Correct phrasing / use of vocabulary for SR

[ModusPwnd]

Well, its clear that I don't know enough to see the distinction you are making. Its been a few years since I have looked at this stuff and I never was that good back then either.

In other words, the observer's rest frame permits him to assign the same coordinate time to distant events that he sees on his local clock and this leads some people to think that also permits him to observe those distant events simultaneously with their occurrence not later as you describe. The term "relativity of simultaneity" applies to the fact the coordinate times of remote events is not absolute but dependent on the chosen frame, just like time dilation and length contraction.

I honestly didnt think anybody was confused about that in the bold. At least, not in this thread. Saying two things happen simultaneously, in my mind, means that after I have collected the signals I calculate that they happened at the same time coordinate, in my frame. You can never observe an event when it happens, unless your observation is the 'event'...

 

[Vandam]

It's not because you have not observed an event that it doesn't or didn't exist yet.
When the signal has not arrived yet, the rover has already landed safely on Mars or crashed. Whether it has landed safely or not is already a real fact before you observe it.

<<Physics is an attempt conceptually to grasp reality as it is thought, independently of its being observed. In this sense, one speaks of physical reality>>quote Einstein.

Einstein looked further than the observations. Quite a few people here do not want to look further than observations. Einstein would not share that kind of approach.

 

[ModusPwnd]

Einstein looked further than the observations. Quite a few people here do not want to look further than observations. Einstein would not share that kind of approach.

You can count me as one of those people. And lacking Einstein's approval honestly does not bother me at all.

Observations can be predicted and described, in qualitative or quantitative ways. "Reality" doesn't really matter. You can postulate any type of underlying reality you like. But if that postulate does not increase our predicative or descriptive power then it is superfluous to the theory. If it does increase our power, then its incorporation into the theory is because of observations and observations alone (observations that the postulate increases predictive ability).

Didn't Einstein also say something about not making any theory more complicated than needed? Isn't presuming an underlying reality with no benifit to the theory doing just that?

 

[Vandam]

You can count me as one of those people. And lacking Einstein's approval honestly does not bother me at all.

Observations can be predicted and described, in qualitative or quantitative ways. "Reality" doesn't really matter. You can postulate any type of underlying reality you like. But if that postulate does not increase our predicative or descriptive power then it is superfluous to the theory. If it does increase our power, then its incorporation into the theory is because of observations and observations alone (observations that the postulate increases predictive ability).

Didn't Einstein also say something about not making any theory more complicated than needed? Isn't presuming an underlying reality with no benifit to the theory doing just that?

Well, reality doesn't matter to you.
If I see a tree in front of me I have a concept of a tree that was there/is there independent of observations. You and many others on this forum reject this because you find this philosophical mumbo jumbo. I'm not a solipsist.

 

[ModusPwnd]

Well, reality doesn't matter to you.

I don't think it matters with respect to science. Outside of science I can conject and hypothesize away.

If I see a tree in front of me I have a concept of a tree that was there/is there independent of observations.

Aww, that's not true man. That like saying a blind mans knows what red looks like. If you never had an observation of a tree how would you create that concept to begin with? Its the collection of many observations you have made over your life that forms the concept of your tree.

You and many others on this forum reject this because you find this philosophical mumbo jumbo.

I reject because I don't see it adding any predictive or descriptive power to our theories. In that sense it is completely superfluous and thus irrelevant to science. It may be relevant to other philosophical areas, but not 'natural' philosophy, not science.

I'm not a solipsist.

A key tenant of science, IMO and I think many others as well, is that all theories are tentative with respect to new observations. All of them. Presuming that any are immune to new counter observations is denying any further investigation. That is counter to science. This is not nearly as hard of a line as I think of a solipsist as taking. But if it is, so be it. We are talking science here - not philosophy at large.

 

[ghwellsjr]

In other words, the observer's rest frame permits him to assign the same coordinate time to distant events that he sees on his local clock and this leads some people to think that also permits him to observe those distant events simultaneously with their occurrence not later as you describe. The term "relativity of simultaneity" applies to the fact the coordinate times of remote events is not absolute but dependent on the chosen frame, just like time dilation and length contraction.

I honestly didnt think anybody was confused about that in the bold. At least, not in this thread. Saying two things happen simultaneously, in my mind, means that after I have collected the signals I calculate that they happened at the same time coordinate, in my frame. You can never observe an event when it happens, unless your observation is the 'event'...

Maybe not in this thread, but haven't you seen many cases of people insisting that it's important for an observer to have a perspective or a point of view from his own rest frame, even he's not inertial?

 

[Vandam]

I don't think it matters with respect to science. Outside of science I can conject and hypothesize away.

Aww, that's not true man. That like saying a blind mans knows what red looks like. If you never had an observation of a tree how would you create that concept to begin with? Its the collection of many observations you have made over your life that forms the concept of your tree.

I reject because I don't see it adding any predictive or descriptive power to our theories. In that sense it is completely superfluous and thus irrelevant to science. It may be relevant to other philosophical areas, but not 'natural' philosophy, not science.
A key tenant of science, IMO and I think many others as well, is that all theories are tentative with respect to new observations. All of them. Presuming that any are immune to new counter observations is denying any further investigation. That is counter to science. This is not nearly as hard of a line as I think of a solipsist as taking. But if it is, so be it. We are talking science here - not philosophy at large.

I'm not saying observations are not important.
I'm saying that based on the observations we know what the exteriour world is made of independent of observations: I see a tree because there was a tree even before it was observed.

In a frame two events are observed simultaneous because they are simultaneous in that framle even if not observed. And those two events are non-simultaneous in another frame because they are non-simultaneous in that frame, even not observed. That's SR and block unverse. For me Block universe is the only correct physical interpretation of SR. All the rest I consider philosophical ad hoc explanations. Of course you do not agree with what I say.

 

[Dale]

I'm not a solipsist.

Nor are most of the people who disagree with you on some of your more extreme block universe positions.

 

[bobc2]

Nor are most of the people who disagree with you on some of your more extreme block universe positions.

"...extreme block universe positions"? I've seen nothing extreme about the positions presented by Vandam. Block universe is widely discussed among physicists--quite a few references have been cited on this forum. LET is usually the concept offered as proof that block universe is not the only world view among physicists. I personally have not dug into the details sufficiently to critique LET.

My grad school prof discussed it only briefly and basically dismissed it as an alternative to the Einstein-Minkowski 4-dimensional universe. So, I took on that same attitude without really doing my own homework on the subject. I've always assumed that LET did not have the natural connection to general relativity that is had by special relativity. The little homework I did with LET years ago left me feeling that one would have to deal in tedious detail with many different special relativity effects and examples before considering LET a valid theory. Contrast that with the ease that the 4-dimensional universe concept clarifies so many different special cases of phenomena related to special relativity.

 

[Vandam]

Nor are most of the people who disagree with you on some of your more extreme block universe positions.

Extreme block positions...
At least I have a position. After all the posts I've read of the non block followers (like you) I still do not understand a word. Even if you try to explain it.
Or there are a lot of solipsists on this forum. Or you all believe in LET, I.e. mathematical illusions to save the physical ether. And probably a combination of both.
Or what else is it?
That all has nothing to do with SR. Solipsism is for philosophy forum. And LET is an ether disaster and old school (Lorentz himself admitted it). So in fact both approaches are off topic on this SR forum.

 

[Dale]

non block followers (like you) I still do not understand a word.

The block universe is my preferred interpretation. I just recognize that it is only an interpretation.

Solipsism is for philosophy forum.

So please stop bringing it up here.

 

[PeterDonis]

My conclusion was that you only believe in the existence of your own present event, nothing else.

And your conclusion was, and is, incorrect. I'm sorry that that is still not clear to you even after all the discussion. But that's off topic for this thread.

In any case, I don't see how your beliefs about my beliefs are relevant to the simple question of whether or not SR requires hard determinism. I addressed that in post #31 in this thread; do you have any comment on what I said there?

 

[PeterDonis]

Contrast that with the ease that the 4-dimensional universe concept clarifies so many different special cases of phenomena related to special relativity.

Yes, it does. As a *model*, with a well-understood domain of validity, SR works great, and the 4-dimensional spacetime concept makes SR easy to understand and use.

As a theory of everything, it's wrong; so trying to use it to justify claims about the ultimate nature of reality doesn't work too well.

I have the same question for you as I asked Vandam: do you have any comment on what I said in post #31?

 

[Vandam]

And your conclusion was, and is, incorrect. I'm sorry that that is still not clear to you even after all the discussion. But that's off topic for this thread.

There's a lot off topic for this thread already.
But it might be the core problem of our disagreement. The wrong phrasing and clumsy vacabulary in SR literature is partly due to refusing to accept the physical implications of SR.

In any case, I don't see how your beliefs about my beliefs are relevant to the simple question of whether or not SR requires hard determinism. I addressed that in post #31 in this thread; do you have any comment on what I said there?

A lot. But that's far too off topic in this thread.
And as long I do not know what kind of physical interpretation of SR you (and others) adhere it is pointless to start discussing that topic.
I started a new thread on 'observation' that you might find interesting in above context. See:https://www.physicsforums.com/showthread.php?p=4048623#post4048623

 

[PeterDonis]

And as long I do not know what kind of physical interpretation of SR you (and others) adhere it is pointless to start discussing that topic.

Sigh. Perhaps you can at least answer an even simpler question: do you think SR, as a physical theory, is exactly correct?

I started a new thread on 'observation'

I'll take a look.

 

[Dale]

And as long I do not know what kind of physical interpretation of SR you (and others) adhere it is pointless to start discussing that topic.

I don't adhere to any. That is the whole point of interpretations, they don't need to be adhered to, there is no experimental evidence to choose one interpretation over another.

My favorite interpretation is the block universe, but I switch between interpretations and use whichever is most convenient for the problem at hand.

 

[bahamagreen]

You should realize that when you examine the clarity of vocabulary as it relates to the meaning of concepts that you are doing fundamental philosophy. "Metaphysics" does not mean "against physics", "opposed to physics", or "not physics"; it means "after physics" - just the label given to the section that came after the "Physics" section... (Aristotle did not name it himself, that was done later).

As Wiki notes,
Traditionally, metaphysics attempts to answer two basic questions in the broadest possible terms:
"What is there?"
"What is it like?"

 

[PeterDonis]

I don't adhere to any. That is the whole point of interpretations, they don't need to be adhered to, there is no experimental evidence to choose one interpretation over another.

Exactly.

 

[harrylin]

Correct. Sorry about that.

So if simultaneous events are observed as non-simultaneous in another frame let's not make the wrong conclusions. The are non-simultaneus, not only observed as non-simultaneous.

Didn't you notice the self contradiction in your statement?
Literally you wrote: "simultaneous events [...] are non-simultaneus".

Which is exactly why many people (Einstein and many others) sometimes use(d) other words than "are".

 

[Dale]

Or you can simply pair each frame dependent statement with a frame:

"Simultaneous events in A are non-simultaneous in B".

The problem isn't with the word "are" and it isn't fixed with the word "appears". The problem is that a frame dependent quantity without a frame is meaningless.

 

[harrylin]

Or you can simply pair each frame dependent statement with a frame:

"Simultaneous events in A are non-simultaneous in B". [..] The problem is that a frame dependent quantity without a frame is meaningless.

That is also better (no self contradiction), but could be misinterpreted as magic (parallel universes). My preferred way of phrasing:

"Simultaneous events according to A are non-simultaneous according to B".

As so often, more precise statements are increasingly longer than shorthand statements.

 

[Dale]

That is also better (no self contradiction), but could be misinterpreted as magic (parallel universes). My preferred way of phrasing:

"Simultaneous events according to A are non-simultaneous according to B".

Yes, "according to" is good. I also use "with respect to".

As so often, more precise statements are increasingly longer than shorthand statements.

Agreed. I think that it is OK to use the shorthand when the more precise statement is clear from context, but as soon as any confusion arises switch immediately to the longer.

 

[ghwellsjr]

Or you can simply pair each frame dependent statement with a frame:

"Simultaneous events in A are non-simultaneous in B".

The problem isn't with the word "are" and it isn't fixed with the word "appears". The problem is that a frame dependent quantity without a frame is meaningless.

Yes, "according to" is good. I also use "with respect to".

Agreed. I think that it is OK to use the shorthand when the more precise statement is clear from context, but as soon as any confusion arises switch immediately to the longer.

Is it an OK shorthand when A and B are non-inertial observers and the word "frame" is never used?

 

[phyti]

That is also better (no self contradiction), but could be misinterpreted as magic (parallel universes). My preferred way of phrasing:

"Simultaneous events according to A are non-simultaneous according to B".

As so often, more precise statements are increasingly longer than shorthand statements.

How about:
Simultaneous in A can be non-simultaneous in B only if the events are not coincident in space.

 

[harrylin]

How about:
Simultaneous in A can be non-simultaneous in B only if the events are not coincident in space.

"is in A" remains ambiguous jargon that can easily be misunderstood, for example as implying (and I cite from the OP!) that "both observers ARE in different 3D worlds", as if they live in a different reality.

 

[Dale]

Is it an OK shorthand when A and B are non-inertial observers and the word "frame" is never used?

No (IMO). I was thinking of A and B being frames (not observers) defined previously. It is OK if A and B are well-defined non-inertial frames.

 

[harrylin]

Why use 'appearent' or 'appears' if one normally does not say that an immobile clock 'appears' to run normal or is apparent running normal? Do you say that an immobile train has an apparent length of 100 m long? So why doing it for the moving clock or trains?

I had missed this one. Einstein avoided "is" at some points where according to you it should have been "is", and in fact there is one instance in another paper where I also prefer "is". I can see two reasons for choosing a less absolute word: either when one isn't sure that "is" is correct, or when one thinks that "is" can be misunderstood.
I could say for example that an immobile train may appear 99 m long in a "moving" reference system if it appears 100 m long in a "stationary" system - "appears" merely stresses the free choice of perspective and there is no reason to prioritize one frame over the other.

 

[ghwellsjr]

No (IMO). I was thinking of A and B being frames (not observers) defined previously. It is OK if A and B are well-defined non-inertial frames.

Then would you have any problem with the first linked post of this thread? (I don't. I'm referring to PeterDonis's post, not Vandam's response.)

https://www.physicsforums.com/showpost.php?p=4041285&postcount=10

 

[Austin0]

Then would you have any problem with the first linked post of this thread? (I don't. I'm referring to PeterDonis's post, not Vandam's response.)

https://www.physicsforums.com/showpost.php?p=4041285&postcount=10

PeterDonis's usage certainly seems appropriate in meaning. But the word sense feels contrived and somehow misleading. How about internal simultaneity??
As far as being non-inertial frames: as such they were completely undefined in the sense DaleSpam is referring to if I am reading him correctly. The exercise is effectively two inertial frames with the "instantaneous" acceleration phases out of the picture. Not suggesting that considering them explicitly would add anything to the demonstration ;-)

 

[phyti]

No (IMO). I was thinking of A and B being frames (not observers) defined previously. It is OK if A and B are well-defined non-inertial frames.

Why can't A & B be observers?
Example: an a-naut with a clock and a laser, floating ouside his ship (away from Earth if necessary), making measurements.
There is no reason there has to be additional objects. The 'frame' has to be a common reference point for a set of measurements. In the final analysis, whether you use devices substituting for the observer, the measurements only have meaning to the observer.