On 7/19/21 7:51 PM, RichD wrote:
> Sean Carroll suggested we banish 'time' from our vocabulary,
> replacing it with 'clock states' and 'process states', observing their
> correspondence. This provides a precise operational definition of
> time, avoiding the semantic thorns.

Hmmm. "Time" will never be "banished from our vocabulary" -- it is far
too useful a concept.

But in physics Carroll's suggestion is effectively obeyed: "Time is what
clocks measure [Einstein and others]", because in any experiment that
uses time, it is measured by a clock.

Tom Roberts

On Tuesday, 20 July 2021 at 06:17:52 UTC+2, tjrob137 wrote:
> On 7/19/21 7:51 PM, RichD wrote:
> > Sean Carroll suggested we banish 'time' from our vocabulary,
> > replacing it with 'clock states' and 'process states', observing their
> > correspondence. This provides a precise operational definition of
> > time, avoiding the semantic thorns.
> Hmmm. "Time" will never be "banished from our vocabulary" -- it is far
> too useful a concept.
>
> But in physics Carroll's suggestion is effectively obeyed: "Time is what
> clocks measure [Einstein and others]", because in any experiment that
> uses time, it is measured by a clock.

Theoretically; practically in physics time is what an idiot physicist
imagine the clocks are FORCED to measure.
Of course, in the real world time is really what clocks measure,
and, as anyone can check in GPS, it's t'=t.

"RichD" wrote in message
news:9e634d46-33a2-4f31-bcf6-a28c535812b4n@googlegroups.com...

>On July 9, Kevin Aylward wrote:
> >Sure, when one measure clocks they are differences associated with
> >motion.
>> That is *not* in dispute. We know, clocks read different, it *why*
>> is what is in debate.
>
>> SR states that these differences are *not* because clocks *physically*
>> tick
>> less, but that they cover more "space-time", that is travel into the
>> future
>> say at a rate of 100sec/sec
>
>> LET type approaches state that the clock really do tick less as the POR
>> states that clocks *must *tick the independent of inertial motion.
> LET approaches state that clocks *do* actually slow down and achieves this
> >by rejecting the POR. The POR is taken to be a measurement artefact.

>Your notion that "clocks slow down" is nebulous.
>I'm curious regarding your concept/definition of time and clock.

Its not my notion. It, apparently, arose from Lorentz. Its clearly an
immediate inference from taking clocks on round trips and noting that they
read differernt form a referance clock.

There is nothing nebulous about a direct physical measurement of clocks.

>Al has a Timex, with which he times a leaky faucet.
>Bob has identical clock and faucet, in his new Tesla Model S,
>on the Utah salt flats.
>Do they record different ticks/drip rate?

>i.e. Your claim that clock rate and POR is tautological, hence
>unfalsifiable, is false.

Nope.

Its, essentially, tautological to the SOL. To verify that the POR is true,
must be able to verify that cloaks are not effected by inertial motion. That
is, that the physics of the operation of clocks is independent of inertial
motion. How does one do this, if one cannot define time without using
clocks?

Its circular taken on trips read different, and that that measuring clocks
in motion, e.g. GPS, on the face of it, says clock ticks do change.

>The point is, the 'true clock rate' is a
>vacuous concept, in isolation. Clocks have only one function:
>to record process evolution. Processes evolve, at rates which
>may or may not depend on frame velocity; an empirical question.

Produce a method to measure time, without using clocks to verify that "time"
is measured correctly by moving clocks.

SR makes definitions that are mathematically consistent. However, SR is
fundamentally based on the axiom that clocks always read the correct same
time, independent of velocity profile. SR does this, whilst being completely
ignorant of what time physically means or is, other than simply defining
time, as what a clock reads. This is, clearly, entirely circular.

A clock always reads the correct time, and time is what a clock reads.
Dah.....

>You're confused because you believe that time is something
>separate from physical processes, therefore it can slow.
>Modern physics denies this.

Strawman.

You are totally out of it here. Its absolutely the opposite. My position is
that time is 100% determined by physical processes. Its a real physical
process that decides how objects age.

SR takes the complete opposite viewpoint. SR just states that time is what a
clock reads. SR states that clocks cover more of this nebulous entity named
"time", such that objects can travel into the future as per Dr. Who and his
TARDIS.

Many take the view that such a view, is dubious.

Time is accounting for the fact that objects change their position and
momentum. Its a statement on the physical state of every object in the
universe. Whan an object changes state, time has changed.

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

>"Tom Roberts" wrote in message
>news:KfKdnam5fMhlznP9nZ2dnUU7_83NnZ2d@giganews.com...

>On 7/9/21 2:34 PM, Kevin Aylward wrote:
> It has been stated quite clearly that LET *type* approaches are er...
>>> Lorentz Invariant. Dah... Lorentz Invariance is not in dispute.
>> What is in dispute are the *axioms* that get to that point.

>LET postulates an essential and unique ether rest frame, which violates
>Lorentz invariance. Its ether is an utterly unobservable "unmoved mover" --
>such postulates have fallen out of favor (to say the least). Even Lorentz
>himself said that Einstein's approach was better.

A classical LET is clearly problematic, that isn't the point. The idea that
physics is so simple that a result can not be true for the wrong reason is.

>> We know that when we measure clocks the do read different. The simplest
>> explanation is that their ticks changed due to motion, thus the POR is
>> false.

>You overreach FAR too much, taking the desire for the deed. One cannot
>conclude "the POR is false" because a theory in which the POR is valid (SR)
>also agrees with all the experiments.

Sure, and I explained this many times.

You seem to be on a quest to resurrect LET -- that's hopeless. History
and theoretical physics are against you; experimental physics is also
against you (because of experiments involving the strong, weak, and
gravitational interactions).

>> Construct an experiment that absolutely proves that the difference in
>> readings on re-united clocks clocks are not due to clocks simply slowing
>> down rather than taking "a longer path in space-time", i.e. time travel.

>Impossible. There is no possible experiment (within their common domain)
>that can distinguish SR from LET.

Exactly.

>> You have made many statements in the past that they are an infinite set
>> of assumptions that lead to the LT.

>No. Why make such stuff up and pretend it is true?

You have. I will try and dig them out.

>There are several different sets of postulates that can be used to derive
>the LT, but not an infinite set.

Well, its impossible to verify both the POL and SOL independently, this
implies an infinite set of solutions.

That is, the SOL requires clocks, the POR requires clocks. Thus clocks can
cancel out of the equation.

For example:

A1) All that is red is a plant
A2) Grass is red
C0) Thus grass is a plant

A1) All that is blue is a plant
A2) Grass is blue
C0) Thus grass is a plant

There are an infinite number of ways to get to "grass is a plant", with
wrong axioms.

> I am simply stating that the axioms of SR are not required to explain LI

>Hmmm. Lorentz Invariance implies the POR and the invariance of c [#]. So
>you cannot have LI without the axioms of SR.

One cannot have one result implying two results in this manner. Its a
fundamental and basic logic fallacy. See above.

That's why LET works. It dispenses with the POR & SOL yet still results in
*observational* LI. It has to. LI relies on the LT.

>> SR inherently relies on the notion that the present state of the system
>> absolutely determines the next state of the system, that is, the block
>> universe.

>Hmmm. ALL classical theories of physics do this, including LET.

>But nobody in their right mind would base any cosmology on SR or LET or
>Newtonian mechanics.

>Cosmologies based on GR are deterministic. But this does not bother anybody
>because we KNOW that GR cannot be the ultimate theory. (Ditto for the
>others I mentioned.)

> Its the elephant in the room. SR is not compatible with QM,

>You keep repeating this. IT IS WRONG.

Nope. Its correct.

>SR is fully compatible with QM, and their combination yields QED, QCD,
>electro-weak theory, and the standard model.

Nope. QM can be formulated as compatible with the LI/LT. This does not imply
SR is compatible with QM. Its a subtle distinction. It don't work both ways.

The only way SR can be correct is if the future is strictly deterministic.
Its the block universe. End of.

QED, QCD, electro-weak theory, and the standard model all exist by way of
LT/LI. Observational LT/LI does not require SR.

>It is GR that is not fully compatible with QM. That's quite a different
>kettle of fish....

Different issue.

> Its a subtlety many, clearly don't get.

>Including you. Especially you.

Unfortunately, you just don't get that the SR/LET equations form the entire
mathematical content of SR/LET.

QM has no problem with LI/LT. SR has problems with QM

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

>"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.

>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. 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.

The fundamental issue is assuming that "space-time" has real physical
meaning. It doesn't.

There are many main stream academics that understand that SR/GR space time
is truly only a model, that just cannot account for reality, despite
notional success.

> (There is a property called “proper length” which is no more
>complicated than the projection of any coordinate length onto the object’s
>rest frame, but there’s no real reason to think of this as any more
>“physical” than any other.)

Sure there is.

Physical objects and reality don't care how they are measured.

Physical reality is that I age and die. No amount of traveling or
mathematical manipulation will change when I die. My age is real.

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

"Arthur Adler" wrote in message
news:24dc8a8c-135e-47b1-9875-79215735198fn@googlegroups.com...

On Thursday, July 15, 2021 at 11:30:13 AM UTC-7, Kevin Aylward wrote:
> > Special relativity is based on the premise that all the equations of
> > physics
> > (whether they be deterministic or not) take the same homogeneous and
> > isotropic form in terms of every local system of inertia-based
> > coordinates.
>
> That's Covariance. All equations can be put in General Covariance
> form. Its a principle of mathematics not physics.

No, 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.

> Nope. Coordinate systems have no physical content whatsoever. Period.

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. This is a
crucially significant physical fact. Until you understand this, you will
understand nothing about special relativity.

> > Again, the local Lorentz invariance of all physical laws does not imply
> >that the laws of physics are (or are not) deterministic.
>
> Oh yes they do.

Nope, 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.

> Roger Penrose "The Emperor's New Mind" p.393:

Appeals to authority are pointless, but I'll 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. He
basically fell prey to the Fontenot/Harnagel Fallacy while writing Emperors,
but fortunately pulled out of it.

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

That's 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* over determinism, and he (Einstein)
did not maintain that determinism is required (and he forever lamented the
too quotable flippant dice comment), but rather the apparently non-locality.
But we now know that quantum mechanics is perfectly consistent with the
locality of Lorentz invariance, i.e., spacelike observables commute.

> this basic, well known principle that SR must be strictly deterministic.
> Thus, it fundamentally
> contradicts QM

To the contrary, what you have in your brain is the well-known sophomoric
misconception, and in fact 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, but that's why relativistic QM was
invented. Duh.

> ... not relevant to the above point.

Huh? You claim that QFT is incompatible with special relativity, and I
point out that you are mistaken, since QFT is founded on local Lorentz
invariance (special relativity), and you say that's not relevant to your
point? What is wrong with you?

> 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 derived, it is
>defined as the tensor that encodes all the Gaussian curvatures of a
>manifold at any given point.

Word salad. So no brownie points there. Yeah "The curvature tensor is
defined as er... ho hummm.... a curvature" . What part of circular argument
do you not understand?

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

>The geodesic paths satisfy the geodesic equation, which involves the
Christoffel symbols, which are defined in terms of the metric coefficients,
which must satisfy the field >equations. What part of this don't you
understand?

In other words, no, "I cant find where the minus sign was dropped in, so I
will just spout words I read somewhere to sound impressive"

https://www.kevinaylward.co.uk/gr/riemann/riemann.html

>> *Physical* "length contraction" is a feature of LET (Lorentz Ether
>> Theory) not SR.

>No, 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.
Why do you think its named the "The Lorentz transformation" and not the
"Einstein Transformation". Dah.....

>They are the same physical theory, the only semantic difference being that
>LET declares one particular system of inertial coordinates as the "true"
>one, but this can be >*any* system, and the designation "true" has no
>physical significance.

Nope. The physics assumed by LET and SR are fundamentally different. One has
an ether, one don't. Dah. However, the mathematics are identical.

> Time dilation *cannot* be physically real because *both* observers see the
> *other* dilated...

>Your conclusion does not follow from your premise.

Yep it does.

>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. If they
both move apart turn around again and meet up, despite reading the other
clocks slow whilst in uniform motion, their final clock readings for a
symmetric acceleration profile will be the same. Thus "dilation" isn't
physically real

> If your definition of "physically real" refers to something other than
> verifiable objective facts, then you are using non-standard terminology.

Physically real is the state that a reunited clock will read different from
its reference. Clocks taking different acceleration profiles will physically
read different.

-- 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: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.

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.

>
>> 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.

> 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”. If you mean, is it predictable in
a clockwork universe way, then there are some interesting questions there.
The Schrodinger equation is, after all, a time-evolution equation. That’s
what the partial derivative with respect to time means. It is also true
that a complete state description does not involve all the variables that a
classical model would contain. Variables that don’t commute cannot be both
evolved in the same way. So what?

>
> The fundamental issue is assuming that "space-time" has real physical
> meaning. It doesn't.
>
> There are many main stream academics that understand that SR/GR space time
> is truly only a model, that just cannot account for reality, despite
> notional success.
>
>> (There is a property called “proper length” which is no more
>> complicated than the projection of any coordinate length onto the object’s
>> rest frame, but there’s no real reason to think of this as any more
>> “physical” than any other.)
>
> Sure there is.
>
> Physical objects and reality don't care how they are measured.

That’s true. But is length one of the properties in that reality that is
innate?
Is kinetic energy of an object innate? What about the magnetic field around
a charged object?

What you are doing is saying, “Reality is real, and the properties that
belong to that reality are [R, S, T, U, V, W, X, Y, Z]” by fiat, rather
than asking the question whether the innateness can be tested rather than
stiff-upper-lip declared.

>
> Physical reality is that I age and die. No amount of traveling or
> mathematical manipulation will change when I die. My age is real.
>
>
> -- 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

>"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.

A coordinate system doesn't know whether its subjected to forces or not.

>Coordinates of an inertial frame are special, in that inertia is
>homogeneous and isotropic relative to them, and the laws of physics take
>their simplest form when projected onto such coordinates.

Sure, coordinates specifically *locked* to a *real* physical frame may be
treated "as if" they are equivalent in certain circumstances.

The coordinates themselves are massless, and are not subject to inertia at
all. They are are virtual. "wafer thin" with a French accent as the meaning
of life would say....

>> Coordinates systems are abstractions, they have no physical
>> properties at all.

>Hmmmm. The numbers themselves have no physical properties, but
>coordinates on an inertial frame have the properties I just described.

Sure, coordinates of course, may be used to *model* physical objects that do
have physical properties.

> For example, one can have a rotating coordinate system describing an
> inertial frame,

>That is an oxymoron -- you need to learn what these words actually mean.

Twaddle. You just don't seem to get this. There is no fundamental reason
coordinate systems have to be locked to the motion of what they are
describing. One can have a box moving with events described by x'=x-vt, or
one can simply perform a change of variables, say x=r.sin(wt) where r and w
are referenced to some other *virtual* coordinate system. One can describe
the box entirely in r and w terms.

You need to learn the difference between a physical box moving and how it is
described.

>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 rotating coordinates have
>mutually orthogonal axes.

Completely irrelevant to the point.

>Note these are all coordinates
>on spacetime, not just space.

You are way, way confused. Its crucial to distinguish between arbitrary
coordinate systems and systems that may, for *convenience*, be *locked* to
that coordinate system.

For example, in J.D Norton "General Covariance and the Foundations of
General Relativity: eight decades of dispute"

"In traditional developments of special and general relativity it has been
customary not to distinguish between two quite distinct ideas. The first is
the notion of a coordinate system, understood simply as the smooth,
invertible assignment of four numbers to events in The second, the frame of
reference, refers to an idealized physical system used to assign such
numbers. More precisely, since the physical systems tend to be space
filling, one is concerned with how such hypothetical systems would behave
were they to be constructed."

Confusion on physical frames with coordinate systems has led to the
erroneous view that because, the laws of physics can be described "as if"
they are independent of "inertial coordinate" systems, in conjunction with
the idea that, by construction, all physical systems must be independent of
coordinate systems, that the laws of physics are independent of
"acceleration".

Its a subtle conflation of ideas. You just don't seem to understand the
distinction.

A physical frame is a *real* *system*, with members of that system that
undergoes, for example , inertial and gravitation *forces*. These forces
effect the behaviour of the system.

A coordinate system is, essentially, imaginary. It doesn't exist in the real
world. Its a virtual construct not subject to any forces and cannot be
effected by inertial and gravitation forces.

Failure to distinguish frames and coordinates led to:

"Gravitation, by Misner, Thorne and Wheeler", often called MTW in the news
groups. The relevant quote is:

"Mathematics was not sufficiently refined in 1917 to cleave apart the
demands for "no prior geometry" and for a geometric, co-ordinate independent
formulation of physics. Einstein described both demands by a single phrase,
"general covariance" The "no prior geometry" demand actually fathered
General Relativity, but by doing so anonymously, disguised as "general
covariance", it also fathered half a century of confusion."

The fact that physical systems can be described independent of coordinates,
does not imply that all physical systems can be described independent of
motion. It only works for inertial motion. Einstein confused these points.

> Coordinate systems and physical reference frames are not the same.

>You attempt to make a distinction without a difference. In normal usage
>among physicists, inertial coordinates and the frame they implement are
>synonymous.

Sure, many physicists confuse the two. It leads to false ideas and false
conclusions.

>Yes, technically there are an infinite number of
>coordinate systems on a given inertial frame, differing
>by spatial rotations. We ignore this technicality as it
>is invariably irrelevant to the discussion.

Sure, in most applications, not all.

>When different observers measure the length of a given object, that
>object's length does not change and does not "rotate in spacetime"; rather
>it is the different observers' instruments that are oriented differently in
>spacetime.
>IOW: objects at rest in different inertial frames are oriented differently
>in spacetime -- each has a constant orientation, and there is a (constant)
>rotation between them. It is acceleration that rotates an object in
>spacetime, not inertial motion.

Oh dear..... what drugs are you on?

The standard pole problem. Pole travels horizontally and gets knocked
downwards and can fit through a hole of smaller diameter than the pole. Its
described as staying the same real length, with the front and back of the
pole going through the hole at different points in time. Its described as a
rotation.

>> Time "dilation" is,
>> essentially an "optical illusion".

>Not at all -- you REALLY need to learn what the words you use actually
>mean.

Of course it is. Reunite clocks on a symmetrical acceleration profile and
their will read the same, despite notional time dilation during the inertial
motion part.

>For instance, "time dilation" permits Fermilab and CERN to build
>high-energy pion beamlines a kilometer long -- no "illusion" could do that.

Sure. Of course illusions can have physical effects.

>> Time
>> dilation *cannot* be physically real because *both* observers see the
>> *other* dilated,

>You are confused. Yes, for two inertial observers moving differently they
>each see the other's clock ticking slower than their own. There is no
>contradiction or problem here, as they are making DIFFERENT MEASUREMENTS.

Who is claiming that there is a contradiction?

>"Time dilation" and "length contraction" are geometrical projections, and
>must therefore behave as such projections do. That includes being
>reciprocal under appropriate circumstances (such as between inertial
>frames).

This contradicts your "time dilation is real claim" above.

A "geometric projection" that has the shadow of a sun dial's pole change its
position does not mean that the pole actually changes it positions. The
position change is an illusion, but sure, that illusion has real physical
effects that needs to be accounted for.

>> much like both observers viewing the other through a
>> magnifying glass see the other larger.

>Not at all. Rather, this is like you and your friend seeing each other as
>smaller when you are further apart. This is GEOMETRY, not optics.

Ho hummmm... totally lost the plot. Sure, there are many other equivalent
different examples of mutual effects to illustrate the point. Dah......

>> Its nonsensical for both
>> observers to be physically larger.

>Yes, that would be nonsensical, but relativity does not predict that.

Sure. Who is claiming that SR does?

>Both "Length contraction" and "time dilation" are about the way
>measurements behave under certain geometrical projections. For them, no
>object changes (proper) length, and no clock changes its (proper) tick
>rate.

On Tuesday, July 20, 2021 at 1:53:04 PM UTC-7, Kevin Aylward wrote:
> > [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, and in addition I'll 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. He basically fell prey to the Fontenot/Harnagel Fallacy while writing Emperors, but fortunately pulled out of it.

> > [quoting Penrose Emperror] Indeed, this seems to have been Einstein's own
> > conclusion (cf. Paris 1982 p.444).
That's 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* over determinism, and he (Einstein) did not maintain that determinism is required (and he forever lamented the too quotable flippant dice comment), but rather the apparently 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, but that's why relativistic QM was invented. Duh.

> > > 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 didn't make sense, because the curvature tensor isn't derived, it is defined, and to give you a little clue about how it is defined, I note that the components of the curvature tensor are essentially the pair-wise 2D intrinsic curvature scalars (which of course any competent freshman knows how to define) 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 involves the Christoffel symbols, which are defined in terms of the metric coefficients, which must satisfy the field equations, which involve the Ricci tensor (the contraction of the Riemann curvature tensor). What part of this don't you understand?

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

What you typed on that web page is gibberish. Again, the geodesic paths satisfy the geodesic equation, which involves 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 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 with the addition of 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 failed to read what I wrote: 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, their final clock readings for a symmetric
> acceleration profile will be the same.

Of course.

> 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). This sentence tells you everything you need to know (with integration) 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.

On Tuesday, 20 July 2021 at 22:53:57 UTC+2, bodk...@gmail.com wrote:
> 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...@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.
>
> 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

But, of course, it doesn't change in the slightest way the fact, that
objectively real length and objectively real velocity always match
the prophecies of our beloved Giant Guru!

On Tuesday, July 20, 2021 at 1:53:04 PM UTC-7, Kevin Aylward wrote:
> > [Blatant misconceptions about general coveriance versus the principle of
> > relativity, and erroneous claim that special relativity implies determinism.]

You are 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's 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'll 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's 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, but that's why relativistic QM was invented.

> > > 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 isn't 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).. What part of this don't you understand?

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

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's 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're 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's 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: 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". 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 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 sentence 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.

On Wednesday, 21 July 2021 at 10:21:14 UTC+2, Arthur Adler wrote:

> Again, there's 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.

Again, no, there is no such class, the assumption is not strong enough
to create it unambigously.

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.

>
> A coordinate system doesn't know whether its subjected to forces or not.
>
>> Coordinates of an inertial frame are special, in that inertia is
>> homogeneous and isotropic relative to them, and the laws of physics take
>> their simplest form when projected onto such coordinates.
>
> Sure, coordinates specifically *locked* to a *real* physical frame may be
> treated "as if" they are equivalent in certain circumstances.
>
> The coordinates themselves are massless, and are not subject to inertia at
> all. They are are virtual. "wafer thin" with a French accent as the meaning
> of life would say....
>
>>> Coordinates systems are abstractions, they have no physical
>>> properties at all.
>
>> Hmmmm. The numbers themselves have no physical properties, but
>> coordinates on an inertial frame have the properties I just described.
>
> Sure, coordinates of course, may be used to *model* physical objects that do
> have physical properties.
>
>> For example, one can have a rotating coordinate system describing an
>> inertial frame,
>
>> That is an oxymoron -- you need to learn what these words actually mean.
>
> Twaddle. You just don't seem to get this. There is no fundamental reason
> coordinate systems have to be locked to the motion of what they are
> describing. One can have a box moving with events described by x'=x-vt, or
> one can simply perform a change of variables, say x=r.sin(wt) where r and w
> are referenced to some other *virtual* coordinate system. One can describe
> the box entirely in r and w terms.
>
> You need to learn the difference between a physical box moving and how it is
> described.
>
>> 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.

As an example, it would be interesting for you to take a set of objects,
including a ping-pong ball being swatted between two bats, and describe the
motion of the ping-pong ball WITHOUT a set of coordinates. Care to try?

>
>> No rotating coordinates have
>> mutually orthogonal axes.
>
> Completely irrelevant to the point.
>
>> Note these are all coordinates
>> on spacetime, not just space.
>
> You are way, way confused. Its crucial to distinguish between arbitrary
> coordinate systems and systems that may, for *convenience*, be *locked* to
> that coordinate system.
>
> For example, in J.D Norton "General Covariance and the Foundations of
> General Relativity: eight decades of dispute"
>
> "In traditional developments of special and general relativity it has been
> customary not to distinguish between two quite distinct ideas. The first is
> the notion of a coordinate system, understood simply as the smooth,
> invertible assignment of four numbers to events in The second, the frame of
> reference, refers to an idealized physical system used to assign such
> numbers. More precisely, since the physical systems tend to be space
> filling, one is concerned with how such hypothetical systems would behave
> were they to be constructed."
>
> Confusion on physical frames with coordinate systems has led to the
> erroneous view that because, the laws of physics can be described "as if"
> they are independent of "inertial coordinate" systems, in conjunction with
> the idea that, by construction, all physical systems must be independent of
> coordinate systems, that the laws of physics are independent of
> "acceleration".
>
> Its a subtle conflation of ideas. You just don't seem to understand the
> distinction.
>
> A physical frame is a *real* *system*, with members of that system that
> undergoes, for example , inertial and gravitation *forces*. These forces
> effect the behaviour of the system.
>
> A coordinate system is, essentially, imaginary. It doesn't exist in the real
> world. Its a virtual construct not subject to any forces and cannot be
> effected by inertial and gravitation forces.
>
> Failure to distinguish frames and coordinates led to:
>
> "Gravitation, by Misner, Thorne and Wheeler", often called MTW in the news
> groups. The relevant quote is:
>
> "Mathematics was not sufficiently refined in 1917 to cleave apart the
> demands for "no prior geometry" and for a geometric, co-ordinate independent
> formulation of physics. Einstein described both demands by a single phrase,
> "general covariance" The "no prior geometry" demand actually fathered
> General Relativity, but by doing so anonymously, disguised as "general
> covariance", it also fathered half a century of confusion."
>
> The fact that physical systems can be described independent of coordinates,
> does not imply that all physical systems can be described independent of
> motion. It only works for inertial motion. Einstein confused these points.
>
>> Coordinate systems and physical reference frames are not the same.
>
>> You attempt to make a distinction without a difference. In normal usage
>> among physicists, inertial coordinates and the frame they implement are
>> synonymous.
>
> Sure, many physicists confuse the two. It leads to false ideas and false
> conclusions.
>
>> Yes, technically there are an infinite number of
>> coordinate systems on a given inertial frame, differing
>> by spatial rotations. We ignore this technicality as it
>> is invariably irrelevant to the discussion.
>
> Sure, in most applications, not all.
>
>
>> When different observers measure the length of a given object, that
>> object's length does not change and does not "rotate in spacetime"; rather
>> it is the different observers' instruments that are oriented differently in
>> spacetime.
>> IOW: objects at rest in different inertial frames are oriented differently
>> in spacetime -- each has a constant orientation, and there is a (constant)
>> rotation between them. It is acceleration that rotates an object in
>> spacetime, not inertial motion.
>
> Oh dear..... what drugs are you on?
>
> The standard pole problem. Pole travels horizontally and gets knocked
> downwards and can fit through a hole of smaller diameter than the pole. Its
> described as staying the same real length, with the front and back of the
> pole going through the hole at different points in time. Its described as a
> rotation.
>
>
>
>>> Time "dilation" is,
>>> essentially an "optical illusion".
>
>> Not at all -- you REALLY need to learn what the words you use actually
>> mean.
>
> Of course it is. Reunite clocks on a symmetrical acceleration profile and
> their will read the same, despite notional time dilation during the inertial
> motion part.
>
>> For instance, "time dilation" permits Fermilab and CERN to build
>> high-energy pion beamlines a kilometer long -- no "illusion" could do that.
>
> Sure. Of course illusions can have physical effects.
>
>>> Time
>>> dilation *cannot* be physically real because *both* observers see the
>>> *other* dilated,
>
>> You are confused. Yes, for two inertial observers moving differently they
>> each see the other's clock ticking slower than their own. There is no
>> contradiction or problem here, as they are making DIFFERENT MEASUREMENTS.
>
> Who is claiming that there is a contradiction?
>
>
>> "Time dilation" and "length contraction" are geometrical projections, and
>> must therefore behave as such projections do. That includes being
>> reciprocal under appropriate circumstances (such as between inertial
>> frames).
>
> This contradicts your "time dilation is real claim" above.
>
> A "geometric projection" that has the shadow of a sun dial's pole change its
> position does not mean that the pole actually changes it positions. The
> position change is an illusion, but sure, that illusion has real physical
> effects that needs to be accounted for.
>
>>> much like both observers viewing the other through a
>>> magnifying glass see the other larger.
>
>> Not at all. Rather, this is like you and your friend seeing each other as
>> smaller when you are further apart. This is GEOMETRY, not optics.
>
> Ho hummmm... totally lost the plot. Sure, there are many other equivalent
> different examples of mutual effects to illustrate the point. Dah......
>
>>> Its nonsensical for both
>>> observers to be physically larger.
>
>> Yes, that would be nonsensical, but relativity does not predict that.
>
> Sure. Who is claiming that SR does?
>
>> Both "Length contraction" and "time dilation" are about the way
>> measurements behave under certain geometrical projections. For them, no
>> object changes (proper) length, and no clock changes its (proper) tick
>> rate.
>
> So...you agree length and time dilations are essentially, illusions, that
> is, geometric projections. A projection don't mean that what is projected
> physicaly changes, only that how it is perceived changes.
>
>> When your friend walks away from you, you see them
>> getting progressively smaller. Do you really think that
>> they are physically smaller, or is this just an artifact
>> of the way you are observing them? -- Ditto for "length
>> contraction" and "time dilation".
>
> You are rally getting your tits in a tangle in an effort not to agree with
> me, but do.
>
>> I repeat: you REALLY need to learn something about the subject before
>
> Yeah..... oh dear....
>
>
> -- Kevin Aylward
> http://www.kevinaylward.co.uk/gr/index.html
> http://www.kevinaylward.co.uk/qm/index.html
>
>

Kevin Aylward wrote:

>> That's Covariance. All equations can be put in General Covariance form.
>> Its a principle of mathematics not physics.
>
> No, 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

Are you sure?

gavi, criminal private organization, with 100% diplomatic immunity around
the globe, cooking covid-19 genocide depopulation through mass global
vaccination before 2019, selling *covid-19_test_kits* already 2017.

(Tedros came to WHO directly from GAVI (!!))

(when the fake "pandemic" hit january 2020, they already had covid-19 test
kits ready to go. You are not paying attention: they knew the RNA
sequences those PCR kits are made to test for, before the "virus" hit!!
All countries! Got it now?)

Among countries govt donor contributions, your tax money, guess who else
are interested in having you vaccinated and chipped like cattle:

google.org, MasterCard, the VISA foundation, UPS, TikTok, Shell
international etc. They are all in this together.

start boycott now, use yandex.com. 31:20 mark for the table.

W.H.O. WHISTLEBLOWER CONNECTS THE DOTS
https://www.bitchute.com/video/HZ94izRdfvnW/

"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.

As I noted before in J.D Norton "General Covariance and the Foundations of
General Relativity: eight decades of dispute"

http://www.pitt.edu/~jdnorton/jdnorton.html

"In traditional developments of special and general relativity it has been
customary not to distinguish between two quite distinct ideas. The first is
the notion of a coordinate system, understood simply as the smooth,
invertible assignment of four numbers to events in The second, the frame of
reference, refers to an idealized physical system used to assign such
numbers.

>As an example, it would be interesting for you to take a set of objects,
>including a ping-pong ball being swatted between two bats, and describe the
>motion of the ping-pong ball WITHOUT a set of coordinates. Care to try?

Sure, its difficult to mathematically describe playing tennis without
coordinates. Fortunately, no one requires coordinate systems to play tennis.
The brain is quite an amazing object. It guides the juggling of multiple
balls at once, all without any explicit differential equations.

Unfortunately for the England football team, it also seems quite unable to
guide penalty shoots into the back of the net for all.

-- 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: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. 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.

>
> As I noted before in J.D Norton "General Covariance and the Foundations of
> General Relativity: eight decades of dispute"
>
> http://www.pitt.edu/~jdnorton/jdnorton.html
>
> "In traditional developments of special and general relativity it has been
> customary not to distinguish between two quite distinct ideas. The first is
> the notion of a coordinate system, understood simply as the smooth,
> invertible assignment of four numbers to events in The second, the frame of
> reference, refers to an idealized physical system used to assign such
> numbers.
>
>
>> As an example, it would be interesting for you to take a set of objects,
>> including a ping-pong ball being swatted between two bats, and describe the
>> motion of the ping-pong ball WITHOUT a set of coordinates. Care to try?
>
> Sure, its difficult to mathematically describe playing tennis without
> coordinates. Fortunately, no one requires coordinate systems to play tennis.
> The brain is quite an amazing object. It guides the juggling of multiple
> balls at once, all without any explicit differential equations.

But the mind is not describing in any quantitive way the motion of the ball
in playing the game.
That’s the point. Coordinates are important for the quantitative
description of motion, which is an important mental construct in physics as
a mental activity. Other mental activities surrounding those same objects
may not involve quantitative descriptions of the motion or may not involve
any physics at all — that’s noted but irrelevant.

I do note with interest that you admit that the quantitative description of
motion of an object — that which would be important in physics — is in fact
something you’d be hard pressed to produce without coordinates, and hence
without a reference frame.

>
> Unfortunately for the England football team, it also seems quite unable to
> guide penalty shoots into the back of the net for all.
>
>
> -- 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 7/20/21 2:44 PM, Kevin Aylward wrote:
> To verify that the POR is true, must be able to verify that cloaks
> are not effected by inertial motion. That is, that the physics of
> the operation of clocks is independent of inertial motion. How does
> one do this, if one cannot define time without using clocks?

This is excessively limited. To verify the POR, one must show that the
LAWS OF PHYSICS are the same when referenced to different inertial
frames. THINK about that -- as the earth orbits the sun, it is at rest
in a succession of different inertial frames, yet the laws of physics we
observe are unchanged. This includes comparing the tick rates of clocks
implemented with many different technologies (and hence based on
different laws of physics).

> Its circular taken on trips read different, and that that measuring
> clocks in motion, e.g. GPS, on the face of it, says clock ticks do
> change.

This is garbled and unintelligible.

GPS satellite clocks are modified so the effects on their signals due to
their motion and earth's gravity result in the correct frequency being
received on the ground. This also cancels the long-term effects of their
different paths through spacetime compared to clocks on the ground (geoid).

> Produce a method to measure time, without using clocks to verify
> that "time" is measured correctly by moving clocks.

No need. You are obsessed with one aspect of the POR, when it is quite
general, and literally zillions of experiments show it is valid.

> SR is fundamentally based on the axiom that clocks always read the
> correct same time, independent of velocity profile.

No. SR's premise is the POR. Your obsession is wrong.

> Physical reality exists.

Sure. Without that, physics would be impossible.

> There is a common misunderstanding among those that discuss physics
> that mathematics is reality.

I have no idea who you mean. Certainly not physicists, or people who
actually understand basic physics. I suppose this might apply to some of
the idiots around here, but that is not obvious to me....

> 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.

Hmmm. SR is a physical model (i.e. a model of "real physical
processes"). Like all modern physical models, it uses
mathematics.

> For example, "space-time" results in (GR) the result that one can go
> backwards in time.

Not true. No future-directed timelike trajectory can be rotated into a
past-directed timelike trajectory, while remaining timelike.

There are some manifolds of GR that contain closed timelike curves, and
an observer following one of them would willy-nilly be transported into
the last lightcone of some events that occurred earlier on their
trajectory. But these manifolds CLEARLY do not correspond to the world
we inhabit.

Note that unlike GR, Newtonian mechanics has no prohibition of an
observer or object "going backwards in time", it's just a convention: we
don't do that.

> Neither does the future exist. QM tells us that it doesn't. Its
> really that simple.

Like most simple "solutions" this one is wrong. QM says nothing of the sort.

> The fundamental issue is assuming that "space-time" has real
> physical meaning. It doesn't.

This depends on the meanings you assign to words. Spacetime is a MODEL,
not a part of the world we inhabit -- it is a CONCEPT, not any physical
entity. It has no "existence" in the world, it only appears inside
peoples' minds.

> Physical objects and reality don't care how they are measured.

Sure. But differently-moving observers can obtain different results for
measuring some things. It OUGHT to be obvious that such differences are
simply due to the different relationships between such observers'
instruments and the object being measured.

> its impossible to verify both the POL and SOL independently, this
> implies an infinite set of solutions.

What is "POL"???? -- I assume it is a typo for "POR".

One certainly can verity both the POR and the constancy of the (vacuum)
speed of light: verify many different laws of physics in many different
inertial frames, and measure the (vacuum) speed of light in many
different inertial frames. Of course this happens naturally in
laboratories on earth as the earth orbits the sum. Both the POR and the
constancy of the (vacuum) speed of light are solidly established.

> That is, the SOL requires clocks, the POR requires clocks. Thus
> clocks can cancel out of the equation.

Nonsense. This is not an "equation", this is a set of tests of physical
theories.

Tom Roberts

On 7/20/21 4:00 PM, Kevin Aylward wrote:
>> "Tom Roberts" wrote in message
>> news:R_mdndzJsOpAoG79nZ2dnUU7_83NnZ2d@giganews.com... On 7/15/21
>> 1:29 PM, Kevin Aylward wrote:
>>> "inertial coordinates" is, technically, a meaningless statement.
>
>> No. Not even close.
>
> Yep. Absolutely nuts on. Its, essentially, an "oxymoron".

No. You are confused. "Inertial coordinates" is well defined and used
throughout physics. But the meaning has morphed since the 17th century,
becoming both more general and more specific.

> Coordinates, by construction, have no physical properties
> whatsoever.

Sure, because coordinates are part of the model, not the world; physical
properties are aspects of the world.

You seem unaware of the distinction between world and model, and
frequently attempt to intermix them. That's hopeless, as they are
completely incommensurate.

> "Inertial", describes a system, loosely, that is not subjected to
> any physical forces.

Sure, loosely. This is a statement about the world.

But that is not the only meaning of the word. For instance, "inertial
coordinate systems" are those in which the metric components are
diag(-1,1,1,1) (units with c=1); relative to such coordinates, free
particles move in uniform straight lines (Newton's first law), inertia
is isotropic and homogeneous, the laws of physics take their simplest
expression, etc. This is a statement about the model.

> A coordinate system doesn't know whether its subjected to forces or
> not.

Hmmmm. "Forces" do not apply to a coordinate system, because forces are
part of the world while coordinates are part of the model. It makes no
sense to attempt to mix model and world.

The humans that use it know whether a given coordinate system is
inertial or not.

> The coordinates themselves are massless, and are not subject to
> inertia at all.

That makes no sense. Coordinates are part of the MODEL, not the world.
Mass and inertia are properties of objects in the world.

[Inertia is part of the world, but "inertial coordinates"
are part of the model. One must be careful because
history has conflated and confused the meanings of many
words; language evolves.]

>> For example, one can have a rotating coordinate system describing
>> an inertial frame,
>
>> That is an oxymoron -- you need to learn what these words actually
>> mean.
>
> Twaddle. You just don't seem to get this. There is no fundamental
> reason coordinate systems have to be locked to the motion of what
> they are describing.

Sure, but it is YOU who is confused, in part by not understanding the
meanings of the words you use. Inertial coordinates are as I described
above, and that precludes them having any rotation. (See below about
"inertial frame" vs "inertial coordinates".)

[Rotating coordinates necessarily have metric components
with at least one non-zero off-diagonal value. Inertial
coordinates necessarily have all off-diagonal components
equal to zero.]

>> 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.

As I said, YOU really need to learn what these words and phrases
actually mean. In physics, "inertial frame" and "inertial coordinates"
are SYNONYMS.

*** "Frame" is ambiguous -- it can be either part of the
*** world or part of the model. A frame made of steel rods
*** is part of the world; a frame made of coordinate axes
*** is part of the model. "Inertial frame" involves the
*** latter.

You keep trying to use "frame" as simultaneously part of the model and
part of the world -- that's hopeless.

>> When different observers measure the length of a given object,
>> that object's length does not change and does not "rotate in
>> spacetime"; rather it is the different observers' instruments that
>> are oriented differently in spacetime. IOW: objects at rest in
>> different inertial frames are oriented differently in spacetime --
>> each has a constant orientation, and there is a (constant) rotation
>> between them. It is acceleration that rotates an object in
>> spacetime, not inertial motion.
>
> Oh dear..... what drugs are you on?

None. That _IS_ how this is described in relativity. The fact that you
don't recognize it merely demonstrates your lack of understanding.

>>> Time "dilation" is, essentially an "optical illusion".
>
>> Not at all -- you REALLY need to learn what the words you use
>> actually mean.
>
> Of course it is.

No. "time dilation" refers to the different orientations of clocks that
are moving relative to each other, and how they project geometrically
onto various inertial coordinate systems.

>> For instance, "time dilation" permits Fermilab and CERN to build
>> high-energy pion beamlines a kilometer long -- no "illusion" could
>> do that.
>
> Sure. Of course illusions can have physical effects.

Then they aren't illusions. These are different perspectives, not
illusions at all.

Note that optical illusions occur IN YOUR MIND, not in your eyes or
the optical rays involved. AFAIK illusions always occur inside peoples'
minds. So illusions are not "real" in the sense that they affect any
physical object(s), but they definitely are "real" to the person
experiencing them -- this merely illustrates how slippery and
ill-defined the word "real" is, and why I avoid it.

>> "Time dilation" and "length contraction" are geometrical
>> projections, and must therefore behave as such projections do.
>> That includes being reciprocal under appropriate circumstances
>> (such as between inertial frames).
>
> This contradicts your "time dilation is real claim" above.

Go back and READ WHAT I WROTE. I disagreed with your assertion that
"time dilation" is an illusion, but I never used the word "real",
precisely because it is so ambiguous and poorly defined. You attempt to
apply a dichotomy: "real or illusion", when in fact there are other
possibilities, such as geometrical projections (which are neither).

"Time dilation" is not an "illusion", it is a GEOMETRICAL PROJECTION.
I would not apply the word "real" to it, as most people would
misinterpret that (some aspects of "real" apply, some don't, and it is
best to avoid the confusion altogether by simply not using the word).

> A "geometric projection" that has the shadow of a sun dial's pole
> change its position does not mean that the pole actually changes it
> positions. The position change is an illusion, but sure, that
> illusion has real physical effects that needs to be accounted for.

You OBVIOUSLY don't understand what a geometrical projection actually
is. Your supposed example is NOT a geometrical projection. Nor is it an
illusion.

[Your sundial is part of the world; geometry is part of
the model.]

Example in 2-D Euclidean geometry: lay down a set of Cartesian
coordinates (x,y), and consider the line segment (0,0) to (1,0): It has
a projection along x of 1 and a projection along y of 0. Now construct
a second set of Cartesian coordinates (x',y') rotated by 45 degrees from
(x,y). That line segment has a projection along x' of 0.707, and a
projection along y' of 0.707.

"Time dilation" and "length contraction" are similar, but one axis is
the time axis and the other is a spatial axis, and they occur in
hyperbolic geometry.

>> Both "Length contraction" and "time dilation" are about the way
>> measurements behave under certain geometrical projections. For
>> them, no object changes (proper) length, and no clock changes its
>> (proper) tick rate.
>
> So...you agree length and time dilations are essentially, illusions,

No. Not at all! You need to READ WHAT I WROTE. And you REALLY need to
learn what the words you use ACTUALLY mean. You seem to think "illusion"
means how things are viewed -- that is PERSPECTIVE, not "illusion".
"Illusion" does not apply to either "time dilation" or "length
contraction" -- but geometrical projection applies to both.

Tom Roberts

On 7/21/21 1:15 PM, Kevin Aylward wrote:
> [...] the classic false statement by Einstein, to wit:

It's not "false", it is your confusion that makes you think so.

> "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.

Of course not -- he is describing GR and a general constraint on
physical theories; the POR is from SPECIAL relativity. The POR applies
to inertial coordinates, not the general coordinates Einstein is
discussing here.

> "Equations that hold good for all systems of coordinates" can always
> be written, if the equation is actually true in a particular
> coordinate system.

Hmmmm. While possible in principle, in practice we want to write down a
SINGLE equation expressing the physical relationship(s) involved, which
requires coordinate-independent notation, such as tensors.

> The POR is a *physical* principle, not a principle as to how clever
> a mathematician is in writing equations.

Apparently you have never read the POR. Let me enlighten you:

"The laws by which the states of physical systems undergo
change are not affected, whether these changes of state
be referred to the one or the other of two systems of co-
ordinates in uniform translatory motion." [Einstein, 1905]

This is clearly a statement ABOUT THE MODEL, not the world [#], so it is
not "physical" at all. It quite clearly _IS_ about writing equations,
but no "cleverness" is involved, as it essentially states the laws
(equations) are the same in any inertial coordinates.

[#] Laws, states, and coordinates are all clearly
parts of the model. By "laws" he means equations.

But the remarkable fact is that this model applies to the world we
inhabit, as demonstrated by zillions of experiments. That, of course, is
why SR has become the foundation of all modern physical theories.

Challenge to Aylward: Try to state this as a "physical
principle" in terms of the world, not the model.
Hint: you cannot use words or symbols, as they are
all models -- this difficulty is why physics is about
making and refining models of the world, and not
about "explaining how the world works". EVERYTHING you
think you know about the world is actually about some
MODEL you have of the world.

As I have said so often: you REALLY need to learn about the distinction
between world and model, including the meanings of words and which words
apply to model and which to world.

> Without understanding exactly what the POR means, one is going
> nowhere....

Yes. So YOU had better learn what it actually means. Einstein's POR is
clearly about the model; but the model applies accurately to the world
we inhabit.

Tom Roberts

On Sunday, July 25, 2021 at 6:12:25 PM UTC-7, tjrob137 wrote:
> "Time dilation" is not an "illusion", it is a GEOMETRICAL PROJECTION.
> I would not apply the word "real" to it...

Your conceptual mistakes are always the words you put in caps. You are conflating semantics and interpretational aspects with the actual facts, and more importantly you are overlooking the crucial distinction between passive and active transformations. The only thing in your brain is passive transformations with tacitly accepted bases, but this is meaningless without grasping the connection to the corresponding active transformations. Understanding this is fundamental to understanding the ontological status of relativistic effects.

> 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...

As always, you contradict yourself. Re-read what you typed above, and keep re-reading it until you recognize the fundamental and blatant incoherence of your statements.

On 7/25/21 11:01 PM, Arthur Adler wrote:
> On Sunday, July 25, 2021 at 6:12:25 PM UTC-7, tjrob137 wrote:
>> "Time dilation" is not an "illusion", it is a GEOMETRICAL
>> PROJECTION. I would not apply the word "real" to it...
>
> Your conceptual mistakes are always the words you put in caps.

So give an example of "Time dilation" that does not correspond to a
geometrical projection.

> You are conflating semantics and interpretational aspects with the
> actual facts,

Empty words. The actual facts are that whenever "time dilation" is
measured, computed, or discussed, it corresponds to a geometrical
projection.

> and more importantly you are overlooking the crucial distinction
> between passive and active transformations.

You keep claiming this, but have never explained.

It's easy to see your objection here cannot be valid, because "time
dilation" is a geometrical projection -- that does not require any
transformation at all, active or passive.

Hint: when an instrument is used to measure the tick
interval of a moving clock, the calculation is the dot
product of the clock's 4-velocity and the instrument's
4-velocity -- clearly a geometrical projection of the
clock's tick interval onto the instrument. (This is an
instance of the general fact that all instruments
project whatever they are measuring onto themselves.)

In more detail, using your language:
For boosts, an active transformation is a physical acceleration of the
object in question, from one to a second inertial frame; the
relationship between its new frame and the original frame is precisely
the same as the corresponding passive transformation. And still, any
"time dilation" is measured by the corresponding geometrical projection
between those frames (either the active pair or the passive pair, as the
projections are the same).

Bottom line: using this language, "time dilation" depends on the
geometrical relationship between the relevant inertial frames, and does
not depend on the history of how objects and measuring instruments
happened to be at rest in them. (I prefer the language of my Hint above.)

IOW: you attempt to make a distinction without a difference.

Hint: in this context a transformation occurs between
inertial frames. The difference between active and
passive is how the transform is applied, but the
Lorentz transform between the two frames is the same
(or its inverse if you interchange their order).

>> 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...
>
> As always, you contradict yourself.

Nope. Describe something you think you know about the world that is not
actually about a model of the world.

Hint: words and symbols, insofar as they relate to
the world, are models. It will be interesting to see
you attempt to describe something without using them.

> Re-read what you typed above, and keep re-reading it until you
> recognize the fundamental and blatant incoherence of your
> statements.

Apparently YOU can't describe that "fundamental and blatant
incoherence". Please do so, or shut up.

Tom Roberts

On Wednesday, July 28, 2021 at 2:35:22 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...
> >
> > As always, you contradict yourself.
>
> Nope.

You're mistaken. Look again at the two sentences you typed. Do you see why they are mutually contradictory?

> >> "Time dilation" is not an "illusion", it is a GEOMETRICAL
> >> PROJECTION. I would not apply the word "real" to it...
> >
> > Your conceptual mistakes are always the words you put in caps.
> So give an example of "Time dilation" that does not correspond to a
> geometrical projection.

Time dilation (no scare quotes) never corresponds to a literal geometrical projection, not even for passive transformations, let alone for active transformations (without which, transformations would be physically meaningless anyway). In the former case, note that the so-called "geometrical interpretation" is only a semantic analogy, because time is not space, and the Minkowski "metric" (which is where you should deploy your scare quotes), is not technically a metric, it is a pseudo-metric, not even satisfying the triangle inequality, etc. Further, we can define arbitrarily many sets of coordinate systems and describe events in terms of those, and some sets will exhibit differences in elapsed times between events and some will not. The relationships between these systems are what you call "projections", but coordinate systems are not efficacious they are merely descriptive. The relativistic effects such as time dilation and length contraction are not merely artifacts of arbitrarily-defined systems of coordinates, they are due to the dynamical facts of Lorentz invariance, which can be described in terms of a single system of coordinates:

Given any system of inertia-based coordinates x,t, the incremental elapsed proper time dtau along a given path segment with coordinate increments dx and dt is given by dtau = sqrt[(dt)^2 - (dx/c)^2], and dividing through by dt this is equivalent to dtau/dt = sqrt(1 - v^2/c^2). Augmented with the physical meaning of "proper time" (equivalence class of characteristic temporal advance, etc.), this fully describes the physical facts of time dilation. We then are free to use sets of coordinate systems that make the passive transformations match the active, and we are free to make semantic analogies with the geometry of actual metrical spaces, but those are just imperfect analogies (in a pseudo-metrical context), and they certainly don't convey the dynamical basis and meaning of relativistic effects and Lorentz invariance.

> An active transformation is a physical acceleration of the
> object in question...

Right, in terms of some system of coordinates S, and the spatial length and rate of elapsed proper time (at corresponding equilibrium configurations) in terms of S is different after the acceleration than before the acceleration.

> from one to a second inertial frame...

The concept of "frame" is vague, because it is sometimes defined as just the spatial coordinates provided conceptually by a grid of standard rulers with no associated assignment of time, and sometimes it is defined as an equivalence class of spacetime coordinate systems. To be clear, you need to talk about coordinate systems. And, no, the active transformation doesn't refer to multiple inertial coordinate systems, it refers to the transformation of attributes such as spatial length and rate of proper time in terms of a single system of coordinates.

> the relationship between its new frame and the original frame is precisely
> the same as the corresponding passive transformation.

Stated correctly, we can define a class of coordinate systems in terms of which the passive transformations match the active transformations. Of course, nothing requires us to use those coordinate systems, and in practice we rarely do, but conceptually we can.

> And still, any "time dilation" is measured by the corresponding geometrical projection
> between those frames...

Nope, see above.

On Thursday, 29 July 2021 at 10:11:42 UTC+2, Arthur Adler wrote:
> On Wednesday, July 28, 2021 at 2:35:22 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...
> > >
> > > As always, you contradict yourself.
> >
> > Nope.
> You're mistaken. Look again at the two sentences you typed. Do you see why they are mutually contradictory?

What to expect from Tom, religious cranks never do.

> Given any system of inertia-based coordinates x,t, the incremental elapsed proper time dtau along a given path segment with coordinate increments dx and dt is given by dtau = sqrt[(dt)^2 - (dx/c)^2], and dividing through by dt this is equivalent to dtau/dt = sqrt(1 - v^2/c^2). Augmented with the physical meaning of "proper time"

Auggmented with leninist meaning of "best system" communism is
the best system.

On 7/29/21 3:11 AM, Arthur Adler wrote:
> On Wednesday, July 28, 2021 at 2:35:22 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...
>>>
>>> As always, you contradict yourself.
>>
>> Nope.
>
> You're mistaken. 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, or shut up.

[Your first "..." omitted my words that make it clear
that "this model" refers to SR.]

>>>> "Time dilation" is not an "illusion", it is a GEOMETRICAL
>>>> PROJECTION. I would not apply the word "real" to it...
>>>
>>> Your conceptual mistakes are always the words you put in caps.
>> So give an example of "Time dilation" that does not correspond to a
>> geometrical projection.
>
> Time dilation (no scare quotes) never corresponds to a literal
> geometrical projection,

That is just plain wrong. You followed with a slew of words that did not
include any example of "time dilation", much less one that is not a
geometrical projection.

[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.]

> 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 that everybody who
understand the basics of relativity knows. Physics is not math,
and we DO call it a metric.

Challenge to Adler: cite any physics textbook that calls
it a pseudo-metric (other than perhaps a brief mention).
I just looked in six, and they all call it a metric.

> The concept of "frame" is vague

Oh for goodness sake. In relativity, "inertial frame' is not vague at
all (which is the phrase I used). You keep picking at nits that
everybody who understands the basics of relativity already knows.

> To be clear, you need to talk about coordinate systems.

Oh for goodness sake. In physics, "inertial frame" _IS_ a coordinate
system. You keep picking at nits that everybody who understands the
basics of relativity already knows.

[An inertial frame is a set of coordinates with
mutually-orthogonal axes, having three spatial and
one temporal coordinates.]

You are behaving indistinguishably from a troll (but with a lot more
words than most trolls use). There's no point in continuing, unless you
can explain yourself, and start concentrating on real issues.

Hint: focusing on nits that everybody knows, and wasting
hordes of words on them, makes your posts just about
unreadable. There is a need for precision, but not
obfuscation or logorrhea.

Tom Roberts

On Monday, August 2, 2021 at 3:24:58 PM UTC-5, tjrob137 wrote:

> There is a need for precision, but not
> obfuscation or logorrhea.

Wow! Nice word that I didn't know before!