externo Posted April 23 Author Posted April 23 (edited) 11 hours ago, swansont said: I don’t know what you mean by “simultaneity must vary physically” Things are simultaneous or not, and it’s a temporal effect. Events that are simultaneous in one frame are not simultaneous in other frames. It's simple: we synchronize the clocks according to Einstein's procedure so that the one-wat speed of light is measured constant. If this speed is physically constant, the synchronization must indicate the physical time. As each inertial frame has a different synchronization this means that the simultaneity is physically different in each frame. If you think that simultaneity is not physical you also think that the constant one-way speed of light is not physical. 11 hours ago, swansont said: The earth twin sends out a continuous signal at some frequency, with some wavelength. The space twin travels at some speed, and sees this signal as red-shifted - they get the crest of one wave, but have moved away before the next crest can reach them, so they measure the signal with a longer wavelength and lower frequency. Then they turn around, and are now moving toward the source. They get the crest of one wave, but have moved closer before the next crest reaches them. Since the signal was sent continuously, this happens immediately - the light is already there to be detected. They measure the crests as being closer together and with a higher frequency. Blue-shifted. So, you see, his speed is not constant relative to the waves... 11 hours ago, swansont said: I can’t fathom why you think this would not happen as soon as they started moving toward earth. I'm not saying that it doesn't happen as soon as they started moving toward earth, on the contrary, but for it to happen instantly they have to change speed in relation to the waves and therefore the speed of light cannot remain constant when they accelerate, therefore the postulate of the constancy of the speed of light cannot be true. That's all I'm saying. -------------------------------- 3 hours ago, Markus Hanke said: I never mentioned any U-turn - I made it explicitly clear that I made no assumptions about what the path actually looks like, other than it being light-like (thus differentiable everywhere). Why? Because that’s irrelevant, since the difference in clock readings only depends on the total lengths of the two paths. It’s a global measure along the entire journey. Others here have repeatedly pointed this out too. And since both path length and proper acceleration are invariant measures, both twins agree on the outcome. So you don't have any explanation, you just stick to the math. 3 hours ago, Markus Hanke said: That’s a meaningless statement. I used Einsteinian SR to show how the twin scenario requires no “resolution”. You used Lorentz mathematics, they are the ones who mathematically resolved the paradox. As for EInstein, to show that he is right you have to prove that the one-way speed of light is constant, which the Dopller effect denies. 3 hours ago, Markus Hanke said: In relation to the emitter, not the signal. There’s no rest frame for light. Why does the frequency of the signal increase as soon as it turns around? Because it is he who causes this increase in the signal by changing its speed relative to the waves. For its part, the Earth must wait for the redshift to propagate at the speed of light to it because its velocity relative to the waves don't change, this is what causes the asymmetry: the speed of light changes relative to the twin which turns around but not relative to the Earth. ---------------------------- 2 hours ago, Eise said: I think I found an even better challenge for you, @externo because it seems you have problems with even simple math. This is the formula for the Doppler effect in a medium: vr = is the speed of the receiver relative to the medium, added to ± (above the division) = if the receiver is moving towards the source, subtracted if the receiver is moving away from the source vs = is the speed of the source relative to the medium, added to ± (below the division) if the source is moving away from the receiver, subtracted if the source is moving towards the receiver And last, but not least: c = is the propagation speed of waves in the medium Now this is the Doppler formula for light, assuming the source and the receiver are moving in a straight line from/to each other: where ß is the usual v/c. Now tell me, where do you see the speed of light in a medium? How do you explain that it does not appear in the formula? The above formula, AFAIK, can be derived from the Lorentz transformations, in which, you probably noticed, the speed of light in a medium does not occur either. Another problem I seem to see, is that you are thinking that relativity has something to do with signal delay. It hasn't. So the blueshift that the observer on earth sees after the traveler has turned around, of course takes time to reach earth. That is just signal time delay, nothing special. The relativistic Doppler effect is calculated assuming that the receiver or transmitter is stationary relative to the medium. In classical physics, if we assume that the receiver is moving, it receives the waves emitted by the source at the frequency: fr = fe (1- v/c) = fe (1- β) with fr = reception frequency and fe emitter frequency If we assume that it is the source which moves, fr = fe/(1+ v/c) = fe/(1+ β) If we add the time dilation factor y² = 1/(1-β²) if we assume that it is the receiver which moves: fr = fe (1- β) * y = sqrt( (1-β)/(1+β)) fe if we assume that it is the transmitter which moves: fr = fe (1- β) / y = sqrt( (1-β)/(1+β)) fe https://fr.wikipedia.org/wiki/Effet_Doppler#Calcul_relativiste_rapide https://fr-m-wikipedia-org.translate.goog/?_x_tr_sl=fr&_x_tr_tl=en&_x_tr_hl=fr&_x_tr_pto=wapp&_x_tr_hist=true#Calcul_relativiste_rapide So the result is identical. If, in classical physics, we assume that the object which moves relative to the medium undergoes time dilation, there is no longer any way to distinguish observationally whether it is the source or the receiver which moves relative to the medium. The relativistic Doppler effect is therefore symmetrical in classical kinematics and we cannot deduce from it that the medium does not exist, but simply that there is observational symmetry and not physical symmetry. 2 hours ago, Eise said: Another problem I seem to see, is that you are thinking that relativity has something to do with signal delay. It hasn't. So the blueshift that the observer on earth sees after the traveler has turned around, of course takes time to reach earth. That is just signal time delay, nothing special. And why does the turning twin not need to wait for the signal emitted from Earth to propagate to him before observing the blueshift? He instantly observes it when he turns around because it is he who changes speed in relation to the waves. Edited April 23 by externo
externo Posted April 23 Author Posted April 23 1 hour ago, externo said: https://fr-m-wikipedia-org.translate.goog/?_x_tr_sl=fr&_x_tr_tl=en&_x_tr_hl=fr&_x_tr_pto=wapp&_x_tr_hist=true#Calcul_relativiste_rapide https://fr-m-wikipedia-org.translate.goog/wiki/Effet_Doppler?_x_tr_sl=fr&_x_tr_tl=en&_x_tr_hl=fr&_x_tr_pto=wapp#Calcul_relativiste_rapide
Eise Posted April 23 Posted April 23 3 hours ago, externo said: The relativistic Doppler effect is calculated assuming that the receiver or transmitter is stationary relative to the medium. (Bold by me) What does 'stationary' mean? Against what? The Lorentzian aether? How can that be, if the LTs do not contain any reference to the velocity of light measured in this 'aether'?
swansont Posted April 23 Posted April 23 2 hours ago, externo said: It's simple: we synchronize the clocks according to Einstein's procedure so that the one-wat speed of light is measured constant. If this speed is physically constant, the synchronization must indicate the physical time. Physical time? You keep using expressions like this, and they make no sense. 2 hours ago, externo said: So, you see, his speed is not constant relative to the waves... The speed of a wave is frequency*wavelength The frequency increases by the same factor as the wavelength decreases. These terms cancel. The speed of the wave is the same. 2 hours ago, externo said: I'm not saying that it doesn't happen as soon as they started moving toward earth, on the contrary, but for it to happen instantly These are the same thing 2 hours ago, externo said: they have to change speed in relation to the waves and therefore the speed of light cannot remain constant when they accelerate, therefore the postulate of the constancy of the speed of light cannot be true. That's all I'm saying. -------------------------------- And you’re wrong. The speed of the wave is constant (it’s right there in the math) since both frequency and wavelength are changed.
Mordred Posted April 23 Posted April 23 (edited) @externo A solid piece of advise. You really need to stop trying to tell us how SR and GR works or describes. We have gone numerous pages with posters correcting your misunderstandings. Which you continue to repeat. I highly suggest that instead of trying to tell us what SR states that instead you start asking questions concerning SR. Use the math and the knowledge of the posters here and try to properly understand SR. This is article was written by a Ph.D that regularly uses forums. He developed this article to provide corrections to all the numerous misconceptions posters regularly have with regards to SR. http://www.lightandmatter.com/sr/ This article describes the basics of SR in a very easy to understand format and explains the reasons behind its mathematics. Relativity: The Special and General Theory" by Albert Einstein http://www.gutenberg.org/files/30155/30155-pdf.pdf It is an archive reprint. Edited April 23 by Mordred 2
externo Posted April 23 Author Posted April 23 (edited) 8 hours ago, Eise said: (Bold by me) What does 'stationary' mean? Against what? The Lorentzian aether? How can that be, if the LTs do not contain any reference to the velocity of light measured in this 'aether'? When we say that the speed of light is invariant with respect to all frames of reference, it is as if all frames of reference were the frame of the ether. This is also how Einstein saw it, he thought that there was an ether which was stationary for everyone. So the observer is always at rest and the object observed is in motion. The relativistic Doppler effect is therefore postulated as always produced by the observed object. LTs do not contain any indication of the speed relative to light because they are symmetrical and we cannot distinguish this speed. I gave the calculations. ----------------------------- 7 hours ago, Mordred said: @externo A solid piece of advise. You really need to stop trying to tell us how SR and GR works or describes. We have gone numerous pages with posters correcting your misunderstandings. $ I can't stop because you really don't understand relativity. You don't even know that the hypothesis of the invariance of the speed of light is a useless hypothesis for the theory, and that it only serves to get rid of the ether. ------------------------------- 8 hours ago, swansont said: Physical time? You keep using expressions like this, and they make no sense. Time is not physical, so you don't age? 8 hours ago, swansont said: The speed of a wave is frequency*wavelength The frequency increases by the same factor as the wavelength decreases. These terms cancel. The speed of the wave is the same. And you’re wrong. The speed of the wave is constant (it’s right there in the math) since both frequency and wavelength are changed. Why would the wavelength decrease? Edited April 23 by externo -2
Mordred Posted April 23 Posted April 23 (edited) 59 minutes ago, externo said: I can't stop because you really don't understand relativity. You don't even know that the hypothesis of the invariance of the speed of light is a useless hypothesis for the theory, and that it only serves to get rid of eather I don't know relativity oh my that's a laugh. I would never have have gotten my degrees without knowing let alone past the undergraduate stage. It's literally part of my job dealing with SR on a regular basis lmao. You might want to try again mate For me it's not a hobby or a curiosity but a career requirement Edited April 23 by Mordred 2
swansont Posted April 23 Posted April 23 1 hour ago, externo said: Time is not physical, so you don't age? Aging is a biological process. Time is time. Time passes at a different rate (i.e. frequency) in different reference frames 1 hour ago, externo said: Why would the wavelength decrease? Because that’s what happens in the Doppler effect. Red shift is shifted toward longer wavelengths and blue shift toward shorter. It’s observed to happen, so there’s no point in denying it.
Mordred Posted April 23 Posted April 23 1 hour ago, swansont said: Because that’s what happens in the Doppler effect. Red shift is shifted toward longer wavelengths and blue shift toward shorter. It’s observed to happen, so there’s no point in denying it. Lol every single spectrograph I've ever examined has some form of redshift. The only time it doesn't is if it was reading some object in the lab. I even had an instructor that was testing the class with a falsified dataset that not only didn't have redshift but also incorrect elements.
Eise Posted April 24 Posted April 24 9 hours ago, externo said: This is also how Einstein saw it, he thought that there was an ether which was stationary for everyone. Really? From his article that introduced the theory that later would be named 'Special Relativity': Quote The introduction of a “luminiferous ether” will prove to be superfluous inasmuch as the view here to be developed will not require an “absolutely stationary space” provided with special properties, nor assign a velocity-vector to a point of the empty space in which electromagnetic processes take place. On the electrodynamics of moving bodies I think it is time to close the thread? 1
Markus Hanke Posted April 24 Posted April 24 20 hours ago, externo said: So you don't have any explanation, you just stick to the math. The explanation is exactly what the maths says - pick a different path, and you’ll walk a different distance. There’s nothing else to it. 20 hours ago, externo said: You used Lorentz mathematics, they are the ones who mathematically resolved the paradox. No, I showed you that there’s no paradox that needs resolving. It seems to me that you’re wilfully refusing to “get” this. 20 hours ago, externo said: Because it is he who causes this increase in the signal by changing its speed relative to the waves. There’s no such thing as “relative to waves”, because light has no rest frame. The speed is always between emitter and receiver. 20 hours ago, externo said: And why does the turning twin not need to wait for the signal emitted from Earth to propagate to him before observing the blueshift? Because it’s he who experiences acceleration locally in his frame. The equivalence principle tells us that uniform acceleration is locally equivalent to a uniform gravitational field; differently put, the accelerated twin sits at a different gravitational potential, which implies frequency shift. 2
DanMP Posted April 24 Posted April 24 8 hours ago, Markus Hanke said: The equivalence principle tells us that uniform acceleration is locally equivalent to a uniform gravitational field; differently put, the accelerated twin sits at a different gravitational potential, which implies frequency shift. So, here, on the Earth surface, we also see the light coming from stars straight above us "blueshifting" as long as our accelerometer shows that we are "accelerating" upward?
geordief Posted April 24 Posted April 24 9 hours ago, Markus Hanke said: The explanation is exactly what the maths says - pick a different path, and you’ll walk a different distance. There’s nothing else to it This is clearly right as it has been shown experimentally. Do you have any other (or complementary) intuitive ways of sitting this process in our pattern of thoughts? I have always tried to think of this as some kind of "work done" as a body travels through both space and time, following different possible paths but that approach doesn't satisfy me (and is probably wrong as well) I find no fault with your description but I wonder could there be other ways to describe this using words.
Mordred Posted April 24 Posted April 24 3 hours ago, DanMP said: So, here, on the Earth surface, we also see the light coming from stars straight above us "blueshifting" as long as our accelerometer shows that we are "accelerating" upward? As light climbs in and out of a gravity well it will blue shift or redshift. For example an outside observer looking at infalling material at the EH of a blackhole will see infinite redshift but an observer at the EH will see infinite blue shift. This is due to gravitational redshift 3 hours ago, geordief said: This is clearly right as it has been shown experimentally. Do you have any other (or complementary) intuitive ways of sitting this process in our pattern of thoughts? I have always tried to think of this as some kind of "work done" as a body travels through both space and time, following different possible paths but that approach doesn't satisfy me (and is probably wrong as well) I find no fault with your description but I wonder could there be other ways to describe this using words. The path will be determined by the Principle of least action which correlates the Potential energy and kinetic energy terms. What most ppl don't realize is that the path is never truly straight. That's just the mean average. If you consider all the little infinitesimal changes in direction (sometimes up/down left right etc) then it becomes much easier to understand. As Markus the geodesic equations are the extremum of all the miniscule deviations
externo Posted April 24 Author Posted April 24 (edited) 14 hours ago, Eise said: Really? From his article that introduced the theory that later would be named 'Special Relativity': On the electrodynamics of moving bodies I think it is time to close the thread? You don't know anything about it: https://mathshistory.st-andrews.ac.uk/Extras/Einstein_ether/ He later changed his mind. Quote Recapitulating, we may say that according to the general theory of relativity space is endowed with physical qualities; in this sense, therefore, there exists an ether. According to the general theory of relativity space without ether is unthinkable; for in such space there not only would be no propagation of light, but also no possibility of existence for standards of space and time (measuring-rods and clocks), nor therefore any space-time intervals in the physical sense. But this ether may not be thought of as endowed with the quality characteristic of ponderable media, as consisting of parts which may be tracked through time. The idea of motion may not be applied to it. Edited April 24 by externo
swansont Posted April 24 Posted April 24 28 minutes ago, externo said: He later changed his mind. Not really. He concluded that space has properties, but it’s not a medium that represents a preferred frame of reference, or is required for light. The aether he spoke of later is not the luminiferous aether of Lorentz theory.
externo Posted April 24 Author Posted April 24 (edited) 14 hours ago, Markus Hanke said: The explanation is exactly what the maths says - pick a different path, and you’ll walk a different distance. There’s nothing else to it. The mathematics simply says that the traveling twin's own time is shorter, it explains nothing. Moreover, the path taken by the twin is longer and not shorter, what is shorter is its proper time. You can call proper time a "path" if you please, that's not why it will be a real one, show me this "path" in the sky if you can. 14 hours ago, Markus Hanke said: No, I showed you that there’s no paradox that needs resolving. It seems to me that you’re wilfully refusing to “get” this. Yet, Wikipedia says that there is a paradox except in the case where we postulate a privileged reference frame. 14 hours ago, Markus Hanke said: There’s no such thing as “relative to waves”, because light has no rest frame. The speed is always between emitter and receiver. How do you know that there is no preferred reference frame where the light is isotropic? You can't know. 14 hours ago, Markus Hanke said: Because it’s he who experiences acceleration locally in his frame. The equivalence principle tells us that uniform acceleration is locally equivalent to a uniform gravitational field; differently put, the accelerated twin sits at a different gravitational potential, which implies frequency shift. There is no gravitational field in an accelerated frame of reference, we are in flat space-time, the distance between the accelerating object and the stars varies unlike in a gravitational field, the Doppler effect is therefore kinematic, not gravitaionnel. ---------------------------- 17 minutes ago, swansont said: Not really. He concluded that space has properties, but it’s not a medium that represents a preferred frame of reference, or is required for light. The aether he spoke of later is not the luminiferous aether of Lorentz theory. I wrote "This is also how Einstein saw it, he thought that there was an ether which was stationary for everyone." It is called the relativistic aether, but it is also a luminiferous ether, it is the Lorentz ether deprived of its state of motion. Edited April 24 by externo
swansont Posted April 24 Posted April 24 2 hours ago, externo said: Yet, Wikipedia says that there is a paradox except in the case where we postulate a privileged reference frame. Is that the part where it says “Therefore, the twin paradox is not actually a paradox in the sense of a logical contradiction”? 2 hours ago, externo said: I wrote "This is also how Einstein saw it, he thought that there was an ether which was stationary for everyone." It is called the relativistic aether, but it is also a luminiferous ether, it is the Lorentz ether deprived of its state of motion. Just saying this doesn’t make it so. ”It may be added that the whole change in the conception of the ether which the special theory of relativity brought about, consisted in taking away from the ether its last mechanical quality, namely, its immobility.” doesn’t support that notion neither does “We may assume the existence of an ether; only we must give up ascribing a definite state of motion to it”
Mordred Posted April 24 Posted April 24 (edited) 3 hours ago, externo said: Yet, Wikipedia says that there is a paradox except in the case where we postulate a privileged reference frame. Who cares what wiki states it's never written by a professor in the field involved. It's never been nor will ever be an authority in physics or any other science. 3 hours ago, externo said: There is no gravitational field in an accelerated frame of reference, we are in flat space-time, the distance between the accelerating object and the stars varies unlike in a gravitational field, the Doppler effect is therefore kinematic, not gravitaionnel Garbage not even close to being accurate regardless if your describing LET or SR/GR.. Tell me do even understand what an inertial frame is as opposed to a non inertial frame ? It's no different in LET and you cannot even describe LET correctly if you don't know the difference. Tell me many more pages will it take before you realize that you never convince anyone that you are correct when you cannot describe the theories under discussions without being full of errors? Everyone is literally forced to correct your errors to the point where discussing the Pros and Cons between the two theories simply isn't happening. Edited April 24 by Mordred
Markus Hanke Posted April 25 Posted April 25 (edited) 13 hours ago, DanMP said: So, here, on the Earth surface, we also see the light coming from stars straight above us "blueshifting" as long as our accelerometer shows that we are "accelerating" upward? Technically yes, there will be some amount of frequency shift, though in practice the effect is quite small for a weak field such as the Earth’s. 13 hours ago, geordief said: Do you have any other (or complementary) intuitive ways of sitting this process in our pattern of thoughts? That’s hard to answer, since whether something is considered intuitive or not depends on the person. I kind of like the paths lengths way of looking at it, since most people can relate to it. 8 hours ago, externo said: Moreover, the path taken by the twin is longer and not shorter, what is shorter is its proper time. Total accumulated proper time equals the geometric length of the path through spacetime, as I’ve mentioned already. The crucial point is that the two paths are not of equal lengths. 8 hours ago, externo said: Yet, Wikipedia says that there is a paradox except in the case where we postulate a privileged reference frame. I think you should read the article more carefully. 8 hours ago, externo said: How do you know that there is no preferred reference frame where the light is isotropic? You can't know. I said there’s no rest frame to light, so it makes no sense to speak of “speed relative to waves”. 8 hours ago, externo said: There is no gravitational field in an accelerated frame of reference, we are in flat space-time, There’s no tidal gravity in an accelerated frame, meaning that \[R_{\mu\nu}=0; W{^{\mu}}{_{\nu\alpha\beta}}=0\] and therefore \[R{^{\mu}}{_{\nu\alpha\beta}}=0\] However, there is a homogenous gravitational field due to proper acceleration locally, according to the equivalence principle. The Riemann tensor vanishes for such homogenous fields, so spacetime remains of course flat as expected. The metric in the accelerating frame, which now contains a term which is equivalent to a gravitational potential, is isomorphic to the Minkowski metric, also as expected. Edited April 25 by Markus Hanke
externo Posted April 25 Author Posted April 25 (edited) 9 hours ago, swansont said: Is that the part where it says “Therefore, the twin paradox is not actually a paradox in the sense of a logical contradiction”? It is the part where it says "No twin paradox in an absolute frame of reference" https://en.wikipedia.org/wiki/Twin_paradox#No_twin_paradox_in_an_absolute_frame_of_reference 9 hours ago, swansont said: Just saying this doesn’t make it so. ”It may be added that the whole change in the conception of the ether which the special theory of relativity brought about, consisted in taking away from the ether its last mechanical quality, namely, its immobility.” doesn’t support that notion neither does “We may assume the existence of an ether; only we must give up ascribing a definite state of motion to it” It takes away his absolute immobility, he becomes stationary for everyone, it no longer has any state of motion ---------------------------- 9 hours ago, Mordred said: Who cares what wiki states it's never written by a professor in the field involved. It's never been nor will ever be an authority in physics or any other science. Who cares what you states ? it has no authority, unlike a public text read and corrected by dozens of people including university professors. 9 hours ago, Mordred said: Tell me do even understand what an inertial frame is as opposed to a non inertial frame ? It's no different in LET and you cannot even describe LET correctly if you don't know the difference. You don't seem to know that a non-inertial frame changes speed relative to the outside world while a gravitational field is stationary. ------------------------------ 4 hours ago, Markus Hanke said: Total accumulated proper time equals the geometric length of the path through spacetime, as I’ve mentioned already. The crucial point is that the two paths are not of equal lengths. The path you speak of is the elapsed time in the traveler's frame of reference, the fact that it is a path in space-time is a mathematical invention, not a physical reality. All we can deduce is that an object that moves MORE in space ages less. 4 hours ago, Markus Hanke said: I said there’s no rest frame to light, so it makes no sense to speak of “speed relative to waves”. But there can exist a unique reference frame relative to which the speed of light is c, and therefore it would make sense to talk about the speed relative to waves because it would depend on the chosen measurement reference frame, if this is not the unique reference frame, this speed will be different from c. This is Lorentz theory. 4 hours ago, Markus Hanke said: There’s no tidal gravity in an accelerated frame, meaning that Rμν=0;Wμναβ=0 and therefore Rμναβ=0 However, there is a homogenous gravitational field due to proper acceleration locally, according to the equivalence principle. The Riemann tensor vanishes for such homogenous fields, so spacetime remains of course flat as expected. The metric in the accelerating frame, which now contains a term which is equivalent to a gravitational potential, is isomorphic to the Minkowski metric, also as expected. A gravitational field is stationary, an acceleration is not. In a gravitational field time flows more or less quickly in space, in an acceleration time always flows in the same way in space, the object which accelerates does not have the power to change the the flow of time around it, what's more, the Doppler effect perceived by the one accelerating is a kinematic Doppler effect and not a gravitational one, it comes from the fact that the objects move in relation to it. Edited April 25 by externo
swansont Posted April 25 Posted April 25 3 hours ago, externo said: It is the part where it says "No twin paradox in an absolute frame of reference" Saying this is not the same as “there is a paradox except in the case where we postulate a privileged reference frame” but at this point I’m not surprised that you don’t see this. ! Moderator Note At this point you’re just repeating earlier claims, without making any correction to your errors, so there’s no point in continuing. Closed. Don’t re-introduce the topic.
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