arxiv.org/abs/quant-ph/9905055) seems to be quite robust.

    I'm just maintaining that there exists differing opinions and the subject is still open to debate.
  13. Feb 4, 2004 #12
    There is inflation theory. This is a possible (and highly theoretical) solution to the cosmological problems. It states that space itself can expand at faster than the speed of light. Any matter within the space isn't actually moving since its the space itself thats moving. If space can really do this it is concievable that eventually we will be able to control this effect. I must reiterate that this is highly theoretical, its only the currently excepted theory since nothing else solves the cp's and assuming they are unsolvable means accepting GR is wrong.
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