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the Atemporal Universe - Resolving the Problem of Time

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  • Registered Users Posts: 2,552 ✭✭✭roosh


    You may have missed it previously, so I'll put it at the top this time.

    Can you at least see that there is an alternative interpretation, one which doesn't rely on RoS, an Ether, or an absolute reference frame??
    Fourier wrote: »
    Well although I used the word "assume" I should say she "finds" it to be a functioning definition of time as she will empirically observe it and her definitions of spatial directions to satisfy the axioms of a coordinate system. So the assumption isn't that it behaves like a functioning coordinate definition of time, empirically it does.
    There's no need to backtrack. Your wording was correct in the first instance.

    You touch on an important point above, something I have been repeatedly trying to emphasise, namely what is empirically observed. The clock synchronisation experiment allows us to investigate this and, as has been repeatedly stressed, the totality of emprical observations demonstrate that the [clock synchronisation] events in her "stationary frame" were not simultaneous.

    It is not possible for her to extract empirical evidence - from the totality of empirical observations - for her assumption of simultaneity of the [clock synchronisation] events, in her "stationary system". The empirical evidence supporting her assumption of this simultaneity, simply does not exist, it can only be assumed.

    That this totality of empirical evidence supports her interpretation is similar to the way in which the totality of the empirical evidence that a universe exists, supports the position that a Flying Spaghetti Monster created the universe - it is entirely based on assuming the conclusion.
    Fourier wrote: »
    The "assumption" is simply that if it empirically seems like a coordinate system on a 4D space, then it is a coordinate system on a 4D space.
    It only seems like that if one makes the assumption that events in their own frame of reference are simultaneous, despite the totality of empirical evidence demonstrating that those events are not simultaneous.

    I was going to say that, it only seems like one is living in a universe created by a Flying Spaghettti Monster if one assumes that they are but actually, I don't think it works like that. Maybe more like this:

    It would be more like having observational evidence of the Universe being created, with no sign of a Flying Spaghetti Monster, and saying that it if it empirically seems like living in a universe created by a Flying Spaghetti Monster, then it is such a universe.

    It needs a bit of work, I know.


  • Registered Users Posts: 10,558 ✭✭✭✭Fourier


    It is not possible for her to extract empirical evidence - from the totality of empirical observations - for her assumption of simultaneity of the [clock synchronisation] events, in her "stationary system"
    I don't know how many more times this can be repeated if I'm honest, if there isn't much progress on this I will have to leave the conversation as it will simply consist of repeating the same points again and again.

    The only necessary thing is that her definition of her temporal coordinate along with her spatial coordinates satisfies the axioms of a coordinate system. Do you understand this initial point that her working definition of time, along with the three spatial dimensions, satisfies the axioms of a coordinate system?


  • Registered Users Posts: 2,552 ✭✭✭roosh


    I'm not playing "gotcha" when I ask: can you see that there are two empirically equivalent, contradictory interpretations? You can take that to mean the Lorentz-Poincare Ether theory if you like, but do you acknowledge that two such interpretations exist?
    Fourier wrote: »
    I don't know how many more times this can be repeated if I'm honest, if there isn't much progress on this I will have to leave the conversation as it will simply consist of repeating the same points again and again.

    The only necessary thing is that her definition of her temporal coordinate along with her spatial coordinates satisfies the axioms of a coordinate system. Do you understand this initial point that her working definition of time, along with the three spatial dimensions, satisfies the axioms of a coordinate system?
    The contention isn't that the Minowski metric doesn't satisfy the axioms of a co-ordinate system. Again, the Minkowski interpreation is one of [at least] 2 competing interpretations and the Einsteinian/Minkowski metric is internally self-consistent. There is no contention there.

    Regardless of how the discussion is framed, the thought experiment represents a plausible, real-world experimental set-up that can be used to examine the competing interpretations - even if there were only one interpretation, the thought experiment could be used to to examine it. Examining this plausible, real-world set-up, allows us to draw conclusions and make inferences about the competing interpretations, what they necessitate, and how they interpret experimental results. Do you agree with this point?


  • Registered Users Posts: 3,457 ✭✭✭Morbert


    I'll try and avoid treading old ground. You made an important statement here:
    Yes, she assumes - assumes being the operative word - that it is a functioning way of defining time for her own purposes and she also knows that others will disagree with it. The whole point being made is that Alice assumes it is functioning way of defining time, while others base their disagreements on emprical observations.

    There's nothing problematic with her assuming that her frame of reference offers a functioning way of defining time for her own purposes (as opposed to her assuming some metaphysical fact about her synchronised clocks, which she does not do). Others will not disagree though. They will have no problem acknowledging that her frame of reference is suitable for her purposes.


  • Registered Users Posts: 10,558 ✭✭✭✭Fourier


    roosh wrote: »
    I'm not playing "gotcha" when I ask: can you see that there are two empirically equivalent, contradictory interpretations? You can take that to mean the Lorentz-Poincare Ether theory if you like, but do you acknowledge that two such interpretations exist?
    There are a few different versions of the Lorentz-Poincaré interpretation, I don't want to get into discussing them while we're still talking about the standard interpretation.
    roosh wrote:
    The contention isn't that the Minowski metric doesn't satisfy the axioms of a co-ordinate system
    The Minkowski metric cannot satisfy the axioms because it is a metric, not a coordinate system.
    roosh wrote:
    Regardless of how the discussion is framed, the thought experiment represents a plausible, real-world experimental set-up that can be used to examine the competing interpretations - even if there were only one interpretation, the thought experiment could be used to to examine it. Examining this plausible, real-world set-up, allows us to draw conclusions and make inferences about the competing interpretations, what they necessitate, and how they interpret experimental results. Do you agree with this point?
    Yes, although within limits. In some cases what are initially interpretations actually lead to different predictions. In some cases they're purely a different conceptualisation of the symbols of the mathematics.

    As Morbert says above, she's not assuming anything about her clocks. She's simply defining her coordinate system through a well-defined procedure that results in four coordinates satisfying the usual axioms for such systems. Other observers will not hold the same notion of simultaneous but they will agree that hers is a valid coordinate system.
    Then all coordinates are related by a group which has the Minkowski space as its homogeneous space, homogeneous here meaning it is the simplest space with that group as its symmetry group.

    Thus if you have a bunch of observers all holding valid coordinate systems and all of those coordinates are related via a well-defined group, the simplest thing to do is just to conceptualise this as being due to everybody living on the simplest space carrying that group as a symmetry. In this case Minkowski space.


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  • Registered Users Posts: 2,552 ✭✭✭roosh


    Morbert wrote: »
    I'll try and avoid treading old ground. You made an important statement here:

    There's nothing problematic with her assuming that her frame of reference offers a functioning way of defining time for her own purposes (as opposed to her assuming some metaphysical fact about her synchronised clocks, which she does not do). Others will not disagree though. They will have no problem acknowledging that her frame of reference is suitable for her purposes.
    Again, the internal consistency of the Einsteinian interpretation is not being challenged here. The above is all fine as it is simply a statement as to what the Einsteinian interpretation is.

    While you suggest that she is not making a metaphysical assumption about her synchronised clocks, she is making the assumption that her clocks are synchronised - whether this is a metaphysical claim or not is irrelevant. Well, apart from the fact that her assumption that her clocks are synchronised has metaphysical consequences pertaining to simultaneity. To put it more plainly, while her choice of a mathematial co-ordinate system might not [strictly] be a metaphysical claim, its description of the physcial world certainly has metaphysical implications. It is not the only possible interpretation, however.


    As I've asked Fourier, do you at least acknowledge that there are [at least] 2 mutually exclusive, interpretations of the evidence?

    Also, do you agree that regardless of how the discussion is framed, the thought experiment represents a plausible, real-world experimental set-up that can be used to examine the competing interpretations - even if there were only one interpretation, the thought experiment could be used to to examine it. Examining this plausible, real-world set-up, allows us to draw conclusions and make inferences about the competing interpretations, what they necessitate, and how they interpret experimental results.


  • Registered Users Posts: 10,558 ✭✭✭✭Fourier


    roosh wrote: »
    While you suggest that she is not making a metaphysical assumption about her synchronised clocks, she is making the assumption that her clocks are synchronised
    She's not.

    She can check if her definition of t,x,y,z (or however she paramterises space) satisfies the definition of a coordinate system. They do. Then she simply can check if under such a definition are the t values of those two events equal. They are.

    Thus purely mathematically she has a coordinate system with two events at times t_1 and t_2 obeying t_1 = t_2. She hasn't been forced to assume anything. Her notions of time and space form a consistent set of coordinates and those different events occur at the same time value. No different from somebody setting up "forward-back" and "left-right" coordinates for the land about them and concluding two things are directly left.


  • Registered Users Posts: 2,552 ✭✭✭roosh


    Fourier wrote: »
    There are a few different versions of the Lorentz-Poincaré interpretation, I don't want to get into discussing them while we're still talking about the standard interpretation.
    That's fair enough. I think, for now, it should probably suffice to say that there are [at least] 2 mutually exclusive interpretations.
    Fourier wrote: »
    The Minkowski metric cannot satisfy the axioms because it is a metric, not a coordinate system.
    Apologies, I have a tendency to sometimes use collocations imprecisely. Nevertheless, the contention isn't that the Einstein/Minkowski interpretation employs co-ordinates that don't satisfy the axioms of co-ordinate systems. That is to say, it's internal consistency is not being questioned.

    Indeed, Poincaré anticipated the seminal work of Herman Minkowski on the four-dimensional formulation of special relativity. However, unlike relativity in four-dimensional space-time, in the ether theory these properties represent mere mathematical niceties that do not have a physical meaning. (Acuna - On the Empirical Equivalence between  Special Relativity and Lorentz’s Ether Theory). So  presumably the same is true for the Lorentz-Poincare interpretation.

    Fourier wrote: »
    Yes, although within limits. In some cases what are initially interpretations actually lead to different predictions. In some cases they're purely a different conceptualisation of the symbols of the mathematics.
    We can try to stick within those limits.
    Fourier wrote: »
    As Morbert says above, she's not assuming anything about her clocks. She's simply defining her coordinate system through a well-defined procedure that results in four coordinates satisfying the usual axioms for such systems. Other observers will not hold the same notion of simultaneous but they will agree that hers is a valid coordinate system.
    Then all coordinates are related by a group which has the Minkowski space as its homogeneous space, homogeneous here meaning it is the simplest space with that group as its symmetry group.
    The choice of mathematical co-ordinates does not determine whether or not her physical clocks are synchronized with each other - regardless of whether they satisfy the axioms or not. That is to say, clocks in the physical world are not synchronised using mathematics.

    The co-ordinate system- and the choice thereof - can only serve as a description of the physical world. Indeed, in certain cases - as per Poincare's four-dimensional formalism - those co-ordinate systems can be viewed, not as descriptions of the physical world  but, as mathematical tools.
    Fourier wrote: »
    Thus if you have a bunch of observers all holding valid coordinate systems and all of those coordinates are related via a well-defined group, the simplest thing to do is just to conceptualise this as being due to everybody living on the simplest space carrying that group as a symmetry. In this case Minkowski space.
    This is one possible interpretation.

    Fourier wrote: »
    She's not.

    She can check if her definition of t,x,y,z (or however she paramterises space) satisfies the definition of a coordinate system. They do. Then she simply can check if under such a definition are the t values of those two events equal.

    Thus purely mathematically she has a coordinate system with two events at times t_1 and t_2 obeying t_1 = t_2. She hasn't been forced to assume anything. Her notions of time and space form a consistent set of coordinates and those different events occur at the same time value. No different from somebody setting up "forward-back" and "left-right" coordinates for the land about them and concluding two things are directly left.
    In the [plausible] real-world, experimental set-up, Alice does not perform the synchronisation procedure purely mathematically. She performs it using physical equipment and physical clocks.


    We can use the time labels you use above - times t_1 and t_2 - and see if we can make progress. Obviously times t_1 and t_2 refer to readings on physical clocks, as opposed to being purely mathematical labels.


    Imagine the thought experiment again: Alice is located at the mid-point between her two clocks ( call them B1 and B2); she is co-located with her emitter and a clock (clock A - used to provide timestamps for events).
    t_0 is the time she sends the light signals. Imagine that the clock ticks uniformly with increasing increments: t_1, t_2, t_3, etc.

    Let's also label the events:
    B1 = light pulse making physical contact with clock B1
    B2 = light pulse making physical contact with clock B2


    At t_0, Alice sends a light pulse in the direction of each clock. How does she determine:
    a) the reading on her physical clock A, that co-incides with event B1
    b) the reading on her physical clock A, that co-incides with event B2
    c) that events B1 and B2 have the same timestamp i.e. that they are simultaneous

    How does she determine the readings on her physical clocks? Bearing in mind that her choice of mathematical co-ordinates doesn't determine what she observes.


  • Registered Users Posts: 10,558 ✭✭✭✭Fourier


    Apologies, I have a tendency to sometimes use collocations imprecisely
    They are completely different concepts and I've never known anybody familiar with Relativity to mix them up. Can I ask what books you have read on the subject? This might provide a better path for discussion. I suspect you are not familiar enough with Special Relativity to see the point being made here.
    In the [plausible] real-world, experimental set-up, Alice does not perform the synchronisation procedure purely mathematically. She performs it using physical equipment and physical clocks.
    You're making an artificial division between physics and mathematics. Defining something as simultaneous experimentally necessarily involves mathematics because you need to define a parameter t, assign values of t to two events giving you t_1 and t_2 and then check that t_1 = t_2 from your recordings.
    Obviously times t_1 and t_2 refer to readings on physical clocks, as opposed to being purely mathematical labels
    Once again this is an artificial division. What is "purely mathematical"? You've stated this above and I believe this is exactly why you are missing the point. Alice's operational definition of time from her equipment combined with similar definitions of the spatial directions obeys the mathematical axioms of a coordinate system. There is no division between "pure mathematics" and "physics" of the sort you are using here. Mathematics is simply the precise symbolic language with which we discuss physics. Your objection is analogous to:
    Obviously "Alice's clock" refers to an actual physical clock not to purely lexemic English language labels


  • Registered Users Posts: 2,552 ✭✭✭roosh


    Fourier wrote: »
    They are completely different concepts and I've never known anybody familiar with Relativity to mix them up. Can I ask what books you have read on the subject? This might provide a better path for discussion. I suspect you are not familiar enough with Special Relativity to see the point being made here.
    I haven't read any books on that specific topic, I've encountered the term in my [self study] of Relativity. But, there is no contention of the point. I'm content that it does obey the axioms of co-ordinate systems and that it is internally consistent.

    It represents one of [at least] 2 contradictory interpretations. So, the point is moot, unless your contention is that the Lorentz-Poincare interpretation doesn't obey the axioms of a co-ordinate system.
    Fourier wrote: »
    You're making an artificial division between physics and mathematics. Defining something as simultaneous experimentally necessarily involves mathematics because you need to define a parameter t, assign values of t to two events giving you t_1 and t_2 and then check that t_1 = t_2 from your recordings.
    The thought experiment represents that checking of recordings. It is entirely the case in point.

    At t_0, Alice sets the light pulses off towards clocks B1 and B2; clock A is ticking uniformly - at any rate it is the same for both signals; how does Alice determine what reading on clock A co-incides with event B1 and the reading on clock A that co-incides with event B2?

    I'm not asking for you to tell me what the reading is, rather how she determines what it is. Bearing in mind that light must travel from the clocks to her so that she can actually make an observation.
    Fourier wrote: »
    Once again this is an artificial division. What is "purely mathematical"? You've stated this above and I believe this is exactly why you are missing the point. Alice's operational definition of time from her equipment combined with similar definitions of the spatial directions obeys the mathematical axioms of a coordinate system. There is no division between "pure mathematics" and "physics" of the sort you are using here. Mathematics is simply the precise symbolic language with which we discuss physics. Your objection is analogous to:
    Obviously "Alice's clock" refers to an actual physical clock not to purely lexemic English language labels
    How does she determine the reading on her physical clock A that co-incides with event B1 and the reading on clock A that corresponds to event B2 - bearing in mind the travel time/distance for light signals involved in making observations.


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  • Registered Users Posts: 10,558 ✭✭✭✭Fourier


    I haven't read any books on that specific topic
    I'm asking what books have you read on Relativity in general, textbooks specifically so that I can refer to them.
    So, the point is moot, unless your contention is that the Lorentz-Poincare interpretation doesn't obey the axioms of a co-ordinate system.
    Even here I think you don't understand. The Lorentz-Poincaré interpretation doesn't "obey the axioms of a coordinate system", neither does the standard interpretation. Alice's operational definition of her four spatio-temporal parameters does.
    How does she determine the reading on her physical clock A that co-incides with event B1 and the reading on clock A that corresponds to event B2 - bearing in mind the travel time/distance for light signals involved in making observations.
    We all know the procedure. What is the purpose in asking this? It's based solely on the constancy of the speed of light ultimately.


  • Registered Users Posts: 2,552 ✭✭✭roosh


    Fourier wrote: »
    I asking what books have you read on Relativity in general, textbooks specifically so that I can refer to them.
    I generally tend to download textbooks and go straight to the parts that are of interest, without necessarily taking note of the name. At the moment I've got books by Feynman; Physics: principles and applications by Giancoli; the Problem of Time by Anderson; and an uncountable number of online material. Oh, and @Morbert =D

    Fourier wrote: »
    Even here I think you don't understand. The Lorentz-Poincaré interpretation doesn't "obey the axioms of a coordinate system", neither does the standard interpretation. Alice's operational definition of her four spatio-temporal parameters does.
    while I don't fully understand the point, I can deduce that it isn't enough to decide between mutually exclusive interpretations. I know that if it satisfies the axioms for a co-ordinate system that essentially just means it is a valid - in terms of the axioms - co-ordinate system. Since it's robustness as a co-ordinate system isn't in question - I clearly wouldn't know where to start in that regard - it's not a decisive point.
    Fourier wrote: »
    We all know the procedure. What is the purpose in asking this? It's based solely on the constancy of the speed of light ultimately.
    As it pertains to Einstein's clock synchronization convention, which states that the synchronisation of clocks [in "the stationary system"] must be established by definition i.e. clocks must be assumed to be synchronized, in "the stationary system".


  • Registered Users Posts: 10,558 ✭✭✭✭Fourier


    roosh wrote: »
    I generally tend to download textbooks and go straight to the parts that are of interest, without necessarily taking note of the name. At the moment I've got books by Feynman; Physics: principles and applications by Giancoli; the Problem of Time by Anderson; and an uncountable number of online material. Oh, and @Morbert =D
    This indicates to me you haven't read an account of Relativity systematically. It's actually hard to conduct this conversation because you're clearly (and I don't mean this in a rude way) not fully conversant in the theory or its mathematics.

    I'd recommend working through Ray d'Iverno's "Introducing Einstein's Relativity".

    You've mixed up things like metrics and coordinate systems. This is very basic to the theory and I don't fully understand why one wouldn't just learn the theory first before attempting to argue against it.
    while I don't fully understand the point, I can deduce that it isn't enough to decide between mutually exclusive interpretations
    The purpose isn't to decide between two interpretations, it's to demonstrate that the standard one is non-circular. Coordinate systems are a fundamental part of Relativity and not knowing them properly does hinder this discussion.
    As it pertains to Einstein's clock synchronization convention, which states that the synchronisation of clocks must be established by definition i.e. clocks must be assumed to be synchronized.
    It doesn't assume this. If you look up treatments of this in textbooks that assumption is never made because it is unnecessary to assume. If you knew the mathematics this would be easier to demonstrate (and that is the point of the coordinate system argument) however I will attempt a simpler one.

    Light always travels at a constant speed

    From this we know that a specific travel time for light is associated with a specific distance and vice versa, i.e. if light travels for t seconds it must have covered ct meters. It also means if light travels a distance d, then returns along d the travel time to d must be half that of the total journey.

    When Alice receives the light back from B1 at time T, it must have reached the reflectors at T/2 since the speed of light is constant. For B2 she receives it at T, thus it must have reached B2 at T/2.

    Hence from the constancy of the speed of light she concludes that they were simultaneous, not from an assumption of simultaneity.


  • Registered Users Posts: 2,552 ✭✭✭roosh


    Fourier wrote: »
    This indicates to me you haven't read an account of Relativity systematically. It's actually hard to conduct this conversation because you're clearly (and I don't mean this in a rude way) not fully conversant in the theory or its mathematics.

    I'd recommend working through Ray d'Iverno's "Introducing Einstein's Relativity".
    I don't take it in a rude way at all. I do undestand that this places limitations on my ability to discuss certain aspects of the theory. It is also why I am appreciative of people like yourself and Morbert taking the time to discuss this. While it does place limitations on my ability to discuss certain aspects of the theory, I believe that sufficient deductions can be made while sticking within those limits.

    The thought experiments represent one such avenue through which deductions and inferences can be made. Within limits, yes, but we can stick within those limits.

    Thank you for the recommendation. I'm always on the lookout for resources like that.
    Fourier wrote: »
    You've mixed up things like metrics and coordinate systems. This is very basic to the theory and I don't fully understand why one wouldn't just learn the theory first before attempting to argue against it.
    I haven't necessarily mixed them up. I'm more familiar with coordinate systems than I am with the idea of metrics. Not fully knowing what the latter was, I misapplied the term thinking the terms were somewhat interchangable. While I don't know what the axioms of a coordinatee system are, I undertand what it means to satify the axioms of something. I knew, therefore, that I wasn't arguing the proposition that Alice's chosen coordinate system disobeyed the axioms.

    That is an important point when we have mutually exclusive interpretations, both of which employ a coordinate system which satisfy the axioms of a coordinate system - both, I'm inferring, using the same coordinate system.
    Fourier wrote: »
    The purpose isn't to decide between two interpretations, it's to demonstrate that the standard one is non-circular. Coordinate systems are a fundamental part of Relativity and not knowing them properly does hinder this discussion.
    Given the limitations imposed by my limited understanding of this point, I can't argue against it. What I can do however, is examine the tought experiments and make inferences and deductions within the aforementioned limits

    It's by examining the thought experiment that we can deduce, that circular reasoning is employed and is a matter of necessity for that particular interpretation. So, while the construction of the coordinate system might follow certain axioms, which make it non-circular (in the context of constructing coordinate systems), circular logic mut be applied to the interpretation of the observational evidence, it would seem, in order to reconcile it with the mathematical description; or rather, to reconcile it with one particular interpreation of the mathematics.

    Just to reiterate, we have [at least] two mutually exclusive interpretations which are mathematically identical, both of which employ a cordinaate system which satisfy the axioms of a coordinate system, so the two cannot be distinguished on that basis. We can however, make inferences and deductions about the differnt interpretations (of the mathematics and evidence) by means of the thought experiments.

    Fourier wrote: »
    It doesn't assume this. If you look up treatments of this in textbooks that assumption is never made because it is unnecessary to assume. If you knew the mathematics this would be easier to demonstrate (and that is the point of the coordinate system argument) however I will attempt a simpler one.

    Light always travels at a constant speed
    Bear in mind that there is more than one interpretation of "the constancy of the speed of light".

    It can be taken in the Einsteinian sense or it can be taken to mean that the average speed of light is constant i.e. the two-way speeed of light is constant, as opposed to the one way speed of light.
    The "one-way" speed of light, from a source to a detector, cannot be measured independently of a convention as to how to synchronize the clocks at the source and the detector. What can however be experimentally measured is the round-trip speed (or "two-way" speed of light) from the source to the detector and back again. Albert Einstein chose a synchronization convention (see Einstein synchronization) that made the one-way speed equal to the two-way speed. The constancy of the one-way speed in any given inertial frame is the basis of his special theory of relativity,

    It could be taken to mean that the speed of light is always measured to be the same. This could be the result of some form of Lorrentzz-Poinccare conspiracy of dynamics, or it could be a quirk of nature that can be described kinematically [by following the reasoning of Einstein but offering a different interpretation] and could be illustrrated through the thought experiments used to demonstrate the Einsteinian interpretation..

    Fourier wrote: »
    From this we know that a specific travel time for light is associated with a specific distance and vice versa, i.e. if light travels for t seconds it must have covered ct meters. It also means if light travels a distance d, then returns along d the travel time to d must be half that of the total journey.

    When Alice receives the light back from B1 at time T, it must have reached the reflectors at T/2 since the speed of light is constant. For B2 she receives it at T, thus it must have reached B2 at T/2.

    Hence from the constancy of the speed of light she concludes that they were simultaneous, not from an assumption of simultaneity.
    It is precisely the idea that "it must have reached the reflectors at T/2" that Einstein says must be estabished by definition i.e. that must be assumed. Therein lies the assumption of simultaneity of [clock synchroonisation] events.


    Alice's own observations [should] demonstrate [to her] why this assumption is not justfied. She observes Bob, with the exact same set-up, attempt the exact same synchronisation procedure, with the exct same obervational results. As observed by Alice, the light signal for Bob also returns simultaneously to him, corresponding to time t_1 on Bob's clock. However, Alice makes the obsservation that the evnts were not simultaneous and Bob's clocks are not ssynchhronised.

    This should give Alice pause for thought.

    On the basis of this obervational evidence, Alice should be able to deeduce that just because the light signals return to her simultaneously at t_1, it doesn't necessarily mean that both reached the clocks/reflectors at t/2. It's possiblle that the journey time to one was not equal to the journey time to the other and that this difference was canceled out on the return journey.

    This is a possible, alternative interpretation for her actual observations i.e. the signals returning simultaneouusly at t_1. Alice canot determinee, by way of experiment, which scenario is the correct one - both are possible.

    The cruciall point, and the point that has been argued, is that within the totality of observational evidence, there is no empirical observation of her clocks being synchronised. All the evidence shows that her clocks are not synchronised.

    So, all other observers make the observation that Alice's [clock synchronization] events were not simultaneous (this is what they observe). If Alice assumes that the [clock synchronization] events are simultaneous, the conclusion of relativity of simultaneity follows as amatter of necessity. This is solely on the basis of Alice's assumption that her the [clock synchronisation] events were simultaneous, in spite of the observational evidence not supporting this assumption.

    If Alice drops her assumption, then the conclusion, that simultaneity is relative, disappears - thus demonstrating that it is the assumption of the observer, in the "stationary sysstem" (Alice), that the [synchronisation] events [of her clocks] are simultaneous, which leads to the conclusion that simultaneity is relative i.e. the conclusion is assumed - with regard to the interpretation of the empirical evidence.


    To reiterate, yes, the obserrational evidence - that the events are not simulttaneous - is consisent with the Einteinian interpretation. It represents the "are not simultaneous in relatively moving frames" part of the conclusion.. That part on it's own, however, doesn't lead to the conclusion that simultaneity is relative. For that, the first part of the conclusion - "events which are simultaneous in one frame" - is also required. It is this first part that must be assumed. Thus, for the observational evidence (non-simultaneous events) to lead to the conclusion of the relativity of simultaneity, it requires the additional assumption that events in a given frame are simultaneous i.e. the conclusion must be assumed.

    To summarise, while the coordinate system employed in the Einsteinian interpretation may satisfy the axioms of a coordinaate system, the interpretation of [plausible] real-wold, empirical observations requires the application of circular reaoning, in order to reconcile it with that particular interpretation of the mathematics.


    The map is not the territory. Where there are different interpretations of the map, we must look to the territory for additional information. In doing so, we see that one interpretation relies on/incorporates/necessitates/however you want to phrase it/requires the assumption of its conclusions.


  • Registered Users Posts: 10,558 ✭✭✭✭Fourier


    It is precisely the idea that "it must have reached the reflectors at T/2" that Einstein says must be estabished by definition i.e. that must be assumed. Therein lies the assumption of simultaneity of [clock synchroonisation] events.
    The fact that it occurs at T/2 follows from the constancy of the speed of light.


  • Registered Users Posts: 2,552 ✭✭✭roosh


    Fourier wrote: »
    The fact that it occurs at T/2 follows from the constancy of the speed of light.
    And that the clock reads T/2 at the moment the light signal makes physical contact with the clock can be verified by observation, as opposed to being "established by definition"? I'm sure you know that the answer to this is, simply, that it cannot. Hence, it must be "establlished by definition" i.e. it must be assumed.

    Thus is the simultaneity of clock synchronisation events in the "stationary system", assumed, along with it the conclusion that "events which are [assumed] to be simultaneous in one frame, are [obseerved as being] not simultaneous in relatively moving frames".


    You probably didn't miss it, but just for posterity in case it is pressumed that the above response somehow addressed the points below:

    Bear in mind that there is more than one interpretation of "the constancy of the speed of light".

    It can be taken in the Einsteinian sense or it can be taken to mean that the average speed of light is constant i.e. the two-way speeed of light is constant, as opposed to the one way speed of light.
    The "one-way" speed of light, from a source to a detector, cannot be measured independently of a convention as to how to synchronize the clocks at the source and the detector. What can however be experimentally measured is the round-trip speed (or "two-way" speed of light) from the source to the detector and back again. Albert Einstein chose a synchronization convention (see Einstein synchronization) that made the one-way speed equal to the two-way speed. The constancy of the one-way speed in any given inertial frame is the basis of his special theory of relativity,

    It could be taken to mean that the speed of light is always measured to be the same. This could be the result of some form of Lorrentzz-Poinccare conspiracy of dynamics, or it could be a quirk of nature that can be described kinematically [by following the reasoning of Einstein but offering a different interpretation] and could be illustrrated through the thought experiments used to demonstrate the Einsteinian interpretation..


  • Registered Users Posts: 10,558 ✭✭✭✭Fourier


    And that the clock reads T/2 at the moment the light signal makes physical contact with the clock can be verified by observation, as opposed to being "establlished by definition"? I'm sure you know that the answer to this is, simply, that it cannot. Hence, it must be "establlished by definition" i.e. it must be assumed.
    Yes, it is assumed that the speed of light (as opposed to the average speed of light over a two way trip) is constant. That's what implies the reading is T/2. The assumption is not one of simultaneity as you original posited, nor is there a circularity.
    It can be taken in the Einsteinian sense or it can be taken to mean that the average speed of light is constant i.e. the two-way speeed of light is constant, as opposed to the one way speed of light.
    Of course that's where the different interpretations come in. I'm not sure what is your actual point. That there is an assumption? Naturally there is otherwise one could not make any statements about observations at all aside from the brute fact of their occurrence. One has to propose something in some form in order to model the observations. The assumption is not circular though.

    However Einstein's assumption strikes most physicists as the most natural one. It is very difficult to believe this quirk of nature or conspiracy of dynamics that allows all of nature to appear as if the structure of spacetime is Minkowskian.

    If one constantly sees light return from a distance d in time 2d/c, no matter how small or large d is made, it seems the simplest assumption to say this is because light is always moving at c. Otherwise why would the physical constituency of all objects make it appear to be the case. Think about it, you are claiming that the world deludes one into thinking light is always travelling at one speed. Since different physical objects reflect light via completely different dynamics this requires a vast fine-tuning over all chemical substances so that the reflected speeds match this assumption. Specifically one needs a different ether-material coupling for each material in order to replicate that speed in the Lorentz-Poincaré case.

    The simpler assumption than assuming every material has a specifically fine-tuned and unique coupling to give the appearance of the constancy of the speed of light is to just assume that yes in fact light speed is constant. One assumption replacing multiple coupling assumptions.


  • Registered Users Posts: 2,552 ✭✭✭roosh


    Fourier wrote: »
    Yes, it is assumed that the speed of light (as opposed to the average speed of light over a two way trip) is constant. That's what implies the reading is T/2. The assumption is not one of simultaneity as you original posited, nor is there a circularity.
    It is an assumption of simultaneity though!

    The assumption that the time for the signals to reach each clock is the same, necessarily means that the events - the signals reaching each clock - are simultaneous, in the "stationary system". Hence the timestamp for each event is assumed to be T/2. This is an assumption of simultaneity.

    Fourier wrote: »
    Of course that's where the different interpretations come in. I'm not sure what is your actual point. That there is an assumption? Naturally there is otherwise one could not make any statements about observations at all aside from the brute fact of their occurrence. One has to propose something in some form in order to model the observations. The assumption is not circular though.

    However Einstein's assumption strikes most physicists as the most natural one. It is very difficult to believe this quirk of nature or conspiracy of dynamics that allows all of nature to appear as if the structure of spacetime is Minkowskian.

    If one constantly sees light return from a distance d in time 2d/c, no matter how small or large d is made, it seems the simplest assumption to say this is because light is always moving at c. Otherwise why would the physical constituency of all objects make it appear to be the case. Think about it, you are claiming that the world deludes one into thinking light is always travelling at one speed. Since different physical objects reflect light via completely different dynamics this requires a vast fine-tuning over all chemical substances so that the reflected speeds match this assumption. Specifically one needs a different ether-material coupling for each material in order to replicate that speed in the Lorentz-Poincaré case.

    The simpler assumption than assuming every material has a specifically fine-tuned and unique coupling to give the appearance of the constancy of the speed of light is to just assume that yes in fact light speed is constant. One assumption replacing multiple coupling assumptions.
    There is no need to depend on any sort of dynamics. I'm not sure if you're familiar with the following idea pertaining to the Lorentz-Poincare interpretation:
    wiki LET wrote:
    By this point, most vestiges of a substantial ether had been eliminated from Lorentz's "ether" theory, and it became both empirically and deductively equivalent to special relativity. The main difference was the metaphysical postulate of a unique absolute rest frame, which was empirically undetectable and played no role in the physical predictions of the theory
    My contention is that even the absolute reference frame can be divested.

    Essentially, we can take Einstein's kinemtical formulation and examine it through the aforementioned thought experiments to see the possible interpretions of the empirical evidence.

    The Einstein/Minkowski interpretation is one possible interpretation but it does require the assummption of simultaneity of events in "the stationary system".

    An alternative interpretation of the evidence would see the extension of the Galilean Principle of Relativity to the concepts of simultaneity/synchronisation - given that there is no experiments that can be conducted to determine these (yet). Simply dropping the assumption that the simultaneity of events "in the stationary system" can be determined.

    Without such an assumption RoS simply disappears and we are left with absolute simultaneity - despite the fact that we cannot actually determine which events are simultaneous. This is done without reference to an absolute reference frame or conspiratorial dynamics, simply from following Einstein's kinematical description and looking at the alternative interpretation. Einstein's thought experiments actually show us how nature "conspires" to ensure that we always get the same measurement for the speed of light.

    I do realise that it would be need to be formalised a touch more rigorously than that, but that is the reasoning.


  • Registered Users Posts: 10,558 ✭✭✭✭Fourier


    roosh wrote: »
    It is an assumption of simultaneity though!

    The assumption that the time for the signals to reach each clock is the same, necessarily means that the events - the signals reaching each clock - are simultaneous, in the "stationary system". Hence the timestamp for each event is assumed to be T/2. This is an assumption of simultaneity.
    This is a very simple point.

    If one assumes that the speed of light is always constant, then the signals reach the clock at T/2.

    Do you see, you don't assume the time to reach them is the same, that fact is derived from the constancy of the speed of light.

    Something derived is not an assumption.


  • Registered Users Posts: 3,457 ✭✭✭Morbert


    roosh wrote: »
    Again, the internal consistency of the Einsteinian interpretation is not being challenged here. The above is all fine as it is simply a statement as to what the Einsteinian interpretation is.

    Maybe it's a case of crossed wires but, in section 5 of your paper you say

    "under the Einsteinian paradigm an observer can explain their own observations but they cannot reconcile those observation with those of their counterpart – as represented by the video footage. That is, when Alice and Bob view the other’s video footage they will see that their clocks are not synchronised. There’s no way to explain the video footage while maintaining the assumption that their clocks are synchronised."

    I interpreted this as a claim that the orthodox geometric account of relativity results in an inconcistency between assumptions held by different observers.

    Would you, instead, agree that the orthodox account of relativity does not result in an inconsistency between assumptions held by different observers since, under the orthodox account of relativity, clock synchronisation if a frame-dependent description?
    As I've asked Fourier, do you at least acknowledge that there are [at least] 2 mutually exclusive, interpretations of the evidence?

    Also, do you agree that regardless of how the discussion is framed, the thought experiment represents a plausible, real-world experimental set-up that can be used to examine the competing interpretations - even if there were only one interpretation, the thought experiment could be used to to examine it. Examining this plausible, real-world set-up, allows us to draw conclusions and make inferences about the competing interpretations, what they necessitate, and how they interpret experimental results.

    Sure.


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  • Registered Users Posts: 2,552 ✭✭✭roosh


    Fourier wrote: »
    This is a very simple point.

    If one assumes that the speed of light is always constant, then the signals reach the clock at T/2.

    Do you see, you don't assume the time to reach them is the same, that fact is derived from the constancy of the speed of light.

    Something derived is not an assumption.
    I think you must mean that it is derived mathematically, from the chosen coordinate system because it isn't derived from observation. All that can be derived from the observations is that the Galilean Principle of Relativity extends to simultaneity/synchronisation such that there is no experiment which a co-moving observer can perform to determine the simultaneity of events in their frame of reference.

    The mathematical derivation essentially represents a prediction of the Einsteinian interpretation. It is a key prediction of the theory upon which the whole concept of the Relativity of Simultaneity rests. It is of course a prediction whose resut must be assumed in order to prop up the notion of RoS.

    Even further than that, it is a prediction which is, it would seem, entirely untestable. This isn't a desirable feature for physical theories from what I gather.


  • Registered Users Posts: 10,558 ✭✭✭✭Fourier


    roosh wrote: »
    I think you must mean that it is derived mathematically, from the chosen coordinate system because it isn't derived from observation.
    ....
    Even further than that, it is a prediction which is, it would seem, entirely untestable. This isn't a desirable feature for physical theories from what I gather.
    All physical theories have a point where you are stating something "axiomatically". With pure observations you'd have no theory.

    Consider the path of a particle in the presence of one solenoid and the path of a particle in the presence of another with a different chemical battery. Observationally the paths are just different and that's as far a simple observation can go.

    Electromagentism shows all such paths correspond to paths of particles in response to a vector field generated by the current in the solenoid in a form made by Maxwell's equations.

    This is the ontological assumption of electromagnetism. That there are entities B, E, J etc obeying a set of differential equations and it is due to their action that we have these paths.

    Observationally there are just a bunch of paths. I can never observationally prove that the paths "must" come from an E, B, J field etc.

    Similarly one can never prove that the speed of light is constant in the way Einstein claims absolutely. However it begins to get difficult to explain when the relationship holds precisely no matter how short the two-way trip is or in what direction. You have to start inventing substance and velocity dependent coefficients for every reflective substance. Einstein's claim is the most economical conceptually and mathematically. All other solutions have to be over fitted to the data.


  • Registered Users Posts: 2,552 ✭✭✭roosh


    Morbert wrote: »
    Maybe it's a case of crossed wires but, in section 5 of your paper you say

    "under the Einsteinian paradigm an observer can explain their own observations but they cannot reconcile those observation with those of their counterpart – as represented by the video footage. That is, when Alice and Bob view the other’s video footage they will see that their clocks are not synchronised. There’s no way to explain the video footage while maintaining the assumption that their clocks are synchronised."

    I interpreted this as a claim that the orthodox geometric account of relativity results in an inconcistency between assumptions held by different observers.

    Would you, instead, agree that the orthodox account of relativity does not result in an inconsistency between assumptions held by different observers since, under the orthodox account of relativity, clock synchronisation if a frame-dependent description?
    Thank you for taking the time to read that far!

    I simply meant that she cannot reconcile Bob's observational evidence with her own assumption. She instead must disagree with Bob's observations, otherwise she must accept the notion that the clocks on board her spaceship/platform are both synchronised with each other and not syncronised with each other. That is, that the light signals from her emitter [on board her spaceship], made physical contact with the clocks [on board her spaceship] both simultaneously and non-simultaneously. To re-iterate this all happens inside her spaceship during the single synchronisation procedure.

    Either way, that isn't the key point. The key point is that the conclusion of RoS must, as a matter of necessity, be assumed.

    Morbert wrote: »
    Sure.
    Do you accept that one of those interpretations, which is empirically and mathematically equivalent, is based on the idea that the time from one emitter to clock A does not equal the time from emitter to clock B?


  • Registered Users Posts: 10,558 ✭✭✭✭Fourier


    The key point is that the conclusion of RoS must, as a matter of necessity, be assumed
    But it's not assumed, it is derived from the isotropic constancy of the speed of light.


  • Registered Users Posts: 2,552 ✭✭✭roosh


    Fourier wrote: »
    All physical theories have a point where you are stating something "axiomatically". With pure observations you'd have no theory.

    Consider the path of a particle in the presence of one solenoid and the path of a particle in the presence of another with a different chemical battery. Observationally the paths are just different and that's as far a simple observation can go.

    Electromagentism shows all such paths correspond to paths of particles in response to a vector field generated by the current in the solenoid in a form made by Maxwell's equations.

    This is the ontological assumption of electromagnetism. That there are entities B, E, J etc obeying a set of differential equations and it is due to their action that we have these paths.

    Observationally there are just a bunch of paths. I can never observationally prove that the paths "must" come from an E, B, J field etc.

    Similarly one can never prove that the speed of light is constant in the way Einstein claims absolutely. However it begins to get difficult to explain when the relationship holds precisely no matter how short the two-way trip is. You have to start inventing substance and velocity dependent coefficients for every reflective substance. Einstein's claim is the most economical conceptually and mathematically. All other solutions have to be over fitted to the data.
    A kinematic interpretation is similarly possible without the assumption of simultaneity of events in the stationary frame. It's simply Einstein's theory without assuming the conclusion of RoS.

    As far as the thought experiment can be said to represent the Einsteinian interpretation, we can see where the concluion is assumed. Simply drop the assumption that evets in the stationary frame are simultaneous and you are left with Einstein's theory withou RoS with no reference to an Ether, dynamics, or an absolute reference frame.

    I know it's not as simple as that, and it would have to be stated in a rigorous manner, but the reasoning should lead us to conclude that such a formulation is possible.


  • Registered Users Posts: 10,558 ✭✭✭✭Fourier


    roosh wrote: »
    Simply drop the assumption that evets in the stationary frame are simultaneous and you are left with Einstein's theory withou RoS with no reference to an Ether, dynamics, or an absolute reference frame.
    This point has been made several times to no avail. Simultaneity is not assumed, it is derived from the isotropic constancy of the speed of light.

    This is not an assumption of the theory of relativity. Repeatedly saying it is, when it clearly is not, is pointless. Any textbook on relativity shows the constancy of c isotropically for all observers is the main assumption. Simultaneity in the form you are talking about is derived, not assumed.


  • Registered Users Posts: 3,457 ✭✭✭Morbert


    roosh wrote: »
    she cannot reconcile Bob's observational evidence with her own assumption.She instead must disagree with Bob's observations, otherwise she must accept the notion that the clocks on board her spaceship/platform are both synchronised with each other and not syncronised with each other. That is, that the light signals from her emitter [on board her spaceship], made physical contact with the clocks [on board her spaceship] both simultaneously and non-simultaneously. To re-iterate this all happens inside her spaceship during the single synchronisation procedure.

    If you want to use a thought experiment to interrogate a physical theory as it is normally presented, it's vital that you relate your thought experiment to the physical theory to be interrogated. You have made a number of statements above, none of which follow from the theory of relativity applied to this thought experiment. According to relativity:

    i) She has no problem reconciling Bob's observations with any and all assumptions she makes.
    ii) She entirely agrees with Bob's observations.
    iii) She does not have to conclude the clocks are both synchronised and not synchronised.
    iii) She does not have to conclude the light beams struck the clocks simultaneously and non-simultaneously

    All the reasoning you've carried out around the thought experiment has been reasoning from premises at odds with relativity.
    Either way, that isn't the key point. The key point is that the conclusion of RoS must, as a matter of necessity, be assumed.

    As Fourier mentions: RoS is a consequence of the orthodox theory of relativity, not a postulate of it. It only has to be assumed by Alice if she starts with some other theory, and she wants to include it later in some ad hoc manner.
    Do you accept that one of those interpretations, which is empirically and mathematically equivalent, is based on the idea that the time from one emitter to clock A does not equal the time from emitter to clock B?

    I'm not sure I understand this question: The normal interpretation says "the time from one emitter to clock A does not equal the time from emitter to clock B" is a frame-dependent claim.


  • Registered Users Posts: 2,552 ✭✭✭roosh


    Fourier wrote: »
    But it's not assumed, it is derived from the isotropic constancy of the speed of light.
    Fourier wrote: »
    This point has been made several times to no avail. Simultaneity is not assumed, it is derived from the isotropic constancy of the speed of light.

    This is not an assumption of the theory of relativity. Repeatedly saying it is, when it clearly is not, is pointless. Any textbook on relativity shows the constancy of c isotropically for all observers is the main assumption. Simultaneity in the form you are talking about is derived, not assumed.

    I thought I had forgotten to reply to you post above, but I see you're just restating a point I already addressed to which you subsequently replied. I'll try to clarify again.

    You're saying that it is not assumed, that it is derived, but I think you must be conflating the mathematical description used to make predictions with the observational evidence used to verify those predictions. Yes, the value T/2 - for both events - might be derived mathematically from the chosen coordinate system but it isn't derived from observation.

    This mathematical derivation represents a prediction of the theory. Indeed, it is an essential prediction required for one of its most fundamental conclusions, that of RoS; yet, it is a fundamentally untestable prediction according to the very foundational assumptions of the theory itself - rendering that part of the theory unfalsifiable!

    So, the derivation you talk of is simply a prediction. As said, it is not derived from obervation. The veracity of this mathematically derived prediction must be assumed that is, the key foundational observation, pertaining to RoS, must be assumed i.e. we have to assume that the clocks do actually read T/2 for both events.

    Again, what is derived is a prediction. The accuracy of this - critical - prediction is what is assumed. So the theory predicts RoS and the conclusion is assumed!



    It's a bit like assuming that the Flying Spaghetti Monster created the initial conditions of the Universe and then saying that derivations about the current state of the Universe, from that, somehow add validity to conclusions about the FSM's role in the current state of the universe.


  • Registered Users Posts: 10,558 ✭✭✭✭Fourier


    roosh wrote: »
    I thought I had forgotten to reply to you post above, but I see you're just restating a point I already addressed to which you subsequently replied. I'll try to clarify again.

    You're saying that it is not assumed, that it is derived, but I think you must be conflating the mathematical description used to make predictions with the observational evidence used to verify those predictions. Yes, the value T/2 - for both events - might be derived mathematically from the chosen coordinate system but it isn't derived from observation.
    It's derived from the assumption of the isotropic constancy of the speed of light.

    As I said above all theories have brute assumptions. Similarly Poincaré-Lorentz theory assumes that the two halves of the light beams paths occur at different speeds. This also cannot be directly confirmed. It's an ontological assumption about what is occurring behind the scenes.

    These two different assumptions lead to the same mathematics. In the standard case it's because the structure described by those mathematics, Minkowski space, is assumed to be real, in the Lorentz-Poincaré case it's all a complex illusion due to the odd dynamical properties of the aether.

    Since the former is simpler we usually go with it. Also there doesn't seem to be a clear way to explain General Relativity from the latter. Also when you move to Quantum Field Theory particles that actually live in a Galilean background operate completely differently from those in a Lorentz background. Massless Spin-1 particles for example have different polarization states. To allow the Lorentz-Poincaré picture to be extended to particle physics you'd have to assume there is some complex mechanism in detectors that always "masks" one of the three polarization states of light to make it seem like there are two.

    The whole construct just becomes increasingly ad-hoc and complex.


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  • Registered Users Posts: 2,552 ✭✭✭roosh


    Morbert wrote: »
    If you want to use a thought experiment to interrogate a physical theory as it is normally presented, it's vital that you relate your thought experiment to the physical theory to be interrogated. You have made a number of statements above, none of which follow from the theory of relativity applied to this thought experiment. According to relativity:

    i) She has no problem reconciling Bob's observations with any and all assumptions she makes.
    ii) She entirely agrees with Bob's observations.
    iii) She does not have to conclude the clocks are both synchronised and not synchronised.
    iii) She does not have to conclude the light beams struck the clocks simultaneously and non-simultaneously

    All the reasoning you've carried out around the thought experiment has been reasoning from premises at odds with relativity.
    That part of the argument is somewhat separate to the primary conclusion that is drawn. It is more along the lines of the Einsteinian interpretation conflicting with itself, but it isn't necessary.

    The primary conclusion is that the simultaeity of [clock synchronisation] evens in the stationary system is not supported by observational evidence. The theory makes a critical prediction about the time value on two physical clocks which is entirely untestable by the foundational assumptions of the theory. This accuracy of this prediction - upon which the Relativity of Simultaneity rests - must thereore be assumed. Rendering that aspect of the theory unfalsifiable - but still, clearly requiring the conclusion to be assumed.

    Morbert wrote: »
    As Fourier mentions: RoS is a consequence of the orthodox theory of relativity, not a postulate of it. It only has to be assumed by Alice if she starts with some other theory, and she wants to include it later in some ad hoc manner.
    As a consequence/conclusion of the the theory, predicated on the basis of a prediction about the reading on two physical clocks, a prediction which is untestable under the foundational assumptions of the the theory itself, a prediction whose accuracy must be assumed to be true, it is a consequene/conclusion which is assumed and indeed unfalsifiable under the foundational assumptions of the theory itself.

    Again, just to reiterate, it is entirely based on circular logic.

    Morbert wrote: »
    I'm not sure I understand this question: The normal interpretation says "the time from one emitter to clock A does not equal the time from emitter to clock B" is a frame-dependent claim.
    I'm asking about the alternative interpretation.


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