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Why the speed of light is so fast?

  1. Apr 13, 2005 #1
    I would just like to know, in the simplest explanation possible, why the speed of light is so fast? A student of mine asked me the question and I wasn't able to come up with a good enough answer. thanks
     
  2. jcsd
  3. Apr 13, 2005 #2

    HallsofIvy

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    What do you mean by "so fast"? Compared to what? The great majority of individual objects in the universe, alpha rays, etc., move right up there close to the speed of light! The real question is why are WE so slow? I suspect that comparitively huge mass has something to do with it.

    It is, of course, due to relativity that nothing can go faster than light.
     
  4. Apr 14, 2005 #3

    Ich

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    The speed of light is so fast because we are run by chemical processes. These produce only some eV/molecule, so it´s quite hard for us to reach relativistic speed. That´s why everything is going very slowly compared to the speed of light.
     
  5. Apr 14, 2005 #4

    Phobos

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    I agree with HallsofIvy. It may seem like a non-answer, but perhaps you can think of it as this...the speed of light is "normal" and everything else works relative to that. Electromagnetic waves are free to move at the normal speed, but spacetime imparts further limitations on particles with mass.
     
  6. Apr 15, 2005 #5

    Ich

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    It is an answer, but not to the question. The speed of light per se is neither fast nor slow, it´s just the maximum speed and could also be set to 1.
    If you ask a cosmic ray it may find c not very impressive. But above all, it would not answer because it can´t think.
    I guess PhysKid24 is made of condensed matter, so all the energies and velocities he ever experienced have to be very low compared to m0 or c.
     
  7. Apr 18, 2005 #6
    This helps explain things from an ether perspective.

    The ether density in "empty space" is far greater than any substance known to man. Sir Oliver Lodge predicted its properties in his 1933 Lecture - The Mode of Future Existence.

    That Ether is a very substantial entity, far denser than any form of matter, has been gradually becoming clear to physicists. At first, we only said that it must be denser than lead or gold or platinum, but now we find that it must be out of all proportion denser. I have made an estimate of its density, in the light of electromagnetic theory, and it comes out inevitably huge. Every cubic millimetre contains as much substance as what, if it were matter, we should call a thousand tons. As the Ether is not matter in the ordinary sense of the term, our ordinary units of measurement are inappropriate; but on the analogy of matter, the Ether is of the order a million million times as dense as water. All its properties are of supernormal magnitude. Its rate of vibration which enables us to see any ordinary object is five hundred million million per second: a number so great that to try to conceive such a number of vibrations per second simply dizzies us. The number of seconds which have passed since ancient geological periods of twenty million years ago is about this number. Yet we familiarly make use of these vibrations. Our wonderful organ, the eye, is constructed so as to cope with them, in the easiest possible manner. And most people are ignorant - as ignorant as are the animals - of the strange ethereal environment amid which we all live, and of which the vibrations convey to us so much information, and awaken so keenly our sense of beauty.
     
  8. Apr 18, 2005 #7

    Phobos

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    Except that it has been demonstrated that there is no Ether.
     
  9. Apr 18, 2005 #8
    No. It only has only been demonstrated that the ether hasn't been detected yet. No experiment proves the ether doesn't exist. There are many experiments that do detect an etherial flow. Anyway a solid ether with strong (similar to nuclear) binding forces and elastic properties would explain the reason why light travels at such high-speed.
     
  10. Apr 18, 2005 #9

    quasar987

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    On that same note, why is Planck's constant so damn small?

    Isn't there a more general answer as to why physical constants are what they are?

    Or at least an hypothesis.

    Or do we have no clue.
     
  11. Apr 19, 2005 #10
    To determine a relationship between the physical constants, you first need to find something that has real physical properties. Currently special and general relativity give no clues whatsoever as to what this physical something is. In fact the theories completely avoid physical issues, even to the point where it describes gravity as a fictitious force. We need something more physical to work with, like the ether.
     
  12. Apr 19, 2005 #11
    Wisp, not to sound like I'm doubting you; but what evidence do you have to support that there might be an ether out there for EM waves to propagate through. I have seen some evidence on both sides and I must say I am more inclined to believe there is no ether. The evidence supporting that claim seems to be stronger than the evidence used to support it.

    I am as curious as Quasar; why is planck's constant so small? My physics text briefly outlined the math used to develop the constant, but it was presented in a rather incomprehensable manner.
     
  13. Apr 20, 2005 #12

    quasar987

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    I was watching 'The Elegant Universe' and it appears string theory provides an hypothesis for this. They suggest that everything in our universe, i.e. every fundamental constants, are what they are because of the way the extradimensions are curled one on another, forcing the string to vibrate in a way such that what we observe on a macroscopic scale is that the mass of the electron is of 10^-31 kg and that the speed of light is of 3x10^8 m/s and so forth.
     
  14. Apr 20, 2005 #13

    Nereid

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    But what is 'something that has real physical properties'? :confused: What is 'a fictitious force'? :surprised

    I don't want to take this thread OT, but the two revolutions in physics in the early 20th century (Relativity and QM) were not only revolutions in that new, general theories were proposed (and extensively tested, during the rest of the 20th century; the testing continues today), but also in the nature of science. Gone is the certainty and our ability to 'feel through' what 'physical reality' 'must' be like, based on our intuitions ... thousands of experiments over the past century or so have shown 'physical reality' to be much stranger than what we feel to be 'right', and GR and QFT shown that we can make good, testable predictions (and build wizzy new gadgets) by 'working the math' ('deep understanding' not included).

    In one way, it doesn't matter how you think of 'physical reality'; as long as your theory is self-consistent, consistent with all good experimental and observational results, (etc), then it's essentially a matter of choice and convenience how you interpret the theory! (tractable analytic forms is, after all, just 'convenience')
     
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