Mordred Posted April 19 Posted April 19 (edited) 1 hour ago, externo said: You are confusing time dilation and simultaneity. The change in simultaneity is the origin of length contraction and is a perspective effect. Time dilation is an absolute effect and comes from the decrease in the average speed of light relative to an objet in motion. No I'm not I know precisely how SR and GR works including the related math. I use it all the time as a professional physicist. Here is a challenge for describe at point between two observers in different reference frames where simultaneaty can be said to occur. Then add a third observer Edited April 19 by Mordred
externo Posted April 19 Author Posted April 19 (edited) 46 minutes ago, swansont said: Speed of light is invariant. It does not decrease for an object in motion. Time dilation is a relative effect for inertial frames. If time dilation was a relative effect, it would not be absolute and the twin would not return younger. If the speed of light does not change relative to a moving object, how does a light clock work? It is the measurement of the speed of light that does not vary, not the speed itself. Meters and measuring standards are transformed in such a way that they always measure the same round-trip speed. Edited April 19 by externo -3
Mordred Posted April 19 Posted April 19 (edited) 7 minutes ago, externo said: If time dilation was a relative effect, it would not be absolute and the twin would not return younger. If the speed of light does not change relative to a moving object, how does a light clock work? It is the measurement of the speed of light that does not vary, not the speed itself. Meters and measuring standards are transformed in such a way that they always measure the same round-trip speed. Precisely time is not absolute. If that's what you believe you need to catch up to modern research. Edited April 19 by Mordred
swansont Posted April 19 Posted April 19 16 minutes ago, externo said: If time dilation was a relative effect, it would not be absolute and the twin would not return younger. You need to read more carefully. I specified inertial frames. 16 minutes ago, externo said: If the speed of light does not change relative to a moving object, how does a light clock work? There are a number of explanations, easily found on the web, of how a light clock would work, based on an invariant c
Bufofrog Posted April 19 Posted April 19 1 hour ago, externo said: If the speed of light does not change relative to a moving object, how does a light clock work? The whole point of the light clock is that the speed of light doesn't change. You don't seem to have much of an understanding of relativity. You should listen to the people on this forum, you will learn a lot.
externo Posted April 19 Author Posted April 19 (edited) 26 minutes ago, Bufofrog said: The whole point of the light clock is that the speed of light doesn't change. You don't seem to have much of an understanding of relativity. You should listen to the people on this forum, you will learn a lot. In a light clock the speed of light is invariant with respect to space but certainly not with respect to the light clock. You are confusing the invariance of the speed of light with respect to space or ether which is Lorentz's postulate and the invariance of the speed of light with respect to all inertial frames which is Einstein's. Edited April 19 by externo -1
Mordred Posted April 19 Posted April 19 33 minutes ago, externo said: In a light clock the speed of light is invariant with respect to space but certainly not with respect to the light clock. You are confusing the invariance of the speed of light with respect to space or ether which is Lorentz's postulate and the invariance of the speed of light with respect to all inertial frames which is Einstein's. The speed of light remains invariant to all observers that is precisely what invariant means. The confusion is on your end
externo Posted April 19 Author Posted April 19 45 minutes ago, Mordred said: The speed of light remains invariant to all observers that is precisely what invariant means. The confusion is on your end You cannot prove that it remains invariant, on the other hand I proved in my first message that it cannot remain invariant. When an object accelerates it necessarily changes speed relative to light, which invalidates Einstein. -1
joigus Posted April 19 Posted April 19 3 hours ago, externo said: If time dilation was a relative effect, it would not be absolute and the twin would not return younger. Will you just read what's answered to you??? Otherwise it's a monumental waste of time for everyone involved. 4 hours ago, swansont said: Time dilation is a relative effect for inertial frames. (my emphasis.) The returning twin is subject to accelerations. Is it not? This is the major bone of contention with people who don't understand the twin's paradox. (Or should I say it just goes over their heads?) It is practically a socio-physical theorem that there will always be people who don't understand it. You are living proof of it.
externo Posted April 19 Author Posted April 19 (edited) 34 minutes ago, joigus said: Will you just read what's answered to you??? Otherwise it's a monumental waste of time for everyone involved. (my emphasis.) The returning twin is subject to accelerations. Is it not? This is the major bone of contention with people who don't understand the twin's paradox. (Or should I say it just goes over their heads?) It is practically a socio-physical theorem that there will always be people who don't understand it. You are living proof of it. What is a acceleration ? it's a change in velocity, so if time dilation is not relative during a change in velocity it cannot be relative after this change, it's the same level of understanding as 1+1 = 2 If time dilation is relative during inertial journeys, how does the twin come back younger knowing that the total journey is only the sum of two inertial journeys? We must add a sudden aging of the Earth during the U-turn, but nothing of the sort occurs in the signals received by the traveler, the Earth does not age suddenly, so there is no physical symetrical time dilation during inertial journeys. The traveler ages less throughout the journeys. Edited April 19 by externo
joigus Posted April 19 Posted April 19 (edited) 15 minutes ago, externo said: it's the same level of understanding as 1+1 = 2 This is only true on a field that is of characteristic > 2. In discrete arithmetics it's not true that 1+1=2. In binary arithmetics 1+1=0 or 2=0 (mod2). The moral of my silly little story: Don't take anything for granted. Not even aether theory. Yes, I know what acceleration is. I wonder whether you do. As to your last statement, it went badly wrong the moment you wrote 'so if'. Because nothing you said after that follows from the antecedent. But don't mind me. Carry on with your enthralling conversation. Edited April 19 by joigus minor correction 2
Mordred Posted April 19 Posted April 19 (edited) 1 hour ago, externo said: You cannot prove that it remains invariant, on the other hand I proved in my first message that it cannot remain invariant. When an object accelerates it necessarily changes speed relative to light, which invalidates Einstein. Oh I certainly can show you 100's of professional peer reviewed literature showing light is invariant to all observers. The tests for lorentz invariance is literally up to 1 part in 10^18 for any possible variance. We literally test SR and GR every single day via particle accelerators etc the amount of research and tests involving the speed of light is astronomical Edited April 19 by Mordred
externo Posted April 19 Author Posted April 19 (edited) 19 minutes ago, Mordred said: Oh I certainly can show you 100's of professional peer reviewed literature showing light is invariant to all observers. The tests for lorentz invariance is literally up to 1 part in 10^18 for any possible variance. We literally test SR and GR every single day via particle accelerators etc the amount of research and tests involving the speed of light is astronomical This is impossible, the one-way speed of light cannot be measured: https://en.wikipedia.org/wiki/One-way_speed_of_light Lorentz's theory is based on a speed of light varying in one direction but = c on the average of the round trip. Edited April 19 by externo
swansont Posted April 19 Posted April 19 43 minutes ago, externo said: This is impossible, the one-way speed of light cannot be measured: https://en.wikipedia.org/wiki/One-way_speed_of_light Lorentz's theory is based on a speed of light varying in one direction but = c on the average of the round trip. And here you admit that there’s no way to test Lorentz’s theory, rendering it unscientific.
Mordred Posted April 19 Posted April 19 47 minutes ago, externo said: This is impossible, the one-way speed of light cannot be measured: https://en.wikipedia.org/wiki/One-way_speed_of_light Lorentz's theory is based on a speed of light varying in one direction but = c on the average of the round trip. Here is the thing modern physics and research states c is invariant to all observers. The modern tests make the Michelson and Morley experiments look like child's play. It has always been a heavily researched topic. It is far too critical in all major theories for any potential error.
swansont Posted April 19 Posted April 19 6 hours ago, externo said: How do you know that the speed of light is invariant? This is a eisteinian postulat, not a physical reality. A postulate based on electrodynamics, which has an invariant speed of light. And given the success of relativity, and its experimental confirmation, it is a physical reality. 6 hours ago, externo said: This has been proven, for example, walking droplets in oil baths obey Lorentz transformations while moving. Lorentz transformations are proof that matter consists of moving standing waves of ether. I am reminded of a certain Sidney Harris cartoon 6 hours ago, externo said: C is invariant, but the speed of light relative to moving objects is not. In the absence of gravitation the speed of light is invariant with respect to ether or space Nope. 6 hours ago, externo said: The Doppler effect comes from relative speed and is generated during the acceleration period. If you don't accelerate you can't move. So the Doppler effect somehow know about some prior acceleration? even if the signal isn't sent until after the object starts moving at constant velocity? That's magic, not science. 6 hours ago, externo said: So you say yourself that the space twin change is velocity and produces a Doppler effect, so if it is the one moving it is not the Earth that is moving and there is no physical symmetry. You've made this error a number of times. Changing velocity does not produce the Doppler shift. Repeating the assertion does not make it true. 6 hours ago, externo said: Matter waves, gravitaional waves, any ether waves. None of which are present in the twins paradox. 6 hours ago, externo said: What you say there is Einstein's interpretation. In this interpretation the lengths contract because the simultaneity physically changes. If simultaneity does not change physically there is no possible length contraction of. But an object which accelerates has no influence on outer space, it therefore cannot change the simultaneity of outer space, it can only change its own simultaneity, that is to say it physically transforms itself because the speed of light changes relative to him and he has to adapt. So the outer space has not changed in simultaneity so there is a simultaneity of the outer space and it is a privileged frame of reference. No. Your conclusion does not follow.
externo Posted April 19 Author Posted April 19 (edited) 42 minutes ago, swansont said: And here you admit that there’s no way to test Lorentz’s theory, rendering it unscientific. Einstein's postulate on the invariance of the one-way speed of light is untestable as well. 36 minutes ago, Mordred said: Here is the thing modern physics and research states c is invariant to all observers. The modern tests make the Michelson and Morley experiments look like child's play. It has always been a heavily researched topic. It is far too critical in all major theories for any potential error. The speed of light is invariant only over a round trip to all observers, making it impossible to decide between Einstein's and Lorentz's theories experimentally on this point. Edited April 19 by externo
swansont Posted April 19 Posted April 19 4 minutes ago, externo said: Einstein's postulate on the invariance of the one-way speed of light is untestable as well. It’s a postulate. The resulting theory is testable, and passes the tests.
Mordred Posted April 19 Posted April 19 (edited) 22 minutes ago, externo said: Einstein's postulate on the invariance of the one-way speed of light is untestable as well. The speed of light is invariant only over a round trip to all observers, making it impossible to decide between Einstein's and Lorentz's theories experimentally on this point. No I know the paper your referring to that proposed that. It was published well over a decade ago. I even recall numerous discussions on its merit on other forums. The claimed that supposed one way speed of light tests were two way tests All that did was motivate the physics community to develop new tests. This paper mentions some of those tests and regularly updated. https://arxiv.org/abs/2111.02029 Though this is the 2021 update. It's not even close to a complete list but it covers some of the major ones. Edited April 19 by Mordred 1
externo Posted April 19 Author Posted April 19 (edited) 1 hour ago, swansont said: A postulate based on electrodynamics, which has an invariant speed of light. And given the success of relativity, and its experimental confirmation, it is a physical reality. in electrodynamics the speed of light was invariant with respect to the ether. The success of special relativity is the success of Lorentz, not of Einstein, the constancy of the one-way speed of light is a useless hypothesis. 1 hour ago, swansont said: You've made this error a number of times. Changing velocity does not produce the Doppler shift. Repeating the assertion does not make it true. A change in velocity produces a change in the Doppler effect. 1 hour ago, swansont said: No. Your conclusion does not follow. My conclusion is absolutely logical. You have no arguments. If you were a little bit impartial, you would pose the problem and study the question of whether Lorentz or Einstein is consistent with physical reality. Einstein's interpretation has been proven false by many scientific papers. I have already cited this one : https://www.researchgate.net/publication/228609140_The_twin_paradox_in_special_relativity_and_in_Lorentz_ether_theory Why do you find it exciting to think that the speed of light is the same for all inertial observers when there is no proof of this phenomenon? 31 minutes ago, swansont said: It’s a postulate. The resulting theory is testable, and passes the tests. Lorentz theory passes the tests as well without this postulate. 19 minutes ago, Mordred said: No I know the paper your referring to that proposed that. It was published well over a decade ago. I even recall numerous discussions on its merit on other forums. All that did was motivate the physics community to develop new tests. This paper mentions some of those tests and regularly updated. https://arxiv.org/abs/2111.02029 Though this is the 2021 update. It's not even close to a complete list but it covers some of the major ones. I don't think that's the point. Lorentz's theory is an Lorentz invariant theory as well as Einstein's. As for general relativity, the difference between the interpretation of Einstein and Lorentz is that the ether is deformed by the effect of gravitation but remains a privileged reference frame, like a material deformed under tension. Edited April 19 by externo
Mordred Posted April 19 Posted April 19 (edited) 21 minutes ago, externo said: I don't think that's the point. Lorentz's theory is an Lorentz invariant theory as well as Einstein's. As for general relativity, the difference between the interpretation of Einstein and Lorentz is that the ether is deformed by the effect of gravitation but remains a privileged reference frame, like a material deformed under tension. No I'm familiar with the research that went into Lorentz ether theroy I also know it's transformation rules including many of the other variations . The thing is the physicists performing those Lorentz invariant tests are also well aware of neo-lorentz. So they also conducted tests for that in that article. Here is the detail many miss. In Lorentz time the only known particles were the photon the electron and the proton. That was at that time the entire standard model. The neutron wasn't even discovered until the mid 30's. So it was quite natural to think there was am ether. Modern physics has gone beyond that including particles that are so weakly interactive they could pass through a chunck of lead one light year in length without a single interaction. (Neutrinos). However it's also well known every particle species contributes to the blackbody temperature in particular the CMB including those neutrinos. So why do we not detect any temperature contribution from the Lorentz ether ? Why does it have no influence on universe expansion ? Every other particle does. The way is if you have a static 100 percent non interacting field but then it wouldn't even interact with gravity let alone photons. Or any other particle. We can certainly gather indirect or direct evidence of every other particle in the standard model. Why not the Lorentz ether ? 37 minutes ago, externo said: I don't think that's the point. Lorentz's theory is an Lorentz invariant theory Then why would you claim otherwise and argue that c isn't invariant ? Sounds like you don't even understand Lorentz ether theory.... 40 minutes ago, externo said: I don't think that's the point. Lorentz's theory is an Lorentz invariant theory Then why would you claim otherwise and argue that c isn't invariant ? Sounds like you don't even understand Lorentz ether theory.... in point of detail. Had you actually studied its mathematics. It was a valiant effort to meet observational evidence and keep c invariant to all observers. That is actually harder than one realizes when you have light travellings through a medium. Edited April 19 by Mordred
swansont Posted April 19 Posted April 19 49 minutes ago, externo said: Lorentz theory passes the tests as well without this postulate. Lorentz theory is ad-hoc. There’s no independent evidence of an ether. Are we moving with respect to the ether, or are we stationary with respect to it?
Mordred Posted April 19 Posted April 19 5 minutes ago, swansont said: Lorentz theory is ad-hoc. There’s no independent evidence of an ether. Are we moving with respect to the ether, or are we stationary with respect to it? That's the real crux a total lack of evidence.
Markus Hanke Posted April 20 Posted April 20 (edited) 19 hours ago, externo said: You are talking about mathematics I was talking about something you claimed - that SR cannot handle acceleration. This is manifestly wrong, because it very much can. 19 hours ago, externo said: I talk about the physical interpretation of these equations What interpretations? The ether in LET is by design undetectable, and its presence has no physical consequences, thus both SR and LET make identical predictions. This isn’t a matter of interpretation, but belief - do you choose to believe and assume the presence of an entity that cannot be detected, has no physical consequences, and is not actually needed to obtain the correct dynamics? 19 hours ago, externo said: There is no doubt that Lorentz's interpretation works because it uses classical kinematics, but Einstein's interpretation uses a anomalous kinematics that must be proven consistent with the physical world. Not only has SR been exhaustively tested over the past ~120 years and thus shown to be consistent with the physical world, but we also use it directly in many aspects of modern technology. A lot of parts of the very machine you are using to make your posts here have been designed based directly or indirectly on SR, and it evidently works well. Also, SR kinematics are classical, just like Newtonian kinematics are. 13 hours ago, externo said: But there is quaternionic spacetime where time is the scalar dimension of space But APS is just based on a subgroup of the full Cl(1,3) Clifford spacetime algebra…? It is a convenient and very useful formalism, but hardly new physics. 6 hours ago, externo said: I have already cited this one : RG is a social network, not a peer review journal. Some stuff there is useful, but one has to use caution. Personally, I stopped reading when the author first talked about twins in Minkowski spacetime, and then gave a scenario as example where one twin is in orbit around a star. Not an especially convincing paper, and the author clearly has an agenda. Edited April 20 by Markus Hanke
Markus Hanke Posted April 20 Posted April 20 On 4/18/2024 at 4:28 PM, externo said: You cannot resolve the paradox with Einstein's SR The discussion seems to be going off on a lot of tangents now, so I propose we bring it back to the above original claim. Here’s how I would approach this personally: The twin scenario concerns two clocks (E-Earth, T-Travelling) which start together at rest at some event A; twin T then separates for a period and eventually they reunite again at rest at another event B. In SR, the total accumulated time on a clock travelling between a pair of events is defined to equal the geometric length of the worldline traced out by that clock through spacetime: \[\tau=\int_{C}ds\] where C(t,x) is the path taken. Since in SR we have \[ds=\sqrt{\eta_{\mu \nu } dx^{\mu}dx^{\nu}}\] we get, for the Earth-bound twin (no change in spatial location!): \[\tau_{E}=\int_{A}^{B}\sqrt{\eta_{\mu \nu } dx^{\mu}dx^{\nu}}=\int_{A}^{B}\sqrt{\eta_{tt}}=c\int_{A}^{B}dt\] For the travelling twin, on the other hand, we get: \[\tau_{T}=\int_{C}\sqrt{\eta_{\mu \nu } dx^{\mu}dx^{\nu}}=\int_{C}\sqrt{c^2dt^2-dx^2-dy^2-dz^2}\] wherein we don’t assume any specifics about the path C, other than that it connects A and B, and remains light-like everywhere. I invite you to verify yourself that \[\tau_{T} < \tau_{E}\] by choosing any light-like path C and running the numbers in these line integrals. What this means is that, in SR, an inertial clock will always trace out the longest path through spacetime between events, ie it will accumulate the most time. Any path deviating from being a geodesic will necessarily be shorter (or vice versa, depending on your sign convention). Since the travelling twin starts out at rest wrt to its partner, but then travels away, it cannot remain on a geodesic - thus SR guarantees that its clock accumulates less time than the Earth-bound twin. Far from being a paradox, it is a natural consequence of the geometry of spacetime. Note that I made no assumptions here about the specific form of the path C, only that it is light-like and runs through A and B; thus it is realisable by any test particle with mass. So yes, SR very much can resolve this, contrary to your claim. It should also be explicitly noted that the total time dilation does not depend on the magnitude of acceleration at any one instant, but only on the total path length of the world line. Lastly, an experimental test of these predictions can be made by comparing the decay rates of unstable particles in accelerators against stationary reference samples. See eg Bailey et al (1977) with regards to CERNs muon storage ring.
Recommended Posts