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Apr 19, 2007, 7:30:57 AM4/19/07

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In 1916 Einstein proposed to extend the principle of relativity to

accelerated frames, and according to him, acceleration as well as

gravitational fields are purely "relative".

accelerated frames, and according to him, acceleration as well as

gravitational fields are purely "relative".

A number of scientists advanced counter arguments, arguing that acceleration

must be "absolute" and not "relative" - a debate that has never really

ended. In 1918, Einstein published a paper in which he attempted to debunk

such arguments. His 1918 paper is highly interesting for its metaphysical

content; and in contrast to most textbooks, he did not duck the issues. It

is also interesting that he explicitly disagreed with claims that GRT did

away with all ether concepts.

I will start by simply linking to an unoffical English translation of his

1918 paper:

http://en.wikisource.org/wiki/Dialog_about_objections_against_the_theory_of_relativity

Einstein's 1918 paper provides so much food for thought, that on purpose I

postpone a discussion of the arguments to a later posting which will include

more counter arguments that were presented by others and, surprisingly, even

by Einstein himself.

Enjoy!

Harald

Apr 20, 2007, 9:26:08 AM4/20/07

to

[Retake, now with first comments:]

In 1916 Einstein proposed to extend the principle of relativity to

accelerated frames, and according to him, acceleration as well as

gravitational fields are purely "relative".

A number of scientists advanced counter arguments, arguing that acceleration

must be "absolute" and not "relative" - a debate that has never really

ended. In 1918, Einstein published a paper in which he attempted to debunk

such arguments. His 1918 paper is highly interesting for its metaphysical

content; and in contrast to most textbooks, he did not duck the issues.

It is also interesting that he explicitly disagreed with claims that GRT did

away with all ether concepts.

I will start by simply linking to an unoffical English translation of his

1918 paper:

http://en.wikisource.org/wiki/Dialog_about_objections_against_the_theory_of_relativity

As Einstein remarked himself in that paper through the mouth of a critic, he

planted the seeds of the controversy when he, in his 1905 paper, at first

suggested that only relative motion between objects should matter, but next

went on to predict asymmetrical aging of relatively moving clocks.

In this context it is also worth mentioning that in 1911, Langevin published

a paper on relativity in which he elaborated on Einstein's prediction with

an example of two space travellers, in order to argue that just as in

classical mechanics, with (special) relativity acceleration is "absolute" in

the sense of being absolute relative to (neo-)Newtonian space. Consequently,

the same old absolutist concepts can be used, but corrections must be made

for relativistic effects which he explained as due to motion relative to

"space".

Thus it must have come as a surprise when in 1916 Einstein again argued that

all motion (incl. acceleration) is only "relative". It must be noted that

the terms "absolute" and "relative" are often used with different meanings;

however, in this case there is a clear disagreement nevertheless. This led

to the "twin" or "clock" paradox.

Now, in his 1918 paper, Einstein claimed that from the perspective of a

co-moving frame, a "homogenous gravitational field comes into being" when

the rocket motors are started, under influence of which the stay-at-home

clock speeds up. He recognized the fact that to many people, his "induced

gravitational fields" are pure fiction, and it may be worth to discuss his

arguments for the physical reality of those fields (as for me, I don't buy

it!).

According to Einstein, "the calculation shows that this speeding up

constitutes exactly twice as much as the lagging behind during the partial

processes 2 and 4." Indeed, later authors such as Moller and also Builder

(1957, "The resolution of the clock paradox", Aus J. P. and 1958(?) Am.J.P.)

confirmed that calculation. However, Builder stressed that this was to be

expected: the imagined gravitational field was *designed* to have that

effect (based on the equivalence principle); so that he argued that the use

of GRT only makes for a circular argument that "can contribute nothing of

physical significance".

Builder made another remark that is pertinent IMO: according to him, "the

specified field would have to be created simultaneously at all points in S'

and be destroyed simultaneously at all points in S0."

Obviously that would be in contradiction with GRT, according to which fields

propagate at a speed equal to c (locally). If anyone thinks that he can show

that this issue isn't lethal for Einstein's 1918 view (Ken?) then I'm very

much interested to see it!

If I understand it correctly, also Einstein himself changed his opinion on

this issue. Although he claimed in 1918 that:

"a complete clarification of the questions you have raised can only be

attained if one envisions for the geometric-mechanical constitution of the

Universe a representation that complies with the theory. I have attempted to

do so last year, and I have reached a conception that - to my mind - is

completely satisfactory";

I am not aware of him having published such a representation. Instead, two

years afterwards (1920), he stated in his Leyden inauguration speech:

"the mechanical behaviour of a corporeal system hovering freely in empty

space depends not only on relative positions (distances) and relative

velocities, but also on its state of rotation, which physically may be taken

as a characteristic not appertaining to the system in itself. [...] what is

essential is merely that besides observable objects, another thing, which is

not perceptible, must be looked upon as real, to enable acceleration or

rotation to be looked upon as something real.

It is true that Mach tried to avoid having to accept as real something which

is not observable by endeavouring to substitute in mechanics a mean

acceleration with reference to the totality of the masses in the universe in

place of an acceleration with reference to absolute space. But inertial

resistance opposed to relative acceleration of distant masses presupposes

action at a distance; and as the modern physicist does not believe that he

may accept this action at a distance, he comes back once more, if he follows

Mach, to the ether, which has to serve as medium for the effects of

inertia."

- http://www.tu-harburg.de/rzt/rzt/it/Ether.html

I now interpret the above as indicative of a change of mind about his own

(strong) general relativity principle that he defended two years earlier.

The equivalence principle and the GRT-based theory of gravitation remained,

but apparently he had abandoned his true relativity of acceleration and its

"induced gravitational fields" at a distance that it requires. If my

interpretation is correct, then Einstein himself realised the abovementioned

problems as early as 1920.

Regards,

Harald

Apr 20, 2007, 4:46:47 PM4/20/07

to

Hi Harald, and all

thank you for your refs to the 1918 article.

thank you for your refs to the 1918 article.

On Apr 20, 6:26 am, "harry" <harald.vanlintelButNotT...@epfl.ch>

wrote:

...

> I now interpret the above as indicative of a change of mind about his own

> (strong) general relativity principle that he defended two years earlier.

> The equivalence principle and the GRT-based theory of gravitation remained,

> but apparently he had abandoned his true relativity of acceleration and its

> "induced gravitational fields" at a distance that it requires. If my

> interpretation is correct, then Einstein himself realised the abovementioned

> problems as early as 1920.

> Regards,

> Harald

The most modern interpretation I know of the

General Principle of Relativity (GPoR), is in the

so-called Principle of General Covariance (GC),

in which any CS (Coordinate System, aka a FoR)

is valid, provided measurements made in any of

those CS's can be related to an inertial frame,

mathematically by a "proper transformation".

(FoR = Frame of Reference).

You can reverse that meaning: wherever the Laws

of Physics are valid (for any FoR subject to the Laws

of nature), GC applies.

In turn that means acceleration is subject to GC

and is therefore relative. IOW's if you get on a roller-

coaster you are subject to the laws of nature,

therefore you have a valid FoR and you can consider

yourself at "rest", in fact you must, since you are at

rest relatively to yourself, it's rather quite simple.

Rhetorically, how can "absolute motion" of any kind

exist, if you can find a FoR wherein you are at rest

relatively to yourself? IOW's you can always find an

FoR where "absolute motion" is zero.

Due to GC, relative acceleration is true throughout

the universe, since absolute acceleration vanishes

wherever the laws of nature apply.

Regards

Ken S. Tucker

Apr 20, 2007, 5:36:47 PM4/20/07

to

On Apr 20, 1:46 pm, "Ken S. Tucker" <dynam...@vianet.on.ca> wrote:

> The most modern interpretation I know of the

> General Principle of Relativity (GPoR), is in the

> so-called Principle of General Covariance (GC),

> in which any CS (Coordinate System, aka a FoR)

> is valid, provided measurements made in any of

> those CS's can be related to an inertial frame,

> mathematically by a "proper transformation".

> (FoR = Frame of Reference).

The Principle of General Covariance relies on the the "principle of

equivalence", which is an assumptions that in the gravitational field

all bodies move with exactly the same acceleration. This acceleration

is supposed to be independent on

1. the composition of the system

2. the mass of the system

3. system's initial velocity.

As far as I know, points 1. and 2. have been verified by experiment

rather accurately. What about point 3? Are there experiments which

demonstrate the independence of the acceleration on the velocity. I

mean velocities comparable with the speed of light c?

Thanks.

Eugene.

Apr 20, 2007, 8:17:57 PM4/20/07

to

Hi Eugene and all.

On Apr 20, 2:36 pm, eugene_stefanov...@usa.net wrote:

> On Apr 20, 1:46 pm, "Ken S. Tucker" <dynam...@vianet.on.ca> wrote:

>

> > The most modern interpretation I know of the

> > General Principle of Relativity (GPoR), is in the

> > so-called Principle of General Covariance (GC),

> > in which any CS (Coordinate System, aka a FoR)

> > is valid, provided measurements made in any of

> > those CS's can be related to an inertial frame,

> > mathematically by a "proper transformation".

> > (FoR = Frame of Reference).

>

> The Principle of General Covariance relies on the the "principle of

> equivalence",

As I defined, my understanding of GC, there is

no need to rely on the Principle of Equivalence,

(PoE), b/c PoE results from GC.

which is an assumptions that in the gravitational field

> all bodies move with exactly the same acceleration. This acceleration

> is supposed to be independent on

>

> 1. the composition of the system

> 2. the mass of the system

> 3. system's initial velocity.

>

> As far as I know, points 1. and 2. have been verified by experiment

> rather accurately. What about point 3? Are there experiments which

> demonstrate the independence of the acceleration on the velocity. I

> mean velocities comparable with the speed of light c?

It becomes more difficult to add energy in a

particle accelerator as the particle approaches "c",

(I think you and the fella's who post to our group

know more that than I do)

Is your point (3) going to become a discussion?

> Thanks.

> Eugene.

Your Welcome, and thank you.

GC is exceptionally foundational, it's one of the

few things in theoretics I hold dear.

Best

Ken

Apr 20, 2007, 9:41:36 PM4/20/07

to

On Apr 20, 5:17 pm, "Ken S. Tucker" <dynam...@vianet.on.ca> wrote:

> > ... the "principle of

> > equivalence" is an assumptions that in the gravitational field

> > all bodies move with exactly the same acceleration. This acceleration

> > is supposed to be independent on

> > .......

> > 3. system's initial velocity.

> Is your point (3) going to become a discussion?

Yes, I would like to discuss this. How well this assumption is

established in experiments? I understand, this is not directly related

to the initial posting. Perhaps I should open another thread about it?

> GC is exceptionally foundational, it's one of the

> few things in theoretics I hold dear.

General covariance is a very nice idea, which allows us to reduce

gravitational physics to an exercise in differential geometry.

However, what if acceleration does depend on velocity? Then the

principle of equivalence does not hold. And general covariance is not

valid as well.

I have my doubts about general covariance (in particular, about the

idea of equivalence between time and space coordinates) primarily

because of its apparent inconsistency with quantum mechanics.

I suggested an alternative quantum theory of gravity

http://www.arxiv.org/physics/0612019 in which the principle of

equivalence is violated (the gravitational acceleration depends on the

velocity at high values of v) but all experimental manifestations of

GR are reproduced. If someone knows an experiment that clearly

establishes the velocity-independence of the gravitational

acceleration, then I should probably withdraw my paper.

Eugene.

Apr 21, 2007, 2:58:52 AM4/21/07

to

Thus spake Ken S. Tucker <dyna...@vianet.on.ca>

>Hi Eugene and all.

>

>On Apr 20, 2:36 pm, eugene_stefanov...@usa.net wrote:

>> On Apr 20, 1:46 pm, "Ken S. Tucker" <dynam...@vianet.on.ca> wrote:

>>

>> > The most modern interpretation I know of the

>> > General Principle of Relativity (GPoR), is in the

>> > so-called Principle of General Covariance (GC),

>Hi Eugene and all.

>

>On Apr 20, 2:36 pm, eugene_stefanov...@usa.net wrote:

>> On Apr 20, 1:46 pm, "Ken S. Tucker" <dynam...@vianet.on.ca> wrote:

>>

>> > The most modern interpretation I know of the

>> > General Principle of Relativity (GPoR), is in the

>> > so-called Principle of General Covariance (GC),

I would prefer to call the principle of general covariance an

application of the general principle of relativity. The gpor is

essentially physical, whereas the pgc is essentially mathematical. I

would prefer to talk of the physical as being an interpretation of the

mathematical, not the other way about. In practice, the principle of

general covariance is the expression of the general principle of

relativity as used in the classical theory of general relativity, but

they are not equivalent. The general principle of relativity is more

general than general covariance, since it assumes that vector and tensor

quantities are always defined independent of measurement. I would not

expect that assumption to hold in a quantum theory, and I have relaxed

it for relational quantum gravity, such that gpor is retained while gc

is not.

>> > in which any CS (Coordinate System, aka a FoR)

Distinguish a coordinate system - i.e. a mathematical representation in

terms of R^n, from a frame of reference, the physical matter used to

determine coordinates through measurement.

>> > is valid, provided measurements made in any of

>> > those CS's can be related to an inertial frame,

>> > mathematically by a "proper transformation".

>> > (FoR = Frame of Reference).

>>

>> The Principle of General Covariance relies on the the "principle of

>> equivalence",

>

>As I defined, my understanding of GC, there is

>no need to rely on the Principle of Equivalence,

>(PoE), b/c PoE results from GC.

Indeed. The principle of equivalence may be used to define what we mean

by the "force" of gravity.

>

>which is an assumptions that in the gravitational field

>> all bodies move with exactly the same acceleration. This acceleration

>> is supposed to be independent on

>>

>> 1. the composition of the system

>> 2. the mass of the system

>> 3. system's initial velocity.

>>

>> As far as I know, points 1. and 2. have been verified by experiment

>> rather accurately. What about point 3? Are there experiments which

>> demonstrate the independence of the acceleration on the velocity. I

>> mean velocities comparable with the speed of light c?

>

If you dispense with the PoE you would also be dispensing with the

general principle of relativity. One is then getting into the area of

theories without experimental support. I would question whether that is

physics.

Regards

--

Charles Francis

moderator sci.physics.foundations.

substitute charles for NotI to email

Apr 21, 2007, 3:25:09 AM4/21/07

to

On Apr 20, 11:58 pm, Oh No <N...@charlesfrancis.wanadoo.co.uk> wrote:

> >> Are there experiments which

> >> demonstrate the independence of the acceleration on the velocity. I

> >> mean velocities comparable with the speed of light c?

>

> If you dispense with the PoE you would also be dispensing with the

> general principle of relativity. One is then getting into the area of

> theories without experimental support. I would question whether that is

> physics.

I don't think that "general principle of relativity" was ever directly

checked by experiment. There are experimental verifications of the

P(rinciple)o(f)E(quivalence), but it seems that all of them involve

slowly moving bodies. We cannot be sure that this principle remain

valid at high velocities. There are not so many firmly established

experimental facts in relativistic gravitational physics:

1. Mercury's perihelion precession

2. Light bending by Sun's gravity

3. Shapiro time delay

4. Gravitational time dilation

5. Gravitational red shift.

.....

If a theory can explain these 5 facts, then it has a chance to compete

with G(eneral)R(elativity).

The theory I proposed does explain these facts. As a bonus, this

theory is fully consistent with quantum mechanics.

Eugene.

Apr 21, 2007, 4:19:30 AM4/21/07

to

Thus spake eugene_st...@usa.net

If you dispense with the idea that the laws of physics are everywhere

the same then you may as well say anything you like and propose it as

physical law. I am not interested in such theories. There is no

experiment which shows magic is not possible. You may as well explain

your five fact by magic. That is essentially what you are doing when you

deny the idea that there is an underling reality beyond experiment. I

don't think this is physics.

Apr 21, 2007, 4:44:50 AM4/21/07

to

Thus spake harry <harald.vanlin...@epfl.ch>

>http://en.wikisource.org/wiki/Dialog_about_objections_against_the_theor

>y_of_relativity

>

>Einstein's 1918 paper provides so much food for thought, that on

>purpose I postpone a discussion of the arguments to a later posting

>which will include more counter arguments that were presented by others

>and, surprisingly, even by Einstein himself.

>

I agree that Einstein did think that general relativity, in its present

form, forces an ether concept. I don't think this represents the full

depth of his thinking in the matter. In fact I think he saw this as a

problem with general relativity, both in the years prior to publication,

and subsequently. There is some discussion of his difficulties prior to

finalising the theory here

>http://en.wikisource.org/wiki/Dialog_about_objections_against_the_theor

>y_of_relativity

>

>Einstein's 1918 paper provides so much food for thought, that on

>purpose I postpone a discussion of the arguments to a later posting

>which will include more counter arguments that were presented by others

>and, surprisingly, even by Einstein himself.

>

form, forces an ether concept. I don't think this represents the full

depth of his thinking in the matter. In fact I think he saw this as a

problem with general relativity, both in the years prior to publication,

and subsequently. There is some discussion of his difficulties prior to

finalising the theory here

http://plato.stanford.edu/entries/spacetime-holearg/

In my view this boils down to a problem with the affine connection.

According to the notion of an affine connection, spacetime is defined

such that an origin of coordinates can be defined anywhere in a

continuous manifold. This has lead to a view that a substantivalist

manifold is required, which I think is broadly equivalent to Einstein's

ether concept expressed in the paper you cite. But this is clearly a

non-empirical assumption and it is one which runs against the

philosophies which Einstein used to develop special relativity. Einstein

continued to have problems with it and later developed the idea of a

remote, or teleparallel, connection

http://www.lrz-muenchen.de/~aunzicker/ae1930.html

Einstein did not make much headway with teleparallelism, but I think

this is in large part because he could not get quantum theory on board.

One man can only do so much. I actually came to a similar idea

independently. I had serious problems with the affine connection when I

was learning general relativity because I could not see its empirical

basis. I came to the notion of a teleconnection by studying the

philosophical foundations of quantum theory and attempting to build a

model according to foundational considerations and applying as much

rigour as I felt able. It is natural then to consider what happens when

initial and final quantum states are determined in different reference

frames. This lead to a different application of teleparallelism from

that of Einstein, and I think it resolves the problems.

Apr 21, 2007, 5:03:08 AM4/21/07

to

On Apr 21, 1:19 am, Oh No <N...@charlesfrancis.wanadoo.co.uk> wrote:

> If you dispense with the idea that the laws of physics are everywhere

> the same then you may as well say anything you like and propose it as

> physical law.

On the contrary, I accept the idea that the laws of physics are the

same everywhere. This is called "translational invariance", and it is

a part of the Poincare group - based approach, which I am trying to

promote.

> I am not interested in such theories. There is no

> experiment which shows magic is not possible. You may as well explain

> your five fact by magic. That is essentially what you are doing when you

> deny the idea that there is an underling reality beyond experiment. I

> don't think this is physics.

I don't deny the idea of "underlying reality". I rather remain

agnostic about it. It is difficult enough to formulate a self-

consistent mathematical theory that explains all facts in "observable

reality" (which is, by the way, physics, in my understanding). So, the

"underlying reality" can wait.

Eugene.

Apr 21, 2007, 5:44:10 AM4/21/07

to

Thus spake eugene_st...@usa.net

>On Apr 21, 1:19 am, Oh No <N...@charlesfrancis.wanadoo.co.uk> wrote:

>

>> If you dispense with the idea that the laws of physics are everywhere

>> the same then you may as well say anything you like and propose it as

>> physical law.

>

>On the contrary, I accept the idea that the laws of physics are the

>same everywhere. This is called "translational invariance", and it is a

>part of the Poincare group - based approach, which I am trying to

>promote.

>On Apr 21, 1:19 am, Oh No <N...@charlesfrancis.wanadoo.co.uk> wrote:

>

>> If you dispense with the idea that the laws of physics are everywhere

>> the same then you may as well say anything you like and propose it as

>> physical law.

>

>On the contrary, I accept the idea that the laws of physics are the

>same everywhere. This is called "translational invariance", and it is a

>part of the Poincare group - based approach, which I am trying to

>promote.

It is difficult to understand the meaning of the Poincare group in a

curved space-time.

Apr 21, 2007, 7:24:18 AM4/21/07

to

Hi Ken, as I stated, I regard Builder's argument againt Einstein's

dynamic "gravitational fields" as pertinent and lethal to that idea.

It was natural for Builder to discover this, as he first made a full

calculation in SRT that included Doppler shifts. As far as I can see

he was roughly correct with his calculation, but actually

underestimated the problem.

For if I'm not mistaken, when taking a very large distance between the

two clocks, even with a (forbidden!) instantaneously propagating

gravitational (pseudo-) field, radio waves that are emitted from the

stay-at-home cannot correctly Doppler shift at the traveller,

immediately after he activates his rockets. Thus, not only is

relativity of gravitational fields conceptually flawed due to a

complete neglect of causality, but even mathematically it only works

at a very superficial level.

I also brought this problem up a few years ago in the relativity

group, see

http://tinyurl.com/2mu4jv

At that time you also participated in that thread, but just ashere,

you did not respond to the main issue (unlike Tom Roberts). If it is

not clear what I'm talking about, I can expand on it with a sketch.

Regards,

Harald

Apr 21, 2007, 7:57:26 AM4/21/07

to

Thus spake harald.v...@epfl.ch

>Hi Ken, as I stated, I regard Builder's argument againt Einstein's

>dynamic "gravitational fields" as pertinent and lethal to that idea.

>It was natural for Builder to discover this, as he first made a full

>calculation in SRT that included Doppler shifts. As far as I can see

>he was roughly correct with his calculation, but actually

>underestimated the problem.

>For if I'm not mistaken, when taking a very large distance between the

>two clocks, even with a (forbidden!) instantaneously propagating

>gravitational (pseudo-) field, radio waves that are emitted from the

>stay-at-home cannot correctly Doppler shift at the traveller,

>immediately after he activates his rockets. Thus, not only is

>relativity of gravitational fields conceptually flawed due to a

>complete neglect of causality, but even mathematically it only works

>at a very superficial level.

>

>Hi Ken, as I stated, I regard Builder's argument againt Einstein's

>dynamic "gravitational fields" as pertinent and lethal to that idea.

>It was natural for Builder to discover this, as he first made a full

>calculation in SRT that included Doppler shifts. As far as I can see

>he was roughly correct with his calculation, but actually

>underestimated the problem.

>For if I'm not mistaken, when taking a very large distance between the

>two clocks, even with a (forbidden!) instantaneously propagating

>gravitational (pseudo-) field, radio waves that are emitted from the

>stay-at-home cannot correctly Doppler shift at the traveller,

>immediately after he activates his rockets. Thus, not only is

>relativity of gravitational fields conceptually flawed due to a

>complete neglect of causality, but even mathematically it only works

>at a very superficial level.

>

I am not clear what the problem is. General relativity is a local

theory. The principle of equivalence describes gravity locally as an

inertial force. I don't understand what you mean by relativity of

gravitational fields. I don't even know that it is meaningful to talk of

a gravitational field, except within a locally defined reference frame.

Apr 21, 2007, 3:22:07 PM4/21/07

to

On Apr 20, 6:41 pm, eugene_stefanov...@usa.net wrote:

> On Apr 20, 5:17 pm, "Ken S. Tucker" <dynam...@vianet.on.ca> wrote:

>

> > > ... the "principle of

> > > equivalence" is an assumptions that in the gravitational field

> > > all bodies move with exactly the same acceleration. This acceleration

> > > is supposed to be independent on

> > > .......

> > > 3. system's initial velocity.

> > Is your point (3) going to become a discussion?

>

> Yes, I would like to discuss this. How well this assumption is

> established in experiments? I understand, this is not directly related

> to the initial posting. Perhaps I should open another thread about it?

> On Apr 20, 5:17 pm, "Ken S. Tucker" <dynam...@vianet.on.ca> wrote:

>

> > > ... the "principle of

> > > equivalence" is an assumptions that in the gravitational field

> > > all bodies move with exactly the same acceleration. This acceleration

> > > is supposed to be independent on

> > > .......

> > > 3. system's initial velocity.

> > Is your point (3) going to become a discussion?

>

> Yes, I would like to discuss this. How well this assumption is

> established in experiments? I understand, this is not directly related

> to the initial posting. Perhaps I should open another thread about it?

"another thread", that's up to you, the OP and the

moderators.

The perihelion shift depends on *orbital velocity* so

your (Eugene's) point (3) is true. I can provide details,

most good GR books will provide that dependence.

This is topical since the GP-b team announced the

confirmation of that as the so-called "geodetic effect",

where the force used for the calculation is a slight

modification to the Newtonian Force "F" to get,

f = F*(1 - V(orbital)^2 / c^2) = true force.

> > GC is exceptionally foundational, it's one of the

> > few things in theoretics I hold dear.

>

> General covariance is a very nice idea, which allows us to reduce

> gravitational physics to an exercise in differential geometry.

AE's GR1916 assumed a continuum, but

his Eq.(65..66) set Lorentz force to zero,

which IMV sets-up the Quantum Theory.

> However, what if acceleration does depend on velocity? Then the

> principle of equivalence does not hold. And general covariance is not

> valid as well.

I think we need a mathematical thread.

I'll snip the rest agreeably...

Regards

Ken

Apr 21, 2007, 4:41:14 PM4/21/07

to

On Apr 20, 11:58 pm, Oh No <N...@charlesfrancis.wanadoo.co.uk> wrote:

> Thus spake Ken S. Tucker <dynam...@vianet.on.ca>>

> >Hi Eugene and all.

>

> >On Apr 20, 2:36 pm, eugene_stefanov...@usa.net wrote:

> >> On Apr 20, 1:46 pm, "Ken S. Tucker" <dynam...@vianet.on.ca> wrote:

>

> >> > The most modern interpretation I know of the

> >> > General Principle of Relativity (GPoR), is in the

> >> > so-called Principle of General Covariance (GC),

>

> I would prefer to call the principle of general covariance an

> application of the general principle of relativity. The gpor is

> essentially physical, whereas the pgc is essentially mathematical. I

> would prefer to talk of the physical as being an interpretation of the

> mathematical, not the other way about. In practice, the principle of

> general covariance is the expression of the general principle of

> relativity as used in the classical theory of general relativity, but

> they are not equivalent. The general principle of relativity is more

> general than general covariance, since it assumes that vector and tensor

> quantities are always defined independent of measurement. I would not

> expect that assumption to hold in a quantum theory, and I have relaxed

> it for relational quantum gravity, such that gpor is retained while gc

> is not.

Understood, to disect that issue I'll use a scalpel.

The Absolute Derivative of the metric tensor,

D g_uv = 0.

((IOW,s g_uv;w dx^w =0)).

IMHO that equation is under-respected,

let me explain why.

If one can transform a set of measurements from

an accelerating FoR to an inertial FoR, then we'll

find D g_uv =0 in the free-falling "inertial FoR".

( That's the basic PoE too).

(the ordinary differentials like dg_uv vary by using

different FoR's and CS's.)

So I suppose I should ask my fellow collegues,

(Especially Charles and Eugene)

does D g_uv =0 hold in your theories?

Best regards...

Ken

PS: I'm setting a trap.

Apr 21, 2007, 11:58:28 PM4/21/07

to

On Apr 21, 12:22 pm, "Ken S. Tucker" <dynam...@vianet.on.ca> wrote:

> This is topical since the GP-b team announced the

> confirmation of that as the so-called "geodetic effect",

> where the force used for the calculation is a slight

> modification to the Newtonian Force "F" to get,

>

> f = F*(1 - V(orbital)^2 / c^2) = true force.

This sounds troubling to me. When I ride in an accelerating elevator,

all objects around me have the same acceleration independent on their

velocity. According to the principle of equivalence we should expect

the same for objects moving under the force of gravity: their

acceleration should not depend on their velocity. Am I missing

something?

Eugene.

Apr 22, 2007, 12:13:02 AM4/22/07

to

On Apr 21, 2:44 am, Oh No <N...@charlesfrancis.wanadoo.co.uk> wrote:

> >On the contrary, I accept the idea that the laws of physics are the

> >same everywhere. This is called "translational invariance", and it is a

> >part of the Poincare group - based approach, which I am trying to

> >promote.

>

> It is difficult to understand the meaning of the Poincare group in a

> curved space-time.

Poincare transformations are applied to the system as a whole (e.g.,

the Solar system). Whatever is the mechanism of interaction within the

system (space-time curvature or anything else) this interaction must

remain the same independent on the system's position in space,

orientation, time, and total velocity. So, the Poincare group remains

a valid concept even within Einsteinian theory of gravity.

Eugene.

Apr 22, 2007, 12:13:02 AM4/22/07

to

On Apr 21, 1:41 pm, "Ken S. Tucker" <dynam...@vianet.on.ca> wrote:

> So I suppose I should ask my fellow collegues,

> (Especially Charles and Eugene)

> does D g_uv =0 hold in your theories?

I don't use 4D tensor notation (metric tensor, etc.) at all, because I

do not believe in the Einstein-Minkowski "symmetry" between space and

time coordinates. In quantum mechanics, position is a quantum-

mechanical operator while time is an external parameter. Boost

transformations of particle's position have simple Lorentz-like form

only if the particle does not interact with anything. For interacting

systems, Lorentz transformations are valid only approximately. So, the

idea of 4D Minkowski space-time is just an approximation.

Eugene.

Apr 22, 2007, 5:58:44 AM4/22/07

to

Thus spake eugene_st...@usa.netYou are saying things about differential geometry which have no validity

whatsoever.

whatsoever.

Apr 22, 2007, 5:54:27 AM4/22/07

to

Thus spake eugene_st...@usa.net

I think you are missing that this acceleration is not defined in a

sufficiently local reference frame. That is true for the inverse square

law anyway, where F depends on position.

Apr 22, 2007, 6:03:56 AM4/22/07

to

Thus spake Ken S. Tucker <dyna...@vianet.on.ca>

>On Apr 20, 11:58 pm, Oh No <N...@charlesfrancis.wanadoo.co.uk> wrote:

>

>The Absolute Derivative of the metric tensor,

>

>D g_uv = 0.

>

>((IOW,s g_uv;w dx^w =0)).

>

>IMHO that equation is under-respected,

>let me explain why.

>On Apr 20, 11:58 pm, Oh No <N...@charlesfrancis.wanadoo.co.uk> wrote:

>

>The Absolute Derivative of the metric tensor,

>

>D g_uv = 0.

>

>((IOW,s g_uv;w dx^w =0)).

>

>IMHO that equation is under-respected,

>let me explain why.

I think the reason is that it is not true. At any rate, allowing for

ASCII, I cannot think of a true equation which looks a bit like this.

>

>If one can transform a set of measurements from

>an accelerating FoR to an inertial FoR, then we'll

>find D g_uv =0 in the free-falling "inertial FoR".

>( That's the basic PoE too).

>

>(the ordinary differentials like dg_uv vary by using

>different FoR's and CS's.)

>

>So I suppose I should ask my fellow collegues,

>(Especially Charles and Eugene)

>does D g_uv =0 hold in your theories?

Exactly the same formulae hold in the teleconnection theory as in

classical gtr, up to the connection itself.

>

>Best regards...

>Ken

>PS: I'm setting a trap.

>

Apr 22, 2007, 12:46:17 PM4/22/07

to

On Apr 22, 3:03 am, Oh No <N...@charlesfrancis.wanadoo.co.uk> wrote:

> Thus spake Ken S. Tucker <dynam...@vianet.on.ca>

>

> >On Apr 20, 11:58 pm, Oh No <N...@charlesfrancis.wanadoo.co.uk> wrote:

>

> >The Absolute Derivative of the metric tensor,

>

> >D g_uv = 0.

>

> >((IOW,s g_uv;w dx^w =0)).

>

> >IMHO that equation is under-respected,

> >let me explain why.

>

> I think the reason is that it is not true. At any rate, allowing for

> ASCII, I cannot think of a true equation which looks a bit like this.

> Thus spake Ken S. Tucker <dynam...@vianet.on.ca>

>

> >On Apr 20, 11:58 pm, Oh No <N...@charlesfrancis.wanadoo.co.uk> wrote:

>

> >The Absolute Derivative of the metric tensor,

>

> >D g_uv = 0.

>

> >((IOW,s g_uv;w dx^w =0)).

>

> >IMHO that equation is under-respected,

> >let me explain why.

>

> I think the reason is that it is not true. At any rate, allowing for

> ASCII, I cannot think of a true equation which looks a bit like this.

Yeah ASCII is a problem, see the "vanishing of the

covariant derivative of the metric" here.

http://en.wikipedia.org/wiki/Christoffel_symbol#Definition

I should have written it as g_uv;w = 0.

> >If one can transform a set of measurements from

> >an accelerating FoR to an inertial FoR, then we'll

> >find D g_uv =0 in the free-falling "inertial FoR".

> >( That's the basic PoE too).

>

> >(the ordinary differentials like dg_uv vary by using

> >different FoR's and CS's.)

>

> >So I suppose I should ask my fellow collegues,

> >(Especially Charles and Eugene)

> >does D g_uv =0 hold in your theories?

>

> Exactly the same formulae hold in the teleconnection theory as in

> classical gtr, up to the connection itself.

Good, if g_uv;w =/=0 math get's complicated.

Thanks Charles

Sorry for the bad notation.

Ken

Apr 22, 2007, 1:17:22 PM4/22/07

to

Thus spake Ken S. Tucker <dyna...@vianet.on.ca>

I should have recognised it, but sometimes things just don't fall into

place.

Apr 22, 2007, 2:22:22 PM4/22/07

to

On Apr 21, 1:57 pm, Oh No <N...@charlesfrancis.wanadoo.co.uk> wrote:

> Thus spake harald.vanlin...@epfl.ch

> Thus spake harald.vanlin...@epfl.ch

Einstein's relativity of gravitational fields is directly related to

his relativity of acceleration, as he explained rather well in his

1918 article that this thread discusses. Note: I could copy-paste his

article in this thread (and I originally had in mind to do so!), but

instead, I count on everyone who participates here to have clicked on

the link I provided and studied Einstein's solution of the clock

paradox before reading my comments on that. Here it is again:

http://en.wikisource.org/wiki/Dialog_about_objections_against_the_theory_of_relativity

Einstein's solution from the traveller's perspective was far from

"local": instead, it consisted of homogeneous "induced gravitational

fields" that are supposed to act over astronomical distances. Here

below I wil paste back the comments that I wrote in this thread as

well as some of the comments by myself and Tom Roberts to which I

referred, and I'll add a few more clarifications and a sketch for more

clarity.

In his 1918 paper, Einstein claimed that from the perspective of a co-

moving frame, a "homogenous gravitational field comes into being" when

the rocket motors are started, under influence of which the stay-at-

home clock speeds up.

IMO, relativity of acceleration as based on relativity of

gravitational fields is conceptually flawed due to a complete neglect

of causality. But I think that we even don't need to discuss that,

because also mathematically the paradox messes up with Einstein's 1916

point of view.

According to Einstein, "the calculation shows that this speeding up

constitutes exactly twice as much as the lagging behind during the

partial processes 2 and 4."

Indeed, later authors such as Moller and also Builder (1957, "The

resolution of the clock paradox", Aus J.P. and 1959, Am.J.P.)

confirmed that calculation, and many people stop thinking at that

point.

However, Builder made another remark that is pertinent IMO. According

to him, "the specified field would have to be created simultaneously

at all points in S' and be destroyed simultaneously at all points in

S0."

Obviously that would be in contradiction with GRT, according to which

fields propagate at a speed equal to c (locally).

As I stated, I regard Builder's argument againt Einstein's dynamic

"gravitational fields" (from the perspective of the traveller) as

pertinent and lethal to Einstein's idea. It was natural for Builder to

discover this, as he first made a full calculation in SRT that

included Doppler shifts. As far as I can see he was roughly correct

with his calculation, but actually underestimated the problem.

If I'm not mistaken, when taking a very large distance between the two

clocks, even with a (forbidden!) instantaneously propagating

gravitational (pseudo-) field that originates from C2, radio pulses

that are emitted from C1 (the stay-at-home) cannot correctly Doppler

shift at C2 (the traveller), immediately after its rockets are fired.

Looking at the problem in 2D instead of in 1D, we obtain the following

picture with another clock C12 aligned at a far distance to the side

of C1, "when" the rockets of C2 fire for the turn-around and with

signals sent from the stay-at-home clocks towards the traveller:

C1 C12 [higher "gravitational potential"]

Ś /

Ś /

Ś / [distance of for example 1 light day]

Ś /

Ś/

C2 [firing its rockets]

Here clock C12 must accelerate synchronously with clock C1, and radio

pulses that are emitted from C1 as well as C12 must immediately

Doppler shift at C2 when the rockets of C2 fire. Obviously that cannot

work.

Thus, even mathematically Einstein's solution only works at a very

superficial level. As soon as one looks at it in more detail, it turns

out to be unworkable.

I also brought this problem up a few years ago in the relativity

group, see http://tinyurl.com/2mu4jv .

There, Tom Roberts was more outspoken than me, calling Einstein's

solution of the clock paradox "Mathematical magic":

"This is magic invoked by Stella to "explain" how she can remain

motionless in spite of turning on her thrusters. It is no real

"gravitational force", it is mathematical magic invented by Stella --

analogous to "centrifugal force" in Newtonian mechanics: when one

starts

rotating, the "centrifugal force" must turn on INSTANTLY throughout

the

universe; it, too, is mathematical magic invented by the rotating

observer to maintain the fiction that in the rotating coordinates

Newton's laws remain valid."

I fully agree with that, and thus I also support the following

clarification by Baez in the FAQ:

" So modern usage demotes the uniform "gravitational" field back to

its old status as a pseudo-field, with all the pejorative connotations

of the prefix "pseudo". "

- http://www.physics.adelaide.edu.au/~dkoks/Faq/Relativity/SR/TwinParadox/twin_gr.html

Of course, as I said before, if anyone thinks that he can show that

this issue isn't lethal for Einstein's 1918 view about relativity of

acceleration and gravitational fields, then I'm very much interested

to see it!

Best regards,

Harald

Apr 22, 2007, 3:34:08 PM4/22/07

to

Thus spake harald.v...@epfl.ch

>

>In his 1918 paper, Einstein claimed that from the perspective of a co-

>moving frame, a "homogenous gravitational field comes into being" when

>the rocket motors are started, under influence of which the stay-at-

>home clock speeds up.

>

>IMO, relativity of acceleration as based on relativity of

>gravitational fields is conceptually flawed due to a complete neglect

>of causality.

>

>In his 1918 paper, Einstein claimed that from the perspective of a co-

>moving frame, a "homogenous gravitational field comes into being" when

>the rocket motors are started, under influence of which the stay-at-

>home clock speeds up.

>

>IMO, relativity of acceleration as based on relativity of

>gravitational fields is conceptually flawed due to a complete neglect

>of causality.

I don't think causality has anything to do with it. This is an illusory

field brought about by a coordinate choice, not a physical field. The

point of the equivalence principle is that any gravitational field is

likewise illusory in the sense of it being a force field.

>

>According to Einstein, "the calculation shows that this speeding up

>constitutes exactly twice as much as the lagging behind during the

>partial processes 2 and 4."

>Indeed, later authors such as Moller and also Builder (1957, "The

>resolution of the clock paradox", Aus J.P. and 1959, Am.J.P.)

>confirmed that calculation, and many people stop thinking at that

>point.

>

>However, Builder made another remark that is pertinent IMO. According

>to him, "the specified field would have to be created simultaneously

>at all points in S' and be destroyed simultaneously at all points in

>S0."

As I have said, that is the choice of coordinates too. If one defines

coordinates from the radar method then the field does not appear

simultaneously, but forward and back along the light cone from the point

of accelerations.

>Obviously that would be in contradiction with GRT, according to which

>fields propagate at a speed equal to c (locally).

Possibly Builder's analysis may actually be wrong. I don't know if he

has used a physically defined set of coordinates, as given by radar. Of

course you can choose coordinates in which light speed is not c in gtr,

so this isn't necessarily a contradiction with gtr.

>As I stated, I regard Builder's argument againt Einstein's dynamic

>"gravitational fields" (from the perspective of the traveller) as

>pertinent and lethal to Einstein's idea. It was natural for Builder to

>discover this, as he first made a full calculation in SRT that

>included Doppler shifts. As far as I can see he was roughly correct

>with his calculation, but actually underestimated the problem.

I think the problem is in thinking that gravity is an active force. It

isn't.

>

>

>Thus, even mathematically Einstein's solution only works at a very

>superficial level. As soon as one looks at it in more detail, it turns

>out to be unworkable.

I don't agree that it is unworkable, but it is superficial in the sense

that gravitational fields are not real force fields.

>

>I also brought this problem up a few years ago in the relativity

>group, see http://tinyurl.com/2mu4jv .

>There, Tom Roberts was more outspoken than me, calling Einstein's

>solution of the clock paradox "Mathematical magic":

That is a good description.

>

>"This is magic invoked by Stella to "explain" how she can remain

>motionless in spite of turning on her thrusters. It is no real

>"gravitational force", it is mathematical magic invented by Stella --

>analogous to "centrifugal force" in Newtonian mechanics: when one

>starts

>rotating, the "centrifugal force" must turn on INSTANTLY throughout

>the

>universe; it, too, is mathematical magic invented by the rotating

>observer to maintain the fiction that in the rotating coordinates

>Newton's laws remain valid."

>

>I fully agree with that, and thus I also support the following

>clarification by Baez in the FAQ:

>

>" So modern usage demotes the uniform "gravitational" field back to

>its old status as a pseudo-field, with all the pejorative connotations

>of the prefix "pseudo". "

>- http://www.physics.adelaide.edu.au/~dkoks/Faq/Relativity/SR/TwinParad

>ox/twin_gr.html

>

>Of course, as I said before, if anyone thinks that he can show that

>this issue isn't lethal for Einstein's 1918 view about relativity of

>acceleration and gravitational fields, then I'm very much interested

>to see it!

I am less interested in Einstein's view at a particular time than in the

physics. I would not want to say what his view really was if I could not

get inside his head.

Apr 22, 2007, 5:04:51 PM4/22/07

to

"Oh No" <No...@charlesfrancis.wanadoo.co.uk> wrote in message

news:3YO3F7DN...@charlesfrancis.wanadoo.co.uk...

If I'm not mistaken, in a certain reference frame, the coordinate

acceleration (a=d^2x/dt^2) should go to zero as time goes by, otherwise the

object would surpass the velocity of light sooner or later. That means that

the acceleration actually does depend on the (coordinate) velocity, right?

(This "coordinate" characterization is obviously essential here, since we

are dealing with "relative" concepts, so one must always specify: velocity

and acceleration with respect to whom.)

Regards, Andrea.

Apr 23, 2007, 12:10:35 AM4/23/07

to

Dear Eugene,

I think you are right about Poincare invariance applying as a global

transformation to any set of charts, (uh providing that the charts

are flat at infinity as would be appropriate in things smaller than

cosmology). The Poincare transformation on the flat space

can be continued on to all the other charts (where it has

no effect under the usual assumptions of GR of course).

And you are right about QM treating time different

from space and this being a strong clue incompatible

with GR.

As far as showing that GR is incompatible with QM, the best

things I've seen recently are the evidence for black holes having

a violation of the spin statistics theorem for spin-0 and spin-2

(Higgs and graviton) Hawking radiation. See

http://www.arxiv.org/abs/gr-qc/0212096 for the "tripled Pauli

statistics". A discussion is here:

http://www.physicsforums.com/showthread.php?t=164471

The spin statistics theorem is amazingly complicated. It

is a "theorem" only in the sense that a mathematics theorem

depends on its assumptions. Since humanity has access to

absolutely no measurements that are exact, extended over

all space, have duration equal to the age of the universe,

or probe distances infinitely small, there are no experimental

observations that have been proven exact.

Furthermore, it is widely accepted that QM and GR do not

marry up very well. In such a circumstance, that is where

the postulates contradict one another, one expects that as

a matter of probability, blatant errors will show up in sufficiently

complicated "theorems", while sufficiently simple "theorems"

will be fully consistent with observations.

If one wishes to avoid the very large number of assumptions

built into the spin statistics theorem (for a list, read the

book "Spin, Statistics, and all that"), one can simply suppose

that all normal matter is composite and built from spin-1/2

objects that have Fermi statistics. Spin - statistics then

follows.

This is far simpler than the route physics has taken, and it

is also compatible with the above GR evidence that there exist

spin-0 and spin-2 objects that have Fermi statistics.

The other half to this is recent evidence that dark matter and

dark energy do not obey the virial theorem, but have the same

factor of 3 error. See http://arxiv.org/abs/astro-ph/0703462

for the paper. I had difficulty explaining why this comes about

and had to write a long discussion of it in Matt's blog here

(which you are of course welcome to join):

http://matpitka.blogspot.com/2007/04/new-strange-finding-about-dark-matter.html

Also, I love your dressed particle approach. I'm working on a

non perturbational version of this. The usual perturbation

theory ignores very complicated Feynman diagrams because

the simple ones dominate. With a bound state, one cannot

ignore very complicated Feynman diagrams and so the usual

perturbation theory does not work.

However, one can solve a sort of dual problem, where one

ignores the very simple Feynman diagrams and pays

attention only to the very complicated ones. The method

for this is given in section 5 page 24 of this unfinished paper:

http://www.brannenworks.com/dmfound.pdf

The method amounts to looking at the bound state with

long time delays (and therefore complicated Feynman

diagrams only), and where one assumes that all the

important Feynman diagrams are "composite", that is,

can be written as the time ordered product of simpler

Feynman diagrams. Thus one ignores the "prime"

diagrams that figure so importantly in the usual perturbation

theory.

Keep up the posting, not everyone who reads your stuff

disagrees with you.

Carl Brannen

Apr 23, 2007, 9:19:23 AM4/23/07

to

"Ken S. Tucker" <dyna...@vianet.on.ca> wrote in message

news:1177097853.9...@l77g2000hsb.googlegroups.com...

> Hi Harald, and all

> thank you for your refs to the 1918 article.

>

> On Apr 20, 6:26 am, "harry" <harald.vanlintelButNotT...@epfl.ch>

> wrote:

> ...

>> I now interpret the above as indicative of a change of mind about his own

>> (strong) general relativity principle that he defended two years earlier.

>> The equivalence principle and the GRT-based theory of gravitation

>> remained,

>> but apparently he had abandoned his true relativity of acceleration and

>> its

>> "induced gravitational fields" at a distance that it requires. If my

>> interpretation is correct, then Einstein himself realised the

>> abovementioned

>> problems as early as 1920.

>> Regards,

>> Harald

>

> The most modern interpretation I know of the

> General Principle of Relativity (GPoR), is in the

> so-called Principle of General Covariance (GC),

> General Principle of Relativity (GPoR), is in the

> so-called Principle of General Covariance (GC),

> in which any CS (Coordinate System, aka a FoR)

> is valid, provided measurements made in any of

> those CS's can be related to an inertial frame,

> mathematically by a "proper transformation".

> (FoR = Frame of Reference).

>

> You can reverse that meaning: wherever the Laws

> of Physics are valid (for any FoR subject to the Laws

> of nature), GC applies.

> is valid, provided measurements made in any of

> those CS's can be related to an inertial frame,

> mathematically by a "proper transformation".

> (FoR = Frame of Reference).

>

> You can reverse that meaning: wherever the Laws

> of Physics are valid (for any FoR subject to the Laws

> of nature), GC applies.

Hi Ken, the point was that the laws of physics are broken in Einstein's

example, see below.

> In turn that means acceleration is subject to GC

> and is therefore relative. IOW's if you get on a roller-

> coaster you are subject to the laws of nature,

> therefore you have a valid FoR and you can consider

> yourself at "rest", in fact you must, since you are at

> rest relatively to yourself, it's rather quite simple.

As Tom Roberts pointed out so correctly, one must call on magic in order for

the laws of physics to be retained in such a frame; and as I cited, even

Einstein abandoned that idea.

> Rhetorically, how can "absolute motion" of any kind

> exist, if you can find a FoR wherein you are at rest

> relatively to yourself? IOW's you can always find an

> FoR where "absolute motion" is zero.

>

> Due to GC, relative acceleration is true throughout

> the universe, since absolute acceleration vanishes

> wherever the laws of nature apply.

> Regards

> Ken S. Tucker

I don't think so; can you show that that view can correctly handle the

Doppler test for the clock paradox, as I described more specifically in a

parallel sub-thread?

Regards,

Harald

Apr 23, 2007, 9:18:52 AM4/23/07

to

news:KUb4WySZ...@charlesfrancis.wanadoo.co.uk...

> Thus spake harald.v...@epfl.ch

>>

>>In his 1918 paper, Einstein claimed that from the perspective of a co-

>>moving frame, a "homogenous gravitational field comes into being" when

>>the rocket motors are started, under influence of which the stay-at-

>>home clock speeds up.

>>

>>IMO, relativity of acceleration as based on relativity of

>>gravitational fields is conceptually flawed due to a complete neglect

>>of causality.

>

> I don't think causality has anything to do with it. This is an illusory

> field brought about by a coordinate choice, not a physical field. The

> point of the equivalence principle is that any gravitational field is

> likewise illusory in the sense of it being a force field.

> Thus spake harald.v...@epfl.ch

>>

>>In his 1918 paper, Einstein claimed that from the perspective of a co-

>>moving frame, a "homogenous gravitational field comes into being" when

>>the rocket motors are started, under influence of which the stay-at-

>>home clock speeds up.

>>

>>IMO, relativity of acceleration as based on relativity of

>>gravitational fields is conceptually flawed due to a complete neglect

>>of causality.

>

> I don't think causality has anything to do with it. This is an illusory

> field brought about by a coordinate choice, not a physical field. The

> point of the equivalence principle is that any gravitational field is

> likewise illusory in the sense of it being a force field.

I don't understand how you can claim that fields are "illusory" according to

Einstein, just after reading how he argued for the *reality* of such

fields - he was forced to do so, because of his strong desire to keep up the

relativity of physical acceleration.

>>According to Einstein, "the calculation shows that this speeding up

>>constitutes exactly twice as much as the lagging behind during the

>>partial processes 2 and 4."

>>Indeed, later authors such as Moller and also Builder (1957, "The

>>resolution of the clock paradox", Aus J.P. and 1959, Am.J.P.)

>>confirmed that calculation, and many people stop thinking at that

>>point.

>>

>>However, Builder made another remark that is pertinent IMO. According

>>to him, "the specified field would have to be created simultaneously

>>at all points in S' and be destroyed simultaneously at all points in

>>S0."

>

> As I have said, that is the choice of coordinates too. If one defines

> coordinates from the radar method then the field does not appear

> simultaneously, but forward and back along the light cone from the point

> of accelerations.

If you mean that according to GRT, gravitational fields must propagate at

speed c: that's exactly the point. Just keep in mind that the discussion is

not about coordinate acceleration but about physical effects (acceleration

vs gravitational fields) from physical causes (the firing of rockets).

>>Obviously that would be in contradiction with GRT, according to which

>>fields propagate at a speed equal to c (locally).

>

> Possibly Builder's analysis may actually be wrong. I don't know if he

> has used a physically defined set of coordinates, as given by radar. Of

> course you can choose coordinates in which light speed is not c in gtr,

> so this isn't necessarily a contradiction with gtr.

Hmm... that's besides the point. The discussion was about physical fields in

physics, when using valid coordinate systems.

>>As I stated, I regard Builder's argument againt Einstein's dynamic

>>"gravitational fields" (from the perspective of the traveller) as

>>pertinent and lethal to Einstein's idea. It was natural for Builder to

>>discover this, as he first made a full calculation in SRT that

>>included Doppler shifts. As far as I can see he was roughly correct

>>with his calculation, but actually underestimated the problem.

>

> I think the problem is in thinking that gravity is an active force. It

> isn't.

According to Einstein 1918, the stay-at-home is accelerated by the induced

gravitational field. Is that what you mean with "active force"?

>>Thus, even mathematically Einstein's solution only works at a very

>>superficial level. As soon as one looks at it in more detail, it turns

>>out to be unworkable.

>

> I don't agree that it is unworkable, but it is superficial in the sense

> that gravitational fields are not real force fields.

If you think that "induced" but "real" gravitational fields produce a

workable solution (that is, respecting the laws of physics), please do show

how the Doppler shifts in the sketched signals from the stay-at-home can be

observed by the traveller when he fires his rockets (you snipped it!). And

note that Einstein needed those fields for his defence of relativity of

acceleration.

>>I also brought this problem up a few years ago in the relativity

>>group, see http://tinyurl.com/2mu4jv .

>>There, Tom Roberts was more outspoken than me, calling Einstein's

>>solution of the clock paradox "Mathematical magic":

>

> That is a good description.

Good - we agree on the essentials!

>>"This is magic invoked by Stella to "explain" how she can remain

>>motionless in spite of turning on her thrusters. It is no real

>>"gravitational force", it is mathematical magic invented by Stella --

>>analogous to "centrifugal force" in Newtonian mechanics: when one

>>starts

>>rotating, the "centrifugal force" must turn on INSTANTLY throughout

>>the

>>universe; it, too, is mathematical magic invented by the rotating

>>observer to maintain the fiction that in the rotating coordinates

>>Newton's laws remain valid."

>>

>>I fully agree with that, and thus I also support the following

>>clarification by Baez in the FAQ:

>>

>>" So modern usage demotes the uniform "gravitational" field back to

>>its old status as a pseudo-field, with all the pejorative connotations

>>of the prefix "pseudo". "

>>- http://www.physics.adelaide.edu.au/~dkoks/Faq/Relativity/SR/TwinParad

>>ox/twin_gr.html

>>

>>Of course, as I said before, if anyone thinks that he can show that

>>this issue isn't lethal for Einstein's 1918 view about relativity of

>>acceleration and gravitational fields, then I'm very much interested

>>to see it!

>

> I am less interested in Einstein's view at a particular time than in the

> physics. I would not want to say what his view really was if I could not

> get inside his head.

There's certainly no need to get into someone's head after he explained his

view and elaborated on it in very clear terms; and it happens that the cited

view was Einstein's General Relativity Theory of 1916-1918. I brought this

up because that view is still held to be correct by a number of people,

probably because for some reason the issue was swept under the carpet and

modern GRT is presented as a theory of gravitation (frame acceleration was

transferred to SRT, just as Builder suggested).

This failure of the original theory to be truly "relative" provides us with

a standard test for alternative theories: any new theory must correctly

handle the twin paradox, instead of handling it with "distorted nothingness"

(as Heaviside put it harshly).

Regards,

Harald

Apr 23, 2007, 10:03:33 AM4/23/07

to

Thus spake harry <harald.vanlin...@epfl.ch>

>

>"Oh No" <No...@charlesfrancis.wanadoo.co.uk> wrote in message

>news:KUb4WySZ...@charlesfrancis.wanadoo.co.uk...

>> Thus spake harald.v...@epfl.ch

>>>

>>>In his 1918 paper, Einstein claimed that from the perspective of a co-

>>>moving frame, a "homogenous gravitational field comes into being" when

>>>the rocket motors are started, under influence of which the stay-at-

>>>home clock speeds up.

>>>

>>>IMO, relativity of acceleration as based on relativity of

>>>gravitational fields is conceptually flawed due to a complete neglect

>>>of causality.

>>

>> I don't think causality has anything to do with it. This is an illusory

>> field brought about by a coordinate choice, not a physical field. The

>> point of the equivalence principle is that any gravitational field is

>> likewise illusory in the sense of it being a force field.

>

>I don't understand how you can claim that fields are "illusory" according to

>Einstein, just after reading how he argued for the *reality* of such

>fields - he was forced to do so, because of his strong desire to keep up the

>relativity of physical acceleration.

>

Actually, what he said was that "the distinction real-unreal is hardly

helpful". I go along with that, in the sense that, relative to a non-

inertial frame, the field exists in a mathematical sense, in the same

way that the coriolis and centrifugal forces exist relative to a

rotating reference frame. If one doubts that these are real forces, get

on a childs roundabout. You can feel them, so they are real in that

sense. At the same time, they are inertial, i.e. not transmitted by

interactions between matter, and a product of motion relative to a

particular frame.

>

>"Oh No" <No...@charlesfrancis.wanadoo.co.uk> wrote in message

>news:KUb4WySZ...@charlesfrancis.wanadoo.co.uk...

>> Thus spake harald.v...@epfl.ch

>>>

>>>In his 1918 paper, Einstein claimed that from the perspective of a co-

>>>moving frame, a "homogenous gravitational field comes into being" when

>>>the rocket motors are started, under influence of which the stay-at-

>>>home clock speeds up.

>>>

>>>IMO, relativity of acceleration as based on relativity of

>>>gravitational fields is conceptually flawed due to a complete neglect

>>>of causality.

>>

>> I don't think causality has anything to do with it. This is an illusory

>> field brought about by a coordinate choice, not a physical field. The

>> point of the equivalence principle is that any gravitational field is

>> likewise illusory in the sense of it being a force field.

>

>I don't understand how you can claim that fields are "illusory" according to

>Einstein, just after reading how he argued for the *reality* of such

>fields - he was forced to do so, because of his strong desire to keep up the

>relativity of physical acceleration.

>

helpful". I go along with that, in the sense that, relative to a non-

inertial frame, the field exists in a mathematical sense, in the same

way that the coriolis and centrifugal forces exist relative to a

rotating reference frame. If one doubts that these are real forces, get

on a childs roundabout. You can feel them, so they are real in that

sense. At the same time, they are inertial, i.e. not transmitted by

interactions between matter, and a product of motion relative to a

particular frame.

>>>According to Einstein, "the calculation shows that this speeding up

>>>constitutes exactly twice as much as the lagging behind during the

>>>partial processes 2 and 4."

>>>Indeed, later authors such as Moller and also Builder (1957, "The

>>>resolution of the clock paradox", Aus J.P. and 1959, Am.J.P.)

>>>confirmed that calculation, and many people stop thinking at that

>>>point.

>>>

>>>However, Builder made another remark that is pertinent IMO. According

>>>to him, "the specified field would have to be created simultaneously

>>>at all points in S' and be destroyed simultaneously at all points in

>>>S0."

>>

>> As I have said, that is the choice of coordinates too. If one defines

>> coordinates from the radar method then the field does not appear

>> simultaneously, but forward and back along the light cone from the point

>> of accelerations.

>

>If you mean that according to GRT, gravitational fields must propagate at

>speed c: that's exactly the point.

in grt gravitational fields propagate at the speed of light - this is a

speed depending on the coordinate system, and is c in a local Minkowski

frame.

> Just keep in mind that the discussion is

>not about coordinate acceleration but about physical effects (acceleration

>vs gravitational fields) from physical causes (the firing of rockets).

I don't agree. The gravitational field depends on the coordinate system.

In this case the firing of rockets means the coordinate system is not

defined in an inertial frame, hence the field.

>

>>>Obviously that would be in contradiction with GRT, according to which

>>>fields propagate at a speed equal to c (locally).

>>

>> Possibly Builder's analysis may actually be wrong. I don't know if he

>> has used a physically defined set of coordinates, as given by radar. Of

>> course you can choose coordinates in which light speed is not c in gtr,

>> so this isn't necessarily a contradiction with gtr.

>

>Hmm... that's besides the point. The discussion was about physical fields in

>physics, when using valid coordinate systems.

in gtr loads of coordinate systems are valid. If you choose a non-

inertial frame, you find non-inertial forces. Just like the coriolis and

centrifugal forces in classical mechanics, but now gravity also appears

as a non-inertial force.

>>>As I stated, I regard Builder's argument againt Einstein's dynamic

>>>"gravitational fields" (from the perspective of the traveller) as

>>>pertinent and lethal to Einstein's idea. It was natural for Builder to

>>>discover this, as he first made a full calculation in SRT that

>>>included Doppler shifts. As far as I can see he was roughly correct

>>>with his calculation, but actually underestimated the problem.

>>

>> I think the problem is in thinking that gravity is an active force. It

>> isn't.

>

>According to Einstein 1918, the stay-at-home is accelerated by the induced

>gravitational field. Is that what you mean with "active force"?

The opposite. That is what I mean by an inertial force.

>>>Thus, even mathematically Einstein's solution only works at a very

>>>superficial level. As soon as one looks at it in more detail, it turns

>>>out to be unworkable.

>>

>> I don't agree that it is unworkable, but it is superficial in the sense

>> that gravitational fields are not real force fields.

>

>If you think that "induced" but "real" gravitational fields produce a

>workable solution (that is, respecting the laws of physics), please do show

>how the Doppler shifts in the sketched signals from the stay-at-home can be

>observed by the traveller when he fires his rockets (you snipped it!). And

>note that Einstein needed those fields for his defence of relativity of

>acceleration.

I have a diagram of this somewhere in my files I think, but it is too

complicated for ASCII. The Doppler shift is not much of a problem. That

changes from red to blue at the point when the rocket is fired. Showing

the time expansion/contractions in the non-inertial frame is a little

more subtle, but quite doable. The real point is that it is an artefact

of coordinates though.

Apr 23, 2007, 10:30:23 AM4/23/07

to

news:h4t3rgE0...@charlesfrancis.wanadoo.co.uk...

> Thus spake harry <harald.vanlin...@epfl.ch>

>>http://en.wikisource.org/wiki/Dialog_about_objections_against_the_theor

>>y_of_relativity

>>

>>Einstein's 1918 paper provides so much food for thought, that on

>>purpose I postpone a discussion of the arguments to a later posting

>>which will include more counter arguments that were presented by others

>>and, surprisingly, even by Einstein himself.

>>

> I agree that Einstein did think that general relativity, in its present

> form, forces an ether concept. I don't think this represents the full

> depth of his thinking in the matter. In fact I think he saw this as a

> problem with general relativity, both in the years prior to publication,

> and subsequently. There is some discussion of his difficulties prior to

> finalising the theory here

>

> http://plato.stanford.edu/entries/spacetime-holearg/

> Thus spake harry <harald.vanlin...@epfl.ch>

>>http://en.wikisource.org/wiki/Dialog_about_objections_against_the_theor

>>y_of_relativity

>>

>>Einstein's 1918 paper provides so much food for thought, that on

>>purpose I postpone a discussion of the arguments to a later posting

>>which will include more counter arguments that were presented by others

>>and, surprisingly, even by Einstein himself.

>>

> I agree that Einstein did think that general relativity, in its present

> form, forces an ether concept. I don't think this represents the full

> depth of his thinking in the matter. In fact I think he saw this as a

> problem with general relativity, both in the years prior to publication,

> and subsequently. There is some discussion of his difficulties prior to

> finalising the theory here

>

> http://plato.stanford.edu/entries/spacetime-holearg/

Nice one! Thanks for the link, I had never heard of the hole argument! Only

a strange thing: to my knowledge (and in any case in 1918 and 1920),

Einstein discussed the substance of space and not of space-time which avoids

much of the problems. If anyone has his paper, I'm interested to read it (or

even just a precise reference may do)!

> In my view this boils down to a problem with the affine connection.

> According to the notion of an affine connection, spacetime is defined

> such that an origin of coordinates can be defined anywhere in a

> continuous manifold. This has lead to a view that a substantivalist

> manifold is required, which I think is broadly equivalent to Einstein's

> ether concept expressed in the paper you cite.

That paper is in the first place about the clock (or twin) paradox. But

indeed, he does mention his ether concept, and the issues are related - one

tries to come up with both a conceptual model for the physics (=metaphysics)

and a mathematical description.

> But this is clearly a

> non-empirical assumption and it is one which runs against the

> philosophies which Einstein used to develop special relativity. Einstein

> continued to have problems with it and later developed the idea of a

> remote, or teleparallel, connection

>

> http://www.lrz-muenchen.de/~aunzicker/ae1930.html

Thanks, that's an interesting approach. However, at first sight it's about

his efforts to combine EM with gravitation, and not so much about the

realtivity of motion. Which of the cited articles do you recommend for

reading, in the context of this thread?

> Einstein did not make much headway with teleparallelism, but I think

> this is in large part because he could not get quantum theory on board.

> One man can only do so much. I actually came to a similar idea

> independently. I had serious problems with the affine connection when I

> was learning general relativity because I could not see its empirical

> basis. I came to the notion of a teleconnection by studying the

> philosophical foundations of quantum theory and attempting to build a

> model according to foundational considerations and applying as much

> rigour as I felt able. It is natural then to consider what happens when

> initial and final quantum states are determined in different reference

> frames. This lead to a different application of teleparallelism from

> that of Einstein, and I think it resolves the problems.

I'm curious to see if it really works, and if so, what it means for physics.

Regards,

Harald

Apr 23, 2007, 1:50:39 PM4/23/07

to

Thus spake harry <harald.vanlin...@epfl.ch>

>> But this is clearly a

>> non-empirical assumption and it is one which runs against the

>> philosophies which Einstein used to develop special relativity. Einstein

>> continued to have problems with it and later developed the idea of a

>> remote, or teleparallel, connection

>>

>> http://www.lrz-muenchen.de/~aunzicker/ae1930.html

>

>Thanks, that's an interesting approach. However, at first sight it's

>about his efforts to combine EM with gravitation, and not so much about

>the realtivity of motion. Which of the cited articles do you recommend

>for reading, in the context of this thread?

>> But this is clearly a

>> non-empirical assumption and it is one which runs against the

>> philosophies which Einstein used to develop special relativity. Einstein

>> continued to have problems with it and later developed the idea of a

>> remote, or teleparallel, connection

>>

>> http://www.lrz-muenchen.de/~aunzicker/ae1930.html

>

>Thanks, that's an interesting approach. However, at first sight it's

>about his efforts to combine EM with gravitation, and not so much about

>the realtivity of motion. Which of the cited articles do you recommend

>for reading, in the context of this thread?

This is the problem. The papers are concerned with unifying EM with

gravitation. They don't go into the philosophical ideas which he may

have had. My take on that has to do with my own approach to problems

which I know he considered and ultimately did not solve. One may

summarise the problem in a similar way to his original sr paper, which

asks how to assign space and time coordinates to a point remote from a

clock. In general relativity one is concerned not just with the

coordinates, but one has to ask what is the relationship between a

coordinate system with an origin at one point and one with an origin at

a remote point. In differential geometry that relationship is called a

connection. An affine connection defines the relationship between

coordinates in the limit when the distance between origins goes to zero.

In a continuous manifold one can then slide a coordinate system from one

point to another along a path, and thus find a more distant

relationship. But, following Einsteins sr ideas this never seemed right

to me. If we want to compare a coordinate system on earth to one in

space we do so by looking at the light which passes from one to the

other. It seems to me that this physical process must be used to define

the connection.

>

>> Einstein did not make much headway with teleparallelism, but I think

>> this is in large part because he could not get quantum theory on board.

>> One man can only do so much. I actually came to a similar idea

>> independently. I had serious problems with the affine connection when I

>> was learning general relativity because I could not see its empirical

>> basis. I came to the notion of a teleconnection by studying the

>> philosophical foundations of quantum theory and attempting to build a

>> model according to foundational considerations and applying as much

>> rigour as I felt able. It is natural then to consider what happens when

>> initial and final quantum states are determined in different reference

>> frames. This lead to a different application of teleparallelism from

>> that of Einstein, and I think it resolves the problems.

>

>I'm curious to see if it really works, and if so, what it means for

>physics.

Obviously I think it works, but no math should be taken as error free

without independent checking from another qualified mathematician. That

is difficult to get. Hopefully my paper on stellar motions will be

accepted and that will get people's interest going.

What it means for physics is that local physics remains unchanged,

according to the general principle of relativity which is preserved. It

does mean that gtr and qt are unified and explains gravity as an

adjustment to qed. What it means for cosmology is more important. It

implies we are in an "Einstein preferred" closed finite universe, and no

need for exotic cold dark matter or cosmological constant, and resolves

a number of problems which have been described as a "crisis in

cosmology".

Apr 23, 2007, 1:55:45 PM4/23/07

to

news:asDG$OMU2K...@charlesfrancis.wanadoo.co.uk...

Such fields only exist in mathematical sense if the related physics is

valid; however, such is not the case, except for a very limited set of

problems.

> If one doubts that these are real forces, get

> on a childs roundabout. You can feel them, so they are real in that

> sense. At the same time, they are inertial, i.e. not transmitted by

> interactions between matter, and a product of motion relative to a

> particular frame.

Sorry but that argument is based on a confusion, the force you feel in a

merry-go-round is definitely a contact force! One way to clear up the

confusion is to refer to Newton who discussed centrifugal force, while at

the same time rejecting the use of fictitious forces. This is rather well

explained in Wikipedia:

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

>>>>According to Einstein, "the calculation shows that this speeding up

>>>>constitutes exactly twice as much as the lagging behind during the

>>>>partial processes 2 and 4."

>>>>Indeed, later authors such as Moller and also Builder (1957, "The

>>>>resolution of the clock paradox", Aus J.P. and 1959, Am.J.P.)

>>>>confirmed that calculation, and many people stop thinking at that

>>>>point.

>>>>

>>>>However, Builder made another remark that is pertinent IMO. According

>>>>to him, "the specified field would have to be created simultaneously

>>>>at all points in S' and be destroyed simultaneously at all points in

>>>>S0."

>>>

>>> As I have said, that is the choice of coordinates too. If one defines

>>> coordinates from the radar method then the field does not appear

>>> simultaneously, but forward and back along the light cone from the point

>>> of accelerations.

>>

>>If you mean that according to GRT, gravitational fields must propagate at

>>speed c: that's exactly the point.

>

> in grt gravitational fields propagate at the speed of light - this is a

> speed depending on the coordinate system, and is c in a local Minkowski

> frame.

Exactly. That was neglected in Einstein's discussion of the paradox.

>> Just keep in mind that the discussion is

>>not about coordinate acceleration but about physical effects (acceleration

>>vs gravitational fields) from physical causes (the firing of rockets).

>

> I don't agree. The gravitational field depends on the coordinate system.

> In this case the firing of rockets means the coordinate system is not

> defined in an inertial frame, hence the field.

Perhaps here we disagree on words...

>>>>Obviously that would be in contradiction with GRT, according to which

>>>>fields propagate at a speed equal to c (locally).

>>>

>>> Possibly Builder's analysis may actually be wrong. I don't know if he

>>> has used a physically defined set of coordinates, as given by radar. Of

>>> course you can choose coordinates in which light speed is not c in gtr,

>>> so this isn't necessarily a contradiction with gtr.

>>

>>Hmm... that's besides the point. The discussion was about physical fields

>>in

>>physics, when using valid coordinate systems.

>

> in gtr loads of coordinate systems are valid. If you choose a non-

> inertial frame, you find non-inertial forces. Just like the coriolis and

> centrifugal forces in classical mechanics, but now gravity also appears

> as a non-inertial force.

Newtonian mechanics does not permit fictitious forces. And in both cases,

whoever introduces them will have to face the consequences. Einstein fought

bravely. :-)

>>>>As I stated, I regard Builder's argument againt Einstein's dynamic

>>>>"gravitational fields" (from the perspective of the traveller) as

>>>>pertinent and lethal to Einstein's idea. It was natural for Builder to

>>>>discover this, as he first made a full calculation in SRT that

>>>>included Doppler shifts. As far as I can see he was roughly correct

>>>>with his calculation, but actually underestimated the problem.

>>>

>>> I think the problem is in thinking that gravity is an active force. It

>>> isn't.

>>

>>According to Einstein 1918, the stay-at-home is accelerated by the induced

>>gravitational field. Is that what you mean with "active force"?

>

> The opposite. That is what I mean by an inertial force.

Then that's not the problem.

>>>>Thus, even mathematically Einstein's solution only works at a very

>>>>superficial level. As soon as one looks at it in more detail, it turns

>>>>out to be unworkable.

>>>

>>> I don't agree that it is unworkable, but it is superficial in the sense

>>> that gravitational fields are not real force fields.

>>

>>If you think that "induced" but "real" gravitational fields produce a

>>workable solution (that is, respecting the laws of physics), please do

>>show

>>how the Doppler shifts in the sketched signals from the stay-at-home can

>>be

>>observed by the traveller when he fires his rockets (you snipped it!). And

>>note that Einstein needed those fields for his defence of relativity of

>>acceleration.

>

> I have a diagram of this somewhere in my files I think, but it is too

> complicated for ASCII. The Doppler shift is not much of a problem. That

> changes from red to blue at the point when the rocket is fired. Showing

> the time expansion/contractions in the non-inertial frame is a little

> more subtle, but quite doable. The real point is that it is an artefact

> of coordinates though.

According to Einstein-1918 it's not an artefact but as "real" as any other

field in physics - for if it were an artefact, it could not be physical and

acceleration would be "absolute", as he denied then but admitted in 1920.

Again, the situation of Einstein's 1918 theory is the following: the

traveller fires his rockets, thus inducing a homogeneous gravitational field

that upon reaching the very distant stay-at-home, causes the stay-at home

(as well as other clocks at a far distance next to it) to accelerate towards

the traveller. Signals that are consecutively sent from the stay-at-home (as

well as from other clocks) will be Doppler-shifted when these reach the

traveller, and we can estimate how long after firing the rockets this

Doppler shifted signal will arrive at the traveller, from the traveller's

point of view. However, we know that all the received signals will be

Doppler shifted immediately after the traveller fires his rockets.

Note that for v<0.1c, the shift is roughly equal to the classical Doppler

shift; in fact, the error is most obvious for even lower speeds while

maintaining large distances as then the signal propagation time is the most

important factor to take into account.

Regards,

Harald

Apr 23, 2007, 2:30:54 PM4/23/07

to

Thus spake harry <harald.vanlin...@epfl.ch>

>

>"Oh No" <No...@charlesfrancis.wanadoo.co.uk> wrote in message

>news:asDG$OMU2K...@charlesfrancis.wanadoo.co.uk...

>> Thus spake harry <harald.vanlin...@epfl.ch>

>>>

>

>"Oh No" <No...@charlesfrancis.wanadoo.co.uk> wrote in message

>news:asDG$OMU2K...@charlesfrancis.wanadoo.co.uk...

>> Thus spake harry <harald.vanlin...@epfl.ch>

>>>

>> Actually, what he said was that "the distinction real-unreal is hardly

>> helpful". I go along with that, in the sense that, relative to a non-

>> inertial frame, the field exists in a mathematical sense, in the same

>> way that the coriolis and centrifugal forces exist relative to a

>> rotating reference frame.

>

>Such fields only exist in mathematical sense if the related physics is

>valid; however, such is not the case, except for a very limited set of

>problems.

>> helpful". I go along with that, in the sense that, relative to a non-

>> inertial frame, the field exists in a mathematical sense, in the same

>> way that the coriolis and centrifugal forces exist relative to a

>> rotating reference frame.

>

>Such fields only exist in mathematical sense if the related physics is

>valid; however, such is not the case, except for a very limited set of

>problems.

A field exists in a mathematical sense if it is defined as a function on

R^n. That says nothing of physical existence.

>

>> If one doubts that these are real forces, get

>> on a childs roundabout. You can feel them, so they are real in that

>> sense. At the same time, they are inertial, i.e. not transmitted by

>> interactions between matter, and a product of motion relative to a

>> particular frame.

>

>Sorry but that argument is based on a confusion, the force you feel in a

>merry-go-round is definitely a contact force!

Depends on how you think of it. If you move you will feel a sideways

force. That is not a contact force.

>One way to clear up the

>confusion is to refer to Newton who discussed centrifugal force, while at

>the same time rejecting the use of fictitious forces.

Fictitious forces were invented by Huygens I believe. There is nothing

wrong with them. They are defined by mass x acceleration relative to a

given coordinate system. It is important to understand them in order to

understand gravity.

>> in gtr loads of coordinate systems are valid. If you choose a non-

>> inertial frame, you find non-inertial forces. Just like the coriolis and

>> centrifugal forces in classical mechanics, but now gravity also appears

>> as a non-inertial force.

>

>Newtonian mechanics does not permit fictitious forces.

It certainly does, according to the definition

F = ma

They are forces relativity to a coordinate system.

>And in both cases,

>whoever introduces them will have to face the consequences. Einstein fought

>bravely. :-)

I think I disagree about the message of the equivalence principle.

Einstein showed gravity as a fictitious force, i.e. a force relative to

a coordinate system. His language was different though. If force is

defined as F = ma, then a "fictitious" force is "real". But like he

said, this language is unhelpful.

>

>

>>>>>Thus, even mathematically Einstein's solution only works at a very

>>>>>superficial level. As soon as one looks at it in more detail, it turns

>>>>>out to be unworkable.

>>>>

>>>> I don't agree that it is unworkable, but it is superficial in the sense

>>>> that gravitational fields are not real force fields.

>>>

>>>If you think that "induced" but "real" gravitational fields produce a

>>>workable solution (that is, respecting the laws of physics), please do

>>>show

>>>how the Doppler shifts in the sketched signals from the stay-at-home can

>>>be

>>>observed by the traveller when he fires his rockets (you snipped it!). And

>>>note that Einstein needed those fields for his defence of relativity of

>>>acceleration.

>>

>> I have a diagram of this somewhere in my files I think, but it is too

>> complicated for ASCII. The Doppler shift is not much of a problem. That

>> changes from red to blue at the point when the rocket is fired. Showing

>> the time expansion/contractions in the non-inertial frame is a little

>> more subtle, but quite doable. The real point is that it is an artefact

>> of coordinates though.

>

>According to Einstein-1918 it's not an artefact but as "real" as any other

>field in physics

I think that is probably because he was using the mathematical notion of

"real", i.e. the equations are satisfied, not that there is something

ontologically there. As he said, discussion of "reality" in that sense

is unhelpful.

Apr 23, 2007, 3:52:45 PM4/23/07

to

Hi Harald and all, permit me a top post.

Harald, you've stated above two contradictory statements.

1) You do not understand tensor notation.

2) You find GR mathematics superficial.

The legalese of GR is written in tensor analysis.

Harald, you've stated above two contradictory statements.

1) You do not understand tensor notation.

2) You find GR mathematics superficial.

The legalese of GR is written in tensor analysis.

The analogies, like the elevator experiment, are

indeed superficial extentions of the mathematical

theory of GR, (GToR), but to turn around and use

those to disect GToR or it's Principles is trouble.

I got "whomped" for over-use of analogies in HS,

in explaining GR. Looking back it was a good thing,

because I went on to learn Vector Analysis and it's

Calculus then Curvilinear CS's and Tensor Analysis.

If the moderators will permit, I'd be happy to use

some analogies to support my point of view, that's

fine with me.

Regards

Ken

On Apr 23, 6:19 am, "harry" <harald.vanlintelButNotT...@epfl.ch>

wrote:

> "Ken S. Tucker" <dynam...@vianet.on.ca> wrote in messagenews:1177097853.9...@l77g2000hsb.googlegroups.com...

======================================= MODERATOR'S COMMENT:

Top posting is ok, leaving so much unsnipped is not. Go ahead with the analogies.

Apr 23, 2007, 8:25:39 PM4/23/07

to

On Apr 23, 8:30 pm, Oh No <N...@charlesfrancis.wanadoo.co.uk> wrote:

> Thus spake harry <harald.vanlintelButNotT...@epfl.ch>

>

>

>

> >"Oh No" <N...@charlesfrancis.wanadoo.co.uk> wrote in message

> >news:asDG$OMU2K...@charlesfrancis.wanadoo.co.uk...

> >> Thus spake harry <harald.vanlintelButNotT...@epfl.ch>

>

> >> Actually, what he said was that "the distinction real-unreal is hardly

> >> helpful". I go along with that, in the sense that, relative to a non-

> >> inertial frame, the field exists in a mathematical sense, in the same

> >> way that the coriolis and centrifugal forces exist relative to a

> >> rotating reference frame.

>

> >Such fields only exist in mathematical sense if the related physics is

> >valid; however, such is not the case, except for a very limited set of

> >problems.

>

> A field exists in a mathematical sense if it is defined as a function on

> R^n. That says nothing of physical existence.

> Thus spake harry <harald.vanlintelButNotT...@epfl.ch>

>

>

>

> >"Oh No" <N...@charlesfrancis.wanadoo.co.uk> wrote in message

> >news:asDG$OMU2K...@charlesfrancis.wanadoo.co.uk...

> >> Thus spake harry <harald.vanlintelButNotT...@epfl.ch>

>

> >> Actually, what he said was that "the distinction real-unreal is hardly

> >> helpful". I go along with that, in the sense that, relative to a non-

> >> inertial frame, the field exists in a mathematical sense, in the same

> >> way that the coriolis and centrifugal forces exist relative to a

> >> rotating reference frame.

>

> >Such fields only exist in mathematical sense if the related physics is

> >valid; however, such is not the case, except for a very limited set of

> >problems.

>

> A field exists in a mathematical sense if it is defined as a function on

> R^n. That says nothing of physical existence.

Physical existence or non-existence is hard to show and debatable, but

mathematical non-existence as part of a theory is easier to show. If

it conflicts with the theory, it can't mathematically exist as part of

it.

> >> If one doubts that these are real forces, get

> >> on a childs roundabout. You can feel them, so they are real in that

> >> sense. At the same time, they are inertial, i.e. not transmitted by

> >> interactions between matter, and a product of motion relative to a

> >> particular frame.

>

> >Sorry but that argument is based on a confusion, the force you feel in a

> >merry-go-round is definitely a contact force!

>

> Depends on how you think of it. If you move you will feel a sideways

> force. That is not a contact force.

Please indicate where you snipped some of my text... by chance(?),

here you snipped my explanation with the link that explains what is

erroneous about that statement...

> >One way to clear up the

> >confusion is to refer to Newton who discussed centrifugal force, while at

> >the same time rejecting the use of fictitious forces.

>

> Fictitious forces were invented by Huygens I believe. There is nothing

> wrong with them. They are defined by mass x acceleration relative to a

> given coordinate system. It is important to understand them in order to

> understand gravity.

Hmm... I have no use for fiction or magic!

> >> in gtr loads of coordinate systems are valid. If you choose a non-

> >> inertial frame, you find non-inertial forces. Just like the coriolis and

> >> centrifugal forces in classical mechanics, but now gravity also appears

> >> as a non-inertial force.

>

> >Newtonian mechanics does not permit fictitious forces.

>

> It certainly does, according to the definition

>

> F = ma

Actually, it's F = d(mv)/dt and it describes the force of inertia. Of

course, if according to your definition, Newton's postulated physical

space is fiction, then inertia may be fiction too and the force you

feel is just fantasy. However, the force you feel is a contact force

that can be measured using Hooke's law. :-)

> They are forces relativity to a coordinate system.

>

> >And in both cases,

> >whoever introduces them will have to face the consequences. Einstein fought

> >bravely. :-)

>

> I think I disagree about the message of the equivalence principle.

> Einstein showed gravity as a fictitious force, i.e. a force relative to

> a coordinate system. His language was different though. If force is

> defined as F = ma, then a "fictitious" force is "real". But like he

> said, this language is unhelpful.

>

Indeed, metaphysical language is tricky. Therefore, instead I

approached the problem from another angle by showing that Einstein's

1918 solution even fails mathematically, as soon as one digs a little

deeper.

[...]

Cheers,

Harald

Apr 23, 2007, 8:27:54 PM4/23/07

to

On Apr 23, 9:52 pm, "Ken S. Tucker" <dynam...@vianet.on.ca> wrote:

> Hi Harald and all, permit me a top post.

> Harald, you've stated above two contradictory statements.

> 1) You do not understand tensor notation.

> 2) You find GR mathematics superficial.

> Hi Harald and all, permit me a top post.

> Harald, you've stated above two contradictory statements.

> 1) You do not understand tensor notation.

> 2) You find GR mathematics superficial.

Hi Ken,

In fact I must disagree with your top posting, for it leads to errors:

I certainly didn't state that I find GR mathematics superficial!

Instead I pointed out - as also acknowledged by Tom Roberts - that

Einstein used mathematical magic in his claimed solution of the clock

paradox (and I equally doubt that he finds GR mathematics

superficial).

What I did show, elaborating on Builder's rejection, is that such

magic has its limits so that when one examines it more closely, it

doesn't really work at all - as was confirmed to me in the relativity

group three years ago. And below once more I kindly invited you to

show, if you disagree, how it does work:

> > I don't think so; can you show that that view can correctly handle the

> > Doppler test for the clock paradox, as I described more specifically in a

> > parallel sub-thread?

Here it's not about comparisons but about a straightforward

calculation of signal propagation time. Probably you agree with Moller

and Builder that rather simple equations suffice for describing these

events (certainly for v<<c)? If so, then this is really not a

complicated matter.

Best regards,

Harald

Apr 24, 2007, 5:43:25 PM4/24/07

to

On Apr 23, 5:27 pm, harald.vanlin...@epfl.ch wrote:

> On Apr 23, 9:52 pm, "Ken S. Tucker" <dynam...@vianet.on.ca> wrote:

>

> > Hi Harald and all, permit me a top post.

> > Harald, you've stated above two contradictory statements.

> > 1) You do not understand tensor notation.

> > 2) You find GR mathematics superficial.

>

> Hi Ken,

>

> In fact I must disagree with your top posting, for it leads to errors:

> I certainly didn't state that I find GR mathematics superficial!

> On Apr 23, 9:52 pm, "Ken S. Tucker" <dynam...@vianet.on.ca> wrote:

>

> > Hi Harald and all, permit me a top post.

> > Harald, you've stated above two contradictory statements.

> > 1) You do not understand tensor notation.

> > 2) You find GR mathematics superficial.

>

> Hi Ken,

>

> In fact I must disagree with your top posting, for it leads to errors:

> I certainly didn't state that I find GR mathematics superficial!

Sorry I have misunderstood what you wrote Apr.22, 11:22am, quote,

"Thus, even mathematically Einstein's solution only works at a very

superficial level. As soon as one looks at it in more detail, it turns

out to be unworkable."

> Instead I pointed out - as also acknowledged by Tom Roberts - that

> Einstein used mathematical magic in his claimed solution of the clock

> paradox (and I equally doubt that he finds GR mathematics

> superficial).

"Einstein used mathematical magic"

What does that mean?

> What I did show, elaborating on Builder's rejection, is that such

> magic has its limits so that when one examines it more closely, it

> doesn't really work at all - as was confirmed to me in the relativity

> group three years ago. And below once more I kindly invited you to

> show, if you disagree, how it does work:

> > > I don't think so; can you show that that view can correctly handle the

> > > Doppler test for the clock paradox, as I described more specifically in a

> > > parallel sub-thread?

>

> Here it's not about comparisons but about a straightforward

> calculation of signal propagation time. Probably you agree with Moller

> and Builder that rather simple equations suffice for describing these

> events (certainly for v<<c)? If so, then this is really not a

> complicated matter.

>

> Best regards,

> Harald

GR is basically fairly simple. It subtlely varies

measurements, from those of Newtons theory,

because light is form of energy (E=mc2) and is

subject to gravitation.

Regards

Ken

PS: my email is dynamics (at) uniserve.com

perhaps we should discuss some of that privately.

Apr 25, 2007, 6:08:06 AM4/25/07

to

news:1177392963....@b40g2000prd.googlegroups.com...

> On Apr 23, 5:27 pm, harald.vanlin...@epfl.ch wrote:

>> On Apr 23, 9:52 pm, "Ken S. Tucker" <dynam...@vianet.on.ca> wrote:

>>

>> > Hi Harald and all, permit me a top post.

>> > Harald, you've stated above two contradictory statements.

>> > 1) You do not understand tensor notation.

>> > 2) You find GR mathematics superficial.

>>

>> Hi Ken,

>>

>> In fact I must disagree with your top posting, for it leads to errors:

>> I certainly didn't state that I find GR mathematics superficial!

>

> Sorry I have misunderstood what you wrote Apr.22, 11:22am, quote,

> "Thus, even mathematically Einstein's solution only works at a very

> superficial level. As soon as one looks at it in more detail, it turns

> out to be unworkable."

>

>> Instead I pointed out - as also acknowledged by Tom Roberts - that

>> Einstein used mathematical magic in his claimed solution of the clock

>> paradox (and I equally doubt that he finds GR mathematics

>> superficial).

>

> "Einstein used mathematical magic"

>

> What does that mean?

> On Apr 23, 5:27 pm, harald.vanlin...@epfl.ch wrote:

>> On Apr 23, 9:52 pm, "Ken S. Tucker" <dynam...@vianet.on.ca> wrote:

>>

>> > Hi Harald and all, permit me a top post.

>> > Harald, you've stated above two contradictory statements.

>> > 1) You do not understand tensor notation.

>> > 2) You find GR mathematics superficial.

>>

>> Hi Ken,

>>

>> In fact I must disagree with your top posting, for it leads to errors:

>> I certainly didn't state that I find GR mathematics superficial!

>

> Sorry I have misunderstood what you wrote Apr.22, 11:22am, quote,

> "Thus, even mathematically Einstein's solution only works at a very

> superficial level. As soon as one looks at it in more detail, it turns

> out to be unworkable."

>

>> Instead I pointed out - as also acknowledged by Tom Roberts - that

>> Einstein used mathematical magic in his claimed solution of the clock

>> paradox (and I equally doubt that he finds GR mathematics

>> superficial).

>

> "Einstein used mathematical magic"

>

> What does that mean?

See the linked discussion (here once more: http://tinyurl.com/2mu4jv ).

>> What I did show, elaborating on Builder's rejection, is that such

>> magic has its limits so that when one examines it more closely, it

>> doesn't really work at all - as was confirmed to me in the relativity

>> group three years ago. And below once more I kindly invited you to

>> show, if you disagree, how it does work:

>

>> > > I don't think so; can you show that that view can correctly handle

>> > > the

>> > > Doppler test for the clock paradox, as I described more specifically

>> > > in a

>> > > parallel sub-thread?

>>

>> Here it's not about comparisons but about a straightforward

>> calculation of signal propagation time. Probably you agree with Moller

>> and Builder that rather simple equations suffice for describing these

>> events (certainly for v<<c)? If so, then this is really not a

>> complicated matter.

>>

>> Best regards,

>> Harald

>

> GR is basically fairly simple. It subtlely varies

> measurements, from those of Newtons theory,

> because light is form of energy (E=mc2) and is

> subject to gravitation.

Indeed. However, Einstein wanted to do more with it, he wanted to obtain

that all motion is purely "relative". And I have put your attention that his

solution of the twin paradox messes up when when goes over it again with a

finer brush, as most easily seen at low speeds and large distances.

> Regards

> Ken

> PS: my email is dynamics (at) uniserve.com

> perhaps we should discuss some of that privately.

Yes we could and we may do so later; but it's important for further

discussions in this group to make clear for all that this is not just a

matter of opinion - it should not be ducked.

Regards,

Harald

Apr 25, 2007, 7:04:40 AM4/25/07

to

Thus spake harald.v...@epfl.ch

>On Apr 23, 8:30 pm, Oh No <N...@charlesfrancis.wanadoo.co.uk> wrote:

>> Thus spake harry <harald.vanlintelButNotT...@epfl.ch>

>>

>>

>

>On Apr 23, 8:30 pm, Oh No <N...@charlesfrancis.wanadoo.co.uk> wrote:

>> Thus spake harry <harald.vanlintelButNotT...@epfl.ch>

>>

>>

>

>Physical existence or non-existence is hard to show and debatable, but

>mathematical non-existence as part of a theory is easier to show. If

>it conflicts with the theory, it can't mathematically exist as part of

>it.

>mathematical non-existence as part of a theory is easier to show. If

>it conflicts with the theory, it can't mathematically exist as part of

>it.

Indeed. That is why Einstein describes valid mathematical relationships

as though they are "real". As he also says, there are semantic

difficulties which make it best to avoid this kind of terminology.

>

>> >> If one doubts that these are real forces, get

>> >> on a childs roundabout. You can feel them, so they are real in that

>> >> sense. At the same time, they are inertial, i.e. not transmitted by

>> >> interactions between matter, and a product of motion relative to a

>> >> particular frame.

>>

>> >Sorry but that argument is based on a confusion, the force you feel in a

>> >merry-go-round is definitely a contact force!

>>

>> Depends on how you think of it. If you move you will feel a sideways

>> force. That is not a contact force.

>

>Please indicate where you snipped some of my text... by chance(?),

>here you snipped my explanation with the link that explains what is

>erroneous about that statement...

I looked at the explanation. I saw no indication in it that anything I

have said is erroneous. It is better to think of the physics than third

party explanations, however. To discuss inertial forces such as gravity

one must be very clear about definitions, and about the distinction

between active and inertial forces.

>

>> >One way to clear up the

>> >confusion is to refer to Newton who discussed centrifugal force, while at

>> >the same time rejecting the use of fictitious forces.

>>

>> Fictitious forces were invented by Huygens I believe. There is nothing

>> wrong with them. They are defined by mass x acceleration relative to a

>> given coordinate system. It is important to understand them in order to

>> understand gravity.

>

>Hmm... I have no use for fiction or magic!

"fiction" is just a word, meaning that the forces are not-active, or

inertial. Magic is just a word for something which is true but one does

not understand.

>

>> >> in gtr loads of coordinate systems are valid. If you choose a non-

>> >> inertial frame, you find non-inertial forces. Just like the coriolis and

>> >> centrifugal forces in classical mechanics, but now gravity also appears

>> >> as a non-inertial force.

>>

>> >Newtonian mechanics does not permit fictitious forces.

>>

>> It certainly does, according to the definition

>>

>> F = ma

>

>Actually, it's F = d(mv)/dt

Makes no difference. Matter does not change mass.

>and it describes the force of inertia.

Force of inertia??? That is almost an oxymoron. Inertia means not-

active. F = ma describes both inertial and non-inertial forces relative

to a coordinate system. That is the definition which is extended to

include gravity in gtr.

> Of

>course, if according to your definition, Newton's postulated physical

>space is fiction, then inertia may be fiction too

Perfect inertia implies perfect isolation. That may be a fiction, but

the concept that actions on a body are negligible is still valid, so it

is not reasonable to call inertia a fiction, particularly in classical

mechanics.

> and the force you

>feel is just fantasy.

The force is not a fantasy. It is a mass acceleration relative to a

given coordinate system. That is a real mathematical relationship. I

think your confusion comes from thinking that a real mathematical

relationship means a real underlying physical process. It doesn't.

> However, the force you feel is a contact force

>that can be measured using Hooke's law. :-)

I think you should try the test. What you feel is something which causes

you to accelerate relative to your coordinate system. That is the

definition of force.

>

>> They are forces relativity to a coordinate system.

>>

>> >And in both cases,

>> >whoever introduces them will have to face the consequences. Einstein fought

>> >bravely. :-)

>>

>> I think I disagree about the message of the equivalence principle.

>> Einstein showed gravity as a fictitious force, i.e. a force relative to

>> a coordinate system. His language was different though. If force is

>> defined as F = ma, then a "fictitious" force is "real". But like he

>> said, this language is unhelpful.

>>

>

>Indeed, metaphysical language is tricky. Therefore, instead I

>approached the problem from another angle by showing that Einstein's

>1918 solution even fails mathematically, as soon as one digs a little

>deeper.

Except that it doesn't fail mathematically, until such point as you

recognise that real forces of gravity are caused by space-time geometry

and may be distinguished from g-forces on that ground. The only thing

that fails is the idea that a field necessarily has an ontological

analogue, and Einstein attempts to distance himself from that idea.

Apr 25, 2007, 9:26:32 AM4/25/07

to

news:HNHuh0Ew...@charlesfrancis.wanadoo.co.uk...

According to physics theory, what you feel is the inertial force that your

body exerts against the merry-go-round in reaction to the centripetal

acceleration of the merry-go-round. If one knows the elasticity modulus of

the skin on your arm that squizes against the side of the merry-go-round,

the value of that contact force can be determined by means of a ruler and

Hooke's law.

>>> >One way to clear up the

>>> >confusion is to refer to Newton who discussed centrifugal force, while

>>> >at

>>> >the same time rejecting the use of fictitious forces.

>>>

>>> Fictitious forces were invented by Huygens I believe. There is nothing

>>> wrong with them. They are defined by mass x acceleration relative to a

>>> given coordinate system. It is important to understand them in order to

>>> understand gravity.

>>

>>Hmm... I have no use for fiction or magic!

>

> "fiction" is just a word, meaning that the forces are not-active, or

> inertial. Magic is just a word for something which is true but one does

> not understand.

Magic is Harry Potter on his magic broom. To put it in other words: we have

no use of replacing understanding by distorted nonsense.

>>> >> in gtr loads of coordinate systems are valid. If you choose a non-

>>> >> inertial frame, you find non-inertial forces. Just like the coriolis

>>> >> and

>>> >> centrifugal forces in classical mechanics, but now gravity also

>>> >> appears

>>> >> as a non-inertial force.

>>>

>>> >Newtonian mechanics does not permit fictitious forces.

>>>

>>> It certainly does, according to the definition

>>>

>>> F = ma

>>

>>Actually, it's F = d(mv)/dt

>

> Makes no difference. Matter does not change mass.

>

>>and it describes the force of inertia.

>

> Force of inertia??? That is almost an oxymoron. Inertia means not-

> active. F = ma describes both inertial and non-inertial forces relative

> to a coordinate system. That is the definition which is extended to

> include gravity in gtr.

No inertia, no force against acceleration. For that reason, m is even

sometimes called "inertial mass".

>> Of

>>course, if according to your definition, Newton's postulated physical

>>space is fiction, then inertia may be fiction too

>

> Perfect inertia implies perfect isolation. That may be a fiction, but

> the concept that actions on a body are negligible is still valid, so it

> is not reasonable to call inertia a fiction, particularly in classical

> mechanics.

>

>> and the force you

>>feel is just fantasy.

>

> The force is not a fantasy.

At least we agree on that.

> It is a mass acceleration relative to a

> given coordinate system.

But here the disagreement could not be greater. Coordinate systems are our

free choice, they cannot affect our measurements.

> That is a real mathematical relationship. I

> think your confusion comes from thinking that a real mathematical

> relationship means a real underlying physical process. It doesn't.

No, but I'm glad to see that you acknowledge that. However, forces are

defined by means of real physical processes. My physics textbooks were not

perfect (especially their history was crappy), but at least the authors did

very well in avoiding any use of fictitious forces when explaining and

deriving relative rotational motion. I am still thankful to them for that,

and I can understand why some teachers even want to put a ban on the term

"centrifugal force" (some went as far as putting up angry web pages about

it). However, there is nothing wrong with the way that term was used by

Newton.

>> However, the force you feel is a contact force

>>that can be measured using Hooke's law. :-)

>

> I think you should try the test. What you feel is something which causes

> you to accelerate relative to your coordinate system. That is the

> definition of force.

That's not physics. I can make you accelerate at will relative to any

coordinate system that I set up. You won't feel anything!

>>> They are forces relativity to a coordinate system.

>>>

>>> >And in both cases,

>>> >whoever introduces them will have to face the consequences. Einstein

>>> >fought

>>> >bravely. :-)

>>>

>>> I think I disagree about the message of the equivalence principle.

>>> Einstein showed gravity as a fictitious force, i.e. a force relative to

>>> a coordinate system. His language was different though. If force is

>>> defined as F = ma, then a "fictitious" force is "real". But like he

>>> said, this language is unhelpful.

>>>

>>

>>Indeed, metaphysical language is tricky. Therefore, instead I

>>approached the problem from another angle by showing that Einstein's

>>1918 solution even fails mathematically, as soon as one digs a little

>>deeper.

>

> Except that it doesn't fail mathematically, until such point as you

> recognise that real forces of gravity are caused by space-time geometry

> and may be distinguished from g-forces on that ground. The only thing

> that fails is the idea that a field necessarily has an ontological

> analogue, and Einstein attempts to distance himself from that idea.

This has nothing to do with my views. The published explanation of how

Einstein's solution fails is rather short; therefore I have elaborated on

it. I also invited you to show the contrary, i.e. that it doesn't fail and

that instead I made a calculation error (as well as Builder and his

referees). Perhaps I should have given an example with numbers? Indeed, the

difference between delta_t = 0 and delta_t = <a large number> can be more

striking. In any case, I'm of course willing to discuss alternative

calculations. I'm afraid that this is as far as a discussion can go.

Regards,

Harald

Apr 25, 2007, 11:02:46 AM4/25/07

to

Thus spake harry <harald.vanlin...@epfl.ch>

Then you agree with me. Good.

>

>>>> >One way to clear up the

>>>> >confusion is to refer to Newton who discussed centrifugal force, while

>>>> >at

>>>> >the same time rejecting the use of fictitious forces.

>>>>

>>>> Fictitious forces were invented by Huygens I believe. There is nothing

>>>> wrong with them. They are defined by mass x acceleration relative to a

>>>> given coordinate system. It is important to understand them in order to

>>>> understand gravity.

>>>

>>>Hmm... I have no use for fiction or magic!

>>

>> "fiction" is just a word, meaning that the forces are not-active, or

>> inertial. Magic is just a word for something which is true but one does

>> not understand.

>

>Magic is Harry Potter on his magic broom. To put it in other words: we have

>no use of replacing understanding by distorted nonsense.

I just call that nonsense. The context we were talking of was

mathemagical magic.

They are fundamental to our measurements. We cannot make measurements

without first setting up a coordinate system.

>> That is a real mathematical relationship. I

>> think your confusion comes from thinking that a real mathematical

>> relationship means a real underlying physical process. It doesn't.

>

>No, but I'm glad to see that you acknowledge that. However, forces are

>defined by means of real physical processes.

That contradicts the notion you described earlier, that of an inertial

force.

> My physics textbooks were not

>perfect (especially their history was crappy), but at least the authors did

>very well in avoiding any use of fictitious forces when explaining and

>deriving relative rotational motion. I am still thankful to them for that,

>and I can understand why some teachers even want to put a ban on the term

>"centrifugal force" (some went as far as putting up angry web pages about

>it). However, there is nothing wrong with the way that term was used by

>Newton.

I agree. The reason to ban inertial forces is because of the confusion

they cause students who misunderstand them, not because they are not a

valid concept.

Probably. I don't see any calculation errors. Only possible semantic

confusions. They are always difficult to resolve.

Apr 25, 2007, 1:15:26 PM4/25/07

to

Hi Frank and Harald,

I have the impression that a major part of your discussion stems from using

the same words for different contents. Hopefully, my questions below will

help to clarify that :-)

> >> >> If one doubts that these are real forces, get

> >> >> on a childs roundabout. You can feel them, so they are real in that

> >> >> sense. At the same time, they are inertial, i.e. not transmitted by

> >> >> interactions between matter, and a product of motion relative to a

> >> >> particular frame.

One should clearly discriminate cause and effect.

The curvilinear motion is accompagnied by 'inertial forces'.

If a body is bound to another body that is not moving parallel to the first

body on its own, a force between both bodies occurs. In case both bodies are

in contact and the force appears as a pressure one may call it a 'contact

force'.

To agree one with another, you both must have got the same notions and

wordings of the different forces involved. Which exactly are they?

> >> >One way to clear up the

> >> >confusion is to refer to Newton who discussed centrifugal force, while

> at

> >> >the same time rejecting the use of fictitious forces.

> >> Fictitious forces were invented by Huygens I believe. There is nothing

> >> wrong with them. They are defined by mass x acceleration relative to a

> >> given coordinate system.

This corresponds to my understanding. It's a translation of a kinematical

problem (relative motion) to dynamics. This concept seems to be beloved by

practioners like meteorologists. I'm not sure about its usefulness for

axiomatics.

> >> It is important to understand them in order to

> >> understand gravity.

Is gravity a fictitious force?

> ..."fiction" is just a word, meaning that the forces are not-active, or

> inertial.

What means "not-active"?

> Magic is just a word for something which is true but one does

> not understand.

fine definition :-)

> >> >> in gtr loads of coordinate systems are valid. If you choose a non-

> >> >> inertial frame, you find non-inertial forces.

For me, the definitions of inertial frame and non-inertial forces appear like

a circle...

...

> >> >Newtonian mechanics does not permit fictitious forces.

> >> It certainly does, according to the definition

> >>

> >> F = ma

Note that, (i), there are force that cause acceleration and, (ii), that

acceleration causes ('counter') forces.

> >Actually, it's F = d(mv)/dt...

> Makes no difference. Matter does not change mass.

There is a difference, but not for the issue of fictitious forces.

> >...and it describes the force of inertia.

> Force of inertia??? That is almost an oxymoron.

Indeed, such a force appears in the Definitions of 'Principia', Book I, but

not more in the Laws.

> Inertia means not-active.

What exactly means "not-active"? (Sorry when this was explained in aforegoing

postings!)

> F = ma describes both inertial and non-inertial forces relative

> to a coordinate system.

Is this formulation equivalent to my notion above, "...that, (i), there are

force that cause acceleration and, (ii), that acceleration causes ('counter')

forces."?

...

> Perfect inertia implies perfect isolation. That may be a fiction

No, it may not, at least not in the same sense as 'fictive' was used above.

For this, it's more accurate to call it an approximation, as you have in mind

with your explanation

> , but

> the concept that actions on a body are negligible is still valid, so it

> is not reasonable to call inertia a fiction, particularly in classical

> mechanics.

...

What do you think?

Best,

Peter

Apr 25, 2007, 2:32:18 PM4/25/07

to

Thus spake Peter <end...@dekasges.de>

>Hi Frank and Harald,

>> >> >One way to clear up the

>> >> >confusion is to refer to Newton who discussed centrifugal force, while

>> at

>> >> >the same time rejecting the use of fictitious forces.

>

>> >> Fictitious forces were invented by Huygens I believe. There is nothing

>> >> wrong with them. They are defined by mass x acceleration relative to a

>> >> given coordinate system.

>

>This corresponds to my understanding. It's a translation of a kinematical

>problem (relative motion) to dynamics. This concept seems to be beloved by

>practioners like meteorologists. I'm not sure about its usefulness for

>axiomatics.

>Hi Frank and Harald,

>> >> >One way to clear up the

>> >> >confusion is to refer to Newton who discussed centrifugal force, while

>> at

>> >> >the same time rejecting the use of fictitious forces.

>

>> >> Fictitious forces were invented by Huygens I believe. There is nothing

>> >> wrong with them. They are defined by mass x acceleration relative to a

>> >> given coordinate system.

>

>This corresponds to my understanding. It's a translation of a kinematical

>problem (relative motion) to dynamics. This concept seems to be beloved by

>practioners like meteorologists. I'm not sure about its usefulness for

>axiomatics.

I don't see how to understand general relativity without them.

>

>> >> It is important to understand them in order to

>> >> understand gravity.

>

>Is gravity a fictitious force?

In a sufficiently local (in time and space) coordinate system, it is. In

this case one can always transform to an inertial coordinate system in

which it is absent. That is the principle of equivalence.

>

>> ..."fiction" is just a word, meaning that the forces are not-active, or

>> inertial.

>

>What means "not-active"?

It is the literal meaning of inert or inertial, from latin which Newton

of course would have spoken.

>

>> >> >> in gtr loads of coordinate systems are valid. If you choose a non-

>> >> >> inertial frame, you find non-inertial forces.

>

>For me, the definitions of inertial frame and non-inertial forces appear like

>a circle...

They are. Ultimately this is tautology. In the absence of a background

like Newtonian absolute space, we can best talk of motions relative to a

frame of reference defined from inertial matter.

>

>> Inertia means not-active.

>

>What exactly means "not-active"? (Sorry when this was explained in aforegoing

>postings!)

As I recall, Newton talks of active forces, meaning forces caused by the

physical action of one body on another. An inertial state is one in

which this is not happening.

>

>> F = ma describes both inertial and non-inertial forces relative

>> to a coordinate system.

>

>Is this formulation equivalent to my notion above, "...that, (i), there are

>force that cause acceleration and, (ii), that acceleration causes ('counter')

>forces."?

I don't think simply to define force by F=ma contains that, although it

is true.

> ...

>> Perfect inertia implies perfect isolation. That may be a fiction

>

>No, it may not, at least not in the same sense as 'fictive' was used above.

>For this, it's more accurate to call it an approximation, as you have in mind

>with your explanation

ok, an approximation.

Apr 26, 2007, 4:26:07 AM4/26/07

to

Oh No <No...@charlesfrancis.wanadoo.co.uk> writes:

> >> >> Fictitious forces were invented by Huygens I believe. There is

> nothing

> >> >> wrong with them. They are defined by mass x acceleration relative to

> a given coordinate system.

> >This corresponds to my understanding. It's a translation of a kinematical

> >problem (relative motion) to dynamics. This concept seems to be beloved by

> >practioners like meteorologists. I'm not sure about its usefulness for

> >axiomatics.

> I don't see how to understand general relativity without them.

I would understand this if knowing your understanding of general relativity,

but there seems to be a pause in your thread ;-)

> >> >> It is important to understand them in order to

> >> >> understand gravity.

> >Is gravity a fictitious force?

> In a sufficiently local (in time and space) coordinate system, it is. In

> this case one can always transform to an inertial coordinate system in

> which it is absent. That is the principle of equivalence.

Unfortunately, I know little about general relativity. With Newton I see

gravity as a direct force between bodies. In contrast, there is no distance-

dependent force law for the Coriolis force.

> >> ..."fiction" is just a word, meaning that the forces are not-active, or

> >> inertial.

> >What means "not-active"?

> It is the literal meaning of inert or inertial, from latin which Newton

> of course would have spoken.

The fact that Newton wrote in the definitions about inertia as internal force

of bodies, bot didn't mention it in the laws, can be seen as indication of

that Newton felt the conceptual difficulties herein.

What speaks again the view that the 'inertial force' is the net result of the

gravitative interaction with all other masses? I find Sciama's (1953)

exposition of it by means of the gravito-electrodynamic equations fascinating

in its simplicity and clarity :-)

> >> >> >> in gtr loads of coordinate systems are valid. If you choose a non-

> >> >> >> inertial frame, you find non-inertial forces.

Consider your (or my) house and that of a neighbour. There is a gravitative

attraction between them, counterbalanced by their bound to the ground. Which

are the fictious and non-fictious forces?

Now, consider two electrically charged body kept at distance by some

isolating bond. Which are here the fictious and non-fictious forces? Vanishes

the electromagnetic force between them when the bond is removed?

Thank you,

Peter

Apr 26, 2007, 5:08:04 AM4/26/07

to

Thus spake Peter <end...@dekasges.de>

>

>> >Is gravity a fictitious force?

>

>> In a sufficiently local (in time and space) coordinate system, it is. In

>> this case one can always transform to an inertial coordinate system in

>> which it is absent. That is the principle of equivalence.

>

>Unfortunately, I know little about general relativity. With Newton I see

>gravity as a direct force between bodies.

>

>> >Is gravity a fictitious force?

>

>> In a sufficiently local (in time and space) coordinate system, it is. In

>> this case one can always transform to an inertial coordinate system in

>> which it is absent. That is the principle of equivalence.

>

>Unfortunately, I know little about general relativity. With Newton I see

>gravity as a direct force between bodies.

Indeed, but it is a force without physical cause. This taxed minds for

two hundred years before gtr gave an explanation.

> In contrast, there is no distance-

>dependent force law for the Coriolis force.

The force law now comes from the geometry of space-time, not from

kinematic behaviour. In other respects it behaves as an inertial force

like coriolis.

>> >> ..."fiction" is just a word, meaning that the forces are not-active, or

>> >> inertial.

>

>> >What means "not-active"?

>

>> It is the literal meaning of inert or inertial, from latin which Newton

>> of course would have spoken.

>

>The fact that Newton wrote in the definitions about inertia as internal force

>of bodies, bot didn't mention it in the laws, can be seen as indication of

>that Newton felt the conceptual difficulties herein.

>

>What speaks again the view that the 'inertial force' is the net result of the

>gravitative interaction with all other masses? I find Sciama's (1953)

>exposition of it by means of the gravito-electrodynamic equations fascinating

>in its simplicity and clarity :-)

I am not familiar with Sciama's account. I find Machian attempts at

explaining inertia in terms of the behaviour of other masses lack

coherence. Locally "straight" is defined by the relative paths of

inertial bodies. There is no other definition which makes sense in my

view.

>

>

>

>> >> >> >> in gtr loads of coordinate systems are valid. If you choose a non-

>> >> >> >> inertial frame, you find non-inertial forces.

>

>Consider your (or my) house and that of a neighbour. There is a gravitative

>attraction between them, counterbalanced by their bound to the ground. Which

>are the fictious and non-fictious forces?

The active forces are the forces of the ground on the houses.

>

>Now, consider two electrically charged body kept at distance by some

>isolating bond. Which are here the fictious and non-fictious forces? Vanishes

>the electromagnetic force between them when the bond is removed?

>

What is the bond if it is not electromagnetic in origin?

Apr 26, 2007, 6:03:14 AM4/26/07

to

[somehow this message did not show up in my newsreader]

On Apr 25, 7:15 pm, Peter <end...@dekasges.de> wrote:

> Hi Frank and Harald,

>

> I have the impression that a major part of your discussion stems from

> using

> the same words for different contents. Hopefully, my questions below will

> help to clarify that :-)

Thanks but in fact, it was just a side issue and we largely came to

agreement about it.

> > >> >> If one doubts that these are real forces, get

> > >> >> on a childs roundabout. You can feel them, so they are real in

> > >> >> that

> > >> >> sense. At the same time, they are inertial, i.e. not transmitted

> > >> >> by

> > >> >> interactions between matter, and a product of motion relative to a

> > >> >> particular frame.

>

> One should clearly discriminate cause and effect.

> The curvilinear motion is accompagnied by 'inertial forces'.

> If a body is bound to another body that is not moving parallel to the

> first

> body on its own, a force between both bodies occurs. In case both bodies

> are

> in contact and the force appears as a pressure one may call it a 'contact

> force'.

Yes indeed, and now it seems we agree on this.

[...]

> Is gravity a fictitious force?

That is a good question; the answer depends in part on definition, and also

in part on theory. Obviously the force that deforms the spring on the

balance scale on which you stand is real by definition, and usually this is

called the force of gravity.

Note that because of such debatable notions, my focus in this thread is much

more down-to-earth, it's about relatively simple calculations. In a nutshell

(in case you missed it):

When accounting for GRT's speed limit of physical information (radiation and

gravitational fields), Einstein's 1918 solution of the clock paradox fails

to correctly predict observed Doppler shifts. Any alternative theory must be

able to deal with that same consistency test.

However, it turns out that neither a single sentence in a publication, nor a

few additional clarifying sentences in a newsgroup suffice to drive that

point down. And of not surprisingly, statements by experts who call it

"magic" or "pseudo" (again without fully explaining why) are similarly

insufficient. Thus it will certainly be useful to publish a full article on

it.

[...]

> For me, the definitions of inertial frame and non-inertial forces appear

> like

> a circle...

Indeed, Newton's postulate has been replaced by a circular definition. This

thread is related to Einstein's 1916 attempt to resolve that problem.

Best regards,

Harald

Apr 26, 2007, 6:34:24 AM4/26/07

to

Thus spake harry <harald.vanlin...@epfl.ch>

>Note that because of such debatable notions, my focus in this thread is

>much more down-to-earth, it's about relatively simple calculations. In

>a nutshell (in case you missed it): When accounting for GRT's speed

>limit of physical information (radiation and gravitational fields),

>Einstein's 1918 solution of the clock paradox fails to correctly

>predict observed Doppler shifts.

>Note that because of such debatable notions, my focus in this thread is

>much more down-to-earth, it's about relatively simple calculations. In

>a nutshell (in case you missed it): When accounting for GRT's speed

>limit of physical information (radiation and gravitational fields),

>Einstein's 1918 solution of the clock paradox fails to correctly

>predict observed Doppler shifts.

This does not appear to me to be true. If one defines coordinates in

which the non-inertial observer is stationary, such that the speed of

light is constant, the path of the inertial observer consists of three

parts. In the backward light cone from the acceleration the inertial

observer is in uniform motion away, and Doppler shift is as expected.

The same is true for the part of the motion in the forward light cone,

when the inertial observer is approaching. In the intermediate stage,

outside the light cone, the inertial observer's is stationary in this

coordinate system, and his clock is subjected to a gravitational shift

sufficient to resolve the paradox.

Apr 26, 2007, 8:36:19 AM4/26/07

to

news:GC1k0sDq...@charlesfrancis.wanadoo.co.uk...

Thanks for coming to the point, or, I should say, for attempting to do so.

:-)

For the issue is about Doppler shifts during Einstein's process 3. Please

specify how you calculated the time in K' that the gravitational induction

reaches C1 ("U1" in the article, from the German Uhr instead of the English

clock), and how you calculated the time in K' that emitted radiowaves from

the accelerated C1 and C12 reach C2.

As a reminder, here it is once more:

When taking a very large distance between the two clocks, even with a

(forbidden!) instantaneously propagating gravitational (pseudo-) field that

originates from C2, radio pulses that are emitted from C1 (the stay-at-home)

cannot correctly Doppler shift at C2 (the traveller), immediately after its

rockets are fired.

Looking at the problem in 2D instead of in 1D, we obtain the following

picture with another clock C12 aligned at a far distance to the side of C1,

"when" the rockets of C2 fire for the turn-around and with signals sent

from the stay-at-home clocks towards the traveller:

C1 C12 [higher "gravitational potential"]

Ś /

Ś /

Ś / [distance of for example 1 light day]

Ś /

Ś/

C2 [firing its rockets]

Here clock C12 must accelerate synchronously with clock C1, and radio pulses

that are emitted from C1 as well as C12 must immediately Doppler shift at C2

when the rockets of C2 fire. Obviously that cannot work.

To make it more concrete (I do this fast so I may make an error, but that

can be straightened out later): We can ch