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Speed of Light

  1. Dec 14, 2003 #1
    For something to travel at any speed it has to exist.

    Light does not exist as a physical entity. It is the stimulation of Primary Force.

    Light does not travel.

    Think of it this way. Suppose you had a steel bar of x feet. Hit the end with a hammer. Then ask how long does it take for the impact of that blow to move the other end?

    Instantaneous. No.

    What exactly is travelling from the point of impact to the other end?

    It is the movement at the other end of the steel bar that is a result of the blow from the hammer.

    If the steel bar were long enough there would be a difference in time from the blow to the movement at the other end.

    Mathematically the difference in time could be calculated and represented as speed. But what was actually moving?

    It was not the hammer.

    Light does the same thing to Primary Force as a blow to the steel bar. It forces a movement in the field that can be measured in terms of speed.

    There is no speed of light, only the time it's impact on Primary Force takes to get from A to B.
  2. jcsd
  3. Dec 14, 2003 #2


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    A compression wave that travels at the speed of sound through the steel bar. This speed is

    [tex]V = \sqrt{\frac{e}{d}}[/tex]

    With e and d being the elasticity and density of the steel.

    Light is a disturbance of the electromagnetic field which travels as a wave with the speed of

    [tex]v=\frac{1}{\sqrt{\epsilon \mu}}[/tex]

    With [tex]\epsilon[/tex] and [tex]\mu[/tex] being the permittivity and permeability of the medium.
  4. Dec 15, 2003 #3
    My example of the steel bar was not to illustrate the bar as a wave medium but there are two ends to the bar.

    One end is hit by a hammer and the entire bar moves. The end farthest from where it was intially struck and moved also moves.

    If the bar were short it would seem instantaneous, but if the bar were very long there would be a delay in its movement.

    The difference could be measured in terms of speed, but my question is: The speed of what?
  5. Dec 16, 2003 #4


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    Asked and answered: the speed of sound.

    So applied to light, even if light were entirely a wave phenomenon like sound (it isn't) it would still have its own specific speed.
  6. Dec 16, 2003 #5
    The actual time it takes for a light source to travel is well documented. My only point is that it is not the light itself that is travelling, but the movement of the medium (Primary Force).

    I like Janus' response, but I don't believe Primary Force is an electro magnetic field. I think Primary Force is space itself, and Gravity is the acceleration of Primary Force.
  7. Dec 16, 2003 #6


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    Even if light were entirely a wave phenomenon (again - it isn't), that isn't how wave phenomenon to work. Again, using sound as an example, the "sound" is the wave traveling on the medium and it has a specific associated velocity. The medium oscillates but has no cumulative displacement.

    So for light, the wave is the light itself traveling.
  8. Dec 18, 2003 #7
    Reply to Russ Waters,

    You got me. You are right.

    Thanks for your thoughtful input.

  9. Dec 18, 2003 #8


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    No prob. Thanks for keeping an open mind - its sometimes a rarity here.
  10. Dec 20, 2003 #9
    And what regulates its speed in various local areas of space?
  11. Dec 20, 2003 #10

    Light in the presence of a gravitational field will change direction, but photons which are not subjected to an outside force must travel in straight lines at a constant speed, when viewed in an inertial frame, and in absence of a gravitational field, by Newton's law of inertia. So in a sense, Newton's law of inertia regulates the speed of light. That law says that something which is moving will continue to move in a right line, unless something exterior acts to change this. Euclid himself worked out the ray theory of light over two thousand years ago. As for the exact speed of light in an inertial frame, this is found by experiment to be roughly 186,000 miles per second. It is presumed that this has been the case since time eo ipso. And one of the postulates of the theory of relativity is that the speed of light in an inertial frame is a universal constant c. So in any inertial frame, the derivative of the speed of light with respect to the spatial and temporal coordinates of that frame, must equal zero, when the photon isn't feeling any force.
    Last edited: Dec 20, 2003
  12. Dec 20, 2003 #11
    Do you know why it does that? Do you understand what Einstein said about it in 1911? Do you know what a “plane wave” is and why light bends when it enters glass?

    What you are repeating to me as if from memory is incorrect 8th grade science stuff. Just like I was taught in the 1950s that electrons “orbit” the nucleus of an atom just like planets orbit the sun, even though this description of atoms went out in the 1920s. It was not true when it was taught to me, and my teachers knew it was not true, but it was easier to explain than the truth, so that’s what they taught me, along with the fable about “green plants” growing on the surface of Mars, the “gradualism only” story of geology, and the “Piltdown” ape-man hoax. I have spent a lifetime trying to un-learn the lies my science teachers taught me in the 1950s.
  13. Dec 20, 2003 #12
    Reply to David,

    Lighten up.

    What you have unlearned and re-learned may also be wrong.

    We are in a zone of the unknowable. Its all theory. Facts are scare. Conjecture is fun.
  14. Dec 21, 2003 #13


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    Couldn't agree more. Drop the attutude, David, and maybe you will learn something.
  15. Dec 21, 2003 #14
    I think you need to learn that light photons/waves both speed up and slow down relative to the earth, during their travel through space, and there’s plenty of observation and theory to back this up.
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