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Quote from: Hal on 09/03/2021 02:53:52Consider a hypothetical terrestrial light speed experiment. Assume that the speed of light is constant in the reference frame of the Earth. For you it is an inertial reference frame and for me it is an absolute reference frame.There is a sationary light source at some point on the Earth. Let’s say the north pole then, one of the few way one can be easily stationary relative to the inertial frame of Earth. Alternatively we could just presume a non-spinning flat Earth with zero mass. It is unclear what purpose is served by there being a large mass underneath our observers. I presume Earth is stationary in this absolute reference frame above, so we’re talking the same frame then. If this is not so, you need to specify.All measurements without a frame reference as assumed to be relative to this frame.Quote from: Hal on 09/03/2021 12:54:27I think since v is much smaller than c so that gamma factor is almost equal to one, clock synchronization is not a problem. It has nothing to do with gamma. You said ‘distant observer’, so the sync convention means everything.We’ll assume all stationary clocks are synced in Earth’s frame, but realize that it means they are very much not in sync in other frames, even ones with low velocity differences relative to our Earth frame.QuoteA distant observer is moving directly away from the source with velocity V , along the line connecting the source and the observer.OK, so he’s say 300 km away and moving away, not moving with the spin of the planet below. The light goes that far in a millisecond.QuoteWe have synchronized clocks both at the source and at the observer.No we don’t. Clocks moving relative to each other cannot be meaningfully in sync since they run at different rates relative to each other. Relative to Earth, the moving clock runs slow.Perhaps you can reword it as the moving observer passing a clock stationary to the first one. That works at least.QuoteThe light source emits a short light pulse. At the instant of emission, the distance between the source and the observer is D.That observer event is useless since he doesn’t observe anything then. OK, he passes a clock 1 at that time, and it reads time zero since that’s the time of the emission event. Clock 1 is D away from the pole where the pulse is emitted. Clock 2 is stationary, synced, and located where the observer will be when the pulse is observed, which is insanely close to clock1 since they’re separated only by how far our slow moving observer travels in about a millisecond.QuoteMy question is, according to special relativity, what will be the time interval between emission and detection of the light pulse? Is it D/c or D / ( c - V ) ?D/c is when the pulse reaches clock1. D/(c-V) is the time to get to the observer as measured by clock 2, but not as measured by a clock carried by our observer since no sync convention was specified for it. Perhaps it was synced with clock 1 when in its presence, but your story didn’t say. Relatively moving clocks can be synced to each other when in each other’s presence, but no matter the convention, they cannot stay in sync.QuoteYou cannot claim that we would not be able to know the distance to the moon if it was not for special relativity.SR would not give a distance to the moon at all. As measured by an Earth clock, light moves at greater than c between Earth and moon (or Mars say). SR is not applicable in a situation where gravity is involved, and it is very much involved in this scenario.
Consider a hypothetical terrestrial light speed experiment. Assume that the speed of light is constant in the reference frame of the Earth. For you it is an inertial reference frame and for me it is an absolute reference frame.There is a sationary light source at some point on the Earth.
I think since v is much smaller than c so that gamma factor is almost equal to one, clock synchronization is not a problem.
A distant observer is moving directly away from the source with velocity V , along the line connecting the source and the observer.
We have synchronized clocks both at the source and at the observer.
The light source emits a short light pulse. At the instant of emission, the distance between the source and the observer is D.
My question is, according to special relativity, what will be the time interval between emission and detection of the light pulse? Is it D/c or D / ( c - V ) ?
You cannot claim that we would not be able to know the distance to the moon if it was not for special relativity.
Goal: We have shown using the GPS synchronized clocks that the speed of light between fixed points on the surface of the Earth is not the same in all directions; light travels faster west than east! GPS engineers try to mask this fact by assuming light speed c and making the so-called "Sagnac Correction". However, if the correct speed is used, then there is no need for any correction.The light speed postulate of special relativity also requires that light speed be independent of the movement of the observer. (We know that it is independent of the movement of the source.) This requirement of the postulate has received little or no attention, even though this is the aspect of the postulate that is so hard to swallow. It has not been confirmed experimentally. In this paper I have listed three tests of this aspect of the postulate which show clearly that light speed is not independent of the movement of the observer.
Let me restate the problem to avoid misunderstandings.Consider an inertial reference frame S. A light source is at rest at the origin of S, together with clock A. A distant observer is moving directly away from the source with velocity v which is much less than the speed of light c.. The rest frame of the observer is S'. The observer is at the origin of S'.The observer has clock B. Clocks A and B are synchronized when the origins of S and S' coincide.The light source emits a short light pulse. At the instant of light emission the observer is at distance D from the light source, both relative to frame S.
My first question is:What is the time interval between emission and detection of the light pulse as measured by (according to ) clock A and by clock B, according to special relativity?
My second question is:Is your answer supported by experiments?
https://www.researchgate.net/project/Tests-of-the-One-way-Speed-of-Light-Relative-to-a-Moving-ObserverQuote... the speed of light between fixed points on the surface of the Earth is not the same in all directions; light travels faster west than east! GPS engineers try to mask this fact by assuming light speed c and making the so-called "Sagnac Correction".Has anyone worked with GPS to confirm or refute the claim?
... the speed of light between fixed points on the surface of the Earth is not the same in all directions; light travels faster west than east! GPS engineers try to mask this fact by assuming light speed c and making the so-called "Sagnac Correction".
This is because their 'fixed points' are fixed only in a rotating frame of reference,
One of the practical problems with applying special relativity is Einstein wrote the theory with three variables, mass, distance and time.
Could whomever is hacking my computer stop.
Could whomever is hacking my computer stop. I am getting warning signal that this web page is using too much energy. I don't have time for the delay it is causing. My RAM is tight and piggybacking signals me
Quote from: hamdani yusuf on 14/03/2021 12:39:28https://www.researchgate.net/project/Tests-of-the-One-way-Speed-of-Light-Relative-to-a-Moving-ObserverQuote... the speed of light between fixed points on the surface of the Earth is not the same in all directions; light travels faster west than east! GPS engineers try to mask this fact by assuming light speed c and making the so-called "Sagnac Correction".Has anyone worked with GPS to confirm or refute the claim?West does not define a unique direction, since west for me is the exact opposite direction as west in Beijing. This is because their 'fixed points' are fixed only in a rotating frame of reference, and yes, in such a frame, light travels faster west than east, exactly as mandated by SR. SR could be falsified immediately if the Sagnac effect didn't work. In a light tube going around the Earth, light has less distance to move in the west direction than in the east direction, so of course the westbound light gets to the moving source/detect faster than the eastbound. The Sagnac effect relies on that fact to detect absolute rotation.This paper is pretty crackpot sounding since they're billing this as some sort of surprise result despite it being known for over a century. The second paragraph you quote demonstrates a complete lack of understanding of introductory relativity concepts.
Quote from: Hal on 15/03/2021 19:41:29I think that the frame of the fixed points has the same privilege as the Earth centered inertial frame, according to special relativity. Therefore, the speed of light should be constant in that frame also, because it is approximately inertial.Neptune is moving faster than light in that frame. It seems in no way 'approximately inertial'. ECI isn't even inertial, but it at least isn't rotating. Any rotating frame needs the corrections for the rotation. Any inertial frame is pretty useless for a precise reference frame since there seem to be no stationary references to anchor the frame orientation. So they use the non-inertial frame like ECEF and make adjustments, and they don't plot the motion of Neptune in this coordinate system (OK, the pre-Copernican astronomers actually did plot the location of the planets in such a frame).I notice that the author of the paper claims to have measured the one-way speed of light, which puts him in the same bin as the perpetual motion inventors.QuoteYour argument is that the difference in time delays of light in the two directions is because light travels unequal distances in the two directions in the Earth centered inertial frame.Between two points on the Earth's surface, yes, since those 'points' are actually moving eastward in the ECI frame. It's pretty obvious that if there are two observers, one following the other with identical velocity (relative to frame F) along the x axis, then relative to F, light is going to take more time to go from the rear one to the front one than v-v.QuoteBut the observer in the frame of the fixed points also has the right to consider the light to travel equal distances in both directionsYes, in that inertial frame (not in some non-inertial one like ECEF where the sync convention differs significantly), light travel time is indeed identical in both directions. So no contradiction with relativity there.
I think that the frame of the fixed points has the same privilege as the Earth centered inertial frame, according to special relativity. Therefore, the speed of light should be constant in that frame also, because it is approximately inertial.
Your argument is that the difference in time delays of light in the two directions is because light travels unequal distances in the two directions in the Earth centered inertial frame.
But the observer in the frame of the fixed points also has the right to consider the light to travel equal distances in both directions
Consider repeating the experiment in an inertial frame moving in the ECI frame. This frame, unlike the frame of the fixed points on Earth, is not moving with the Earth. Assume that this frame has the same velocity as the frame of the Earth fixed points. The distance between the two points is the same.
What is the prediction of special relativity in the two cases.
QuoteWhat is the prediction of special relativity in the two cases.That's easy. Relative to that inertial frame, light takes the same time to go in either direction since the two mailboxes are both stationary. That's one case. There was another one?
Let me be more clear.
Let us compare the predictions of special relativity for two experiments, the first one is real and the second one hypothetical.
You measure the speed of light in both directions between two points fixed on Earth.
One point is to the east relative to the other, like the mail boxes. The tangential velocity of the two points is around v = 500 m/s.
To make the reference frame of the two fixed points as inertial as possible, imagine that the radius of the Earth is increased enormously, but its rotation speed decreased by the same factor so that the tangential velocity of two nearby points is still 500 m/s eastwards.
If special relativity predicts that the time delay of light is different in the two directions in the first experiment, what is the prediction of special relativity ( SRT) in the second experiment?
If SRT predicts that the time delay of light in the two directions is the same
at which point ( at which hypothetical radius of the Earth) does SRT switch the way it treats the problem?
At which hypothetical Earth radius does SRT start considering the reference frame of
That's easy. Relative to that inertial frame, light takes the same time to go in either direction since the two mailboxes are both stationary. That's one case. There was another one?
The solution is we will try to use space and time; photons, to simulate and estimate the mass. This is two variables; 2-D, used to model 3-D. This is nobody's fault, but it is what we have to deal with.
While positions on or near the Earth can be precisely determined using the GPS based onlight speed constancy in the Earth-Centered Inertial (ECI) frame, the orbital ephemerides of theplanets and other bodies in the solar system are determined using a different set of equationsoperating within the solar barycentric or sun-centered inertial (SCI) frame [31-33]. The SCIframe is a frame that moves with the Sun but does not rotate with it and provides a convenientreference frame for many astronomical events. The associated equations are used to determineround-trip time of an electromagnetic signal that emanates from a transmitting antenna on Earthand is reflected by a spacecraft transponder or planetary body back to the same antenna on Earth.Time measurement is effected using atomic clocks based on Coordinated Universal Time (UTC)and the spatial coordinates are relative to the solar-system barycenter of the SCI frame.
Where is the boundary between ECI system and SCI system?
How far away from earth that light speed is still constant in ECI?How far away from the sun that light speed is still constant in SCI?
Solar system barycenter can be outside of the sun. How does this affect the calculation of the light speed in SCI?
Quote from: Hal on 16/03/2021 05:14:57QuoteYou measure the speed of light in both directions between two points fixed on Earth.And how are you going to do that? If the process involves more than one clock, how are the clocks synced? SR assumes by convention that light speed is identical in all directions relative to any inertial frame, but it does not propose a method to actually prove that. That the speed of light will be measured the same in any frame is a premise, not a conclusion. So we assume that the speed of light in both directions between two points fixed on Earth is c. We don't measure that.QuoteOne point is to the east relative to the other, like the mail boxes. The tangential velocity of the two points is around v = 500 m/s.If the mailboxes have a tangential velocity, then they're not fixed points, are they? This is why you need frame references. The velocity of mailboxes is anything you want it to be depending on the frame you specify, but you need to specify one. Instead of mailboxes, lets just use precision devices at opposite ends of a nice marble slab in a laboratory somewhere, arranged in an east/west orientation.No experiment has been described. We just have two objects and a proposal of a measurement without actually describing how that measurement is to be taken.QuoteTo make the reference frame of the two fixed points as inertial as possible, imagine that the radius of the Earth is increased enormously, but its rotation speed decreased by the same factor so that the tangential velocity of two nearby points is still 500 m/s eastwards.Again, they're not points if they have nonzero velocity. They're moving objects whose location changes over time. Our lab on earth is fine. The objects being close and the experiment being brief serves the same purpose as making Earth bigger. It's is locally inertial motion, so we're fine.QuoteIf special relativity predicts that the time delay of light is different in the two directions in the first experiment, what is the prediction of special relativity ( SRT) in the second experiment?No frame reference specified and no actual measurement procedure proposed, so SR does not predict an outcome to the undefined procedure.If SRTstill predicts that the time delay of light is different in the two directions (as in the first experiment), this would be a self contradiction of SRT because the reference frame in the second experiment is almost inertial.
QuoteYou measure the speed of light in both directions between two points fixed on Earth.And how are you going to do that? If the process involves more than one clock, how are the clocks synced? SR assumes by convention that light speed is identical in all directions relative to any inertial frame, but it does not propose a method to actually prove that. That the speed of light will be measured the same in any frame is a premise, not a conclusion. So we assume that the speed of light in both directions between two points fixed on Earth is c. We don't measure that.QuoteOne point is to the east relative to the other, like the mail boxes. The tangential velocity of the two points is around v = 500 m/s.If the mailboxes have a tangential velocity, then they're not fixed points, are they? This is why you need frame references. The velocity of mailboxes is anything you want it to be depending on the frame you specify, but you need to specify one. Instead of mailboxes, lets just use precision devices at opposite ends of a nice marble slab in a laboratory somewhere, arranged in an east/west orientation.No experiment has been described. We just have two objects and a proposal of a measurement without actually describing how that measurement is to be taken.QuoteTo make the reference frame of the two fixed points as inertial as possible, imagine that the radius of the Earth is increased enormously, but its rotation speed decreased by the same factor so that the tangential velocity of two nearby points is still 500 m/s eastwards.Again, they're not points if they have nonzero velocity. They're moving objects whose location changes over time. Our lab on earth is fine. The objects being close and the experiment being brief serves the same purpose as making Earth bigger. It's is locally inertial motion, so we're fine.QuoteIf special relativity predicts that the time delay of light is different in the two directions in the first experiment, what is the prediction of special relativity ( SRT) in the second experiment?No frame reference specified and no actual measurement procedure proposed, so SR does not predict an outcome to the undefined procedure.
If I detect difference in propagation times of light in opposite directions between two points in a closed lab on Earth, this is nothing other than detection of absolute motion (remember Galileo’s ship thought experiment).