The Relativity of Simultaneity: A Fundamental Concept in Special Relativity

[mangaroosh]

Practice will help but in learning a new language, you also have to listen to people who already speak it when they tell you what the jargon terms mean where they are specific to that language.

The term "relativity of simultaneity" is one of those jargon terms which has a very specific meaning and is not something you can reinvent for yourself if you want to communicate with people who already know the conventional definition. That is why I took the trouble to explain it to you carefully in the previous post.
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No, it is a jargon term so has only one specific meaning which several people including myself have been patiently explaining to you for several weeks. You seem determined to avoid understanding it.
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No, that is where you are making you fundamental mistake, you are confusing your philosophy with the science. The phrase "relativity of simultaneity" refers to clock synchronisation, nothing else.
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No, it refers to the nature of synchronisation of clocks which is an observable fact regardless of any philosophical interpretation.
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You don't get to choose. The term has been defined for decades. Try learning what it means instead.

I haven't reinvented the term at all, the understanding I have of the term, as presented above, is something that has been discussed and agreed in this thread, with people who already know the conventional definition.

My understanding of RoS is that events which are simultaneous in one reference frame are not necessarily simultaneous in other reference frames i.e. if two events are not simultaneous in one reference frame it is possible that they are simultaneous in other reference frames. Is that accurate to any degree?

Yes.

I understand that RoS relates to the synchronisation of clocks, in Einsteinian relativity, at least. The question is whether or not it relates purely to the synchronisation of clocks - please don't simply reply with "it does" here, because I am trying to outline my understanding of why it might not; if it does, then it would apply equally to LET. The issue, however, lies in the fact that both theories make different, fundamental assumptions about the nature of time and what the synchronisation of clocks implies. That the clock synchronisation method relies on an untestable assumption i.e. the one way speed of light, makes it a philosophical consideration, not an experimentally verifiable one. This, in turn, makes RoS a philosophical consideration.

As with any philosophical concepts, there are certain implications as far as RoS is concerned. One such implication is that there is no universal present moment, common to all observers.

This concept is incompatible with the idea that there is a universal present moment i.e. presentism.

That remains a fact regardless of clock synchronisation.


The question is whether or not presentism is assumed/incorporated into LET; you seem to be offering somewhat contradictory opinions on this, but we can look at them below.

Presentism is not "incorporated in LET" as I again tried to explain before. Presentism is a philosophical view while LET is a scientific theory so the two are independent. Let's leave that topic for the philosophy forum.
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It isn't. What I said was that if you assume presentism, you probably get LET but it doesn't follow the other way round. Anyway, let's leave presentism for the philosophy forum.

Firstly, it might be worth addressing the point about philosophy, just to get it out of the way, because it seems to be cropping up a bit.

Whether we like it or not, scientific theories have philosophical implications. Simultaneity is itself a concept, and insofar as we are discussing simultaneity, we are engaged in a philosophical discussion. Insofar as we are engaged in a discussion on RoS we are engaged in a philosophical conversation regarding Einsteinian relativity, which can help to expand our (the collective our, not necessarily you and me) understanding of relativity, and so it is perfectly suited to this section of the forum.

If we were to make no statement about the implications clock synchronisation has on simultaneity, then we wouldn't necessarily be discussing the philosophy of the theory; we could say that relatively moving clocks will not remain synchronised and leave it at that; that would be fine; but when we delve into a discussion about what this means for the simultaneity of events across reference frames, it becomes philosophical.


As for presentism being a part of LET, you mention above that it is not incorporated into LET, but earlier you mentioned

Effectively, LET is a consequence of assuming presentism. Lorentz was assuming Galilean Relativity which is equivalent.

This suggests that presentism is an assumption of LET, and therefore incorporated into it; just as the constancy of the speed of light is an assumption of Einsteinian relativity, and thus incorporated into it.


As you mention, Lorentz was assuming Galilean relativity, and I think it is correct to say that he assumed absolute space and time as Newton did, both of which incorporated, or have (or whatever the suitable verb is) the idea of a universal present moment i.e. presentism.

Indeed, but you have discussed nothing but LET's version of RoS and philosophy, there isn't a single comment related to relativity in anything you have posted.

The discussion relates to the necessary consequences of the Lorentz transform, an integral part of Einsteins theories. By expanding our (again, the collective) understanding of the necessary consequences of the LT, we (collective) expand our understanding of Einsteinian relativity.

Given that there are two theories which implement the LT, it is necessary to compare them and see what differences there are; only by doing so can we determine the necessary consequences of the LT, and thereby expand our understanding of Einsteinian relativity.

You have moved the presentism to the other forum so let's leave that there.

I presumed that people familiar with Newtonian physics would be familiar with the concept of presentism, or a universal present moment; but it appears as though I was mistaken. I started the thread there to try and get a more detailed explanation of it, in such a manner that it might benefit any discussions that refer to the concept; such as this one.

Bob doesn't exist, he's hypothetical. The LTs allow you to do the calculations.

They would also allow Bob to do them, if Bob was real.

Work through those definitions carefully, we went over this some time ago but you still seem to be having trouble with it. I've repeated the description above because it is key to the context.

It might be useful to go through it line by line, to see if there are places where I have misunderstood.

Think about the words. Two clocks are sychronised if their ticks are simultaneous.

No problem with this; it does require an assumption about the one way speed of light though doesn't it?

The time when an event occurs is defined by the reading on a clock local to the event.

This is true in Einsteinian relativity; I have no problem with this.

According to LET, however (which uses the lorentz transform and which it is being said also incorporates RoS) the time when an event occurs isn't defined by the reading on a clock local to the event; the time when an event occurs is defined by the reading on a clock in the preferred, absolute reference frame.

That means that two events are simultaneous if their times are the same as measured by synchronised clocks or, to put it another way, if their time coordinates are the same.

That is if we assume that the clocks are actually synchronised; something we can't actually verify; is that correct? LET doesn't assume the one way speed of light is constant, so how are clocks synchronised in that instance?


Note: that is an important issue in determining the necessary consequences of the Lorentz transform

 

[mangaroosh]

That is a non-sequitur as I clearly never said that. I stated that the condition of indeterminacy would be just as much a fact even if the universe was "actually" presentistic.

Apologies, I might have misunderstood the point you were making:

is RoS compatible with Presentism?
Einstein demonstrated that our idea of simultaneity was indeterminable.
That it was meaningless to say (or think) any two spatially separated events were simultaneous in any absolute sense. But this is just as true if this is a presentistic (?) universe.

SO yes, RoS, is as compatible with presentism as it is with block time, as both are essentially philosophical or metaphysical concepts and questions.

It seemed as though you were saying that presentism is just as indeterminable as Ros, "so" [therefore] RoS is "compatible with presentism"; also, that "as both are essentially philosophical or metaphysical concepts and questions" they are [therefore] compatible.

That, of course, would be a non-sequitir,.

yes I cannot rule out the possibility that the universe is presentistic but that in no way suggests that RoS is indeterminable as it simply deals with what IS determinable i.e. Empirical measurements and observations; CLOCKS

The definition of RoS that has been provided by others, in this thread, extends RoS beyond simple synchronisation of clocks; it includes it, and is entirely based on it, but it extends it beyond that.

My understanding of RoS is that events which are simultaneous in one reference frame are not necessarily simultaneous in other reference frames i.e. if two events are not simultaneous in one reference frame it is possible that they are simultaneous in other reference frames. Is that accurate to any degree?

Yes.

If that is an accurate description of RoS, or its consequences, then it isn't compatible with presentism, because it means that there is no universal present moment.

At the risk of being redundant; the source of much of your confusion and difficulty in understanding what everybody has been telling you is that you are continually mixing apples and oranges.

Presentism and Block Time are philosophies.
These concepts ARE NOT compatible

SR and LET are scientific theories.
AS theories that that make the same empirical predictions they ARE compatible.

Does this mean that LET is equally as valid as Einsteinian relativity; why are they not the exact same theory?

They are scientific theories which offer different explanations for those empirical predictions; explanations which are not necessarily compatible.

It's a bit like saying there is a theory of the universe which says that Gargamoyl the great created the universe in 16hrs, and continues to influence it; and there is also a theory which says that the universe wasn't created by Gargamoyl, and that he doesn't influence it. Both make the same empirical predictions, but both offer entirely different explanations as to why. Both theories are not necessarily compatible.

Some LETists are Presentists and some Relativitists are Block Timers but this is completely irrelevant to the Theories themselves.
Philosophically Newton was an Absolutist but as a scientist he was as much of a Relativitist as Einstein. The theories had no element of absolutism.

Are there any LETists who are Block timers, and are there any relativists who are presentists? That is the critical question.

Newton was a presentist; was Einstein?

Right.

WRONG. RoS says absolutely nothing about a present moment or whether or not a universal present moment actually exists. It simply correlates proper time readings in differing
inertial frames.
Once again you are confusing two different interpretations of simultaneous.
RoS is the idea that the proper time reading is relative for each observer.
You are free to interpret this however you choose. Eg; There is a universal now and the clocks are all incorrectly desynchronized according to the universal instant.
RoS is not incompatible with that interpretation , it is merely irrelevant.

There is no confusion as to the meaning of the term simultaneous.

Again, the definition of RoS, that has been agreed on by Dale and Harry goes beyond the simple clock synchronisation, although it is based on it.

Where RoS refers to the idea that simultaneous events in one reference frame are non-simultaneous in another, this means that there is no universal present moment, and thus it would not be compatible with presentism.

No; block time and presentism are unverifiable

But block time is neither a necessary condition for , nor an inevitable logical derivation from RoS
They are mutually independent. But you seem to keep trying find a necessary correspondence and insisting there is one.

Again, the definition of RoS, that Harry and Dale agreed upon, refers to mutually simultaneous and non-simultaneous events. The simultaneity of events is indeterminable, meaning that, if that definition is accurte, or representative, then RoS is indeterminable.

 

[GeorgeDishman]

Just a quick note:

As for presentism being a part of LET, you mention above that it is not incorporated into LET, but earlier you mentioned

Effectively, LET is a consequence of assuming presentism. Lorentz was assuming Galilean Relativity which is equivalent.

This suggests that presentism is an assumption of LET, and therefore incorporated into it; ...

"Affirming the consequent":

http://en.wikipedia.org/wiki/Affirming_the_consequent

Presentism implies LET.

LET does not imply presentism.

(NB the first is also arguable.)

Or try it as two statements. In LET, I would argue the first is a valid logical deduction but the second isn't:

1) If only the present exists, then the Twins Paradox shows that clocks are affected by motion.

2) If clocks are affected by motion as shown by the Twins Paradox, then only the present can exist.

 

[mangaroosh]

Just a quick note:
"Affirming the consequent":

http://en.wikipedia.org/wiki/Affirming_the_consequent

Presentism implies LET.

LET does not imply presentism.

(NB the first is also arguable.)

Or try it as two statements. In LET, I would argue the first is a valid logical deduction but the second isn't:

1) If only the present exists, then the Twins Paradox shows that clocks are affected by motion.

2) If clocks are affected by motion as shown by the Twins Paradox, then only the present can exist.

If assuming presentism leads to LET;
and RoS implies the absence of a universal present (or not-presentism);
while presentism implies the existence of one (or not-RoS);
then LET cannot be compatible with RoS.

EDIT: unless LET can be arrived at without presentism; either way, it would demonstrate that RoS - as per the definition agreed upon by Harry and Dale - is not a necessary consequence of the loretnz transform.

 

[GeorgeDishman]

"Affirming the consequent":

http://en.wikipedia.org/wiki/Affirming_the_consequent

Presentism implies LET.

LET does not imply presentism.

(NB the first is also arguable.)

Or try it as two statements. In LET, I would argue the first is a valid logical deduction but the second isn't:

1) If only the present exists, then the Twins Paradox shows that clocks are affected by motion.

2) If clocks are affected by motion as shown by the Twins Paradox, then only the present can exist.

If assuming presentism leads to LET;

That is quite possible (though I admit arguable).

and RoS implies the absence of a universal present (or not-presentism);

It does not, RoS is an observation regarding the synchronising of clocks.

while presentism implies the existence of one

Presentism doesn't imply it, it assumes it, and it is rather the rejection of the existence of anything other than the present (which may be different).

(or not-RoS);

No, RoS is an observation regarding the synchronising of clocks, it is not a philosophy.

then LET cannot be compatible with RoS.

EDIT: unless LET can be arrived at without presentism; either way, it would demonstrate that RoS - as per the definition agreed upon by Harry and Dale - is not a necessary consequence of the loretnz transform.

The definition of simultaneity you quote below as having been agreed is:

My understanding of RoS is that events which are simultaneous in one reference frame are not necessarily simultaneous in other reference frames i.e. if two events are not simultaneous in one reference frame it is possible that they are simultaneous in other reference frames.

I too agree that explanation of RoS. Where you are wrong is when you say:

There is no confusion as to the meaning of the term simultaneous.

1) Simultaneous means "At the same time".

2) Time is what a clock reads.

Therefore

3) Simultaneous means "At the same time coordinate as measured by synchronised clocks."

4) Since "synchronised" is frame dependent, the definition of RoS you give above follows.

5) If "synchronised" were not frame dependent, the definition of "simultaneous" would be independent of the frame and RoS would not exist, we would not be having this conversation.

 

[harrylin]

No, crudely, presentism is the philosophy that things that exist are 3-dimensional and that time is an emergent property resulting from the perception of change. It contrasts with eternalism which considers that the past, present and future existence of entities are equally real. [..].

Just a last remark about such philosophical words:
Your "no" implies that presentism is at odds with the "true time" concept. However, "true time" certainly contrasts with the eternalism of the block universe philosophy, and fits with the view of the world as a three-dimensional space that is modulated by the passage of time.
- http://en.wikipedia.org/wiki/Eternalism_(philosophy_of_time)

 

[harrylin]

[..]it would demonstrate that RoS - as per the definition agreed upon by Harry and Dale - is not a necessary consequence of the loretnz transform.

That's a self contradiction, as we stressed many times already. Apparently you never derived this fact yourself, perhaps because you find the equation too complex. Never mind I can simplify it for you. Here is the older, pre-SR Lorentz transformation for time - and it is roughly the same as the modern one for low velocities:

t'= t - x*v/c^2

If you fill in some values you can only find that for a single time t of system S everywhere, the time t' of system S' depends on the x position in S.
Consequently, what is simultaneously (at time t) happening at different x according to S, happens at different times t' according to S'.
Please explain with a numeric example how you think that this result can be avoided.

 

[GeorgeDishman]

Just a last remark about such philosophical words:
Your "no" implies that presentism is at odds with the "true time" concept. However, "true time" certainly contrasts with the eternalism of the block universe philosophy, and fits with the view of the world as a three-dimensional space that is modulated by the passage of time.

It's more subtle than that, eternalism as you say is at odds with presentism and is often associated with the block universe model, but you can apply presentism to the block universe to get either the Growing Block model or the Moving Spotlight model.

Equating presentism with the concepts of absolute time as 'mangaroosh' did is inaccurate and misleading so I hoped I could clarify it before it became seen as an accepted definition within the thread.

 

[Dale]

Presentism refers to the idea that there is a single, universal present moment, common to all observers.

I see that you prefer to dodge the question which I have twice repeated and put in bold so that you could not miss it and instead preferred to simply repeat the very thing that I was asking clarification about (never an effective method of clarification).

Since I prefer to be up front and clear I will simply assume what I think is your most likely answer to my question for clarification and then answer your simple yes or no questions accordingly. If you don't like the answers, then feel free to actually answer the request for clarification.

"What are the experimental consequences of presentism, or is it merely a philosophical viewpoint?"

My best guess for your answer: there are no experimental consesquences, it is merely a philosophical viewpoint.

Firstly, is RoS compatible with Presentism i.e. the idea that there is one, universal present?

Yes. Presentism, as a philosophical viewpoint with no experimental consequences is inherently compatible with all experimental observations.

Secondly, is prensentism incorporated in LET?

LET is certainly compatible with the philosophical viewpoint of presentism, but I don't know if Lorentz explicitly incorporated it in any of his writings. I suspect not, but have no references to provide on the topic either way.

 

[Dale]

just wondering if you guys are familiar with Newtonian physics; am I right in saying that Newton's theory incorporated absolute space and time, as well as the idea of a single, universal present moment?

He definitely wrote specifically about absolute space and time, but I don't recall any of his writings specifically about the present. However, as philosophical viewpoints with no experimental consequences, presentism and alternatives, are all compatible with Newtonian mechanics also.

 

[Dale]

My understanding of RoS is that events which are simultaneous in one reference frame are not necessarily simultaneous in other reference frames i.e. if two events are not simultaneous in one reference frame it is possible that they are simultaneous in other reference frames. Is that accurate to any degree?

Yes.

If that is an accurate description of RoS, or its consequences, then it isn't compatible with presentism, because it means that there is no universal present moment.

That is not implied. As we have discussed multiple times at length and in great and exhaustive detail, simultaneous simply means that they have the same time coordinate. So this definition says that given two reference frames and two events it is possible that one referernce frame assigns the two events the same time coordinate and the other assigns them different time coordinates.

It says nothing whatsoever about whether those time coordinates are in the past, present, or future, or even whether or not there is any distinction between past, present, and future.

 

[mangaroosh]

It is probably worth establishing something from the outset:

If two events are simultaneous in the universal present, then they are simultaneous for all observers everywhere, across all reference frames. Regardless of the readings of any clocks.

If RoS allows for events to be simultaneous in one reference frame and non-simultaneous in another, then it is not compatible with presentism.

This holds true regardless of clock synchronisation.


We can define simultaneity without any reference to time keeping devices, and therefore any philosophical assumptions about them and the nature of time, by stating that two events are simultaneous if, while one event is happening, the other event is also happening.

We may not be able to measure this, without a synchronisation convention, but when our synchronisation convention relies on an unmeasurable, or untestable assumption, it fares no better.

That is quite possible (though I admit arguable).

I think the fact that LET employs a Newtonian concept of time and space implies that it is a presentist theory. Is it possible that the Newtonian concept of space and time could lead to a non-presentist theory?

It does not, RoS is an observation regarding the synchronising of clocks.

Again, if RoS allows for events to be simultaneous in one reference frame, and non-simultaneous in another, then it is incompatible with the idea of a universal present, and therefore presentism.

Presentism doesn't imply it, it assumes it, and it is rather the rejection of the existence of anything other than the present (which may be different).

The term presentism implies the existence of a universal present, was what I meant; it's what the term means.

I don't think the second formalism materially changes it.

No, RoS is an observation regarding the synchronising of clocks, it is not a philosophy.

The synchronisation convention is based on an unverifiable assumption, the one-way speed of light, isn't it? If it is then the synchronisation convention is, itself, a philosophical proposition.

Simultnaeity of events is, itself, a philosophical proposition. If it cannot be determined that events are absolutely simultaneous, then it implies that it is possible that they might be; this means that it cannot be verified that events are simultaneous in one reference frame and non-simultaneous in another; that means RoS is not verifiable, and is therefore a philosophical proposition.

I too agree that explanation of RoS. Where you are wrong is when you say:

There is no confusion as to the meaning of the term simultaneous.

The confusion doesn't so much lie in the idea of simultaneity, rather the concept of "at the same time".

Simultaneity can be expressed, without confusion, as, when one event is happening the other event is also happening. For example, if we take the clapping of our hands; our hand claps are simultaneous if, when my two hands meet , your two hands also meet.

The question arises when we add the qualifier, "at the same time".

1) Simultaneous means "At the same time".

2) Time is what a clock reads.

Therefore

3) Simultaneous means "At the same time coordinate as measured by synchronised clocks."

4) Since "synchronised" is frame dependent, the definition of RoS you give above follows.

5) If "synchronised" were not frame dependent, the definition of "simultaneous" would be independent of the frame and RoS would not exist, we would not be having this conversation.

The issue might lie in the assumption of synchronisation, and the synchronisation convention.

I'm just wondering does such a synchronisation convention exists in LET, given that the assumption about the one-way speed of light isn't incorporated?

 

[GeorgeDishman]

I understand that RoS relates to the synchronisation of clocks, in Einsteinian relativity, at least.

That is the key to understanding the question. The phrase "relativity of simultaneity" was coined specifically in the context of SR hence that is its only defined meaning. You can resolve your doubt by noting that in SR there is no other type of time other than "what a clock reads" and hence the phrase can have only one meaning.

Now certainly, once you have the phrase, you can retrospectively apply it to the same observed behaviour in LET but since LET is then borrowing the phrase, it doesn't change the meaning. In LET as others have already pointed out, the equivalent is what Lorentz called "local time". If you want it to have an alternative meaning, you are re-inventing the term.

The question is whether or not it relates purely to the synchronisation of clocks - please don't simply reply with "it does" here, because I am trying to outline my understanding of why it might not; if it does, then it would apply equally to LET.

Again, there you have your answer. Since RoS is a phrase from SR where it can only apply to clocks, it can apply equally to LET.

That the clock synchronisation method relies on an untestable assumption i.e. the one way speed of light, makes it a philosophical consideration, not an experimentally verifiable one.

No, the technique of bouncing the light back to the source relies only on the fact that the measured speed is isotropic which is a consequence of the Lorentz Transforms and therefore also valid in LET. What isn't testable is LET's extraneous concept of some other form of time, but clock synchronisation in LET refes to "local time" for practical scientific measurement (it is local time values that go into the variables in the transforms obviously, you can't use numbers that are impossible to measure).

Firstly, it might be worth addressing the point about philosophy, just to get it out of the way, because it seems to be cropping up a bit.

Whether we like it or not, scientific theories have philosophical implications.

Science very often has implication for philosophy but seldom vice versa. Science is predicated on discerning knowledge only from objectively verifiable data so only uses philosophy as a last resort.

Simultaneity is itself a concept, and insofar as we are discussing simultaneity, we are engaged in a philosophical discussion.

Two adjacent clocks are synchronised if the tick simultaneously, that is something that can be determined physically without any philosophical input.

Insofar as we are engaged in a discussion on RoS we are engaged in a philosophical conversation regarding Einsteinian relativity,

No, you have only ever discussed the relationship between the philosophy of LET and presentism, not a word about SR. To be honest, I get the impression that you have no knowledge of SR whatsoever but that may simply have been due to the very narrow nature of the conversation.

If we were to make no statement about the implications clock synchronisation has on simultaneity, then we wouldn't necessarily be discussing the philosophy of the theory; we could say that relatively moving clocks will not remain synchronised and leave it at that; that would be fine; but when we delve into a discussion about what this means for the simultaneity of events across reference frames, it becomes philosophical.

Again you are failing to consider the language, two clocks are "synchronised" if they show the same time values "simultaneously".

As you mention, Lorentz was assuming Galilean relativity, and I think it is correct to say that he assumed absolute space and time as Newton did, ..

I don't know whether he did or not but if so, he could potentially have had three different times in his philosophy since the aether might have been dragged. I've never heard of that in LET so I suspect he didn't.

The discussion relates to the necessary consequences of the Lorentz transform, an integral part of Einsteins theories. By expanding our (again, the collective) understanding of the necessary consequences of the LT, we (collective) expand our understanding of Einsteinian relativity.

No, you are becoming so blinkered and focussed on LET, I doubt you will ever be able to learn the basics of SR.

I presumed that people familiar with Newtonian physics would be familiar with the concept of presentism, or a universal present moment; but it appears as though I was mistaken.

They will be familiar with Newton's "absolute time" from the Scholium but may not have studied philosophy so may not know presentism.

They would also allow Bob to do them, if Bob was real.

You seem determined to miss the point at any cost.

Consider an observer, Alice, who has a long rigid pole with a clock at each end, A and B. She uses some practical physical technique to synchronise the clocks, for example by sending a light pulse from A to B where it is immediately reflected back to A. If the time of the pulse being reflected at B is midway between the send and receive times at A, the clocks are defined as being synchronised. A second observer, Bob, traveling past this setup who uses the same technique determines that the clocks are not synchronised. The determination is therefore related to the motion of the observer. That is called the relativity of simultaneity.

1) Can you see that the Lorentz Transforms can be used to calculate by how much Bob will consider the clocks to differ from being synchronised?

2) Can you see that the above scientific definition of synchronisation is independent of any philosophical musing on the nature of time?

Work through those definitions carefully, we went over this some time ago but you still seem to be having trouble with it. I've repeated the description above because it is key to the context.

It might be useful to go through it line by line, to see if there are places where I have misunderstood.

I've repeated it again for your convenience, by all means query any sentence where you have a concern.

Think about the words. Two clocks are sychronised if their ticks are simultaneous.

No problem with this; it does require an assumption about the one way speed of light though doesn't it?

No, look at the sentence, it is only a definition of what we mean by the word "sychronised", it says nothing about any proposed method for achieving the sychronisation of clocks.

The time when an event occurs is defined by the reading on a clock local to the event.

This is true in Einsteinian relativity; I have no problem with this.

According to LET, however (which uses the lorentz transform and which it is being said also incorporates RoS) the time when an event occurs isn't defined by the reading on a clock local to the event; the time when an event occurs is defined by the reading on a clock in the preferred, absolute reference frame.

No. The LTs convert between two frames, say A and B. In theory, if you knew the speed of A and B relative to the aether frame E, you could take "local times" (clock values) in A, use the LTs backwards (they are symmetrical though) to convert to "true times" in E, then apply them forwards to convert from E to clock times in B. However, the nature of the equations is such that if you use the speed of B relative to A and apply them just once, you convert local times in A to local times in B, the philosophical aether times are irrelevant. In order to use the LTs in any practical experimen, you can only use local times. Since the RoS is a result you see in applying the transforms, the RoS applies to clock times in LET.

That is if we assume that the clocks are actually synchronised; something we can't actually verify; is that correct?.

No, the times that go into the LTs are clock times. You can use them to convert from any frame directly to any other frame without any consideration of philosophical aspects. Two clocks are therefore "actually synchronised" if they show the same reading at the same time coordinate.

LET doesn't assume the one way speed of light is constant, so how are clocks synchronised in that instance?

The same way as in SR. The LTs mean that the measured speed of light is isotropic (one way equals two way) and science only concerns itself with measurables.

Note: that is an important issue in determining the necessary consequences of the Lorentz transform

No, it is totally irrelevant since the LTs work directly from any frame to any other, you do not need to do double conversions via the aether frame. As a result, the consequences of the LTs are independent of the existence of any hypothetical aether.

That is also why Ockham's Razor suggests we discard the aether concept and hence discard LET in favour of SR.

 

[mangaroosh]

I see that you prefer to dodge the question which I have twice repeated and put in bold so that you could not miss it and instead preferred to simply repeat the very thing that I was asking clarification about (never an effective method of clarification).

Since I prefer to be up front and clear I will simply assume what I think is your most likely answer to my question for clarification and then answer your simple yes or no questions accordingly. If you don't like the answers, then feel free to actually answer the request for clarification.

"What are the experimental consequences of presentism, or is it merely a philosophical viewpoint?"

My best guess for your answer: there are no experimental consesquences, it is merely a philosophical viewpoint.

I wasn't sure of the answer, as to what the experimental consequences of presentism are, so I simply asked for your opinion as to whether or not you agreed that the two concepts, as presented, were incompatible. If I accurately represneted both concepts, and we agreeed they were incompatible, then that would have offered another means of resolving the issue - and of course, it remains one.

The question also remains as to whether RoS is a philosophical interpretation of clock synchronisation; insofar as RoS refers to events which are simultaneous in one reference frame being non-simultnaeous in another, it is not compatible with the concept of presentism provided. If LET is compatible with that concept of presentism, then it suggests that RoS cannot be a necessary consequence of the LT, because RoS is not compatible with presentism.

So, the question of presentism being a philsophical viewpoint does not resolve the issue, because RoS is arguably a philopsophical viewpoint also - regardless of the assertions to the contrary.

The question of whether or not presentism is compatible with, or incorporated into, LET would help to resolve the issue. Insofar as LET is based on Newtonian, or Galielan time and space, then it suggests that LET does not allow for events that are simultaneous in one reference frame to be non-simultaneous in another.

Yes. Presentism, as a philosophical viewpoint with no experimental consequences is inherently compatible with all experimental observations.

I think it would have experimental consequences, similar in nature to the Principle of Relativity; I probably risk an infraction by stating what they are though, as I suspect it might be classified as a personal theory. I would probably need express permission to do so.

LET is certainly compatible with the philosophical viewpoint of presentism, but I don't know if Lorentz explicitly incorporated it in any of his writings. I suspect not, but have no references to provide on the topic either way.

Is RoS compatible with Newtonian physics, and Galilean relativity?

It's been mentioned that LET is essentially based on the Newtonian concepts of time and space, and Galilean relativity. If that is correct, and RoS is not compatible with those, then it probably means that RoS is not compatible with LET, I would think.

He definitely wrote specifically about absolute space and time, but I don't recall any of his writings specifically about the present. However, as philosophical viewpoints with no experimental consequences, presentism and alternatives, are all compatible with Newtonian mechanics also.

I think presentism is something which can be extrapolated from the theory. Presentism, possibilism and eternalism

It might be worth asking if Newtonian mechanics allowed for RoS, or did it incorporate the idea of a universally shared present moment?

That is not implied. As we have discussed multiple times at length and in great and exhaustive detail, simultaneous simply means that they have the same time coordinate. So this definition says that given two reference frames and two events it is possible that one referernce frame assigns the two events the same time coordinate and the other assigns them different time coordinates.

It says nothing whatsoever about whether those time coordinates are in the past, present, or future, or even whether or not there is any distinction between past, present, and future.

We can extrapolate it though, based on that.

If there is a universal present moment, then events which are simultaneous in the universal present, are simultaneous for all observers; that is, they are simultaneous in my present, and in your present, and we share the same present moment.

RoS is not compatible with that.

 

[GeorgeDishman]

It is probably worth establishing something from the outset:

If two events are simultaneous in the universal present, then they are simultaneous for all observers everywhere, across all reference frames.

You are muddling up several different concepts. The "universal present" is a philosophical concept of no concern to this discussion.

In Newtonian theory, he defined the concept of "absolute time". If two events were simultaneous in Newton's universe, they would be judged to be simultaneous by all observers because clock synchronisation would be independent of speed. However, the universe doesn't work that way.

In LET, if two events are judged to be simultaneous in the local aether rest frame, they will not be judged to be simultaneous by any observer moving relative to the aether in the direction of the line joining the events.

In SR, if a line between two events is perpendicular to one observer's worldline, it cannot be perpendicular to that of another observer moving relative to the first observer in the direction of the line joining the events.

Regardless of the readings of any clocks.

"Simultaneous" is a statement about clock readings in Newtonian physics, LET and SR. If you want to apply some other meaning, you need to be posting in the philosophy forum.

If RoS allows for events to be simultaneous in one reference frame and non-simultaneous in another, then it is not compatible with presentism.

Generally, most scientists would agree that presentism is untenable but there are a few die-hard philosophers still trying to find a way of keeping it.

We can define simultaneity without any reference to time keeping devices ..

Not in LET, SR or the Newtonian model. All of physics is about relationships between measurements.

Is it possible that the Newtonian concept of space and time could lead to a non-presentist theory?

Yes, as I said before, it would be compatible with the block universe. In fact Newton was concerned that that was the case as it had implications for free will.

Again, if RoS allows for events to be simultaneous in one reference frame, and non-simultaneous in another, then it is incompatible with the idea of a universal present, and therefore presentism.

There's no point repeating something when I have already explained several times why it is not true. Try to move on.

The term presentism implies the existence of a universal present, was what I meant; it's what the term means.

It's not what the term means to several decades of professional philosophers, I have given you reliable sources such as the Stanford Encyclopedia where your can see clear definitions of these terms. You are not helping the discussion by trying to invent alternative meanings, especially since you haven't done any work to ensure they are usable. The philosophical community has and those terms are well defined.

I don't think the second formalism materially changes it.

Then you should have no reason not to use the accepted definition.

The synchronisation convention is based on an unverifiable assumption, the one-way speed of light, isn't it?

No, it is based on the well proven knowledge that the measured speed is isotropic in both LET and SR.

I'm just wondering does such a synchronisation convention exists in LET, given that the assumption about the one-way speed of light isn't incorporated?

The practical lab techniques for synchronising clocks were the same regardless. Nothing other than clock times went into the LTs so Lorentz needed nothing more.

 

[harrylin]

[..] If there is a universal present moment, then events which are simultaneous in the universal present, are simultaneous for all observers; that is, they are simultaneous in my present, and in your present, and we share the same present moment.

RoS is not compatible with that.

Well ... after many weeks of discussions and explanations, you keep on denying that observers can not know true simultaneity. However, we explained that that is a basic result of SR that is related to RoS which directly follows from the Lorentz transformations, as we also showed. So, take it or leave it!

 

[yuiop]

The question also remains as to whether RoS is a philosophical interpretation of clock synchronisation;

RoS is not a philosophical interpretation, but a consequence of what can actually be measured and applies equally to SR and LET.

insofar as RoS refers to events which are simultaneous in one reference frame being non-simultnaeous in another, it is not compatible with the concept of presentism provided. If LET is compatible with that concept of presentism, then it suggests that RoS cannot be a necessary consequence of the LT, because RoS is not compatible with presentism.

Assuming that presentism is the notion of a absolute reference frame that defines a universal "now" (as embodied in Newtonian physics) then SR says IF there is a universal reference frame it cannot be detected and LET says there IS a universal reference frame, but it cannot be detected. Both theories acknowledge that the universal reference frame is undectable. Both SR and LET agree that by any measurements any observers with relative motion will disagree on the simultaneity of events. RoS is a consequence of the LT in both SR and LET. IF presentism is the concept of a universal "now" that can be measured, then presentism is incompatible with both LET and SR, but is compatible with Newtonian physics which has been shown to be wrong by experimental evidence.

So, the question of presentism being a philsophical viewpoint does not resolve the issue, because RoS is arguably a philopsophical viewpoint also - regardless of the assertions to the contrary.

We cannot measure a universal "now" or conduct any experiments that can detect a universal absolute reference frame but we can measure RoS. Therefore presentism is philosophical (unmeasurable) and RoS is not philosophical, in that it can be measured.

The question of whether or not presentism is compatible with, or incorporated into, LET would help to resolve the issue.

Presentism, in a form that can be measured, is not compatible with LET.

Insofar as LET is based on Newtonian, or Galielan time and space, then it suggests that LET does not allow for events that are simultaneous in one reference frame to be non-simultaneous in another.

LET is not based on Newtonian or Galilean time and space. In Newtonian physics, time as measured by clocks and space as measured by rulers is absolute. LET on the other hand has time dilation and length contraction and so time measured by clocks and space measured by rulers is not absolute in LET.

Is RoS compatible with Newtonian physics, and Galilean relativity?

No, it is not.

It's been mentioned that LET is essentially based on the Newtonian concepts of time and space, and Galilean relativity. If that is correct, and RoS is not compatible with those, then it probably means that RoS is not compatible with LET, I would think.

That is not correct.

It might be worth asking if Newtonian mechanics allowed for RoS, or did it incorporate the idea of a universally shared present moment?

Newtonian mechanics does not allow for RoS but it did have a universally shared present moment. Newtonian mechanics has been experimentally shown to be incorrect.

 

[Dale]

I wasn't sure of the answer, as to what the experimental consequences of presentism are,

Well, once you have clarified the question then we can work on answering it.

I think it would have experimental consequences, similar in nature to the Principle of Relativity; I probably risk an infraction by stating what they are though, as I suspect it might be classified as a personal theory. I would probably need express permission to do so.

If it has experimental consequences then the only reason it would be a taboo topic is if those predictions were contrary to existing observations, in which case presentism is already falsified.

Is RoS compatible with Newtonian physics, and Galilean relativity?

No, the Galilean transform does not have RoS.

If there is a universal present moment, then events which are simultaneous in the universal present, are simultaneous for all observers; that is, they are simultaneous in my present, and in your present, and we share the same present moment.

Prove it. Simultaneity is well defined, as are the transformations between reference frames. If your concept of the universal present works as you say then you should be able to start with one reference frame and two events which are simultaneous in the universal present, show that those events are simultaneous for some observer, transform to another observer moving at an arbitrary velocity relative to the first, and prove that they are simultaneous for that observer also.