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Thread: Do photons ALWAYS travel at c through their current medium?

  1. #1 Do photons ALWAYS travel at c through their current medium? 
    Forum Sophomore somfooleishfool's Avatar
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    I read on a post that photons have 0 rest mass. This made me wonder if this meant (and this could be ludicrous) that any propulsion applied to them, no matter how small, would accelerate them to c meaning that all photons would either be at c or at rest (if even that is possible).

    Also an entirely different question that I didn't think was worth creating another whole topic for; Is there such a thing as a unit of space so small that it could be said to be an "elementary" unit of space? I guess you could define this as nothing other than a boson could fit more than one of itself into it. I do wonder if the defining an elementary unit of space nullifys the question.

    To give context of where the thought rose, I was reading the "boson" page on Wikipedia and it mentioned that multiple bosons could occupy the same "quantum state" and I didn't really understand the definition of quantum state.


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  3. #2  
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    Photons CANNOT be at rest. They only travel at C.

    There is speculation that at the Planck length the distinction between space and time disappears into a sort of quantum foam. If string theory is correct and elementary particles such as bosons, have a 'size' near Planck length, then yes, maybe only a certain number can fit into this space, unless the strings can overlap.

    A quantum state is not the same as space, rather it is defined by a set of quantum numbers.


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  4. #3  
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    Quantum numbers define the exact location of an electron in an atom.

    Try fundamentals of physics by halliday resnik. And H.C. Verma physics .
    You have to read about a state of matter called bose einstien condensate .
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  5. #4  
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    They have been able to slow photons in cesium gas(cold/liquid?) to a point where we can see it as storing them:

    http://www.cosmosmagazine.com/node/985

    ". They're currently working towards delaying dozens of pulses for as long as several milliseconds, and as many as 10,000 pulses for up to a nanosecond."
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  6. #5  
    Universal Mind John Galt's Avatar
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    But this is achieved through successive absorptions and emissions. While in existence the photon always travels at c.
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  7. #6  
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    Quantum numbers do not define an exact location in space, but a probability of finding a particle in a specified location.
    You should try fundamental physics of Heisenberg and his uncertainty principle upon which all QM is based.
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