The Speed of Light is Not Constant

Discussion in 'Alternative Theories' started by Farsight, Feb 23, 2014.

  1. paddoboy Valued Senior Member


    Missed that beer w/Straw...
    Nice example and quite valid. [on both counts] nudge nudge wink wink

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  3. Declan Lunny Registered Senior Member

    For a defender of the mainstream and enforcer of the tested theory, you sure seem to like making up "theory" out of thin air. Everything you just said it wrong. The light isn't being absorbed and re-emitted as it passes through a lens, it is slowing down. ACTUALLY moving slower. This is not even the slightest bit controversial, it is the most basic of well established physics.

    You shouldn't try so hard in your "defender" role. Because the really basic stuff you need to know is something you have tried to skip. Instead of you doing one of those things you call "word salads", you should have taken the time to do what I suggested, in the same amount of time you could have discovered some very cool, useful and interesting physics.

    It's not the particle construct of the photon that causes this thing to happen, the slowing, it is the wave role of the photon which is slowed. If you "idea" were correct, it would be density dependent, which it is not. Some dense materials transmit a lot of light, and some very rarefied materials are opaque.
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  5. paddoboy Valued Senior Member

    No, I don't believe it is wrong...This maybe another one of these perception things
    Anyway you argue it out with the link...

    OK, I am pretty busy at this time, but so far there is some support for your position.....again, could this just be a way of perceiving/looking at things on face value...

    Here is another for my position......

    An electromagnetic wave (i.e., a light wave) is produced by a vibrating electric charge. As the wave moves through the vacuum of empty space, it travels at a speed of c (3 x 108 m/s). This value is the speed of light in a vacuum. When the wave impinges upon a particle of matter, the energy is absorbed and sets electrons within the atoms into vibrational motion. If the frequency of the electromagnetic wave does not match the resonant frequency of vibration of the electron, then the energy is reemitted in the form of an electromagnetic wave. This new electromagnetic wave has the same frequency as the original wave and it too will travel at a speed of c through the empty space between atoms. The newly emitted light wave continues to move through the interatomic space until it impinges upon a neighboring particle. The energy is absorbed by this new particle and sets the electrons of its atoms into vibration motion. And once more, if there is no match between the frequency of the electromagnetic wave and the resonant frequency of the electron, the energy is reemitted in the form of a new electromagnetic wave. The cycle of absorption and reemission continues as the energy is transported from particle to particle through the bulk of a medium. Every photon (bundle of electromagnetic energy) travels between the interatomic void at a speed of c; yet time delay involved in the process of being absorbed and reemitted by the atoms of the material lowers the net speed of transport from one end of the medium to the other. Subsequently, the net speed of an electromagnetic wave in any medium is somewhat less than its speed in a vacuum - c (3 x 108 m/s).
    Last edited: Feb 24, 2014
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  7. OnlyMe Valued Senior Member

    Paddoboy, those explanations are theoretic and come out of QM where empty space is truly empty space. As such it is concluded that if a ray of light, passes through a transparent medium without the process described, as it is still traveling through empty space it should still be measured to travel at c. So to account for the change in velocity it must be time delayed by an interaction with the electrons of the atoms in the medium, through a process of absorption and reemission.

    The problem is that, that explanation assumes that space is truly just empty . . . nothingness.

    Now recall an earlier question I never addressed,

    If the empty space in the vicinity of the GP-B satellite were true empty nothingness how then could space be drug along by the motion of planet and star?

    Space is either a dynamic partner to mass in a dance we experience as gravitation, or it is simply an empty box that everything else moves within.

    It becomes very problematic when QM and and GR are commingled. That point was the intent of a couple of my earlier posts.

    If space is a dynamic counterpart to gravitationally significant masses moving within it, then the vacuum cannot be thought of as empty and the passage of light through any empty space cannot be thought of as unaffected by the dynamics of the space it passes through.

    So the results of the GP-B experiment suggests that space does interact dynamically with mass.., and proximity plays a part in to what extent.

    How then might the very close proximity of the mass of atom and molecule in transparent mediums affect the dynamics of the empty spaces in between?

    I don't know why light slows down in transparent mediums other than vacuum, just that it does. I don't even know that c is in fact universally constant in vacuum. It's velocity has only ever been accurately measured in vacuum within the limitation of our local gravitational field, at or near the surface of the earth. The universal constant c, remains an a priori assumption. And it will remain so until we at some time in the future experimentally measure the velocity of light in vacuum some distance from the surface of the earth with a gravitationally time dilated clock.

    My intent here has not been to challenge or refute any aspect of SR or GR. It is to once again attempt to draw that line in the sand that separates what we know because we have experimentally proven it and what we accept as an a prior fact because the underlying theory has been exceedingly successful, many other predictions having been experimentally proven.

    All of that to say your reference though accepted to some extent by a portion of the "mainstream", are theoretical. As far as I am aware they have never been experimentally verified and proven.
  8. paddoboy Valued Senior Member


    Interesting coherent post OnlyMe...You need to give lessons to one or two others that seem to post in more inane gobbldydook fashion.

    I don't really see it though as mixing QM and GR....Rightly or wrongly I see it as more an explanation via particle physics, which I think can be distinguished from QM.
    Either way, as I mentioned in my post to Declan, there is support for his position as well as mine.
    That also holds true for Hawking Radiation...
    That also holds true for aspects of what some claim to be abstractions in cosmology, and which others see as having reality.
    So we have a dilemma of sorts.

    Again while not agreeing entirely with your own stance, I do see the differences in thinking as minor and pedant.

    Still when we get down to the nitty gritty of things, this thread was a red herring to add to the anti GR BH forces, along with the time thread :shrug:

    Again, good clear concise coherent post.
  9. Farsight

    You will know all about gravitational lensing, Declan. Have a look at this: Inhomogeneous Vacuum: An Alternative Interpretation of Curved Spacetime. Then take a look at Einstein's 1920 Leyden Address:

    "This space-time variability of the reciprocal relations of the standards of space and time, or, perhaps, the recognition of the fact that “empty space” in its physical relation is neither homogeneous nor isotropic, compelling us to describe its state by ten functions (the gravitation potentials gμν), has, I think, finally disposed of the view that space is physically empty."
  10. James R Just this guy, you know? Staff Member


    It is true that there's some curvature of spacetime in the room I'm in.

    The problem there is one of time in different reference frames, not a change in the speed of light.

    I do. All but one of your quotes was prior to 1916, when Einstein published his general theory. So, we see him groping towards it gradually, up until the last statement you quoted. Of course, in 1916, there was still a lot that Einstein didn't understand about the implications of his own theory. We've had almost 100 years since then to get a handle on it all.
  11. Farsight

    But look at this depiction of gravitational potential. It's like the bowling-ball analogy. Now zoom in to a small portion of it. Your pencil falls down because of the gradient, the first derivative of potential. Spacetime curvature is the second derivative. It isn't why your pencil falls down.

    We've already established that a clock doesn't actually measure the flow of time, it "clocks up" some kind of regular cyclical motion and shows you a cumulative result called "the time". And that two optical clocks in the room you're in don't stay synchronised when one's 30cm above the other. Have we also mentioned that a reference frame is an abstract thing? Optical clocks aren't.

    But "you" haven't. You've screwed it up. Now you flatly contradict Einstein, but you won't admit it. Take a look at this Baez article by Philip Gibbs. See the general relativity section where he says this:

    "Since Einstein talks of velocity (a vector quantity: speed with direction) rather than speed alone, it is not clear that he meant the speed will change, but the reference to special relativity suggests that he did mean so. This interpretation is perfectly valid and makes good physical sense..."

    Now see the last line:

    "Finally, we come to the conclusion that the speed of light is not only observed to be constant; in the light of well tested theories of physics, it does not even make any sense to say that it varies".

    So what Einstein said makes sense, but it doesn't? Yes, screwed up is the word. Look at the OP again. Look at the gif:

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    Image credit: Brian McPherson

    It's an exaggeration, but it is not misleading. Now, are you seriously saying the speed of light is constant?
  12. James R Just this guy, you know? Staff Member


    You seem to be referring to a Newtonian-type potential. General relativity is a bit different.

    I agree with what you say in the Newtonian sense.

    Yes, and we use that regular cyclical motion to define what we mean by time. Time is what clocks measure. Counting time is counting the ticks of a clock.

    It is well understood why clocks above one another don't stay in sync. Time goes slower lower down in a gravitational well.

    I'm mostly agreeing with you. Does that mean you screwed up too?

    I agree with this.

    Did you read the whole article?

    I already told you. Locally it is constant (and by "locally" I mean in a small enough region where we can take spacetime to be approximately flat). With sensitive enough measuring equipment, that 30 cm vertical gap may well mean that you need two locally flat reference frames instead of one. And so, an observer looking from a distance sees one light clock tick slower than the other one. And, indeed, from the point of view of this distant observer, the speed of light does not appear to be constant.

    I said all this in my first reply to this topic, didn't I?

    We agree with one another, don't we?
  13. Declan Lunny Registered Senior Member

    Oh my, well I guess I need to do that thing.

    No? Well just because you read an op-ed piece on what the "speed of light is through a medium" doesn't mean you understand the argument.

    The photon's motion through a medium can only be taken as "abstract" if you are going to present it as an "instantaneous" velocity. The motion can only have any meaning by describing it "Point A" to "Point B" and the time it takes to get there. The reason for that is a "Photon" (as a particle) can never have it's instantaneous velocity known. Never, ever, it is not possible.

    Geared to trying to elucidate for the uninformed general reader. As is too often the case, they don't present the whole story.

    I came up with that "pick up lines" completely independently and had not seen someone else use it. That in itself should suggest something about your presentation and demeanor.

    Does that not suggest anything to you? You chose to play into the anti-mainstreamers, game,,, probably just as they intended that you do. There is a phrase about that,,,, uh, well, it will come to me,,,, oh yeah, it has something to do with feeding and such,,,,,

    I always do, I always do. And you have a good day also.
  14. Captain Kremmen All aboard, me Hearties! Valued Senior Member


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    This diagram is wrong, I think.
    Shouldn't the lower bats be closer together if they are in a stronger gravity field?
  15. Beer w/Straw Transcendental Ignorance! Valued Senior Member

    Paradigm shifts in physics come through gif interpretation.

    Sorry, I had to say it.
  16. Waiter_2001 Registered Senior Member

    I imagine the speed of light varies when moving through different mediums i.e. air or glass (glass=slower.) Hence when light passes through a prism (glass) we find a spectrum (colours).
  17. Farsight

    No. And note that the strength of the gravitational field relates to the gradient in your plot of clock rates. The lower "bats" represent a parallel mirror light clock which like the NIST optical clock runs slower at a lower gravitational potential.
  18. Motor Daddy Valued Senior Member

    Farsight, Is that top pic just floating in space up there?
  19. Farsight

    Sure thing. That image was a just nice big version of the "bowling ball analogy", akin to the picture on the right on the wiki Riemann curvature tensor page.

    Good stuff. Another time maybe we can talk about Newton's thoughts on gravity.

    No problem with that. Now watch this:

    No. That regular cyclic motion goes slower. And when it's a light clock, it's the motion of light going slower.

    No. This is what I wanted. I come out with a series of mundane simple things that are easy to agree with because they match Einstein and the evidence, and I make my case one easy step at a time.

    Cookin' on gas.

    Yes. And I've talked to editor Don Koks about it. And I've tried to talk to Philip Gibbs about it.

    Noted. We should talk about the principle of equivalence another time.

    Yep. Only it isn't a distant observer. You're the observer. Those NIST optical clocks are in front of you. In the room you're in. And yes, the speed of light does not appear to be constant. Because it isn't.

    Yes and yes. And I'm sure we'll continue to do so. Time for the next step methinks. Another thread. Gravity works like this.
  20. Russ_Watters Not a Trump supporter... Valued Senior Member

    The light clock is an SR thought experiment, not a GR thought experiment, so Farsight creates the confusion he is after by misapplying and vaguely defining it.

    But the probable answer to your question is no, you have it backwards: the speed of light should be the same which therefore means the distance is LARGER. This is because the curvature of space curves (and therefore lengthens) what appears to be a straight path.

    So by ignoring GR in his analysis of GR, Farsight obliquely attacks SR. See?
  21. OnlyMe Valued Senior Member

    To start, I don't have a position here re: the variable speed of light issue. But it has for a long time bothered me that it seems a theoretical leap to connect an atomic ground state optical frequency rate, with the speed of light, even where the emission of a photon is associated with electron transions. Locally all light/photons have the same speed in vacuum reguardless of their frequency, or the ground state frequency of the emitting atom.

    Might you reconsider your statement in the above quote with respect to the following?

    Those NIST optical clocks are not based on or measuring the speed of light. They are based on ground state optical frequencies.

    They do say something about how the optical frequencies of specific atoms are affected by location in a gravity well, but not so much about the speed of light... The implied application of a frequency change, to a change in the speed of light, seems to me to remain based on the underlying theory. May be true or may not, it does not seem to have been directly measured, relative to location in a gravity well, the velocity of light that is.

    And aren't those optical clocks only used to set a standard for the second IOW to set other clocks? They don't actually keep time theirselves. Mostly they would just up the accuracy from cesium/microwave frequency clocks, as a standard to adjust or set something like a hydrogen maser...?
  22. Farsight

    Huh? The gif is a parallel-mirror light-clock idealised exaggeration of the NIST optical clocks, which run at noticeably different rates when separated by a vertical distance of 30cm.

    I'm giving you clarity Russ. A light clock runs slower when it's lower just like any other clock. Apart from a pendulum clock of course, where the clock rate depends on strength of field rather than gravitational potential.

    Only it doesn't. Here Russ, have a look at this Baez article. See this bit: "Note: not the curvature of space, but of spacetime. The distinction is crucial." Space isn't curved. Your plot of clock rates is curved.

    No way. How many times do I have to say it? I root for relativity. I'm the one quoting Einstein. I'm the one fighting cargo-cult science and ignorance and Emperor's New Clothes woo.
  23. Russ_Watters Not a Trump supporter... Valued Senior Member

    Farsight, you do know that no one believes that (that you are a champion of Relativity), right? I don't even think most of us believe you believe it. This is just a game you are playing.

    Still: be clear here: you do NOT accept SR's constancy of light speed postulate, right?

    Also, the Baez article: more out of context quotes (that is a key part of your game). Yes, space is curved. That quote means it isn't JUST space that is curved.

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