On Monday, August 2, 2021 at 1:24:58 PM UTC-7, tjrob137 wrote:
> > > EVERYTHING you think you know about the world is actually about
> > > some MODEL you have of the world... the remarkable fact is that
> > > this model applies to the world we inhabit, as demonstrated by
> > > zillions of experiments...
> >
> > Look again at the two sentences you typed. Do you
> > see why they are mutually contradictory?
>
> They are not contradictory, and apparently you cannot explain why you
> think they are. Please explain...

Really? I honestly find it hard to believe that you can't see the blatant self-contradiction between those two assertions. Okay, let's take this v e r y s l o w l y ... Your first assertion is that everything we think we know about the world is actually about some model of the world, not the world itself. But then, willy-nilly, your second assertion claims something about the world itself. So to respect your first assertion to need to re-write your second assertion by replacing "the world" with "some model of the world". Thus your second assertion must be "this model applies to some model of the world".

But wait, it can't say that either, because it still claims something about the world, whereas per your first assertion everything we think we know about the world is really about some model of the world, so we have to replace "the world" with "some model of the world", and hence your second assertion is that "this model applies to some model of some model of the world".

But wait, it still refers to the world... so, jumping ahead, you need to say "This model applies to some model of some model of some model of some model of...." ad infinitum. So there is no "of the world" at the end. And then what you have is a meaningless shambles. In summary, you can't begin by claiming we know nothing about the world, and then immediately make an assertion about the world.

> > Time dilation (no scare quotes) never corresponds to a literal
> > geometrical projection,
>
> That is just plain wrong. You followed with a slew of words...

The "slew of words" explained why time dilation never corresponds to a literal geometrical projection. If you're not able to read and understand that "slew of words", then I'm afraid you've not competent to participate in this discussion.

> [I put "time dilation" in "scare quotes", because it
> is a very poor name for the actual phenomenon, and
> it causes many non-experts to expect it to mean
> something quite different from what it actually means.]

Nope, your understanding of time dilation is faulty, as explained in the slew of words.

> > the Minkowski "metric" (which is where you should deploy your scare
> > quotes), is not technically a metric, it is a pseudo-metric,
>
> Oh for goodness sake. You concentrate on a nit...

It is by no means a nit. The different between a metric and a pseudo-metric in physical terms of enormously profound and significant. This is why geometrical analogies can never be more than analogies, and why you will always run aground when trying to explain time dilation by talking about odometers on cars traveling different paths between two cities. There are analogous aspects to time dilation, but the pseudo-metrical character of spatio-temporal relations ensures that they can never be more than analogies.

> I just looked in six, and they all call it a metric.

This is not about a terminological nicety, it is about the underlying distinction between a metric and pseudo-metric. It doesn't matter what you *call* it, but you have to understand that the spatio-temporal relations do not satisfy a metric in the literal mathematical sense of a metrical space that satisfies the triangle inequality, and so on. The axioms are fundamentally different.

> > The concept of "frame" is vague
>
> In relativity, "inertial frame' is not vague at all

Yes it is. In the foundational literature the word "frame" has different meanings. In some it is defined as an equivalence class of space-time coordinate systems with the same temporal foliations, etc., and in others it is defined purely as the spatial measures, and hence there can be different foliations for the same frame. This is crucial for understanding special relativity.

> > To be clear, you need to talk about coordinate systems.
>
> Oh for goodness sake. In physics, "inertial frame" _IS_ a coordinate system.

No it is not. The two are not synonymous. See above.

> focusing on nits that everybody knows...

They are not nits, and you do not grasp them, so it's essentially (if you're going to make progress) for you to grasp the distinctions in the concepts.. Until you do that, you can't even begin to start trying to understand special relativity.

"Odd Bodkin" wrote in message news:sd7d52$3aj$1@gioia.aioe.org...

Kevin Aylward <kevinRemoveandReplaceATkevinaylward.co.uk> wrote:
>> "Odd Bodkin" wrote in message news:scq3bk$1mj5$1@gioia.aioe.org...
>
> .Kevin Aylward <kevinRemoveandReplaceATkevinaylward.co.uk> wrote:
>> "Arthur Adler" wrote in message
>>> news:a5199219-c800-4a5b-931b-8f391ed7792bn@googlegroups.com...
>>
>>
>>
>>>>> It does not involve signals in any way that supports your denial of
>>>>> the
>>>>> objective facts of time dilation. We have a grid of standard rulers
>>>>> with
>>>>> clocks (inertially synchronized) >at >each node, and the readings of a
>>>>> test clock moving through this grid can be recorded and directly
>>>>> compared
>>>>> with the recorded readings of the coinciding clocks of the grid >as it
>>>>>> passed them. This involves only the recognition of coinciding
>>>>>> events.
>>
>>>> The issue here is that you claim relativistic effects such as time
>>>> dilation
>>>> and length contraction are not "real", and your error has been
>>>> explained
>>>> by
>>>> every competent
>>>> physicist from Einstein to the present day. Fundamentally your
>>>> misconception is based on your failure to recognize that the physical
>>>> significance of Lorentz invariance is not >based on passive
>>>> transformations, it is based on active transformations. Until you
>>>> understand this you'll never be able to understand special relativity.
>>
>>> You seem quite confused. *Physical* "length contraction" is a feature of
>>> LET
>>> (Lorentz Ether Theory) not SR. The "length" of an object in SR rotates
>>> in
>>> "space-time". Length is an invariant in SR. Time "dilation" is,
>>> essentially
>>> an "optical illusion". All real physical effects such as reuniting
>>> clocks
>>> are due to differences in their paths in space time, that is, a result
>>> of
>>> differences in non inertial motion. Time dilation *cannot* be physically
>>> real because *both* observers see the *other* dilated, much like both
>>> observers viewing the other through a magnifying glass see the other
>>> larger.
>>> Its nonsensical for both observers to be physically larger.
>
>> This is a common misunderstanding and is associated with a mental claim
>> that “physical length” is an innate property of an object. Then it
>> follows
>> from that claim that it is impossible for both observers to be
>> “physically
>> larger”.
>
> >Physical reality exists.
>
>> There is a common misunderstanding among those that discuss physics that
>> mathematics is reality.

>Of course, but this does not mean that length is a physically innate
>property of a real object. Length is operationally defined, where that
>definition relies on a condition that is frame-specific. To say, “but
>length is not allowed to be such; it has to be objectively ‘real’” is just
>question-begging nonsense.

An invariant length can be defined that allows objective, non contradictory,
descriptions of observations to be made.

>The same thing is true for velocity. There is no objectively real velocity
>of a real object other than a velocity operationally defined in terms of a
>coordinate system or with respect to another (arbitrarily chosen) reference
>object. To splutter that velocity should be physically “real” in an innate
>and frame-independent way would be pointlessly futile.

False analogy.

Its not possible to define an invariant velocity that is meaningful.

>
>> However in relativity the claim is that length is NOT an innate property
>> of
>> an object.
>
>> SR is clearly only a mathematical model that produces "as if" results.
>> Its
>> trivially obvious that "space-time" is a model of real physical
>> processes.
>
> >For example, "space-time" results in (GR) the result that one can go
>> backwards in time. This is clearly nonsense.

>I know you’re mining here. Godel’s closed timelike loops are fun to talk
>about. There’s no reason to think they point to some horrible flaw, any
>more than black holes are some horrible, impossible flaw that spoils the
>soup.

False analogy.

Totally different issues.

Expand Y=T^2 over the range T=0 to 1 with a Chebychev series.

Does the expansion have meaning for T=-1 ?

*Prove* that the EFEs actually have meaning for *backwards* in time. Where
is there even the slightest of evidence that the EFE are true for such an
extension of the variables?

As I noted, space-time is a model. There is no rational for arguing that it
works backwards, especially since the past clearly no longer exists.

Physical reality tells us what is true, not the equations.

One trivially can't get back to the position and momentum of all the objects
of the universe as it was in the past, for one, because, QM says that the
state today might have come from an infinite number of other prior states.

This is so obvious. People are just in denial because it upsets their view
of the correctness of the SR/GR model, and the reality such a model implies.

As I noted, SR/GR is fundamentally incompatible with QM at a much more
fundamental level than the usual understood incompatibility.

The space-time model only works in a deterministic universe. The block
universe simply cannot be true.

>> The past has gone. The past no
>> longer exists. The state (position, momentum) of all the objects of the
>> universe has changed, never to return. There is simply no way that an
>> object
>> now can go forward in time for itself, yet go backwards in time for all
>> other objects that are not that object. Its completely nonsensical.
>
>> Neither does the future exist. QM tells us that it doesn't. Its really
>> that
>> simple.

>That depends on what you mean by “exist”.

Ahmmm.....

>If you mean, is it predictable in
>a clockwork universe way,

Exists means that it can be measured, right NOW. It exists now.

Predictability is the actually problem, so no, that's not what I mean.
Neither the future or the past is determinable, according to QM, thus
neither can be measured right now., even in principle.

The past and future simply do not exist. Why anyone debates this is a pretty
astounding.

-- Kevin Aylward
http://www.kevinaylward.co.uk/gr/index.html
http://www.kevinaylward.co.uk/qm/index.html

"Odd Bodkin" wrote in message news:sd9p2b$1js1$1@gioia.aioe.org...

>>> Hint: an inertial frame is a FRAME, with mutually
>>> orthogonal coordinate axes.
>>
>>> An inertial frame is a real *physical* system that is undergoing
>>> inertial
>>> motion, it does not require any coordinates at all.
>
>> No. The objects in an coordinate system are not the frame. The frame is
>> the
>> set of coordinates used to describe the position and the motion of those
>> objects.
>
>> I will give you that this is an example of still not being precise enough
>> in
>> statements of which we are all guilty.
>
>> "An inertial frame is used to describe a real *physical* system that is
>> undergoing inertial motion, it does not require any coordinates at all."
>
>> I don't agree "frame" implies coordinates. A frame, for example, is
>> simply
>> an elevator box, and objects in the elevator are being described that are
>> in
>> motion *relative* to that elevator.

>No, that’s not a good meaning for reference frame, as is used in physics.

I disagree. It expresses a key distinction between coordinates and the real,
physical system that they describe.

>Again, you seem to like to cite references that are a bit out of
>mainstream. What a reference frame is, is explicated quite simply and
>commonly in ordinary first-year physics books, to the point where even the
>Wikipedia entry for “inertial reference frame” repeats the same
>description. To say “Well then they’re all wrong” is a bit foolhardy at
>best and just points to a private lexicon at worst.

Essentially, they are wrong.

The reference I quote is J. D. Norton who did his PhD in the history of
General Relativity. He specifically examined the issues that most physicists
have missed, precisely because so many are confused on this. He is an expert
on this subject, most physics don't even think about it. Einstein didn't,
much

A coordinate system and the box it describes are absolutely not the same
concept, and such a distinction must be made if one is to correctly
understand, for example, the POR.

As I noted Einstein's "The general laws of nature are to be expressed by
equations which hold good for all systems of coordinates, that is, are
covariant with respect to any substitutions whatever."

Is absolutely *not* a principle of relativity. Such a condition can always
be constructed, even if the POR were false.

Moving boxes must comply with the forces of physics (read "laws of
physics"), they don't have to comply with mathematics.

It is my view that Einstein's confusion on coordinate systems and real
physical inertial systems led him to mistakenly view that all motion was
equivalent, which it isn't.

Essentially, it was well... all *coordinate* systems are obviously
equivalent, inertial systems appear to be equivalent, thus the false
deduction that all physical accelerating systems were equivalent because it
is clearly true that "accelerating" coordinate systems are just as
equivalent to any other coordinate system, by mathematical definition.

Its subtle.

"accelerating" coordinate systems are just not the same as accelerating
physical (systems) boxes. Thus they must be distinguished.

-- Kevin Aylward
http://www.kevinaylward.co.uk/gr/index.html
http://www.kevinaylward.co.uk/qm/index.html

"Odd Bodkin" wrote in message news:sd9p2b$1js1$1@gioia.aioe.org...

Kevin Aylward <kevinRemoveandReplaceATkevinaylward.co.uk> wrote:
> "Odd Bodkin" wrote in message news:sd929l$cd3$1@gioia.aioe.org...
>
> Kevin Aylward <kevinRemoveandReplaceATkevinaylward.co.uk> wrote:
>>> "Tom Roberts" wrote in message
>>> news:R_mdndzJsOpAoG79nZ2dnUU7_83NnZ2d@giganews.com...
>>
>>> On 7/15/21 1:29 PM, Kevin Aylward wrote:
>>>> Coordinate systems have no physical content whatsoever. Period. They
>>>> are simply labels on events. Events don't depend on coordinates.
>>
>>> Yes to all that.
>>
>>>> "inertial coordinates" is, technically, a meaningless statement.
>>
>>> No. Not even close.
>>
>> Yep. Absolutely nuts on. Its, essentially, an "oxymoron".
>>
>> Coordinates, by construction, have no physical properties whatsoever.
>>
>>> "Inertial", describes a system, loosely, that is not subjected to any
>>> physical forces.
>
>> That’s a bit too loose. It’s not what “inertial” means in this context,
>> and
>> you’ve bent the definition to try to make it seem nonsensical.
>
>> A set of inertial coordinates is one in which Newton’s laws of motion
>> apply, including the first law.
>
>> Note that the first law is about the
>> behavior of OBJECTS as described in this kind of coordinate system, not
>> about the behavior of the coordinates themselves.
>
> Sure, I understand, what you mean, but that is not what that phrase means
> as
> written.
>
> probably....
>
> "A set of inertial coordinates is one in which Newton’s laws of inertial
> motion apply to the objects described by those coordinates as if they
> coordinates were directly representing the inertial motion , including
> the
> first law." or something similar. Probably quite wordy to be precise.
>
> The distinction matters, because confusion of on this is what leads to the
> classic false statement by Einstein, to wit:
>
> "The general laws of nature are to be expressed by equations which hold
> good
> for all systems of coordinates, that is, are covariant with respect to any
> substitutions whatever."
>
> Such statements do not reflect the POR.
>
> "Equations that hold good for all systems of coordinates" can always be
> written, if the equation is actually true in a particular coordinate
> system.
>
> The POR is a *physical* principle, not a principle as to how clever a
> mathematician is in writing equations.
>
> Without understanding exactly what the POR means, one is going nowhere....
>
>>
>>> Hint: an inertial frame is a FRAME, with mutually
>>> orthogonal coordinate axes.
>>
>>> An inertial frame is a real *physical* system that is undergoing
>>> inertial
>>> motion, it does not require any coordinates at all.
>
>> No. The objects in an coordinate system are not the frame. The frame is
>> the
>> set of coordinates used to describe the position and the motion of those
>> objects.
>
> I will give you that this is an example of still not being precise enough
> in
> statements of which we are all guilty.
>
> "An inertial frame is used to describe a real *physical* system that is
> undergoing inertial motion, it does not require any coordinates at all."
>
> I don't agree "frame" implies coordinates. A frame, for example, is simply
> an elevator box, and objects in the elevator are being described that are
> in
> motion *relative* to that elevator.

>No, that’s not a good meaning for reference frame, as is used in physics.
>Again, you seem to like to cite references that are a bit out of
>mainstream.

I would suggest that you have a read of:

J D Norton

"What was Einstein's principle of Equivalence?"

http://pitt.edu/~jdnorton/papers/ProfE_re-set.pdf

e.g.

"The task of explicating Einstein's formulation of the principle of
equivalence and even some of the preceding discussion is by no means
straightforward. To begin, we must deal with Einstein's failure to maintain
such distinctions as those between frames of reference and coordinate
systems and between three-dimensional and four-dimensional concepts. For
example, we shall see that when Einstein speaks of a four-dimensional
coordinate system, he may be referring to a four-dimensional coordinate
system simpliciter, a frame of reference, or even a three-dimensional space
associated with the frame. "

The reality is, most that formally study GR/SR, don't actually study where
it all *really* came from.

-- Kevin Aylward
http://www.kevinaylward.co.uk/gr/index.html
http://www.kevinaylward.co.uk/qm/index.html

Kevin Aylward <kevinRemoveandReplaceATkevinaylward.co.uk> wrote:
> "Odd Bodkin" wrote in message news:sd9p2b$1js1$1@gioia.aioe.org...
>
> Kevin Aylward <kevinRemoveandReplaceATkevinaylward.co.uk> wrote:
>> "Odd Bodkin" wrote in message news:sd929l$cd3$1@gioia.aioe.org...
>>
>> Kevin Aylward <kevinRemoveandReplaceATkevinaylward.co.uk> wrote:
>>>> "Tom Roberts" wrote in message
>>>> news:R_mdndzJsOpAoG79nZ2dnUU7_83NnZ2d@giganews.com...
>>>
>>>> On 7/15/21 1:29 PM, Kevin Aylward wrote:
>>>>> Coordinate systems have no physical content whatsoever. Period. They
>>>>> are simply labels on events. Events don't depend on coordinates.
>>>
>>>> Yes to all that.
>>>
>>>>> "inertial coordinates" is, technically, a meaningless statement.
>>>
>>>> No. Not even close.
>>>
>>> Yep. Absolutely nuts on. Its, essentially, an "oxymoron".
>>>
>>> Coordinates, by construction, have no physical properties whatsoever.
>>>
>>>> "Inertial", describes a system, loosely, that is not subjected to any
>>>> physical forces.
>>
>>> That’s a bit too loose. It’s not what “inertial” means in this context,
>>> and
>>> you’ve bent the definition to try to make it seem nonsensical.
>>
>>> A set of inertial coordinates is one in which Newton’s laws of motion
>>> apply, including the first law.
>>
>>> Note that the first law is about the
>>> behavior of OBJECTS as described in this kind of coordinate system, not
>>> about the behavior of the coordinates themselves.
>>
>> Sure, I understand, what you mean, but that is not what that phrase means
>> as
>> written.
>>
>> probably....
>>
>> "A set of inertial coordinates is one in which Newton’s laws of inertial
>> motion apply to the objects described by those coordinates as if they
>> coordinates were directly representing the inertial motion , including
>> the
>> first law." or something similar. Probably quite wordy to be precise.
>>
>> The distinction matters, because confusion of on this is what leads to the
>> classic false statement by Einstein, to wit:
>>
>> "The general laws of nature are to be expressed by equations which hold
>> good
>> for all systems of coordinates, that is, are covariant with respect to any
>> substitutions whatever."
>>
>> Such statements do not reflect the POR.
>>
>> "Equations that hold good for all systems of coordinates" can always be
>> written, if the equation is actually true in a particular coordinate
>> system.
>>
>> The POR is a *physical* principle, not a principle as to how clever a
>> mathematician is in writing equations.
>>
>> Without understanding exactly what the POR means, one is going nowhere....
>>
>>>
>>>> Hint: an inertial frame is a FRAME, with mutually
>>>> orthogonal coordinate axes.
>>>
>>>> An inertial frame is a real *physical* system that is undergoing
>>>> inertial
>>>> motion, it does not require any coordinates at all.
>>
>>> No. The objects in an coordinate system are not the frame. The frame is
>>> the
>>> set of coordinates used to describe the position and the motion of those
>>> objects.
>>
>> I will give you that this is an example of still not being precise enough
>> in
>> statements of which we are all guilty.
>>
>> "An inertial frame is used to describe a real *physical* system that is
>> undergoing inertial motion, it does not require any coordinates at all."
>>
>> I don't agree "frame" implies coordinates. A frame, for example, is simply
>> an elevator box, and objects in the elevator are being described that are
>> in
>> motion *relative* to that elevator.
>
>> No, that’s not a good meaning for reference frame, as is used in physics.
>> Again, you seem to like to cite references that are a bit out of
>> mainstream.
>
> I would suggest that you have a read of:
>
> J D Norton
>
> "What was Einstein's principle of Equivalence?"
>
> http://pitt.edu/~jdnorton/papers/ProfE_re-set.pdf
>
> e.g.
>
> "The task of explicating Einstein's formulation of the principle of
> equivalence and even some of the preceding discussion is by no means
> straightforward. To begin, we must deal with Einstein's failure to maintain
> such distinctions as those between frames of reference and coordinate
> systems and between three-dimensional and four-dimensional concepts. For
> example, we shall see that when Einstein speaks of a four-dimensional
> coordinate system, he may be referring to a four-dimensional coordinate
> system simpliciter, a frame of reference, or even a three-dimensional space
> associated with the frame. "
>
> The reality is, most that formally study GR/SR, don't actually study where
> it all *really* came from.
>
> -- Kevin Aylward
> http://www.kevinaylward.co.uk/gr/index.html
> http://www.kevinaylward.co.uk/qm/index.html
>
>

You refer to an ambiguity in Einstein’s presentation as presented by a
*philosopher* of physics to argue that your meaning of “reference frame” is
correct and that of physicists is incorrect?

Does that actually make sense to you?

--
Odd Bodkin -- maker of fine toys, tools, tables

Kevin Aylward <kevinRemoveandReplaceATkevinaylward.co.uk> wrote:
> "Odd Bodkin" wrote in message news:sd7d52$3aj$1@gioia.aioe.org...
>
> Kevin Aylward <kevinRemoveandReplaceATkevinaylward.co.uk> wrote:
>>> "Odd Bodkin" wrote in message news:scq3bk$1mj5$1@gioia.aioe.org...
>>
>> .Kevin Aylward <kevinRemoveandReplaceATkevinaylward.co.uk> wrote:
>>> "Arthur Adler" wrote in message
>>>> news:a5199219-c800-4a5b-931b-8f391ed7792bn@googlegroups.com...
>>>
>>>
>>>
>>>>>> It does not involve signals in any way that supports your denial of
>>>>>> the
>>>>>> objective facts of time dilation. We have a grid of standard rulers
>>>>>> with
>>>>>> clocks (inertially synchronized) >at >each node, and the readings of a
>>>>>> test clock moving through this grid can be recorded and directly
>>>>>> compared
>>>>>> with the recorded readings of the coinciding clocks of the grid >as it
>>>>>>> passed them. This involves only the recognition of coinciding
>>>>>>> events.
>>>
>>>>> The issue here is that you claim relativistic effects such as time
>>>>> dilation
>>>>> and length contraction are not "real", and your error has been
>>>>> explained
>>>>> by
>>>>> every competent
>>>>> physicist from Einstein to the present day. Fundamentally your
>>>>> misconception is based on your failure to recognize that the physical
>>>>> significance of Lorentz invariance is not >based on passive
>>>>> transformations, it is based on active transformations. Until you
>>>>> understand this you'll never be able to understand special relativity.
>>>
>>>> You seem quite confused. *Physical* "length contraction" is a feature of
>>>> LET
>>>> (Lorentz Ether Theory) not SR. The "length" of an object in SR rotates
>>>> in
>>>> "space-time". Length is an invariant in SR. Time "dilation" is,
>>>> essentially
>>>> an "optical illusion". All real physical effects such as reuniting
>>>> clocks
>>>> are due to differences in their paths in space time, that is, a result
>>>> of
>>>> differences in non inertial motion. Time dilation *cannot* be physically
>>>> real because *both* observers see the *other* dilated, much like both
>>>> observers viewing the other through a magnifying glass see the other
>>>> larger.
>>>> Its nonsensical for both observers to be physically larger.
>>
>>> This is a common misunderstanding and is associated with a mental claim
>>> that “physical length” is an innate property of an object. Then it
>>> follows
>>> from that claim that it is impossible for both observers to be
>>> “physically
>>> larger”.
>>
>>> Physical reality exists.
>>
>>> There is a common misunderstanding among those that discuss physics that
>>> mathematics is reality.
>
>> Of course, but this does not mean that length is a physically innate
>> property of a real object. Length is operationally defined, where that
>> definition relies on a condition that is frame-specific. To say, “but
>> length is not allowed to be such; it has to be objectively ‘real’” is just
>> question-begging nonsense.
>
> An invariant length can be defined that allows objective, non contradictory,
> descriptions of observations to be made.
>
>> The same thing is true for velocity. There is no objectively real velocity
>> of a real object other than a velocity operationally defined in terms of a
>> coordinate system or with respect to another (arbitrarily chosen) reference
>> object. To splutter that velocity should be physically “real” in an innate
>> and frame-independent way would be pointlessly futile.
>
> False analogy.
>
> Its not possible to define an invariant velocity that is meaningful.

Well, let’s take the model to be the “invariant length” that you mentioned
above, which happens to be the length as measured in the rest frame of the
object.

There is a corresponding invariant velocity in the rest frame of the
object: zero.

And you say that one is meaningful and the other is not. Hmmmmm…. Wonder
why.

>
>>
>>> However in relativity the claim is that length is NOT an innate property
>>> of
>>> an object.
>>
>>> SR is clearly only a mathematical model that produces "as if" results.
>>> Its
>>> trivially obvious that "space-time" is a model of real physical
>>> processes.
>>
>>> For example, "space-time" results in (GR) the result that one can go
>>> backwards in time. This is clearly nonsense.
>
>> I know you’re mining here. Godel’s closed timelike loops are fun to talk
>> about. There’s no reason to think they point to some horrible flaw, any
>> more than black holes are some horrible, impossible flaw that spoils the
>> soup.
>
> False analogy.
>
> Totally different issues.
>
> Expand Y=T^2 over the range T=0 to 1 with a Chebychev series.
>
> Does the expansion have meaning for T=-1 ?
>
> *Prove* that the EFEs actually have meaning for *backwards* in time. Where
> is there even the slightest of evidence that the EFE are true for such an
> extension of the variables?
>
> As I noted, space-time is a model. There is no rational for arguing that it
> works backwards, especially since the past clearly no longer exists.
>
> Physical reality tells us what is true, not the equations.
>
> One trivially can't get back to the position and momentum of all the objects
> of the universe as it was in the past, for one, because, QM says that the
> state today might have come from an infinite number of other prior states.
>
> This is so obvious. People are just in denial because it upsets their view
> of the correctness of the SR/GR model, and the reality such a model implies.
>
> As I noted, SR/GR is fundamentally incompatible with QM at a much more
> fundamental level than the usual understood incompatibility.
>
> The space-time model only works in a deterministic universe. The block
> universe simply cannot be true.
>
>>> The past has gone. The past no
>>> longer exists. The state (position, momentum) of all the objects of the
>>> universe has changed, never to return. There is simply no way that an
>>> object
>>> now can go forward in time for itself, yet go backwards in time for all
>>> other objects that are not that object. Its completely nonsensical.
>>
>>> Neither does the future exist. QM tells us that it doesn't. Its really
>>> that
>>> simple.
>
>> That depends on what you mean by “exist”.
>
> Ahmmm.....
>
>> If you mean, is it predictable in
>> a clockwork universe way,
>
> Exists means that it can be measured, right NOW. It exists now.
>
> Predictability is the actually problem, so no, that's not what I mean.
> Neither the future or the past is determinable, according to QM, thus
> neither can be measured right now., even in principle.
>
> The past and future simply do not exist. Why anyone debates this is a pretty
> astounding.
>
> -- Kevin Aylward
> http://www.kevinaylward.co.uk/gr/index.html
> http://www.kevinaylward.co.uk/qm/index.html
>
>

--
Odd Bodkin -- maker of fine toys, tools, tables

Kevin Aylward <kevinRemoveandReplaceATkevinaylward.co.uk> wrote:
> "Odd Bodkin" wrote in message news:sd9p2b$1js1$1@gioia.aioe.org...
>
>
>>>> Hint: an inertial frame is a FRAME, with mutually
>>>> orthogonal coordinate axes.
>>>
>>>> An inertial frame is a real *physical* system that is undergoing
>>>> inertial
>>>> motion, it does not require any coordinates at all.
>>
>>> No. The objects in an coordinate system are not the frame. The frame is
>>> the
>>> set of coordinates used to describe the position and the motion of those
>>> objects.
>>
>>> I will give you that this is an example of still not being precise enough
>>> in
>>> statements of which we are all guilty.
>>
>>> "An inertial frame is used to describe a real *physical* system that is
>>> undergoing inertial motion, it does not require any coordinates at all."
>>
>>> I don't agree "frame" implies coordinates. A frame, for example, is
>>> simply
>>> an elevator box, and objects in the elevator are being described that are
>>> in
>>> motion *relative* to that elevator.
>
>> No, that’s not a good meaning for reference frame, as is used in physics.
>
> I disagree. It expresses a key distinction between coordinates and the real,
> physical system that they describe.

For you, that seems important. However, as the term is used in physics,
that is not the meaning of “reference frame”.

You might as well be telling a dictionary, “But I don’t like your
definition, so I’ll substitute my own.”

>
>> Again, you seem to like to cite references that are a bit out of
>> mainstream. What a reference frame is, is explicated quite simply and
>> commonly in ordinary first-year physics books, to the point where even the
>> Wikipedia entry for “inertial reference frame” repeats the same
>> description. To say “Well then they’re all wrong” is a bit foolhardy at
>> best and just points to a private lexicon at worst.
>
> Essentially, they are wrong.
>
> The reference I quote is J. D. Norton who did his PhD in the history of
> General Relativity. He specifically examined the issues that most physicists
> have missed, precisely because so many are confused on this. He is an expert
> on this subject, most physics don't even think about it.

Yes, I knew that you were taking Norton’s stance on this and distorting it
further to suit your own biases. Norton is, as you say, a PHILOSOPHER of
physics and not a practitioner of physics. This is what I meant when I say
you like to cite references that are a bit out off the mainstream.

I’ll furthermore mention that an electrical engineer’s view that “Well
then, physicists are all wrong” about physics principles deserves a tin
medal for hubris.

On the other hand, I’ve met a number of engineers that have as much hubris
in their bloodstream as Luke Skywalker had midichlorians.

> Einstein didn't,
> much
>
> A coordinate system and the box it describes are absolutely not the same
> concept, and such a distinction must be made if one is to correctly
> understand, for example, the POR.
>
> As I noted Einstein's "The general laws of nature are to be expressed by
> equations which hold good for all systems of coordinates, that is, are
> covariant with respect to any substitutions whatever."
>
> Is absolutely *not* a principle of relativity. Such a condition can always
> be constructed, even if the POR were false.
>
> Moving boxes must comply with the forces of physics (read "laws of
> physics"), they don't have to comply with mathematics.
>
> It is my view that Einstein's confusion on coordinate systems and real
> physical inertial systems led him to mistakenly view that all motion was
> equivalent, which it isn't.
>
> Essentially, it was well... all *coordinate* systems are obviously
> equivalent, inertial systems appear to be equivalent, thus the false
> deduction that all physical accelerating systems were equivalent because it
> is clearly true that "accelerating" coordinate systems are just as
> equivalent to any other coordinate system, by mathematical definition.
>
> Its subtle.
>
> "accelerating" coordinate systems are just not the same as accelerating
> physical (systems) boxes. Thus they must be distinguished.
>
>
>
>
> -- Kevin Aylward
> http://www.kevinaylward.co.uk/gr/index.html
> http://www.kevinaylward.co.uk/qm/index.html
>
>

--
Odd Bodkin -- maker of fine toys, tools, tables

On 8/2/21 6:36 PM, Arthur Adler wrote:
> On Monday, August 2, 2021 at 1:24:58 PM UTC-7, tjrob137 wrote:
>>>> EVERYTHING you think you know about the world is actually
>>>> about some MODEL you have of the world... the remarkable fact
>>>> is that this model applies to the world we inhabit, as
>>>> demonstrated by zillions of experiments...
>>>
>>> Look again at the two sentences you typed. Do you see why they
>>> are mutually contradictory?
>>
>> They are not contradictory, and apparently you cannot explain why
>> you think they are. Please explain...
>
> Your first assertion is that everything we think we know about the
> world is actually about some model of the world, not the world
> itself. But then, willy-nilly, your second assertion claims
> something about the world itself.

Read it again -- it says the model [SR] applies to the world -- clearly
a statement about the model.

> [my second statement] still claims something about the world,

No, I did not say "the world agrees with the model", I said "the model
[SR] applies to the world" -- clearly a statement about the model.

> But wait, it still refers to the world...

Please re-read my statements. I did NOT say that one cannot refer to the
world, I said "EVERYTHING you think you know about the world is actually
about some MODEL you have of the world". My second statement says that
the model [SR] applies to the world -- clearly a statement about the model.

> [... further nonsense and overblown arguments about words]

You are behaving indistinguishably from a troll (but with a lot more
words than most trolls use). You may have the last word here, as I won't
bother to continue.

Tom Roberts

On 8/8/21 12:14 PM, Kevin Aylward wrote:
> [frame] expresses a key distinction between coordinates and the
> real, physical system that they describe.

Yes and no. The key idea is that "frame" implies mutually orthogonal
stuff, be it the studs and joists of a house, or the axes of a
coordinate system. So "frame" can apply to a physical system, or to a
coordinate system.

[In relativity, of course, coordinate axes can be
mutually orthogonal only for inertial coordinates.]

In physics, "inertial frame" and "inertial coordinates" are used
interchangeably. In most discussions there is a clear and obvious
orientation of the spatial axes, and we ignore the fact that there are
infinitely many inertial coordinate systems with zero relative motion
(related by constant spatial rotations).

> A coordinate system and the box it describes are absolutely not the
> same concept, and such a distinction must be made if one is to
> correctly understand, for example, the POR.

Sure. But the POR explicitly says that it applies to coordinate systems.
Perhaps you should read it.

> As I noted Einstein's "The general laws of nature are to be expressed
> by equations which hold good for all systems of coordinates, that is,
> are covariant with respect to any substitutions whatever."
>
> Is absolutely *not* a principle of relativity. Such a condition can
> always be constructed, even if the POR were false.

Mathematically, yes. But a physical theory is more than a collection of
mathematical theorems, it includes a definition of each symbol in its
equations, AND HOW THEY RELATE TO QUANTITIES IN THE WORLD.

Sure, you can apply an arbitrary change of coordinates to an equation.
But for physicists the issue is: do the resulting quantities still
relate to the physical quantities?

[In general, after applying a coordinate transform, it
is up to the analyst to determine the physical
properties of the new coordinates. The remarkable thing
is that for inertial coordinates, a Lorentz transform
relates clocks and rulers at rest in one frame to
clocks and rulers at rest in a different frame.]

> It is my view that Einstein's confusion on coordinate systems and
> real physical inertial systems led him to mistakenly view that all
> motion was equivalent, which it isn't.

Your "view" is completely inconsistent with Einstein's writings. Why
would you fantasize such silliness? But see below about "equivalent".

> all *coordinate* systems are obviously equivalent,

This is just plain not true, for any useful meaning of "equivalent".

Note that whenever you use the word "equivalent", you MUST describe what
it means: in what sense are these things equivalent? -- your failure to
do so has confused yourself.

> inertial systems appear to be equivalent,

Yes, in the sense of the POR. But not for other possible meanings of
"equivalent".

> thus the false deduction that all physical accelerating systems were
> equivalent because it is clearly true that "accelerating" coordinate
> systems are just as equivalent to any other coordinate system, by
> mathematical definition.

That's another of your personal fantasies. I have no idea how you think
this might be true. The claim is false, as is the (implicit) claim that
Einstein thought that.

> Its subtle.

No, it's rather blatant -- YOU keep making stuff up and claiming it's
what Einstein thought. YOU are not Einstein (duh!).

> An invariant length can be defined that allows objective, non
> contradictory, descriptions of observations to be made.

Yes. We call it an object's proper length.

> Its not possible to define an invariant velocity that is meaningful.

Sure it is. The symmetry speed of SR is an invariant speed that is
very meaningful: it is the same as the (local) vacuum speed of light.

> *Prove* that the EFEs actually have meaning for *backwards* in time.

I have no idea why you want this, but it is trivial: the Einstein field
equation is invariant under the transform t -> -t.

> Where is there even the slightest of evidence that the EFE are true
> for such an extension of the variables?

Hmmmm. See my previous paragraph.

Please note, however, that no future-directed timelike trajectory can
ever become a past-directed timelike trajectory while remaining
timelike. So you seem to be seeking something that is unobtainable.

> The space-time model only works in a deterministic universe.

You misspoke. You mean SR and GR only work in a deterministic universe.
That is true, and applies equally to all other classical theories of
physics.

> The block universe simply cannot be true.

Of course not. Nobody claims it is (except you seem to fantasize that
relativity claims it). SR and GR model deterministic universes, but
neither claims it is "true" (i.e. corresponds to the world we inhabit).

True and false are properties of mathematics, not physics. No physical
theory can ever be "true" -- the actual issue is whether a theory is
valid (i.e. not refuted by experiments).

> The past and future simply do not exist.

You're merely arguing about the meanings of words. I decline to participate.

Tom Roberts

On Monday, August 9, 2021 at 8:55:35 PM UTC-7, tjrob137 wrote:
> >>>> EVERYTHING you think you know about the world is actually
> >>>> about some MODEL you have of the world... the remarkable fact
> >>>> is that this model applies to the world we inhabit, as
> >>>> demonstrated by zillions of experiments...
> >>>
> >>> Look again at the two sentences you typed. Do you see why they
> >>> are mutually contradictory?
> >>
> >> They are not contradictory, and apparently you cannot explain why
> >> you think they are. Please explain...
> >
> > Your first assertion is that everything we think we know about the
> > world is actually about some model of the world, not the world
> > itself. But then, willy-nilly, your second assertion claims
> > something about the world itself.
>
> Read it again -- it says the model [SR] applies to the world -- clearly
> a statement about the model.

You've clearly gone completely insane. You are claiming that the statement "model X accurately applies to the world as demonstrated by zillions of experiments" is not a statement about the world. Wow. And I repeat... Wow. I hope you're getting the care you need.

> > [... further nonsense and overblown arguments about words]

Again, you are completely insane, since I specifically explained that it is *not* about semantics, it is about the concepts that you clearly misunderstand, for the carefully explained reasons that you snipped and ignored again. You will never learn if you don't start paying attention when things are explained to you.

> You may have the last word here, as I won't bother to continue.

Of course you won't... how could you continue spouting such utter idiocy? You will now run away, as always, because it's been made perfectly clear that your juvenile notions about theoretical physics are all self-contradictory nonsense, and you can't even *attempt* to rationally address -- let alone refute -- anything I've said.

On Tuesday, July 20, 2021 at 1:53:04 PM UTC-7, Kevin Aylward wrote:
> > > Let me know where the minus sign is lost in my derivation of the Riemann
> > > Curvature Tensor...
> >
> > Derivation of the curvature tensor? The curvature tensor is not derived, it is
> > defined as the tensor that encodes all the Gaussian curvatures of a
> > manifold at any given point.
>
> Yeah "The curvature tensor is defined as er... ho hummm.... a curvature" .. What
> part of circular argument do you not understand?

It wasn't an "argument", it was informing you that your statement about "deriving" the curvature tensor doesn't make sense, because the curvature tensor is not derived, it is defined, and to give you a little clue about how it is defined, I noted that the components of the curvature tensor are essentially the pair-wise 2D intrinsic curvature scalars (with which of course any competent freshman is very familiar) taking each of the six independent pairs of two of the four coordinates.

> The curvature tensor is defined as the acceleration of geodesics, as I did note.

No, as I explained, the geodesic paths satisfy the geodesic equation, which can be expressed in terms of the Christoffel symbols, which are defined in terms of the metric coefficients, which satisfy the field equations, which involve the Ricci tensor (the contraction of the Riemann curvature tensor).. Which part(s) of this don't you understand?

> In other words, no, "I cant find where the minus sign was dropped in...

No, in other words: "What you typed on that web page is gibberish. Again, the geodesic paths satisfy the geodesic equation, expressed in terms of the Christoffel symbols, which are defined in terms of the metric coefficients, which satisfy the field equations, which involve the Ricci tensor (the contraction of the Riemann curvature tensor). There are no erroneous minus signs in any of this."

> > LET is nothing but an interpretation of special relativity, with a
> >peculiar semantic affectation.
>
> Oh dear... nope.... SR is an interpretation of LET. Hint: LET arrived first.

The point is that there is just a single theory with two different interpretations, which can be called the Lorentzian interpretation and the Einsteinian interpretation. You happen to have the historical sequence backwards, because the Lorentzian interpretations wasn't perfected (in print) until after the Einsteinian interpretation had appeared, but the order is irrelevant.. What matters in that the Lorentzian interpretation is effectively the same as the Einsteinian interpretation, merely augmented with a metaphysical semantic commitment to refer to one particular inertial coordinate system as the "true" one, and all the others merely "apparent"... but this semantic appendage has no physical significance, and (as Lorentz himself admitted) is hypocritical, since we could just as well select any inertial coordinate system and label it the "true" one.

> The physics assumed by LET and SR are fundamentally different.

You are mistaken. To prove this, try to think of some physical prediction that is different for them. Hint: There are none, not even in principle. This signifies that they are the same theory, and differ only semantically.

> One has an ether, one don't.

That is a purely semantic assertion of no physical significance, since, as Einstein and Lorentz agreed, Lorentz had taken from the ether all palpable attributes, and left it only its immobility, i.e., only as a specified frame, and any inertial frame would serve just as well. It is nothing but an arbitrary state of reference.

> >In both SR and LET, in terms of any system of inertial coordinates x,t the
> >elapsed time tau on an ideal clock moving at speed v=dx/dt advances at the
> >rate dtau/dt = sqrt(1-v^2/c^2). This is a verifiable objective fact.
>
> Nope. Both observers will read the other's clocks as running slow.

You didn't read what I wrote: Once again, in terms of any system of inertial coordinates x,t the elapsed time tau on an ideal clock moving at speed v=dx/dt advances at the rate dtau/dt = sqrt(1-v^2/c^2). This is a verifiable objective fact, and of course it entails that each of two relatively moving clocks runs slow in terms of the inertial coordinates in which the other clock is at rest.

> If they both move apart turn around again and meet up, despite reading the other
> clocks slow whilst in uniform motion...

They don't "read the other clock slow". Rather, each clock runs slow in terms of the inertial coordinates in which the other clock is at rest.

> , their final clock readings for a symmetric acceleration profile will be the same.

Of course, entirely consistent with the fact that each of two relatively moving clocks runs slow in terms of the inertial coordinate system in which the other clock is at rest. See above and below.

> Thus "dilation" isn't physically real.

Non-sequitur. Please try to concentrate: In terms of any system of inertial coordinates x,t the elapsed time tau on an ideal clock moving at speed v=dx/dt advances at the rate dtau/dt = sqrt(1-v^2/c^2). With integration, this tells you everything you need to know to compute the elapsed time on any clocks in any arbitrary motions, and (again) the time dilation expressed by that sentence is a verifiable objective fact. If your definition of "physically real" refers to something other than verifiable objective facts, then you are using non-standard terminology.

> > [Blatant misconceptions about general coveriance versus the principle of
> > relativity, and erroneous claim that special relativity implies determinism.]

You're conflating the issue of general covariance (i.e., expressing physical laws as tensor equations) with the principle of special relativity and Lorentz invariance, which asserts that all the equations of physics take their simple homogeneous and isotropic form in terms of a distinguished class of coordinate systems, called inertial coordinates, which are related by Lorentz transformations. This has nothing whatsoever to do with the mathematical concept of general covariance.

Again, there is a distinguished class of coordinate systems, called inertial or inertia-based coordinates, in terms of which the equations of physics uniquely take their simple homogeneous and isotropic form. The local Lorentz invariance of all physical laws does not imply that the laws of physics are (or are not) deterministic. Lorentz invariance merely asserts that the laws of physics -- whatever they may be (e.g., deterministic or not) -- take the same form in terms of any system of inertia-based coordinates. For example, the laws of quantum electrodynamics and Dirac's equation and the relativistic Schrodinger equation of relativistic quantum mechanics are all explicitly Lorentz invariant. These are all consistent with the Heisenberg uncertainty relation.

You referenced Roger Penrose "The Emperor's New Mind" p.393, but appeals to authority are pointless, so I will just mention that you must have a different edition, since that quote is on page 304 of the original 1989 edition, but note that Penrose admits later in the same book that quantum mechanics does not conflict with special relativity is any observable way, and, more importantly, by the time he wrote his "Road to Reality" in 2002 he had realized (prompted by criticisms) that that passage from Emperor's, along with the whole Andromeda paradox stuff, was all nonsense, and he was embarrassed, which is why you find no trace of that nonsense in Road.

> > [quoting Penrose Emperror] Indeed, this seems to have been Einstein's own
> > conclusion (cf. Paris 1982 p.444).

That is a bogus reference, since Pais only recounts the fact that Einstein drafted a paper in which he argued for hidden variables, hoping to evade Heisenberg's uncertainty relation, but before publication Einstein realized the argument was fallacious and withdrew the paper. As all serious scholars know, Einstein explained very carefully to Pauli and Born that his mature objection to quantum mechanics was *not* about determinism, and he (Einstein) did *not* maintain that determinism is required (and he forever lamented the too-quotable flippant dice comment), but rather the apparent non-locality. But we now know that quantum mechanics is perfectly consistent with the locality of Lorentz invariance, i.e., spacelike observables commute.

In summary, special relativity is perfectly compatible with quantum field theory, and indeed Lorentz invariance is one of the cornerstones of QFT. Of course, it goes without saying the relativity is incompatible with non-relativistic QM... that's why relativistic QM was invented.

On Tuesday, 10 August 2021 at 05:55:35 UTC+2, tjrob137 wrote:
> Read it again -- it says the model [SR] applies to the world -- clearly
> a statement about the model.

A lie, anyway; you're more sincere when screaming that we're
all FORCED to apply your wannabe "model" to the world.