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Thread: Light speed is constant because light remains a certain way

  1. #1

    Light speed is constant because light remains a certain way

    Thy does light speed remain constant no matter the observer's speed?

  2. #2
    Experimentally, the locally-measured speed of light in vacuum remains the same no matter the velocity of the observer relative to the source or a third party and no matter the velocity of the source relative to the observer or a third party.

    If you ignore effects due to gravity, the measured speed of light in vacuum remains the same no matter the velocity of the observer relative to the source or a third party and no matter the velocity of the source relative to the observer or a third party. This has been tested with light from moving stars and fast-moving particles in the lab. This has been tested with moving observers to 8 digits of precision in one-way isotropy tests and 18 digits of precision with two-way tests. In 1978 it was discovered that we can measure the speed of light to a greater precision than we could the length of the meter under the old definition, so in 1983 the international definition of the meter was changed to be in terms of the duration of a second and the new definition of the accepted value of the speed of light.

    So not only is light speed constant, in international trade it is defined to be constant. And relying on this has been useful.

  3. #3
    Registered Senior Member
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    well, i had the same doubt for centuries () and this is what i came up with.
    i guess it remains the same to all observers because the rate at which time passes varies along with their motion and it adjusts in a way that makes the speed of light to the observers moving relatively constant.

  4. #4
    Except that observers don't have an absolute motion -- at best they can only measure their motion relative to other things. This is the difference between a line and a line with a zero mark on it, without the mark the best we can say about the position of a point is that is 93 meters left of some other point. We can even assume without contradiction that position is zero, but that is part of our assumptions, not a property of the line itself. The concept of a zero position does not help us understand the line better.

  5. #5
    Quote Originally Posted by rpenner View Post
    Except that observers don't have an absolute motion -- at best they can only measure their motion relative to other things. This is the difference between a line and a line with a zero mark on it, without the mark the best we can say about the position of a point is that is 93 meters left of some other point. We can even assume without contradiction that position is zero, but that is part of our assumptions, not a property of the line itself. The concept of a zero position does not help us understand the line better.

    Hi rpenner, everyone. Still rushed. Can't stay but a few moments; so briefly....

    Mate, I think you're over-thinking relativity on this point.

    May I point out that in any particular interaction between light and observer frames, such observers/frames automatically have their own velocity RELATIVE TO THE INCIDENT LIGHT that they are observing/measuring/calculating etc; and that it is THAT relative velocity compared to the incident light velocity that DEFINES the 'relative/absolute velocities' between the incident light vector and the intercepting-observer 'frame' vectors thus mutually determined for the INTERACTION between the light and the observer in that particular MERGING-FRAMES CONTEXT.

    So perhaps we should avoid making generalisations about 'absolute velocities' etc etc 'in theory', especially where ANY SUCH INTERACTION ITSELF (between the incoming light and the incoming observer) will IN REALITY involve ONLY ITS OWN self-determining SET of relative/absolute 'velocity' vectors/magnitudes arising from, and applying in, ONLY that particular interaction.

    Just trying to forestall possible cross-communications because of possible cross-purpose generalisations being invoked in situations (interactions between incoming light and intercepting observers) where such 'theoretical' generalisations as yours above may not necessarily be called for the purposes of discussing this particular light-observer relative INTERCEPTION velocities aspect which the interception itself determines independently from any other generalisations, factors or theoretical overlays.


    Gotta go! Cheers rpenner, everyone!

    .
    Last edited by RealityCheck; 03-11-12 at 02:36 PM.

  6. #6
    flat Earth skeptic Aqueous Id's Avatar
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    Quote Originally Posted by Cortex_Colossum View Post
    Thy does light speed remain constant no matter the observer's speed?
    My answer is a little simpler.

  7. #7
    Quote Originally Posted by RealityCheck View Post
    Hi rpenner, everyone. Still rushed. Can't stay but a few moments; so briefly....

    Mate, I think you're over-thinking relativity on this point.

    May I point out that in any particular interaction between light and observer frames, such observers/frames automatically have their own velocity RELATIVE TO THE INCIDENT LIGHT that they are observing/measuring/calculating etc; and that it is THAT relative velocity compared to the incident light velocity that DEFINES the 'relative/absolute velocities' between the incident light vector and the intercepting-observer 'frame' vectors thus mutually determined for the INTERACTION between the light and the observer in that particular MERGING-FRAMES CONTEXT.

    So perhaps we should avoid making generalisations about 'absolute velocities' etc etc 'in theory', especially where ANY SUCH INTERACTION ITSELF (between the incoming light and the incoming observer) will IN REALITY involve ONLY ITS OWN self-determining SET of relative/absolute 'velocity' vectors/magnitudes arising from, and applying in, ONLY that particular interaction.

    Just trying to forestall possible cross-communications because of possible cross-purpose generalisations being invoked in situations (interactions between incoming light and intercepting observers) where such 'theoretical' generalisations as yours above may not necessarily be called for the purposes of discussing this particular light-observer relative INTERCEPTION velocities aspect which the interception itself determines independently from any other generalisations, factors or theoretical overlays.


    Gotta go! Cheers rpenner, everyone!

    .
    I don't know about anyone else but the only response I have to this is; what the hell are talking about, mate?

  8. #8
    Valued Senior Member
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    Quote Originally Posted by origin View Post
    I don't know about anyone else but the only response I have to this is; what the hell are talking about, mate?
    Beats me. I read about three or four sentences, said "phooey!!", closed the thread and moved on to something else.

  9. #9

  10. #10
    Arguing with a crank - useless AlexG's Avatar
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    Quote Originally Posted by origin View Post
    I don't know about anyone else but the only response I have to this is; what the hell are talking about, mate?
    That's RC being RC.

    He's a regular woo-woo poster at Physforum. He writes interminable posts, which, while in the English language and syntactically correct, leave you saying

    He also keeps saying he's disappearing for a week, and posts ten minutes later. (promises never kept)

  11. #11
    Quote Originally Posted by origin View Post
    I don't know about anyone else but the only response I have to this is; what the hell are talking about, mate?

    Hi origin. Not much time, so briefly....

    Note that I was responding to rpenner regarding his response to rohIT. rpenner made 'generalisations' about 'motions' and 'velocities' which were redundant in any particular light-meets-observer-event context in which ALL lightspeed measurements/calculations are derived/made based on the self-determined values inherent in ALL 'meeting' between light and observer(s).

    I was pointing out that the 'motions' involved in a meeting of light with an observer is thus automatically determined by that interaction between them, and so we KNOW what velocities were about 'velocities' and 'motions' were involved in that particular event (else the observer measurements/calculations etc would have no 'value' for 'c' as pertaining to that observer frame compared to the light frame merging event.

    Try to understand properly before 'defaulting' to personal disparagement. Thanks.

    .
    Last edited by RealityCheck; 03-11-12 at 07:27 PM.

  12. #12
    Quote Originally Posted by AlexG View Post
    That's RC being RC.

    He's a regular woo-woo poster at Physforum. He writes interminable posts, which, while in the English language and syntactically correct, leave you saying

    He also keeps saying he's disappearing for a week, and posts ten minutes later. (promises never kept)

    What's the matter with you, mate?


    When was the last time I posted at physforum after I said I would not be posting for a couple of days there?

    Ask Lady Elizabeth, who 'divined' that I would be posting again right away. She (he) was WRONG. I did NOT post again right away.

    So, you are factually wrong, I kept my promise there. And I always said I would be 'reading through' as I got the chance. So you are on a hiding to nothing, mate, with your irrelevant and 'personal' posts again. Pity.

    You're still in danger of turning into another "tragic Trout" character. Watch it.


    And anyway, life is unpredictable; and a busy life full of other real world responsibilities/activities even more so. Maybe you should stop your tragic nonsense and get a life instead of trying to become another poor fish like Trout, hey?

    Toodles. back in couple of days OR EARLIER if I can (you can start counting down now...hehehe).
    .
    Last edited by RealityCheck; 03-11-12 at 07:28 PM.

  13. #13
    This may be a shot in the dark but do you own physforum, RC?

  14. #14
    Quote Originally Posted by realitycheck View Post
    ... Light frame merging event.
    wth?

  15. #15
    Quote Originally Posted by Syne View Post
    wth?

    Take the time to understand the thrust.....

    Lightspeed is A CONSTANT. Hence any meeting with an observer automatically confers a motion/velocity to that observer frame with respect TO THAT LIGHTSPED CONSTANT. Hence an 'absolute' motion/velocity aspect arises within the LIGHT/OBSERVER context which is UNIQUE FOR THAT interception/measurement 'event'. Hence the 'generalised' statements about absolute motion etc is not applicable TO LIGHT-MEETS-OBSERVER cases where calculations are based on the relative speeds involved in such an event, ONE SPEED OF WHICH IS KNOWN TO BE A CONSTANT, and hence the observer speed is DETERMINED ABSOLUTELY FOR THAT EVENT.

    And as to the merging frames. it is not hard to realise that the interception event results in the merging of the photon and the receptor/observer into ONE COMMON FRAME NOW MOVING WITH THE OBSERVER who intercepted/measured the merging event, else there would BE no 'interception and hence no 'detection/measurements/calculations etc regarding the respective motions/velocities etc of the two frames (light and observer).

    Sorry, gotta go elsewhere. Back when I can. Cheers!

    .

  16. #16
    Quote Originally Posted by Trooper View Post
    This may be a shot in the dark but do you own physforum, RC?

    Hahaha! I wish!

    I'd soon clear out the spam and negativity etc if I did! Good lateral thinking, though, Trooper. Always good to consider all the possibilities without fear or favour. Certainly was worth a try!

    Anyhow, if I seem to have a sense of 'loyalty' to that forum, it is because they gave me the chance to start that cosmology special project sub-forum. It was very good of the admin/mods to do that, and I appreciated it sincerely. I still like the forum for amny reasons, even though the "trolls' and the 'spoilers' like that poor fish Trout et al were allowed to ruin many a good discussion. My prolonged ill-health absences did not help; nor did the re-arrangements which took place during one of my absences where rpenner was put as mod for all forums on that board. I don't waorry about it though, as I am close to finishing off my overarching perspective for publication and have moved well along that special project on my own. I trust you and others genuinely interested will be pleased with the result.

    Thanks. Trooper, for your persistent good humour and intellectual contributions to the discussions here and elsewhere; they were always respectfully read and appreciated, I assure you!

    Cheers and Regards!

    .
    Last edited by RealityCheck; 03-12-12 at 03:55 PM.

  17. #17
    Arguing with a crank - useless AlexG's Avatar
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    3,714
    Quote Originally Posted by RealityCheck View Post
    Take the time to understand the thrust.....

    Lightspeed is A CONSTANT. Hence any meeting with an observer automatically confers a motion/velocity to that observer frame with respect TO THAT LIGHTSPED CONSTANT. Hence an 'absolute' motion/velocity aspect arises within the LIGHT/OBSERVER context which is UNIQUE FOR THAT interception/measurement 'event'. Hence the 'generalised' statements about absolute motion etc is not applicable TO LIGHT-MEETS-OBSERVER cases where calculations are based on the relative speeds involved in such an event, ONE SPEED OF WHICH IS KNOWN TO BE A CONSTANT, and hence the observer speed is DETERMINED ABSOLUTELY FOR THAT EVENT.

    And as to the merging frames. it is not hard to realise that the interception event results in the merging of the photon and the receptor/observer into ONE COMMON FRAME NOW MOVING WITH THE OBSERVER who intercepted/measured the merging event, else there would BE no 'interception and hence no 'detection/measurements/calculations etc regarding the respective motions/velocities etc of the two frames (light and observer).

    Sorry, gotta go elsewhere. Back when I can. Cheers!

    .

    RC's usual meaningless word salad.

  18. #18
    Quote Originally Posted by AlexG View Post
    RC's usual meaningless word salad.

    AlexG's usual ngativity in lieu of trying to understand new perspectives; Einstein's earliest and unusual perspectives would have been your very first 'juicy targets' for your mindless ridicule if you two had been contemporaries. Stop it, mate, life is too short for your relentless negativity and arrogance. :lol:

    Anyhow, nice going, mate.....are you going for the "Trout Award for Studied Stupidity and Unoriginality to the Max"? You can count on me for your nomination! :lol:

    Cheers and good luck! :lol:

    .
    Last edited by RealityCheck; 03-12-12 at 04:18 PM.

  19. #19
    Quote Originally Posted by RealityCheck View Post
    Take the time to understand the thrust.....
    Don't think I want to know anything about your "thrust". Why can't you just say what you mean instead of having us guess?

    Lightspeed is A CONSTANT. Hence any meeting with an observer automatically confers a motion/velocity to that observer frame with respect TO THAT LIGHTSPED CONSTANT.
    Confers? How does light "confer" anything about the motion of an observer? Is light pushing the observer? Does this happen upon observation?

    Hence an 'absolute' motion/velocity aspect arises within the LIGHT/OBSERVER context which is UNIQUE FOR THAT interception/measurement 'event'.
    Arises? Where, at observation? How is the speed of light constant but the measurement "UNIQUE"?

    Hence the 'generalised' statements about absolute motion etc is not applicable TO LIGHT-MEETS-OBSERVER cases where calculations are based on the relative speeds involved in such an event, ONE SPEED OF WHICH IS KNOWN TO BE A CONSTANT, and hence the observer speed is DETERMINED ABSOLUTELY FOR THAT EVENT.
    I don't think I can make any sense of that statement. What is this "observer speed"? You say it is absolute.

    And as to the merging frames. it is not hard to realise that the interception event results in the merging of the photon and the receptor/observer into ONE COMMON FRAME NOW MOVING WITH THE OBSERVER who intercepted/measured the merging event, else there would BE no 'interception and hence no 'detection/measurements/calculations etc regarding the respective motions/velocities etc of the two frames (light and observer).
    So you're saying the photon actually slows into the frame of the observer?


    Anyone seeing anything resembling physics in the above?

  20. #20
    Quote Originally Posted by Syne View Post
    Don't think I want to know anything about your "thrust". Why can't you just say what you mean instead of having us guess?



    Confers? How does light "confer" anything about the motion of an observer? Is light pushing the observer? Does this happen upon observation?



    Arises? Where, at observation? How is the speed of light constant but the measurement "UNIQUE"?



    I don't think I can make any sense of that statement. What is this "observer speed"? You say it is absolute.



    So you're saying the photon actually slows into the frame of the observer?


    Anyone seeing anything resembling physics in the above?


    I haven't the time for semantics, mate. Just think it through like you would any new idea/perspective and you will answer your own questions. Stop 'kneejerking' and just do the necessary. I haven't time to spoon feed everything 'just so', since the perspectives are novel and would require more time than I have available.

    You are not devoid of intellectual capacity; use it to understand what may be rather than what is supposed to be. Thanks.


    PS: I haven't had more than a few minutes at a time for internet reading/posting here and elsewhere, so I will not pursue LENGTHY and IN DEPTH discussions unless I DO get the time needed to do them justice. In the meantime it is up to YOU and others to discuss or not anything YOU or others wish to make of the matters in those discussion (this goes for the Gedanken the Light Clock discussion too; I will post there before I log out again just to say I will be resuming when I can).

    Cheers!

    .

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