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Speed of light can be attained.

  1. Oct 2, 2003 #1
    dear reader,

    You must have seen my topic "speed of can be arttained". I here in this thread am asking all of you a simple question: Can speed of light be attained.
    I firmly feel it can be attained, all we need to know is when light acts as a particle and when it acts as a wave?

    -benzun
    All for god.
     
    Last edited: Oct 5, 2003
  2. jcsd
  3. Oct 2, 2003 #2
    No, the velocity of light is not attainable. Even going in the most expensive ultra-rapid rocket that you could imagine, you will notice that the velocity of light relative to you is always c.
    You have to forget the idea that there's an absolute space
     
  4. Oct 2, 2003 #3

    chroot

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    Hey, cool... I turned on my flashlight and the light attained light speed very handily.

    All kidding aside, the speed of light as a fundamental obstacle to motion has nothing at all to do with quantum mechanics. The wave-particle duality is a misnomer, anyway. The light does not behave sometimes as a wave or sometimes as a particle. It acts all the time as both. You can design experiments which our brains will identify as dealing with "particle quantities" like momentum, or experiments which our brains will identify as dealing with "wave quantities" like wavelength -- but there is really only one thing in the microscopic world, and it is neither wave nor particle, but a mixture of both concepts.

    Also, you might like to know that, for a captain aboard a starship, there is absolutely no limit to how fast his speedometer can read. He can accelerate until, according to his watch, it takes him only fractions of a second to fly from star to star. He could fly across the galaxy in what would be minutes according to his watch. This may seem like faster than light travel to you, since you know that light takes 100,000 years to cross the galaxy. The trick is what his earth-bound buddies would see: they'd never see him going faster than light; instead, they'd see his watch running slow.

    - Warren
     
  5. Oct 2, 2003 #4
    I saw the title of your post and instantly got my hopes up, wishing you read on a science website somewhere that there is a new theory to contradict Einstein.

    Einstein was a brilliant scientist who proved that all things that have mass cannot quite reach light speed. Damn Einstein for proving that and leaving us wishing there was someway we could!
     
  6. Oct 2, 2003 #5

    chroot

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    Einstein never proved anything, and neither did any other physicist. Physics does not involve proof -- mathematics does. What Einstein did was to develop and publish a theory. The predictions of this theory have thus far agreed incredibly well with experimental results, but that does not mean that the theory has been proved. In a devil's-advocate kind of way, it just means we haven't found the right experiment yet.

    Besides, everyone knows relativity is wrong -- it's not the whole story, because it isn't compatible with quantum mechanics. Something else -- string theory, loop quantum gravity, or something yet to be invented, will eventually amalgamate relativity and quantum theory. This new theory will supplant both its predecessors, including them as special cases of a larger generality. It is entirely possible that faster than light communication or travel will be possible in the framework of that new theory, though in all probability anything like that will be restricted to subatomic domains.

    - Warren
     
  7. Oct 2, 2003 #6

    selfAdjoint

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    When you say relativity is not compatible with quantum mechanics, it is important to stress that it is General Relativity that has that problem (or Quantum Mechanics has that problem with respect to General Relativity).

    Special Relativity has been built into quantum mechanics since Dirac. Including all that stuff about the speed of light.
     
  8. Oct 2, 2003 #7

    chroot

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    Indeed.

    - Warren
     
  9. Oct 3, 2003 #8
    I have to say that relativity is not wrong. Just as Newtonian mechanics isnt wrong. They are just models to help us predict things. Thats what physics is all about, models. Obviously relativity isnt always applicable, just like Newtons laws, but they are not wrong when applied correctly.

    Most of physics is about making the correct approximation (or correct model) in order to get at the science. Most things are simply not solvable analyticaly without approximation. But we have got this far by knowing when we can approximate.

    As pointed out, no theory will ever be right. There are two reasons for this:
    1) it would only take one smart arse to design an experiment where the theory wasnt applicable.
    2) they are not suposed to be right, just models of reality.
     
  10. Oct 3, 2003 #9

    selfAdjoint

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    Granting that what you say is true in general, there has not been any reliable evidence yet to show that special relativity - the Lorentz transformations - is false. And the only evidence that it is a special case is, ta da! general relativity and its experimental evidence.
     
  11. Oct 3, 2003 #10

    russ_watters

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    "Incomplete" is the word I prefer. Too many people misinterpret it when the word "wrong" is used.
     
  12. Oct 6, 2003 #11
    There are no definite laws pertaining to the speed of light as people are always bringing up possible points that may be true. Until there is a theory everybody agrees upon, all things about light is just theoretical. For example, Einstein said that the speed of light was constant, but I believe in an issue of Discover, someone else believes that light is not constant. I however am a believer that the speed of light is constant and that Einstein was correct in stating that matter cannot achieve the speed of light.
     
  13. Oct 6, 2003 #12

    chroot

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    While there are doubtless many theories out there, Einstein's relativity is the only one currently supported by a preponderance of experimental evidence and theoretical consistency.

    - Warren
     
  14. Oct 7, 2003 #13
    ofcourse it is possible to attain speed of light with out caring much on when light turns its nature.
    Dr. Tinto
     
  15. Oct 13, 2003 #14
    i feel.................

    i might be crazy but i feel it is possible due to the following reason..........

    light is always emmited at the 3*10^3 m/s so if they were particles they gould have a opposite fore according to newtons 3rd law which will make us reach that speed.

    the universe is full of radiation so using it you can travel in the speed of light.

    i might be crazy so if i am please correct me.

    benzun
    all for god
     
  16. Oct 13, 2003 #15
    Re: i feel.................

    okay, i will... sorry...
    according to relativity (both of them) time dialation occurs when you approach the speed of light. this means that Δt->0. as Δt/t->0, then force (F=ma=m(d/(t^2))also approaches 0.
    since
    lim(v->c)Δt=0
    and
    lim(Δt->0)F=0
    then
    lim(v->c)F=0
    therefore
    lim(v->c)Δv=0
    QED
     
  17. Oct 13, 2003 #16
    as for the nature of light...

    seems to me that the energy of light changes with time.
    now, before you go denouncing this idea, listen... when light travels, it propagates as a wave. since this is true, this wave has maxima, minima, and zero-amplitude points (nodes). if that is true, then maybe the nodes are the points where photons are fully particles, the maxima and minima are the points where photons are fully wave phenomena, and the in-between parts are some inhomogeneous mixture of matter and energy.

    tell me what you think.
     
  18. Oct 13, 2003 #17

    chroot

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    Re: Re: i feel.................

    I'm sorry, but this is so sloppily said as to be entirely incorrect. Inside the helm of a spaceship moving at 0.999c with respect to the earth, the captain will notice absolutely nothing wrong. His pendulum clock will dutifully continue ticking at the same rate it always did.

    - Warren
     
  19. Oct 13, 2003 #18

    chroot

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    Re: as for the nature of light...

    I think it's equally correct to say that light propagates as discrete particles called photons.

    I further think that there is no distinction between "wave" and "particle" in the quantum realm -- there is only one kind of thing. This kind of thing is not found on macroscopic scales, however, so we have little experience with them, and constantly try to apply "wave" or "particle" properties to them -- rather improperly.

    - Warren
     
  20. Oct 13, 2003 #19
    If I understood correctly, then according to De Broglie every particle can behave like a wave. Everything has a wavelength.

    wavelength = h / (m * v)

    So you are a bit wrong there. This does happen in the macroscopic world, but the effects are so small that we don't even detect it

    I'm still trying to grasp De Broglie's ideas fully here. Can an electron, if it behaves like a wave, (and it does inside an atom) cancel itself out of existance through wave interference? Or can it amplify itself? Wouldn't this contradict a certain law of thermodynamics?
     
  21. Oct 13, 2003 #20

    chroot

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    Keep in mind that the "wave" of an electron is not really something in the electron waving about. What is waving is the probability density function that says where you are likely to find the electron when you look for it. Every such measurement will indicate an electron existing at one specific point in space; many such measurements will show a probability distribution.

    Electrons certainly can interfere, diffract, and so on -- they can do everything photons do. If you fire electrons through two (very!) tiny slits in an opaque wall, the electrons' wavefunctions will interfere. A detector moving parallel to the wall will measure lots of electrons coming through in some places, and no electrons at all coming through in others.

    - Warren
     
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