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Thread: How can 299792458 m/s be different to 299792458 m/s ?

  1. #101  
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    Quote Originally Posted by SpeedFreek View Post
    You say because of the tautology. So the speed of light is only constant locally, because of a tautology. That "in reality", our seconds are either longer or shorter than the "coordinate" seconds, but, because of a tautology, we incorrectly assume them to be the same size.
    Yes, that's just about it. That's what gravitational time dilation is all about.

    Quote Originally Posted by SpeedFreek View Post
    AND SO DO ALL OTHER PROCESSES IN THE UNIVERSE.
    Yes. Because of the wave nature of matter. Because of the way you can quite literally make matter out of light in pair production. Because of the way light and matter are of the same essence.

    Quote Originally Posted by SpeedFreek View Post
    From the frame of the upper clock, the lower clock goes slower. All clocks carry proper time, so the upper clock does not assume it is going fast, it assumes the lower clock is going slow. Because of that universal tautology, you know, the one where all physical processes work according to local proper time, rather than assuming that coordinate time is proper time.
    Physical processes do what they do at the rate they do. The rate varies with gravitational potential, so different clocks at different elevations show different readings. Nobody is saying coordinate time is proper time.

    Quote Originally Posted by SpeedFreek View Post
    If we assume that coordinate time is proper time it would mean that lots of different observers in different frames of reference would all ascribe a different duration for the same process, which would be most confusing, would it not?
    It isn't confusing at all. Different observers "time" that process using some regular cyclical process local to them. One says it took 99 seconds, another one says it took 100 seconds, but they know it took what it took and that they are subject to gravitational time dilation and disagree about the seconds.

    Quote Originally Posted by SpeedFreek View Post
    A: "From my low gravitational potential, that process that occurred at a higher gravitational potential took only half the amount of seconds that the same process takes down here. The time that process took is the real time that it took. That process takes 10 seconds down here, but only 5 up there!"
    B: "Well from my very high gravitational potential, that process occurred at a lower gravitational potential and it took twice the amount of seconds that the same process takes up here. The time that process took is the real time that it took. That process takes 10 seconds up here too, but it took 20 down there!"
    A: "Your seconds are wrong. From down here I measured that process to take 5 seconds where it occurred, halfway between us, and only 2.5 seconds up where you are"
    B: "No, your seconds are wrong. From up here here I measured that process to take 20 seconds where it occurred, halfway between us, and 40 seconds where you are!"
    A: "Well, I know for sure that the process takes 10 seconds, here."
    B: "And I know for sure that the process also take 10 seconds, here.
    A: "No, it takes 2.5 seconds up there, but your seconds are shorter, so you only think it takes 10 seconds"
    B: "You have it wrong, my friend. That process takes 40 seconds where you are, but your seconds are longer, so you only think it takes 10 seconds".
    A: "Yours aren't real seconds, mine are!"
    B: "Rubbish! Mine are the real seconds!"
    Fundamental universal process: "Ummmmm, guys, stop arguing!! I always take 10 seconds, wherever I am! Time is proper time wherever I am! I am not the product of a tautology!!
    A + B: "Shut up! What do you know?!"
    You're inventing a problem here, Speedfreek. A and B understand gravitational time dilation. They know that their timings of the selfsame event don't agree, and that neither has the real seconds.

    Quote Originally Posted by SpeedFreek View Post
    Fundamental universal process: "No listen, it's true! It takes light the same amount of time to travel a metre, wherever it is!"
    Because of the tautology wherein the second is defined using the motion of light.

    Quote Originally Posted by SpeedFreek View Post
    A: "Well light travels at c in a vacuum down here."
    B: "And light travels at c in a vacuum up here too. But you are mistaken - it travels a little slower than c down there."
    A: "No it doesn't, I just measured it!"
    B: "But your seconds are wrong!"
    A: "No, your seconds are wrong!"
    Fundamental universal process: "*Sigh*"
    A and B aren't stupid A knows that B's seconds are different to his and vice-versa. They both know that light travels at the speed of light, and that 299792458 m/s up there is not the same as 299792458 m/s down there because the seconds are different.

    Quote Originally Posted by SpeedFreek View Post
    I didn't say it was symmetrical. I said from the frame of the lower clock, the upper clock goes faster. You quoted me.
    OK.

    Quote Originally Posted by SpeedFreek View Post
    We don't, but he does, and that is exactly my point. A coordinate speed is the reality only from the frame of the observer in the frame that is measuring coordinate speed.
    The reality is that the lower clock goes slower then the upper clock, and the upper clock goes faster than the lower clock. And they're both light clocks. And there ain't no time flowing through them. And these two clocks are only 30cm apart. They're in front of your face.

    Quote Originally Posted by SpeedFreek View Post
    It allows an observer to extend the laws of physics that work locally into places that are remote.
    There's nothing remote about it. The optical clocks are a foot apart, one above the other, and one's going faster than the other.

    Quote Originally Posted by SpeedFreek View Post
    It is not the reality for an observer at the actual coordinates in question. It is not what the universe is actually doing at that remote location, to anyone at that remote location, it is only what the universe is doing at that remote location, relative to you.
    What remote location? It's right in front of you. It isn't remote at all.

    Quote Originally Posted by SpeedFreek View Post
    It just allows one to translate our view of the laws of physics that are working over there, to over here, but it doesn't reflect reality for anyone who is actually over there, it just allows us to reconcile reality over there with reality over here.
    The reality is in front of your face. And it is this: the speed of light varies with position.

    Quote Originally Posted by SpeedFreek View Post
    Therefore coordinate time is NOT about shorter or longer seconds in the way you keep saying.
    Oh yes it is. When you're lower than me, your seconds last a longer duration than mine. We call it gravitational time dilation. We meet up and synchronise our watches, then you go somewhere real low for a while, then we meet up again. And lo, between these two events you recorded 999 seconds and I recorded 1000 seconds. Your seconds aren't the same as mine.

    Quote Originally Posted by SpeedFreek View Post
    It is not that the coordinate speed is the actual, real speed of the object in question, to the object in question. It is only the real speed of the object to you. This is why we have to differentiate between proper and coordinate speed, and why coordinate speed is not just speed as you keep saying. This is why the speed of light "varying with position" is not a reference to a variable speed of light in the sense you seem to mean.
    Einstein said what he said. And Koks and Wright and Stenger and Magueijo and Moffat. It isn't just me telling you this.

    Quote Originally Posted by SpeedFreek View Post
    If one observer near a black hole measures an observer falling into the black hole to be time-dilated asymptotically towards infinity as they approach the event horizon, it does not mean the star is actually frozen when you get there.
    You don't fall through the event horizon in finite proper time because that finite proper time takes infinite coordinate to happen. So it hasn't happened yet, and never ever will.

    Quote Originally Posted by SpeedFreek View Post
    No, everyone agrees on the difference between the clock rates, but the owner of the lower clock does not agree that their clock is going any slower than it was when they used to be higher.
    Bollocks. They know their own clock is going slower because they calibrate it against a distant pulsar.

    Quote Originally Posted by SpeedFreek View Post
    The owner of the lower clock agrees that the upper clock goes faster.
    And so does the owner of the upper clock.

    Quote Originally Posted by SpeedFreek View Post
    See above. In the case of a black hole it is definitely a coordinate effect. The star isn't "frozen" when you get there. Atoms still "vibrate" at the same rate they ever did.
    No they don't. Again, we call it gravitational time dilation.

    Quote Originally Posted by SpeedFreek View Post
    No, it is a good illustration of how coordinate speeds are meaningful only to the person measuring them, but not at the actual remote place you are measuring them at. Anyone measuring that SAME light in its locale will measure the proper speed as c. Because of that universal "tautology" that everything in the universe adheres to.
    Because of the tautology wherein you define your second using the local speed of light. And because of the wave nature of matter.
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  2. #102  
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    Quote Originally Posted by SpeedFreek View Post
    The mods run the show. It is up to us to decide who is being more disruptive - the people peddling bad science or the people that get angered when they see it for what it is. Or the trolls, for that matter.
    I'm not peddling bad science. I'm opposing bad science. Einstein's on my side, remember? And all those other guys. And the hard scientific evidence like the Shapiro delay. In the Fourth Test of General Relativity Irwin Shapiro said this:

    "The proposed experiment was designed to verify the prediction that the speed of propagation of a light ray decreases as it passes through a region of decreasing gravitational potential".

    I'm not lying to you, SpeedFreak. The people who are lying to you are the guys who told you that the speed of light is absolutely constant. It isn't.


    Quote Originally Posted by SpeedFreek View Post
    He is claiming you are wilfully misrepresenting his views.
    I don't. He made a mistake and I caught him out.

    Quote Originally Posted by SpeedFreek View Post
    A lot of people claim you "cherry pick".
    I don't. Einstein said what he said, so did Shapiro, so did the other guys. The people who say I cherry pick are trying to get you to ignore those guys and only listen to them.

    Quote Originally Posted by SpeedFreek View Post
    Let me show you the implications of cherry picking.
    I'm all ears.

    Quote Originally Posted by SpeedFreek View Post
    If "the speed of light is constant at any infinitesimal region of a coordinate system" then there is no region in a coordinate system where the speed of light is not constant.
    Strictly speaking that's only true if the word "only" is present or implied.

    Quote Originally Posted by SpeedFreek View Post
    Take any infinitesimally small region and you will find the speed of light to be constant there.
    How? Are you going to time the light going a metre thataway and back? In an infinitesimal region? When you defined the metre using the motion of light for a fraction of a second? And you defined the second using the motion of light too? The whole thing turns to ashes in your hands.

    Quote Originally Posted by SpeedFreek View Post
    That's any infinitesimally small region. Is there any singular position in that coordinate system where the speed of light is not constant? How many infinitesimally small regions are there in a coordinate system? Is there any place in that coordinate system where there isn't an infinitesimally small region where the speed of light is c?
    An infinitesimally small region is a region of zero extent. It's a region that doesn't exist. It's no region. It's false logic to say the speed of light is constant in no region and therefore is constant in the room you're in. And it directly contradicts Einstein. It's bad science.

    Quote Originally Posted by SpeedFreek View Post
    Can light have two different speeds at the same place?
    No.
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    Quote Originally Posted by tk421 View Post
    Although you were addressing KJW specifically, I feel that you have not answered any of my questions satisfactorily. I'll limit this particular missive to a single, basic issue:

    Forget about 299792458m/s for the moment, and just call it, say, "2". You are acknowledging that 2=2.
    No I'm not. 2 is 2, it isn't 2m/s, wherein one 2m/s isn't the same as another 2 m/s if the seconds aren't the same. And we know the seconds aren't the same because of the thing we call gravitational time dilation.

    Quote Originally Posted by tk421 View Post
    At the same time, you are claiming that this 2 over here is not the same as that 2 over there. As a logical pair of statements, these fail. Once you acknowledge the first statement, the second cannot follow. There are no degrees of freedom in "2" that permit one 2 to differ from some other 2. Two is just...two. All the other verbiage about gravitational time dilation and the current price of Norwegian beaver cheese is simply irrelevant.
    Your argument fails because it's a false assertion to claim you can discard the metres per second.
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  4. #104  
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    Quote Originally Posted by KJW View Post
    How can 299792458 m·s–1 be different to 299792458 m·s–1 or 1 s be different to 1 s?
    Because a concentration of energy in the guise of a massive star alters the surrounding space. It changes it, it makes it inhomogeneous, and the effect diminishes with distance. As a result of this, your measurement of things moving through space is altered. Einstein said the metrical qualities are altered.

    Quote Originally Posted by KJW View Post
    Note that I asked how, not why? So I do not want any mention of gravitational time dilation. It is my claim that any difference is in your mind and not in any way tangible. Answering my question means presenting the difference in a tangible form.
    It's tangible all right. I can feel the weight of my arm on the edge of the desk. That's there because of the wave nature of matter, and because waves don't go straight in inhomogeneous space. They curve "down".

    Quote Originally Posted by KJW View Post
    Also, you avoided giving a satisfactory reply to this: You didn't answer the question "by how much?" or give any quantification of the difference.

    Instead, you said: You know how much. You know how gravitational time dilation affects clocks...

    The point of me asking the question is to give you the opportunity to demonstrate that you know the answer.
    I told you the answer. The ratio between t0 and tf is the ratio between the speed of light at the two locations. Because light clocks don't have time flowing in them. They have light moving in them. What more can I say? It's simple. There isn't anything more to say.

    Quote Originally Posted by KJW View Post
    At this point in the discussion, you've given me nothing to suggest that the differences in the speed of light or of the second are anything more than a figment of your imagination.
    Oh come on. What about all the Einstein quotes and the references to Shapiro and Koks and Wright and Magueijo and Moffat and the NIST optical clocks? What they said isn't some figment of my imagination, nor is gravitational time dilation.

    Quote Originally Posted by KJW View Post
    Apparently not. I take it to mean that the clock is faulty. But that's not the case for a clock at different locations.
    A clock runs slower when its lower because the motion is slower when its lower. End of story.

    Quote Originally Posted by KJW View Post
    You said the clocks tick at different rates at different locations. However, I did consider that a variation of clock rates with respect to change in gravitational potential may not be a violation of the symmetry of the laws of physics. But that would require the mechanism of the clock to be sensitive to the gravitational potential, which given that there is no dependence on the particular type of clock, is unlikely.
    It's true. Because of the way light and matter are "of the same essence". That's in the Wikipedia gravitational time dilation article.

    Quote Originally Posted by KJW View Post
    The article says "appears to go more slowly", whereas you are claiming that it really goes more slowly.
    It really does go more slowly. All observers agree that the lower clock goes slower.

    Quote Originally Posted by KJW View Post
    That is precisely what the empirical evidence says, nothing else.
    The empirical evidence says there is no time moving or passing or flowing inside a clock, so "a clock ticks less time" doesn't square with that empirical evidence.

    Quote Originally Posted by KJW View Post
    And herein lies the problem. Instead of looking at measurement at face value without interpretation, you impose your own interpretation onto the measurement and in doing so distort what the measurement is saying.
    No. I'm the one looking at it at face value without interpretation. You aren't. The lower clock goes slower, and it's a light clock, and there ain't no time flowing through it. So why does it go slower? Because the light goes slower. Just like Shapiro said. And Koks. And Einstein.
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  5. #105  
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    Quote Originally Posted by Farsight View Post
    I'm not lying to you, SpeedFreak. The people who are lying to you are the guys who told you that the speed of light is absolutely constant. It isn't.
    You have claimed before that there are these people. Please produce a citation.
    I don't. He made a mistake and I caught him out.
    Clearly you are lying.

    I made no mistake, I merely wrote the facts of the matter about General Relativity. I did not write all the facts, since I was responding to a very specific question. You know my interpretation of what I said, you know that my statement was of limited scope and says nothing about the speed of light in every coordinate system. So you are making claims that you know to be false. That is a lie.

    This isn't a personal attack: you have already damaged your credibility. This is, again, only me pointing out matters of fact.

    Again, as a matter of fact, let us point out that you have dodged significant questions and you apparently cannot do any of the physics you discuss. I am concerned with a much larger (false) statement that there is some sort of "ersatz GR" that you can distinguish but that nobody else can apparently distinguish, one that, according to you, leads people to make mistakes in calculations. You have yet to produce a single example of a mistake in calculation (except in the case where you attempt a calculation, in which case you almost always make a mistake).

    You are making claims about mathematics, let's see evidence that these claims are true.

    So, back to my unanswered questions.
    Quote Originally Posted by Farsight View Post
    They described a tautology. That's it.
    So you are going to take one quotation out of an entire paper, ignore the rest of the paper and the specific citation that they make in the quotation because the details might not coincide with your claims. This is what we call cherry-picking; it is a fallacious form of argument. At the very least, you have to distinguish between your variable speed of light theory and what those authors describe as a variable speed of light theory.
    I haven't given the reverse of what Einstein actually says. Einstein said a curvature of rays of light can only occur when the speed of light varies with position. The word velocity appears in the English translation but as Don Koks said, Einstein meant speed. This is obvious because he was referring to the SR postulate.
    If this is the case, it should be easy for you to demonstrate the varying of the speed of light by position that Einstein used.
    It just isn't relevant. What is, is the tautology described by Magueijo and Moffat.
    Surely those authors believe that the remainder of their paper on this very topic is relevant. If you cite their paper where they go into great detail on this topic, then you should at least say why everything else in their paper is incorrect. It does a disservice to your reader to make it look like the paper is something that is an authority on the subject when in fact you believe that the authors are very wrong on this very subject. This undermines your argument, since it now seems to be a fluke that the authors made that point at all and that, in general, you think that the work of the authors is work rejecting.
    As I've said repeatedly, there aren't any. I cannot use mathematics to prove that there is no literal time flowing through a clock.
    You are avoiding the real question. I was asking there about the "ersatz version of GR" that you describe. If such a thing exists, you need to demonstrate what it is, what the real version is, and what the difference between them is. It would be nice, ideally, if you could show us where in Einstein's work (not his commentary) the difference lies. This involves showing us the mathematics of the physics, since that is how the work of physics gets done. In order to do his physics, Einstein developed a new field of mathematics. He did this because it was necessary to produce a meaningful physics. If we ignore that, then we ignore his work and insult his memory.
    I'm not. I'm not some my-theory guy.
    You are offering us a claim that there exists an "ersatz version of GR" and a supposedly true version of GR. That is your theory. So far, you have done nothing to defend this theory as you have not addressed the content of GR in a serious way.
    You can reject it if you wish, but others aren't rejecting it. What I'm saying is gaining ground.
    That is a shame, since you seem to be offering us a return to pre-Enlightenment lives where science uses the principles of alchemy and does not use mathematics. I respect the correct reasoning in the correct disciplines, in this case, I cannot accept your textual analysis in the place of real physics.
    [PhysBang: " At this point, it appears that you have no real physics theory, just a claim about the speed of light."] Correct. A claim that is backed up by the evidence and other authors including Einstein.
    Well, I suppose it is a step forward for you to admit that you are not making physics claims.
    My claim is supported by the evidence. Your conviction isn't.
    It is interesting that you use the word "evidence" and not the phrase "measurement evidence". I suppose that this is a sign that you are embracing that you are not doing physics and that you are simply doing a (limited) textual analysis. My conviction that Einstein's work was more complicated than you present is based on the textual analysis of seeing that there is a great deal of mathematics there on this subject that you do not address.
    You're saying nothing. You have no counterargument, all you have is rejection, and you're clutching at straws to reject what I'm telling you and dismiss not just me, but Einstein too.
    That doesn't seem true. As I have said, with the "ersatz version of GR" that you say is incorrect, people can build working machines and can successfully compute and use complicated trajectories. You, on the other hand, offer us what you admit is not a physics claim but merely a claim about the speed of light. That claim cannot be used in any meaningful way.

    It is actually funny that the only case that you predict in one with NIST optical clocks 30cm apart from each other. And even in that case you give a vague prediction. If we were to compare your statement to the rich theory of the "ersatz version of GR", then the evidence in physics clearly lies with the "ersatz version of GR".

    It is funny that you want to lead people away from the practicality of mathematical physics that built things like optical clocks towards the kind of ineffectual textual-analysis in a theological vein that seemed to dominate the Dark Ages.
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  6. #106  
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    Quote Originally Posted by PhysBang View Post
    You have claimed before that there are these people. Please produce a citation.
    See this article on the Baez website. It starts by saying this:

    "Einstein went on to discover a more general theory of relativity which explained gravity in terms of curved spacetime, and he talked about the speed of light changing in this new theory. In the 1920 book "Relativity: the special and general theory" he wrote: . . . according to the general theory of relativity, the law of the constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity [. . .] cannot claim any unlimited validity. A curvature of rays of light can only take place when the velocity of propagation of light varies with position. 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..."

    That's sounds similar to what I've been telling you. But the article then says this:

    "but a more modern interpretation is that the speed of light is constant in general relativity."

    And then it finishes by saying this:

    "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."

    The authors of this article are not alone in thinking it doesn't make sense to say the speed of light varies.

    Quote Originally Posted by PhysBang View Post
    Clearly you are lying. I made no mistake, I merely wrote the facts of the matter about General Relativity. I did not write all the facts, since I was responding to a very specific question. You know my interpretation of what I said, you know that my statement was of limited scope and says nothing about the speed of light in every coordinate system. So you are making claims that you know to be false. That is a lie.
    I'm not lying. You said what you said. You said this:

    "In a sense, this was done in 1905, when Einstein developed special relativity. This constancy of the speed of light is a postulate of the theory, so it is "shown" through the effectiveness and practicality of the theory. The same is true for general relativity, developed in 1915, which holds that the speed of light is constant at any infinitesimal region of a coordinate system".

    Why didn't you say which also holds that the speed of light is constant? Because you are fully aware of the significance of the infinitesimal region. You know full well what Don Koks was talking about in this article when he said Einstein meant speed. You know full well that I'm not lying.

    Quote Originally Posted by PhysBang View Post
    This isn't a personal attack: you have already damaged your credibility. This is, again, only me pointing out matters of fact.
    Not so.

    Quote Originally Posted by PhysBang View Post
    Again, as a matter of fact, let us point out that you have dodged significant questions and you apparently cannot do any of the physics you discuss.
    Not so.

    Quote Originally Posted by PhysBang View Post
    I am concerned with a much larger (false) statement that there is some sort of "ersatz GR" that you can distinguish but that nobody else can apparently distinguish
    Not so. See Einstein's gravitational field which talks about the difference between the "modern interpretation" of GR and what Einstein actually said.

    Quote Originally Posted by PhysBang View Post
    one that, according to you, leads people to make mistakes in calculations.
    I haven't said that. I've said it leads people to errors in understanding, such as the nature of black holes or dark matter.

    Quote Originally Posted by PhysBang View Post
    You have yet to produce a single example of a mistake in calculation (except in the case where you attempt a calculation, in which case you almost always make a mistake).
    That's an ad-hominem.

    Quote Originally Posted by PhysBang View Post
    So you are going to take one quotation out of an entire paper, ignore the rest of the paper and the specific citation that they make in the quotation because the details might not coincide with your claims. This is what we call cherry-picking; it is a fallacious form of argument. At the very least, you have to distinguish between your variable speed of light theory and what those authors describe as a variable speed of light theory.
    I'm giving quotations from multiple sources. People like Einstein and Shapiro said what they said, and everybody can see for themselves what they said. I'm not cherry picking. But you are trying to dismiss what Einstein etc said with false allegations of cherry picking.

    Quote Originally Posted by PhysBang View Post
    If this is the case, it should be easy for you to demonstrate the varying of the speed of light by position that Einstein used.
    Go and read what Irwin Shapiro said: "The proposed experiment was designed to verify the prediction that the speed of propagation of a light ray decreases as it passes through a region of decreasing gravitational potential"

    Quote Originally Posted by PhysBang View Post
    Surely those authors...

    You are avoiding the real question...

    You are offering us a claim that there exists an "ersatz version of GR"...

    That is a shame, since you seem to be offering us a return to pre-Enlightenment lives where science uses the principles of alchemy and does not use mathematics...
    PhysBang, you're carping and throwing out allegations and ad-hominems. It does you no credit. Just face up to what Einstein said: the speed of light varies with position. Face up to the fact that an optical clock goes slower when it's lower, and there ain't no time flowing through it.
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    Quote Originally Posted by Farsight View Post
    See this article on the Baez website. It starts by saying this:

    "Einstein went on to discover a more general theory of relativity which explained gravity in terms of curved spacetime, and he talked about the speed of light changing in this new theory. In the 1920 book "Relativity: the special and general theory" he wrote: . . . according to the general theory of relativity, the law of the constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity [. . .] cannot claim any unlimited validity. A curvature of rays of light can only take place when the velocity of propagation of light varies with position. 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..."

    That's sounds similar to what I've been telling you. But the article then says this:

    "but a more modern interpretation is that the speed of light is constant in general relativity."

    And then it finishes by saying this:

    "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."

    The authors of this article are not alone in thinking it doesn't make sense to say the speed of light varies.
    This is a great example of you cherry-picking quotations to make a claim about an author that is not true.

    Now I wouldn't think that you are lying about this author, I would think that you did not fully read and comprehend what the author was saying. The author was pointing out the specific definition of "constant speed of light" in SR is preserved in GR.

    However, you did knowingly tell falsehoods about the article, and it was a bad, easily discovered falsehood. You wrote,"It starts by saying this:" But the article doesn't start where you say it does, it starts, "Is The Speed of Light Constant? There are a number of senses to the meaning of this question and so there are a number of different answers." So you looked at an article that doesn't believe that there is an absolute constancy to the speed of light, picked specific quotations, and apparently hoped nobody would follow your link.

    I'm not lying. You said what you said.
    Yes, we know what I wrote, that's how we know that you are knowingly telling a falsehood, just like the citation you just gave. Can you please honestly approach this subject?

    Not so. See [physics/0204044] Einstein's gravitational field which talks about the difference between the "modern interpretation" of GR and what Einstein actually said.
    OK, so you can find an internet crank who supports your statement. Do you have any other support for believing in "ersatz GR"? Can you point to a single place where physicists are making a mistake by using "ersatz GR" instead of Farsight-Uncovered-GR that we can see in detail?
    I haven't said that. I've said it leads people to errors in understanding, such as the nature of black holes or dark matter.
    You made specific claims about mistakes in galaxy rotation curves that you have not supported. You said that if one used inhomogeneous space, then one would not need dark matter. You have never supported these claims.
    That's an ad-hominem.
    It is not an ad hominem to point out that your interlocutors are still waiting for you to put forth the required mathematical details for a support of your claims. You have yet to show how your Farsight-Uncovered-GR works in calculating galaxy rotation curves, for example. You uncovered the truth, why not show it to us?
    I'm taking multiple quotations from multiple sources. I'm not cherry picking.
    The more you say that in response to the paper on the variable speed of light, the worse your position is. You brought up these papers that claim that variable speed of light theories demand a violation of Lorentz symmetry, so you should be the one to say why your theory is different from all the other theories they discuss. If we are to take your citations seriously, then we should take seriously their claims and argument, even the ones that you find inconvenient. To do otherwise is cherry-picking. Do you want us to cherry-pick?
    Go and read what Irwin Shapiro said: "The proposed experiment was designed to verify the prediction that the speed of propagation of a light ray decreases as it passes through a region of decreasing gravitational potential"
    That does not answer the question contained in, "If this is the case, it should be easy for you to demonstrate the varying of the speed of light by position that Einstein used." Please do not dodge further and show us how Einstein used the varying speed of light by position.

    PhysBang, you're carping and throwing out allegations and ad-hominems. It does you no credit. Just face up to what Einstein said: the speed of light varies with position.
    That's quite an attempt to dodge my points. Especially the questions about the worth of the Magueijo and Moffat paper. Is it really as useless as you claim, save for the use of one word?

    Let's revisit those points.
    Quote Originally Posted by Farsight View Post
    It just isn't relevant. What is, is the tautology described by Magueijo and Moffat.
    Surely those authors believe that the remainder of their paper on this very topic is relevant. If you cite their paper where they go into great detail on this topic, then you should at least say why everything else in their paper is incorrect. It does a disservice to your reader to make it look like the paper is something that is an authority on the subject when in fact you believe that the authors are very wrong on this very subject. This undermines your argument, since it now seems to be a fluke that the authors made that point at all and that, in general, you think that the work of the authors is work rejecting.
    As I've said repeatedly, there aren't any. I cannot use mathematics to prove that there is no literal time flowing through a clock.
    You are avoiding the real question. I was asking there about the "ersatz version of GR" that you describe. If such a thing exists, you need to demonstrate what it is, what the real version is, and what the difference between them is. It would be nice, ideally, if you could show us where in Einstein's work (not his commentary) the difference lies. This involves showing us the mathematics of the physics, since that is how the work of physics gets done. In order to do his physics, Einstein developed a new field of mathematics. He did this because it was necessary to produce a meaningful physics. If we ignore that, then we ignore his work and insult his memory.
    I'm not. I'm not some my-theory guy.
    You are offering us a claim that there exists an "ersatz version of GR" and a supposedly true version of GR. That is your theory. So far, you have done nothing to defend this theory as you have not addressed the content of GR in a serious way.
    You can reject it if you wish, but others aren't rejecting it. What I'm saying is gaining ground.
    That is a shame, since you seem to be offering us a return to pre-Enlightenment lives where science uses the principles of alchemy and does not use mathematics. I respect the correct reasoning in the correct disciplines, in this case, I cannot accept your textual analysis in the place of real physics.
    [PhysBang: " At this point, it appears that you have no real physics theory, just a claim about the speed of light."] Correct. A claim that is backed up by the evidence and other authors including Einstein.
    Well, I suppose it is a step forward for you to admit that you are not making physics claims.
    My claim is supported by the evidence. Your conviction isn't.
    It is interesting that you use the word "evidence" and not the phrase "measurement evidence". I suppose that this is a sign that you are embracing that you are not doing physics and that you are simply doing a (limited) textual analysis. My conviction that Einstein's work was more complicated than you present is based on the textual analysis of seeing that there is a great deal of mathematics there on this subject that you do not address.
    You're saying nothing. You have no counterargument, all you have is rejection, and you're clutching at straws to reject what I'm telling you and dismiss not just me, but Einstein too.
    That doesn't seem true. As I have said, with the "ersatz version of GR" that you say is incorrect, people can build working machines and can successfully compute and use complicated trajectories. You, on the other hand, offer us what you admit is not a physics claim but merely a claim about the speed of light. That claim cannot be used in any meaningful way.

    It is actually funny that the only case that you predict in one with NIST optical clocks 30cm apart from each other. And even in that case you give a vague prediction. If we were to compare your statement to the rich theory of the "ersatz version of GR", then the evidence in physics clearly lies with the "ersatz version of GR".

    It is funny that you want to lead people away from the practicality of mathematical physics that built things like optical clocks towards the kind of ineffectual textual-analysis in a theological vein that seemed to dominate the Dark Ages.
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    PhysBang, your post is all repetition and ad-hominem. It's a deliberate attempt to derail the thread and bore other posters to death, so you're on ignore.
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    Ah, yes. <Removed for decorum.>
    Last edited by PhysBang; 09-09-2014 at 05:52 PM.
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    Moderator Warning:Your participation in the forum (PhysBAng and FarSight) suggests you are able to read. In that case I suspect you have read Markus's appeal to all members to raise the standard of posting. These last two posts are exactly what he was talking about. They are not acceptable. There are two ways of stopping them. You can choose to stop them, or I can stop them for you. You get a choice. Make the right one.

    No responses to this warning will be made in this thread. Any objections or comments may be made by sending me or another mod a pm, or reporting the post. If any of you like to experiment you can find out what happens when someone ignores this instruction by simply ignoring this instruction.
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    I think Physbang made an exceptional effort.
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    I think Physbang made an exceptional effort.
    That looks a great deal like a comment on/relating to my Moderator Warning. This is a physics forum. Discuss physics, not human behaviour. I am giving you the benefit of the doubt, but do not test my patience. You will discover I do not have any.
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    Ban me.
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    As you wish. One week ban.

    In case I am not making myself clear, this thread is about a physics subject. It is for discussion of that subject. Not petty squabbles. Not discussion of petty squabbles. Not nonsense. I shall be sleeping shortly. Please ensure I do not wake up to a nightmare.
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    So, does anybody still think that a clock measures the flow of proper time? Or the passage of time? Does anybody still think a clock is some kind of cosmic gas meter with time flowing through it? Or are we all now happy that a clock features some kind of regular cyclical motion? Whether it's a mechanical clock with cogs and gears, or a quartz wristwatch with an oscillating crystal, or an atomic clock with a hyperfine spinflip and microwaves, there's always something moving in there. And this motion is essentially accumulated or counted and displayed as a readout that we call "the time". So when a clock goes slower it isn't because time goes slower, but because the motion inside the clock goes slower. Even when it's an optical clock.

    It's that simple. I can't make it any simpler than that. Nor can Einstein, or Shapiro or Koks, or Wright, or Magueijo or Moffat, or Stenger.

    NB: Victor Stenger blogged for the Huffington Post, who haven't mentioned that he died on August 25th. See this.
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    Quote Originally Posted by Farsight View Post
    So, does anybody still think that a clock measures the flow of proper time? Or the passage of time? Does anybody still think a clock is some kind of cosmic gas meter with time flowing through it? ...
    I don't know where this notion is supposed to come from, so I can't comment on that. But I don't see how it's supposed to be the only possible alternative to the notion that time is not some fundamental physical feature like space. Yes, the only possible alternative.
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    Quote Originally Posted by lpetrich View Post
    I don't know where this notion is supposed to come from, so I can't comment on that.
    So what does a clock do? It's a very simple question, but when you ask around, many of the answers you get are nothing like the reality that you can see with your own eyes.

    Quote Originally Posted by lpetrich View Post
    But I don't see how it's supposed to be the only possible alternative to the notion that time is not some fundamental physical feature like space. Yes, the only possible alternative.
    I'm not clear what you mean by that. Please restate.
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    Here is what I think. I will concede that time does not flow through clocks. However, clocks' actions are a function of time, and clocks' actions are for marking out time. It's something like how a ruler is for marking out distances. In fact, we also do not directly perceive space. So space and time are not very different here, and that's not even getting into the close relationship between space and time implied by Lorentz invariance.
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    Quote Originally Posted by Farsight View Post
    So, does anybody still think that a clock measures the flow of proper time? Or the passage of time? Does anybody still think a clock is some kind of cosmic gas meter with time flowing through it? Or are we all now happy that a clock features some kind of regular cyclical motion?
    Why don't we ask Einstein?

    Chapter 28. Exact Formulation of the General Principle of Relativity. Einstein, Albert. 1920. Relativity: The Special and General Theory

    "In gravitational fields there are no such things as rigid bodies with Euclidean properties; thus the fictitious rigid body of reference is of no avail in the general theory of relativity. The motion of clocks is also influenced by gravitational fields, and in such a way that a physical definition of time which is made directly with the aid of clocks has by no means the same degree of plausibility as in the special theory of relativity.

    For this reason non-rigid reference-bodies are used which are as a whole not only moving in any way whatsoever, but which also suffer alterations in form ad lib. during their motion. Clocks, for which the law of motion is any kind, however irregular, serve for the definition of time. We have to imagine each of these clocks fixed at a point on the non-rigid reference-body. These clocks satisfy only the one condition, that the “readings” which are observed simultaneously on adjacent clocks (in space) differ from each other by an indefinitely small amount. This non-rigid reference-body, which might appropriately be termed a “reference-mollusk,” is in the main equivalent to a Gaussian four-dimensional co-ordinate system chosen arbitrarily. That which gives the “mollusk” a certain comprehensibleness as compared with the Gauss co-ordinate system is the (really unqualified) formal retention of the separate existence of the space co-ordinate. Every point on the mollusk is treated as a space-point, and every material point which is at rest relatively to it as at rest, so long as the mollusk is considered as reference-body. The general principle of relativity requires that all these mollusks can be used as reference-bodies with equal right and equal success in the formulation of the general laws of nature; the laws themselves must be quite independent of the choice of mollusk."

    It seems that to Einstein, clocks are not regular: they obey whatever dynamics they wish, as long as one can create a differentiable curve over the readings of the clocks.
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    Farsight: One 299792458 m·s–1 can be different to another 299792458 m·s–1 when the seconds are different. It's that simple. If you're lower than me your seconds are bigger than mine. So your 299792458 m·s–1 is slower than mine. Note that your metres are the same as my metres, because your slower light and your bigger second cancel each other out. Hence we have the parallel-mirror gif which is an idealisation of the NIST optical clocks:

    cinci: Your idealization is not proper. The situation you picture cannot exist for light assuming the two clocks are identical when at rest relatively.

    What would actually happen if the lower clock were moving relative to the upper clock is that the distance between the mirrors would be smaller as measured by an observer at rest with the upper clock.

    The motion of the lower clock would also cause the light path in the direction of motion to be longer and to be shorter in the other direction.

    dt = L/(c - v) in the direction of motion and t = L/(c + v) for the direction opposite the motion.

    The result is that the round trip time for the light is longer which effectively means more time between ticks as seen by an observer at rest with the upper clock.
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