the [possible] fallacy of Lorentz contractions

roosh wrote: »

The issue
The [main] issu, as I see it, is with the treatment of the observer on the train, or more pointedly the treatment of the path length of the photon [in the clock or from the laser] - the treatment of the observer on the platform is debatable as well, but with regard to arriving at the conclusion of Lorentz contractions it is less so.

As we can see from the thought experiment, the path length of the photon is given as twice the distance from the laser to the mirror; this is no different from the light clock thought experiment where the path length is given as twice the distance between mirrors; the measurement is labelled above as 2d.

The issue, however, is that this assumes that the observer on the train, the train itself, the light clock and the laser are all at absolute rest; because anything other than absolute rest would result in a longer path length for the photon. Unless, of course, length contraction and time dilation could be invoked, but if Einstein were to have done so, he would have been guilty, surely, of assuming the conclusion. If we follow the path of reasoning though, I think we can see where the ideas arose from.

roosh wrote: »

I think it is most easily explained by considering the two possibilities of being either at absolute rest, or in motion. If we imagine a clock as being at absolute rest, then the path length of the photon, from the midpoint of one mirror, to the corresponding midpoint of the other, will be 2d.

If we then imagine that, from that position of absolute rest, the clock moves in any direction (at precisely the moment the photon is "leaving" the midpoint of one of the mirrors); then, in order for the photon to hit the midpoint of the other mirror, it must travel a longer distance because the other mirror will have moved from it's original position. The change in path length can be calculated using the Pythagorean theorem, which will give the Lorentz factor without the necessity for invoking length contraction and/or time dilation.

The photon will still travel a distance of 2d relative to the train, but because the train and the apparatus are also in motion, the photon will travel a longer actual distance; indeed, in order to travel a distance of 2d relative to the train, it has to travel a longer distance.

This doesn't involve switching reference frames either; an observer at rest on the train can reason that only a position of absolute rest will result in a path length of 2d, while anything other than absolute rest will result in a longer path length of the photon, while maintaining a distance of 2d relative to the carriage.

roosh wrote: »

The point isn't to determine if the train is in motion, the point is that only a position of absolute rest will result in the photon traveling a path length of 2d.

The very same is true of a clock at rest relative to the ground. Only if the ground is at absolute rest will the photon travel a distance of 2d.Incidentally, if it is the ground that is moving and not the train, then the clock at rest relative to the ground will tick slower, because the photon in it will have to travel a longer distance between mirrors.

The point is that the light clock thought experiment implicitly assumes that both reference frames are at absolute rest, from their own perspective. It is the need to reconcile the actual path length of the photon with the assumed path length that gives rise to the idea of contractions.

It appears as though this second postulate stems from Einstein's appreciation for Maxwell's equations, which appear to imply this; however, the speed of light is, by definition, relative to a clock at rest on the earth, because it is given as approx. 300, 000 km/s: "the second" in that measurement is defined in terms of a caesium atomic clock at rest relative to the earth.

How is the second postulate actually tested though?

It is probably worth noting that absolute motion cannot, by definition, be measured, because measurement is, by practicality, relative i.e. it is the expression of something in relation to something else. Absolute motion is a simple yes or no answer to the question "is the thing actually moving?"

roosh wrote: »

This is only if we assume that the clock at rest on the moving ground ticks at the same rate as that in the train i.e. that the path length is the same.

I'm trying to visualise how it would appear; we must remember though that the clock on the moving ground is actually ticking slower because of the increased path length. If the observer on the moving ground doesn't assume that they are at absolute rest, then they can calculate that the other clock is ticking slower.

It's basically just the same issue in reverse

It makes no explicit reference to absolute rest, there is an implicit assumption, however.

The emboldened parts, above, appear to be contradictory.

Again, though, if we start with the supposition of an absolute rest frame as above, and put a clock at rest in that absolute reference frame; then the photon in a clock on a train, moving at speed u relative to that frame, will have a longer path length as determinable by the Pythagorean theorem; similarly, a clock at rest on the ground, moving at speed v relative to the absolute rest frame, will have a longer path length as determinable by the Pythagorean theorem.

Whichever velocity is higher, u or v, will determine which clock ticks slower.

That may be the nature of Maxwell's equations, but the measurements of the speed of light in the experiments, c, were presumably all relative to a clock at rest relative to the earth.

However, as per the post above:

Both observers will measure the speed of light to be c.

Again, if we consider two scenarios:
- the observer can see the ground moving relative to him
- the observer is in a windowless carriage and cannot see the ground moving relative to him.

Taking the second scenario, the observer will still measure a speed of c; the reason being that, for the observer on the train, the light will have a slower vertical velocity, as you say, but this will be offset by his slower ticking clock; that is "the second" he measures on the train will not be the same "second" measured by the observer on the ground. He will have no way of knowing that his clock is ticking slower.

This isn't "time" dilation, but rather a clock that is ticking slower because of the path length the photon has to travel.

Alternatively, the observer can see the ground moving relative to him; again, he can either assume that he is at absolute rest, or that his is actually in motion. Only by assuming that he is at absolute rest will he measure a path length of 2d. If he is in motion, then he will calculate the actual path length of the photon relative to the ground, realise that it is longer than 2d and that his clock will tick slower as a result.

I read the arxiv paper provided, and unfortunately it was a bit too technical for me, but there was something in the opening and closing paragraphs (before the acknowledgements) which may or may not serve as a useful point of discussion.

It could be just the untrained eye, but, as with the Kennedy-Thorndike Experiment, the Michelson-Morely Experiment appears to employ "figure of 8 reasoning", as opposed to straight forwards circular reasoning.

It appears as though a starting assumption - expressed or otherwise - is that the speed of light is c with respect to all reference frames. It also seems that, in order for the experimental results to match that of relativity, length contraction is required. Now, length contraction isn't actually observed, so it appears as though it is assumed that, from the perspective of the photon, the length of the arms of the interferometers contract - this of course is fundamentally untestable.

So, the conclusion is that length contraction occurs (from the perspective of the photon); but it hasn't actually been observer, but rather assumed; that is, the conclusion is assumed.

The conclusion then, is that the speed of light is c in all directions, which of course, was the starting assumption.

If the conclusion of contractions aren't assumed, do the experimental results of the MMX still support the second postulate?

Despite all this, it has been outlined above that all observers will still measure the speed of light to be c.

himnextdoor wrote: »

I just don't see why a photon should lose velocity in the vertical direction just because it has acquired a horizontal component.

Suppose we were to replace the light-clock with a cannon system. A cannon is arranged to fire balls parallel to the ground; the system is self-loading through entirely mechanical means; the fire/reload cycle has been measured to be a ten-second cycle. All the balls have the same mass and they are fired with the same amount of energy.

There are no clocks governing the cycle and while the system is powered up it will operate at its most efficient.

The train is stationary and the cannon is switched on. It fires its first missile then the train begins to accelerate. Let's assume the train is travelling along a straight line.

When the ball leaves the cannon, it begins to fall due to gravity and will land at some distance, 'd', from the train depending on the energy of propulsion. We are only concerned with the initial impact between ball and ground; we will disregard bounce.

As the train accelerates, firing balls every ten seconds, the distance between the balls increases; at the speed of light, the balls will land ten light-seconds apart. (Let's ignore the fact that these balls will have exceeded escape velocity.)

However, all the balls will land the same distance away from the track. Not only that, the time between firing the ball and it impacting with the ground will also remain constant.

Why should it be any different for photons?

roosh wrote: »

Apologies for the delayed response, I was trying to get a better understanding of the potential issues in postulating an idealised, infinitely precise, pendulum clock.

It does produce an experimental difference; in the first instance it is the clock on the train that ticks slower; in the second instance it is the clock on the earth that ticks slower.

Just to try and address the point again:

I think you might be working off the same assumptions as the thought experiment with this point; the assumption being that both clocks tick at the same rate in their own reference frames. That is the assumption being questioned.

It can be somewhat hard to picture, particularly when the relativity diagrams/videos - which show both clocks ticking at the same rate from their own perspective (path length of 2d) - are ingrained in our subconscious. But if we can drop the notion that they tick at the same rate in their own reference frames, and imagine the clock on the ground actually ticking slower than the one on the train, because of the increased path length [when "the ground is moving and not the train"]; then I don't think you will arrive at the same conclusion - that the observer on the ground will still calculate that the clock on the train is ticking slower.

In terms of the [Lorentz contractions] video you posted in the other thread, it might be helpful to try and imagine the scenario for Henry (the observer on the train) first. In this instance we can imagine that Albert's (the observer on the platform) frame of reference is the absolute rest frame and that the path length, of the photon in his clock, is actually 2d; this will also be the path length relative to his reference frame - again, only an assumption of absolute rest will result in both measurements being the same.

So Henry and his clock are in motion on the train, and Henry's clock is actually ticking slower than Albert's because of the increased path length of the photon, as they pass each other will Henry still measure Albert's clock to be ticking slower? I think if he knows the distance between himself and Albert he will probably be able to calculate that his clock is actually ticking slower.

Only if we assume that both clocks tick at the same rate [in their own reference frames] i.e. that the actual path length is the same in both cases- 2d implying absolute rest - will we arrive at the conclusion that, to each observer, it is the clock in the other reference frame that appears to tick slower.

The contention isn't that "there must be an absolute rest", it is that, in the thought experiment, there is an implicit assumption that, from the perspective of each observer, their reference frame is at absolute rest.

It doesn't follow from the assertion: "There is no reference frame that labels both observers as stationary"; it is a consequence of the assumed measurement of the path length of the photon as 2d; because only a position of absolute rest will result in the photon actually traveling a distance of 2d

Again, the intention isn't to demonstrate that there must be an absolute space, it is to demonstrate that measuring a path lenght of 2d implies absolute rest.

This can be done by considering what the path length of a photon would be at absolute rest, and then reason what it would be if the train moved from this position of absolute rest.

I don't think you demonstrated it though, because you started with the supposition of an absolute rest frame to determine the velocities of the train and the ground, and then calculated the relative velocity of the train to the ground, on the basis of the velocities relative to the absolute rest frame.

As per the example in a previous post, we can follow your line of reasoning and place clocks in each reference frame:

Placing the clocks
You started by assuming an absolute rest frame, against which to determine the velocities of the train and the ground; so if we put a clock at rest there, then the path length of the photon will be 2d.

If we imagine a train, and a clock, moving relative to that rest frame, with a velocity u, then the actual path length of the photon will be longer than 2d and so the clock will tick slower;the difference in path length can be determined using the Pythagorean theorem. The path length relative to the carriage will be 2d but only if the observer assumes a position of absolute rest will he assume that the actual path length [which determines the cycle period of his clock] is 2d.

If we then imagine the earth moving relative to this absolute rest frame, at velocity v, then the actual path length of the photon will be longer than 2d and so the clock will tick slower;the difference in path length can be determined using the Pythagorean theorem. Again, only by assuming that they are at absolute rest, will the observer at rest on earth determine that the actual path length [which determines the cycle period of their clock] is 2d.

Removing the rest frame
So, here we have three clocks; one in the absolute rest frame; one on the train; and one are rest on earth. Both clocks moving relative to the absolute rest frame are ticking slower than the clock in that rest frame, by a rate determinable using the Pythagorean theorem, and by a factor of their velocity relative to the rest frame.

If, for the sake of explanation, we assume that the train is traveling at a higher velocity than the earth, then it is the trains clock which will be ticking the slowest of the three clocks; and therefore, slower than the earths clock.

Now, we can remove the clock in the absolute rest frame, such that we are only left with the trains clock and the earths clock. The trains clock will still run slower than the earths clock.

Are there specific experiments you are referring to?

I was trying to get a better understanding of the potential issues of using such and idealised clock and I think there are a few:
- such a clock would not work in the relocation to deep space
- a pendulum clock in a train moving at constant speed is traveling in a curved path around the earth so it is not experiencing as much g, and so will tick at a different rate to one at rest on earth.

In a footnote to the English translation of his 1905 paper, ON THE ELECTRODYNAMICS OF MOVING BODIES Einstein excluded the possibility of using pendulum clocks

Apologies, I was indeed incorrect about the starting assumption of the MMX (I think anyway), but that the conclusion of length contraction is assumed seems pretty clear. Equally so in the muon decay experiments, because they are not actually observed.

Also, insofar as the second postulate refers to the one way speed of light, it is, by all accounts, an untestable assumption.

roosh wrote: »

It's probably worth highlighting again, that we are discussing a scenario where the relative motion is ascribed to one reference frame or the other, in both reference frames; that is, either the train is moving in both reference frames, or the platform is.

Whichever frame is not moving, the photon of that clock will not trace the hypotenuse and so will tick faster.

Einsteinian relativity might not expressly state anything about an absolute rest frame, but there are certain issues which suggest that it is a tacit assumption.

Firstly, the treatment of reference frames, in Einsteinian relativity, is indistinguishable from such a treatment where reference frames are considered to be at absolute rest, from their own perspectives.

Secondly, the ascription of all motion to the other reference frame, suggests that reference frames are considered to be at absolute rest from their own perspectives; if they weren't, then the vertical velocity component of the photon in their light clock would be less than c and they would thus measure a speed of light lower than c.

The issue is that, in the construction, you started off by assuming an absolute reference frame to define the values of U and V; and, theoretically, there should be an infinite number of possibilities that can give rise to the measured relative velocity between two reference frames; where U and V would be perfectly adequate examples; however, this is only possible when there is a common rest frame which can be used to define the velocities.

The infinite number of possibilities [for making up the relative velocity] should vary from one of the reference frames accounting for 100% of the relative velocity, to both reference frames accounting for 50%, to the other accounting for 100% of the relative velocity, however, if we only consider relative velocities then we have to treat one of the reference frames as being at absolute rest; or, as Einsteinian relativity appears to do, treat each reference frame as being at rest from its own perspecitve.

If we take the example where the relative velocity is 100km/h; if we want to consider the case where the velocities are U and V for the two reference frames, where U = 30km/h and V=100km/h, then we need a common rest frame against which to define those respective velocities, because relative to each other the velocity will always be 100km/h.

For this reason, one reference frame has to be treated as being at absolute rest, and has to ascribe all of the velocity component to the other reference frame; it appears as though, under Einsteinian relativity, each reference frame is treated thusly.

Aren't GPS systems synchronised to an earth centred inertial frame? Does the designation of this preferred frame not marginally favour Lorentzian relativity; despite the fact that Einsteinian relativity could be used.

Is there a contemporary real world experiment that correlates to this thought experiment?

Also, would this scenario be one such scenario where Larmor dilation would apply?

Length contraction isn't observed in any experiment though is it; at least it doesn't appear to be in the interferometer experiments or in the muon decay experiments.

I'm not familiar with that analysis of Lorentzian relativity tbh, but it looks like a bit of a skewed comparison of the two theories.

Minkowski space-time: a glorious non-entity

Other sources suggest the difference lies in the postulation of an absolute rest frame in Lorentzian relativity
wiki-LET current status

I suspect that even that absolute rest frame could be removed - without treating reference frames as being at absolute rest - by simply having a preferred reference frame, or rest frame, for units of measurement.

EDIT: just on the point of relativity of siumultaneity; Lorentzian relativity doesn't have a physical understanding of it, because it's not actually part of it; absolute simultaneity is prevalent un LR.

roosh wrote: »

Would that be the case under the Loerntzian interpretation also?

I don't think they are oxymoronic, are they? They are not contradictory in and of themselves; they only become contradictory if we consider that two reference frames treat themselves as being at absolute rest - which will hopefully be clarified further below.

It is probably worth stating that the tacit assumptions aren't present in the formulation used above, but they are necessary consequences of the treatment discussed below.

I think I may have confused the issue by not sticking more rigidly to the terms you defined from the outset, u and v, and U and V.

The issue is that, in the construction, you started off by assuming an absolute reference frame to define the values of u and v; such that either u or v could have had a higher value, relative to the assumed absolute rest frame; they also could have had equal values, or either could have had a value of zero, relative to the absolute rest frame i.e. it would have been at absolute rest.

Theoretically, that should be correct; there should be an infinite number of values for u and v that will give rise to the relative velocites of V and U (which are essentially the same value [with opposite signs perhaps]). However, in order to facilitate this possibility, a common rest frame is required to define u and v.

For example, if the relative velocity (V or U), between two reference frames, is 100km/h; there should be an infinite range of values for u and v which give rise to this relative velocity: u = 30km/h and v = 70km/h; u = 50km/h and v = 50km/h; u = 1km/h and v = 99km/h; etc. etc.. However, this is only possible if we consider a common rest frame, against which to define the values for u and v; because if we only consider the relative velocity between reference frames, the value will always be 100km/h.

It is for this reason that one reference frame has to be treated as being at absolute rest, and has to ascribe all of the velocity component to the other reference frame; it appears as though, under Einsteinian relativity, from the perspective of each reference frame i.e. from their own perspective, they are treated as being at absolute rest.

EDIT: If they weren't treated as being at absolute rest, then, in the thought experiment, the vertical velocity component of the photon in their light clock would be less than c and they would thus measure a speed of light to be lower than c.

Fair enough, but we probably won't be able to differentiate between Lorentzian relativity and Einsteinian will we, because both are equally supported by the evidence? I've read arguments that Lorentzian relativity is the more straight forward approach, when it comes to the GPS system, because of the preferred reference frame, but that Einsteinian relativity can equally be applied.

There are probably a number of reasons; some of them include the fact that what a clock counter actually measures, or rather counts, is the number of events in the clock, not necessarily the relation between them; that only a spatial relationship between the events in a clock can be deduced, and not a temporal one; the fact that there is no experiment that can ever be conducted that will not be in the present moment, meaning that the temporal dimension (past and future) have to be assumed to exist.

Another reason is that I don't think it is necessary for Lorentzian relativity to assume that an undetectable, absolute reference frame actually exists, we can just treat the possibility that it could exist; as per the principle of invariance; we just wouldn't be able to detect such a frame, even if it did exist.

I also think the need for an absolute reference frame, in LR, is negated simply by defining a rest frame for units of measurement; which is something which, arguably, occurs necessarily in the real world.

roosh wrote: »

The reason for considering u and v is because, in your example, you started off by assuming an absolute rest frame to define the velocities, u and v, of two systems moving relative to that absolute rest frame; you then derived a formula for relative velocity between those two systems, based on the initial velocities, relative to that absolute rest frame.

The labels, 'u' & 'v' and 'U' & 'V', themselves, are essentially immaterial, but we need some placeholders for the relative velocity, so they are as good as any other arbitrary labels. What is under discussion is what those labels represent, and the logical consequences of what they represent.

Relative velocity
As mentioned before, theoretically, there should be an infinite number of values that can contribute to the relative velocity between two systems. The example above was of two systems with a relative velocity of 100km/h, where one system could be traveling at a velocity of 30km/h, and the other at 70km/h, or the infinite range of values that could contribute to a relative velocity of 100km/h. This, however, requires an arbitrary, not necessarily absolute, common rest frame, in order to define that infinite range of values. Einsteinian relativity doesn't allow for such a common rest frame, because only the relative velocities between systems is considered; with contractions being reciprocal between relatively moving systems.

By only considering the relative velocities, one of the systems has to be treated as being at absolute rest; because, in the absence of a common rest frame, or "background", 100% of the velocity has to be ascribed to the other reference frame, meaning that one of the reference frames is ascribed a zero velocity; a system with zero velocity is, I presume, a system at absolute rest.

Apologies, my terminology may have been a little loose, but the point is essentially a semantical.

I should probably have said that their co-ordinate system ascribes a zero velocity to their reference frame and therefore treats that reference frame as being at absolute rest. There is the alternative where their co-ordinate system ascribes a zero velocity to the other reference frame, but that just means that the other reference frame is treated as being at absolute rest.

The point being made is that the co-ordinate labeling system, tacitly, treats specific reference frames as being at absolute rest.

Whether it is mere coincidence or not, the thought experiment involving Albert and Henry lends itself to comparison with a similar thought experiment, where either Albert or Henry is at absolute rest. This is because the two scenarios are indistinguishable from one another. That is, if we consider the Einsteinian thought experiment from Albert's perspective, there would be no difference if we were to consider a similar thought experiment where Albert is at absolute rest. So, we are free to start with this possibility and see what conclusions we can derive.

This is another reason for considering an absolute rest frame.

Henry & Albert
Just for the purpose of explanation, we can formulate the thought experiment where both Albert and Henry are in separate train carriages; replacing Albert's platform for a train carriage doesn't have any material effects; I just think it's more intuitive to talk about a train moving than it is the platform, but either is fine.

If we simply start with the idea of the relative velocity, between Henry and Albert, both, as mentioned above, ascribe a zero velocity (and therefore absolute rest) to their own reference frames; but we can hopefully be demonstrate the point more clearly by considering the mechanics (is that the right use of the term?) of the situation.

The issue is difficult to see initially, if we only consider the Einsteinian thought experiment at it is, with no apparent tacit assumptions or consequences pertaining to absolute rest. However, if we juxtapose the Einsteinian thought experiment with the same thought experiment, except with the notion of absolute rest included, we can, hopefully, see those tacit consequences and/or assumptions emerge.

Absolute Frames
If we start with Albert being at absolute rest, then the photon in his clock would trace a path perpendicular to the centre point of both mirrors, and a path length of 2d.

If Henry were moving relative to Albert's absolute reference frame, then Albert would observe the photon in Hnery's clock to travel a path represented by the hypotenuse of a right angled triangle; hence he would observer his clock to be ticking slower (and lengths in Henry's reference frame as contracted). On the other hand, if Henry was at absolute rest and it was Albert moving relative to this frame, then Henry would see the same effects in Albert's reference frame.

As mentioned, this is indistinguishable from the Einsteinian thought experiment, except with an absolute reference frame expressly stated. What can hopefully demonstrated is that the Einsteinian thought experiment necessarily includes this absolute reference frame.

Absolute Albert
For the purpose of explanation, we can consider the scenario where Albert's co-ordinate labeling system labels him as "at rest".

If Albert's train were traveling at an inertial velocity, relative to the absolute rest frame - as would be necessitated by the scenario where "at rest" doesn't imply "absolute rest" - then the photon in his clock would be imparted with a horizontal velocity component, equal to the horizontal velocity of the train and the clock - much like he would observe in Henry's reference frame. This horizontal velocity component, along with the existing vertical velocity component, would cause the photon to trace a diagonal line between the centre points of the mirrors - because a line perpendicular from the centre point of one mirror would not meet the centre point of the other mirror, if both mirrors are moving; the path of the photon could be represented by the hypotenuse of a right angled triangle. The photon would still travel a distance of 2d relative to the carriage, because the horizontal velocity component of both would be equal. However, as you highlighted in the example above, this would cause the photon to have a vertical velocity component of less than c.

Because Albert measures the vertical velocity component of the photon to be c, it implies that that the clock, the carriage, and Albert himself, are at absolute rest.

Lorentzian relativity applies just as well in the case of particle accelerators, I presume, or else there might be a way to distinguish between the two. As for elegance, I'm not sure reality relies on elegance to decide what is real and what is not. Indeed, Einsteinian relativity might have a number of tacit assumptions itself, that migh make it appear less "elegant".

With regard to Craig: it was only through discussing Einsteinian relativity that I became aware of Lorentzian relativity; and only through searching for information about the latter that I found out that Craig had latched onto Lorentzian relativity for the reason you state above. It is perhaps, paradoxically, both fortunate and unfortunate at the same time. However, I don't think his motivation for doing so should be allowed to cast aspersions on the theory of the late Dutchman; nor should they prejudice people's interpretation of his analysis - even if they do prejudice his own analysis (which is not to suggest that they actually do).

Not necessarily; the counter on an atomic clock actually counts the number of "events" inside the clock without any measurement of the relation between theose events, while there is no counter on a ruler which counts the number of atoms.

The suggestion is not that there is a rest frame which labels the present as the "true present"; the suggestion is that absolute simultaneity prevails in the universe; that a timeless A-theory, if you will, prevails.

roosh wrote: »

I don't think that arriving at the same results, when including the absolute reference frame, demonstrates that it is superfluous; I would be more inclined to say that it demonstrates that the absolute reference frame is a tacit assumption. Also, simply stating that there is no absolute rest, does not mean that absolute rest is not a tacit assumption; in itself, it is indeed a contradiction, but, in order to see more clearly, where the contradictions arise, we need to examine the thought experiment critically.

We can look at it in two ways: ignoring the absolute rest frame and considering only the relative velocity; or including the absolute rest frame and considering the mechanics.

Relative velocity
If we consider only the relative velocity, then we can see that the co-ordinate labeling system of Einsteinian relativity necessitates that one reference frame be ascribed a zero velocity. Again, I presume that a reference frame with a velocity of zero is a reference frame at absolute rest.

Mechanics
Demonstrating the tacit assumption, of absolute rest, is best done by considering the mechanics of both scenarios: where Albert is at absolute rest; and where Albert is not at absolute rest. The position of absolute rest is exactly the same as the thought experiment. But if we consider the scenario where he is not at absolute rest, then the conclusions do not concur with Einsteinian relativity.

Again, if Albert is at absolute rest, then the photon in his clock will have no horizontal velocity component, only a vertical one; which will equal c. If Albert is not at absolute rest - the scenario where "at rest" under his labeling system doesn't mean "absolute rest" - then the photon in his clock will have a horizontal velocity component equal to that of the train (or platform) and clock. As you highlighted above, if this is the case, then the vertical velocity component will be less than c.

If Albert measures the speed of light in his clock to be c, then it implies that he is at absolute rest - or that the vertical velocity component is greater than c, such that it yields a measurement of c, relative to the moving carriage.

Alternatively, the contention of Lorentzian relativity could apply; that the instruments in Albert's reference frame are contracted by an amount unknown to him, due to the motion of the reference frame (where "at rest" doesn't mean "absolute rest"); relative to what, though, is the question which is begged. It can't be relative to Henry's reference frame, because he labels his reference frame as "at rest" relative to that (itself a contradiction perhaps), and he has to ascribe all the velocity to Henry's reference frame; meaning he has to label himself as having a zero velocity.

On the one hand we have a theory which seeks to explain things in the context of the micro-structure of matter (which we know to exist); on the other we have a theory which explains things by introducing a "new kinematical structure for space and time involving essential relativized notions of duration, length, and simultaneity"; which can, incidentally, only be detected by measuring the effects of the micro-structure of matter, or the macro-structure of matter, which we know to be comprised of the micro-structure of matter. In the latter "complex material bodies are constrained (somehow!) to 'directly reflect' its [spacetime's] structure, in a way that is 'independent of all hypotheses concerning microstructure and its dynamics' [again, things we know to exist]."

Brown & Pooley (2004)

The emphasis and brackets are mine, and the quotes are taken out of context and don't represent the authors opinions; but the points made are applicable here.

I haven't read any of his writings on the subject, so I can't offer too much insight; but I would imagine that his entire analysis is not based solely on the contention that a preferred reference frame fits with his theory of God. That is more based on comments in a paper by Brown & Pooley (Minkowski spacetime: a glorious non-entity).

This just demonstrates that matter has a spatial dimension; the same cannot be said for a temporal dimension.

Experimentally, is there a way to determine relativity of simultaneity?

roosh wrote: »

The issue isn't quite as simplistic as saying "I am at rest with respect to myself".

EDIT: of course, the "I am at rest with respect to myself" applies just as much to an observer at absolute rest.

If we were considering a lone observer in an empty universe, or considering the observer without reference to anything else in the universe, then a co-ordinate system which implies "I am at rest with respect to myself" would be fine; but we are considering the co-ordinate labeling system which labels the reference frame as "at rest" and a relatively moving reference frame as "in motion".

When we do this, there is no need to claim that a reference frame has a velocity of zero, it is a logical consequence of the co-ordinate labeling system. If you only consider the relative velocity between systems, then it is impossible not to label one as having a zero velocity, and, therefore, as being at absolute rest; regardless of what mathematicians wish to imply, that is a consequence of such a labeling system. This is what is meant by saying that the co-ordinate labeling system of Einsteinian relativity treats reference frames as being at absolute rest, from it's own perspective, or "according to itself".

The "from it's own perspective" or "according to itself" is a semantical point, with which we shouldn't get bogged down. The essential point is that the co-ordinate labeling system applied to reference frames in Einsteinian relativity, treat that reference frame as being at absolute rest, precisely because it ascribes a zero velocity to it.


Infinite reference frames
If we consider the infinite, possible, reference frames in the universe, and - sticking with the basic thought experiment for now - if we start with the perspective of one observer; then 100% of the velocity, of any relatively moving system, is ascribed to the other system, under that observers co-ordinate labeling system. That means that the co-ordinate labeling system ascribes a zero velocity to the "at rest" reference frame.

If it doesn't imply "at absolute rest" then the reference frame must be in motion relative to something other than the other detectable, relatively moving reference frames; an undetectable reference frame perhaps. But even if we postulate an infinite number of undetectable reference frames which would help satisfy the condition that "at rest" doesn't mean "absolute rest", if we extend the logic of the co-ordinate labeling system, then the co-ordinate labeling system would still apply 100% of the relative velocity to those undetectable reference frames, and consequently imply a state of absolute rest.

The co-ordinate labeling system could, of course, ascribe 100% of the relative velocity to an observers own reference frame, but this just shifts the problem of absolute rest to another reference frame.

To say that Einsteinian relativity says all observers will measure the speed of light to be c, therefore Albert will measure the speed of light to be c, is circular reasoning. The point, which is presumably clear enough at this stage, is that the implication of absolute rest can indeed be made, even if Einsteinian relativity doesn't expressly state it.

I presume you don't have an issue with the notion that the photon in the clock will inherit the horizontal velocity component of the train (or platform) and the clock, if the train is in motion; or if the train is not at absolute rest (which are just two ways of saying the same thing). If not, then there shouldn't really be any issue in following the logic.

"at rest"
If "at rest" doesn't mean "at absolute rest", then it means that "at rest" also means "in motion", which itself is a contradiction in terms; but that is a semantical argument, which doesn't need to be pursued. We only need to reason from some simple principles we already appear to have established - namely, the imparting of a horizontal velocity component to the photon.

If "at rest" doesn't mean "at absolute rest", then, by necessity, the photon in the light clock will be imparted with a horizontal velocity component. You stated above that this would result in the vertical velocity component being less than c, and so the observer on the train would measure the speed of light to be less than c; this would be at odds with Einsteinian relativity.

Alternatively, we can draw the conclusion that the vertical velocity component of the photon is greater than c, such that the observer on the train measures the speed of light to be c, relative to the train carriage; this too is at odds with Einsteinian relativity.

We could conclude that the photon doesn't get imparted with a horizontal velocity component, and only has a vertical velocity component; this however would result in the photon "falling out of the clock"; this is also at odds with Einsteinian relativity, and is contrary to something we have established in discussion.

Another alternative is that Albert is at absolute rest; this fits perfectly with the Einsteinian thought experiment, and indeed with practicalities of Einsteinian relativity, even if it is at odds with certain beliefs about Einsteinian relativity.

Another alternative, if "at rest" doesn't mean "at absolute rest", is that the equipment in Albert's reference frame is contracted by an amount unknown to himself, due to his motion relative to an undetectable reference frame; which result in his measuring a speed of c for the light. This, however, is closer to Lorentzian relativity than it is Einsteinian.

My apologies, I know I added to this line of the discussion, but I'll respond in the neo-Lorentzian thread.

The choice seems to be between mysterious dynamics affecting something we know to exist - the microstructure of matter - and a mysterious universe wide entity, which can only be detected through the observations of the micro-structure of matter, or the macro-structure of matter (which is comprised of the micro-structure).

We've been discussing this already in the thread on clocks, and I don't think it was established that a clock demonstrates a temporal dimension at all; only a spatial relationship between the events in a clock can be demonstrated. This applies equally to any other process.

In other words, "just as 'the true present' cannot be established experimentally, neither can relativity of simultaneity. Also, there is only evidence for the present moment; there is no experiment which has ever been conducted, or can ever be conducted, that was not, or will not be, in the present; therefore, there is no evidence that either 'past' or 'future' exist - they have to be assumed to exist. There is also no evidence for the existence of time, because it cannot be demonstrated that a clock measures time, without the assumption that it does.

If the above scenario occurs, is there a way to determine relativity of simultaneity?

roosh wrote: »

Mushing reference frames

There is no "mushing together" of reference frames, whatsoever. We only
need to consider one single reference frame, Albert's for example; Albert's co-ordinate system ascribes a zero velocity to his reference frame, and ascribes 100% of the [relative] velocity to any other reference frame that is moving relative to his, Henry's for example. Again, a system with a zero velocity is a system at absolute rest. This doesn't involve mixing reference frames any more than the Einsteinian thought experiment does.

Mistakes in logic

If you believe there are mistakes in the logic, it might be worth pointing out where the logic breaks down.

Circular reasoning
If the starting assumption is that all observers will measure the speed of light to be c, regardless of whether they are in motion or at absolute rest, and the conclusion which follows directly afterwards is, therefore an observer will measure the speed of light to be c, regardless of whether they are in motion or at absolute rest; then it is circular reasoning.

Zero velocity
A system at absolute rest has a velocity of zero; and any system moving relative to that system is "responsible" for 100% of the relative velocity; therefore, any system with an [absolute] velocity of zero is at absolute rest.

Example: an observer on a train has a velocity of zero relative to the train;

there is a relative velocity of X between the train (and observer) and another relatively moving system.

If the other system is "responsible" for all of X (positive or minus signs are immaterial), then the train and the observer are at absolute rest.

If a co-ordinate system ascribes a zero velocity to a reference frame, then that co-ordinate system treats the zero velocity reference frame as being at absolute rest - because any system with an [absolute] velocity of zero is at absolute rest.

"at rest" & "at absolute rest"
If a system is not at absolute rest, then, by necessity, it must be "in motion". If "at rest" doesn't mean "at absolute rest", then [by necessity] it means that "at rest" also means "in motion".

If "at rest" means "in motion" then it must mean in motion relative to something. If a co-ordinate labeling system ascribes a zero velocity to a reference frame - and therefore implies that it is not in motion - and ascribes 100% of the relative velocity of all detectable, relatively moving reference frames, to those other reference frames, then, if "at rest" does not mean "at absolute rest" (and therefore means "in motion"), the motion must be relative to some other undetectable relatively moving reference frame. Again, however, the co-ordinate labeling system would still ascribe 100% of the relative velocity to all other detectable, and undetectable reference frames; thereby treating the particular reference frame as being at absolute rest.

Horizontal velocity component
The photon in a clock that is in motion will be imparted with a horizontal velocity component equal to the horizontal velocity component of the clock.

If "at rest" doesn't mean "at absolute rest", then, by necessity, it also means "in motion"; if a clock is "at rest", but not "at absolute rest", then, by necessity, it is "in motion"; if a clock is "in motion" then the photon in the clock will be imparted with a horizontal velocity component equal to that of the clock. Therefore, If "at rest" doesn't mean "at absolute rest", then, by necessity, the photon in the light clock will be imparted with a horizontal velocity component.

A physical entity, which has no substance, permeating the entire universe, which bends, warps, tears, slows down and forms tunnels, due to the presence of matter, or the motion of a system, or some other reason, but which cannot be detected, and whose effects can only be detected through observation of the micro- and macro-structures of matter, sounds a little mysterious to me.

In an ontological sense, it also sounds a little superfluous, even if it is mathematically useful. If there is no region of space that is not filled with matter, then surely all that exists is matter. Any of the observed effects that "give the illiusion of spacetime" are equally attributable effects observed in matter; more so, because they are actually observed in matter. The question of how, might just be another one of those things we don't yet have an answer to; attributing it to a mysterious spacetime structure that exactly resembles all matter and natural forces, which permeates the entire universe, but doesn't affect the micro-structure of matter when it contracts and warps, seems like answering the question of "why something instead of nothing" with the answer that an invisible bearded man in the sky did it.

I don't think I've made that point; but it is perhaps best saved for the other thread.

Have you ever existed in a time that wasn't the present; not the present moment "in time", but that wasn't the present tense?

I wouldn't quite say that; it might be worth pointing out that looking for evidence of an absolute present is a category mistake; it is like being presented with the buildings of a university and saying there is no evidence of the university. Given that the only evidence that any observer has, had, or will ever have, is of the present moment, I would say that evidence to the contrary is required.

Also, the the alternative, as opposed to, euphemistically, requiring a "relaxing" of the assumption of presentism, requires a "new kinematical structure for space and time involving essential relativized notions of duration, length, and simultaneity"; assumptions which directly contradict the experience of every observer, living or dead, as well as assumptions about the measurement of time.

It also seems to require the treatment of reference frames as being at absolute rest, under their respective co-ordinate labeling systems.

roosh wrote: »

There is no implicit introduction of an external, or separate reference frame, because the absolute reference frame is one and the same with Albert's, by virtue of his arbitrary co-ordinate labeling system. We don't say, there is an absolute rest frame and then there is Albert's reference frame; what is being said is that Albert's arbitrary co-ordinate labeling system treats his reference frame as one and the same thing as an absolute reference frame; not external, not separate, but the same - arbitrarily or otherwise.

His arbitrary, co-ordinate labeling system makes no distinction between "absolute" zero and plain old zero, because no distinction can be made without implying that Albert's reference frame is in motion relative to an undetectable reference frame; because his co-ordinate labeling system labels him as having a zero velocity relative to all other, detectable, reference frames. So, if Albert's zero velocity [relative to all detectable reference frames] doesn't correspond to an absolute velocity of zero, then Albert's reference frame must have a velocity relative to some other, undetectable reference frame.

However, even if there was relative velocity between Albert's reference frame and any number of other infinite, undetectable reference frames, Albert's arbitrary co-ordinate labeling system would still label him as being at absolute rest, because it would ascribe a zero velocity him and ascribe 100% of the relative velocity to the other, relatively moving, reference frames.

We are discussing the implications of the co-ordinate labeling system, and the expected behaviour of the photon under different circumstances, and seeing what logical conclusions we can draw from that; we don't need to consider transforming the arbitrary co-ordinate labels into another reference frame just yet.

"P does not imply Q"; however "P and Q are not mutually exclusive"; indeed "Q satisfies the conditions for P, while A-Z (excluding P & Q) arguably don't"; therefore "P must be Q".

The assumption that is, effectivily, being challenged is, that the photon in Albert's clock won't be imparted with a horizontal velocity component, which would mean that the vertical velocity component would be less than c, such that he would measure the speed of light to be less than c, unless - and this is an important point - unless his instruments are contracted by an amount unknown to himself, due to his motion relative to an undetectable, absolute reference frame. We can examine this simply by considering Albert's reference frame, according to his own arbitrary labeling system, in the two possible scenarios under discussion: at absolute rest; and not at absolute rest. As has been outlined, only a position of absolute rest satisfies the conditions for Einsteinian relativity.

Keypoints
OK, so there are two key points that we need to consider, just to see where the issue lies in this; do you agree with the following?

- a system that is not at absolute rest, is, by necessity, in motion? If not, why not?
- the photon in any clock that is in motion will be imparted with a horizontal velocity component equal to the motion of the system? If not, why not?

That a co-ordinate system is just a set of arbitrary labels is not in question; what is in question is the logical implications of such a co-ordinate system. If a co-ordinate system arbitrarily treats a reference frame as being at absolute rest, then regardless of the arbitrariness, it still treats that reference frame as being at absolute rest.

If we look at the two contentions:
A system at absolute rest has a velocity of zero

"Employing an arbitrary coordinate system that labels an object as [having a velocity of zero] implies the object is at absolute rest"

I'm not sure how you can deduce that the conditional can't be used, if you don't know what it means.

What was meant is probably easier explained with an example; if we imagine the relative velocity between two cars is 100 km/h; theoretically there is an infinite range of values that could contribute to the relative velocity of 100km/h; one car could be traveling at 70km/h, the other at 30; both could be traveling at 50km/h; one could be traveling at 99km/h while the other is traveling at 1km/h; of course, another possibility is that one car is stationary, while the other car is traveling at 100km/h. In the intended context, we would say that the proportion of the relative velocity that each car is responsible for corresponds to their speeds.

It is probably further clarified using the now familiar absolute rest frame. If there is relative velocity between the absolute rest frame and another system, then the other system is "responsible" for all of the relative velocity.

If a co-ordinate system ascribes 100% of the relative velocity to every other, relatively moving, reference frame, then that arbitrary, co-ordinate labeling system treats the zero velocity reference frame as being at absolute rest - because it makes every other reference frame "responsible" for the entirety of the relative velocity;à la the absolute reference frame.

I think you might be getting caught up in semantics here; but I'm sure you get the point that is being made, because you've been discussing it thus far without recourse to semantics (at every turn).

Albert's co-ordinate labeling system ascribes a zero velocity to him, and ascribes 100% of the relative velocity to other relatively moving reference frames, à la the absolute reference frame.

The questions are posed abvoe, but for the purpose of re-iteration they can be restated:

Do you agree with the following?

-If something is not at absolute rest, then, by necessity it is in motion
if not, why not?

If you agree that something which is not at absolute rest is, by necessity, in motion, then we can reason thusly:

If something not at absolute rest is necessarily in motion; then, if something doesn't imply absolute rest, it must imply motion; therefore, if "at rest" doesn't imply "absolute rest" then it necessarily implies motion - arbitrarily or otherwise.

I'm not sure introducing euphemisms will be entirely productive, even if euphemisms is the language usually employed.

"A train has a velocity of zero" -> "Consider an arbitrary coordinate system labelling the train as having a zero velocity"

"The relative velocity between the the ground and the train, is X" -> "A coordinate system that labels the train as having a zero velocity, labels the ground has having a velocity |X| i.e. it ascribes the entirety of the relative velocity to the ground"

If we're going to be more rigorous then I don;t think semantics is the way to go; we need to consider the logical implications of the language.

roosh wrote: »

The point being made isn't simply: since Albert's reference frame, which labels him as "at rest" is consistent with the metaphysical statement "Albert is at absolute rest", it must mean Albert's reference frame is making a metaphysical statement about absolute rest.

The point being made is that, given the fact that a photon will inherit the horizontal velocity component of a clock that is in motion, then only a position of absolute rest satisfies the conditions for Einsteinian relativity.

The issue can be distilled down to one foundational question (and possibly a follow up question):
Is a system which is not at absolute rest, necessarily in motion?

If not, why not?