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Thread: Speed of light

  1. #101  
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    Quote Originally Posted by superluminal
    Guitarist,

    Hate to nit-pick but:

    V = (v<sub>1</sub> + v<sub>2</sub>)/1 + v<sub>1</sub>v<sub>2</sub>/c<sup>2</sup>

    should be:

    V = (v<sub>1</sub> + v<sub>2</sub>)/(1 + v<sub>1</sub>v<sub>2</sub>/c<sup>2</sup>)

    (parentheses added).
    Ha! I don't think there was really much ambiguity, but fine, your welcome.

    But if you really want to nit-pick, there's a newbie with attitude just blown in, whose spelling and grammar could do with some correction!
    Not to mention some seriously flawed thinking about the special theory. Frankly, I haven't the energy myself.

    Just wish people wouldn't bring personal grudges with them. Oh well.......
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  2. #102  
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    Guitarist
    Ha! I don't think there was really much ambiguity, but fine, your welcome.
    Nah, don't really want to nit-pick. I know it was just a type-o but in math there's not much room for ambiguity, right?. Those are two totally different equations.

    And yes. Personal grudges aside, there's a lot of relativistic mumbo-jumbo out there.
    Huh?
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  3. #103  
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    MacM:

    On further reading I see this has already been addressed.
    Hi Mac. Has it? Here's a good article:

    http://www.answers.com/topic/photon-2

    Extracted from the article:

    Photons in media

    In a material, photons couple to the excitations of the medium and behave differently. These excitations can often be described as quasi-particles (such as phonons and excitons); that is, as quantized wave- or particle-like entities propagating though the matter. "Coupling" means here that photons can transform into these excitations (that is, the photon gets absorbed and medium excited, involving the creation of a quasi-particle) and vice versa (the quasi-particle transforms back into a photon, or the medium relaxes by re-emitting the energy as a photon). However, as these transformations are only possibilities, they are not bound to happen and what actually propagates through the medium is a polariton; that is, a quantum-mechanical superposition of the energy quantum being a photon and of it being one of the quasi-particle matter excitations.

    According to the rules of quantum mechanics, a measurement (here: just observing what happens to the polariton) breaks this superposition; that is, the quantum either gets absorbed in the medium and stays there (likely to happen in opaque media) or it re-emerges as photon from the surface into space (likely to happen in transparent media).

    Matter excitations have a non-linear dispersion relation; that is, their momentum is not proportional to their energy. Hence, these particles propagate slower than the vacuum speed of light. (The propagation speed is the derivative of the dispersion relation with respect to momentum.) This is the formal reason why light is slower in media (such as glass) than in vacuum. (The reason for diffraction can be deduced from this by Huygens' principle.) Another way of phrasing it is to say that the photon, by being blended with the matter excitation to form a polariton, acquires an effective mass, which means that it cannot travel at c, the speed of light in a vacuum.
    Huh?
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  4. #104  
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    Hi Mac, good to see you again

    Your drawing advocates light appears slower due to an altered path through molecules. That is not the case. Light travels straight. If it hits an atom it is absorbed and then re-emitted. But it continues to travel in a straight line.

    It is the number of absorbtions and re-emissions that produce a delay and hence a longer travel time through the medium.
    Yes you are right but it is not so simple. I think that light will go straight only if it is a beam is composed from many photons. The straight line movement happens via the absorbtion-emition of the photons in atoms , the photons forces each other to go in the initial direction. However the light path is not straight line in the Absolute Space, it is straight line only wrt the relative observer.
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  5. #105  
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    just feel like bringing this topic alive again, drowsy turtle, any reply's?
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