Re: A little challenge for relativists.


John Kennaugh wrote:
> Your posting is full of assertions but you attempt to make no case nor
> to fault my previous detailed arguments.
>
>
> If light is source independent it is because some physical process makes
> it so. Maxwell's Equations may be consistent with that physical process
> but light is not source independent because Maxwell's equations say so.
> You may wish to divorce physical process from the mathematics in order
> to preserve your belief system but I see no evidence that Einstein did.
>
> Maxwell believed he had found equations which represented light
> travelling in the ether. If you decide there is no ether then you have
> to decide what, if anything, those equations are describing. Without an
> ether they can only be describing light leaving the source at c relative
> to the source. Without an ether they cannot be describing light
> travelling w.r.t the observer at c - the mathematical alternative. I say
> that for two reasons:
>

I hate to be the bearer of bad news but you may have to acknowledge
that fluids and fields, massless or not, can go by names other than
"ether". Without an 'ether' we can use Maxwell's equations to show how
the elctromagnetic 'field' behaves. Language marches on.


>
> They also implied that the speed of light would be dependent upon the
> speed of the observer - that is what the MMX was all about. If you
> interpret MMX as showing there to be no ether (which is not what either
> Lorentz or Einstein did) then you have to decide what it is that ME are
> physically describing before you can use them again. As I point out,
> without an ether, ME must be describing light leaving the source at c.
>
> The only physical model which will give you source independence is the
> ether. If the speed of light is not dependent upon the source, either in
> terms of the physical processes taking place in the source, or simply as
> a reference point from which a natural progression starts to take place
> at constant speed - then it must be dependent upon something else and
> that something else must take charge of it the moment it leaves the
> source. That 'something else' is called the ether and it has to be
> physical as it has to take part in a physical process. It requires a
> physical process which Maxwell's equations may (or may not) model within
> their sphere of applicability.
>


I agree - replace the word 'ether' with 'electromagnetic field' and
you'll get a lot more agreement as well without really changing the
content.

> [...]
>
> While Lorentz's theory gave symmetry in the system of experience
> Einstein was not happy with that and tried to remove the asymmetry in
> the theoretical structure of Lorentz's theory. The difference between
> the two theories is that while Lorentz says it *appears* to every
> observer that he is stationary w.r.t the ether Einstein said "Lets just
> assume every observer IS stationary w.r.t the ether".


Not really. They weren't talking here about the same 'ether' that you
were talking about before, the electromagnetic field. The difference
is subtle; here they are talking about coordinate systems and how to
implement them.


>
> The clearest statement of his justification for the second postulate
> comes in 1938
>
> "Light is a propagated wave propagated by a medium called the Aether.
> The velocity of a wave is a function of the medium which propagates it
> and its velocity can only be effected by the source if the movement of
> the source causes movement of the medium. Aether drag experiments,
> passing light close to heavy rotating flywheels has shown that they had
> no effect on the light passing close to them hence the speed of light
> cannot be effected by the speed of the source.
>
> Although the speed of light might be expected to vary with the speed
> of the observer Michelson and Morley had shown that not to be the case
> so it is a strange but indisputable fact that the velocity of light is
> constant independent of the velocity of the source or the observer."
> Infeld/Einstein - The Evolution of Physics. 1938
>
> Later in the book he suggests, possible as a sop to people like you who
> hate the E-word that perhaps something which cannot be detected cannot
> be said to exist but this is false logic. It is only our speed relative
> to the ether which is undetected. Having justified source independence
> as being a property of the ether any experiment showing source
> independence has confirmed the existence of the ether.
>

Standards of detection, direct and indirect, change as people become
more comfortable with concepts.


> >> "The speed of light is always constant w.r.t the source emitting it"
> >> is completely consistent with the PoR and had not been ruled out by
> >> experiment.
> >
> >It could be consistent with the PoR, but not with the M.E.
>
> It is consistent with the PoR and to get Maxwell's equations to describe
> light travelling away from the source at c relative to the source all
> you have to do is assume that the source is stationary w.r.t Maxwell's
> ether.
>

Or that that the source is movnig w.r.t. Maxwell's ether, and clocks
and meter sticks change their tick rates and lengths when at motion in
the ether according to the Lorentz transformations.


> >
> > Just because Einstein used the word "ether" in one paper
> > IN A FORUM ON ETHER does not mean that GR is an ether theory.
> > Moreover, in that quote he explicitly states that what he
> > called "ether" has essentially no relationship to the usual
> > meaning of the word (in particular, it is not possible to
> > measure "speed" relative to what he called "ether").
>
> The emphasis tries to add a bit of spin

Perhaps in more ways than you intended..

> but that statement is totally
> consistent with my understanding. Einstein was after a different sort of
> ether which did not imply a unique FoR stationary w.r.t it but it still
> needs to provide a physical process to wrest control of the speed of
> light from any influence the physical processes taking place in the
> source would otherwise have.
>

He was also after a consistent idea of what we mean by extension and
duration.


> [...]
>
> > IOW: the only viable ether theories known today are those that are
> >experimentally indistinguishable from SR/GR.
>
> Quite so. The only physical theories consistent with the mathematical
> models of SR/GR are ether theories.
>
> What physical process makes the speed of light constant w.r.t the
> observer observing it?
>

The physical process is the observer defining his system of units,
defining what he means by "extension" and "duration".


> That is a valid 'physics' question.
>
> "the speed of light is constant in the observers FoR" is a description
> of the maths and a re-statement of the second postulate. The observers
> FoR is a mathematical abstraction mapping out real physical space. What
> is it in real physical space which provides the properties assumed in
> that mathematical description?
>

The light waves propagate through something that allows propagation.
>>From there we can build up the mathematical description of a
relativistic/modern coordinate system - you don't need to know much
more about the medium for SR, until you start looking at E&M, quantum,
or GR that is.


> >> I would be less reluctant to accept the Maxwell/Lorentz/Einstein
> >>ether theory if I was certain that the alternative no ether, source
> >>dependent option had been properly evaluated.
> >
> >It has been tried and found wanting.
>
> Please explain. Note that the success of a different theory does not
> rule out the possibility that this theory would not be equally
> successful given the necessary resources to develop it. Waldren thought
> so. The success of relativity could be put down to the fact that that is
> where all the effort has gone.
>


Do you think a source-dependent SOL / corpuscular theory still survives
the experimental record? (see link at end)


>
> >
> >And relativity was a clear BREAK from the concept of "ether".
>
> I have shown that not to be the case. See above. You do not make it so
> by constantly asserting that it is so no matter how deeply held your
> belief may be. Can you supply me with one quote where Einstein argues
> that there is no ether and explains why he still assumes source
> independence?
>
> >Ritz died in 1909 -- where is his theory today?
> > (nowhere, becuase it does not agree with numerous experiments)
>
> No one even admits there is an alternative theory let alone routinely
> check whether results fit it.
>

It comes up quite a bit I think.. I saw one presentation on a
conference explaining GRBs with this:
http://www.ebicom.net/~rsf1/grbs.htm



> >
> >> A very good case existed at the start of the 20th century for taking
> >>the no ether Source dependent route suggested by Ritz [...]
> >
> >Except it does not agree with all of the experiments.
>
> Let us distinguish here experiments intended to test Ritz's theory and
> the unjustified assumption that because relativity is successful Ritz's
> wouldn't have been. Also note that had Ritz's theory been adopted it
> would by now have had a century of development. We are totally unable to
> compare present day relativity with the theory which would have
> developed by now had Ritz's theory had the same development. My point is
> that had Ritz's theory been accepted there is no way I can see that it
> would ever converge with relativity no matter how many challenges were
> thrown up because the actual route to relativity makes no sense anyway.
>


I think his point was that it doesn't agree with experiments:

http://math.ucr.edu/home/baez/physics/Relativity/SR/experiments.html#moving-source%20tests

.

Relevant Pages

  • Re: "The Impossibility of Measuring the Velocity of Light"
    ... it but the speed of the observer would. ... Choice 1 - Assume that there is no ether. ... with relativity it supports relativity while in fact the simplest ... Implication is that two clocks at different latitudes will not keep time. ...
    (sci.physics.relativity)
  • Re: Michelson and Morley
    ... This was the moving observer. ... and that isn't the way physics went. ... The answer is that physicists had believed in the ether for more than ... Relativity is now a 'principle ...
    (sci.physics.relativity)
  • Re: Electron-positron annihilation
    ... as would be expected by both relativity and ballistic theory. ... the source whether there is an observer or not. ... It is even more absurd if one tries to deny the existence of the ether. ... A and B coincide it means that it set out at different speeds arrived at ...
    (sci.physics)
  • Re: Electron-positron annihilation
    ... as would be expected by both relativity and ballistic theory. ... the source whether there is an observer or not. ... It is even more absurd if one tries to deny the existence of the ether. ... A and B coincide it means that it set out at different speeds arrived at ...
    (sci.physics.relativity)
  • Re: Anyone ever read this Einstein physics book?
    ... >for source and observer regardless of velocity, ... In relativity the light seen by B is a different frequency to that seen ... Maxwell thought that light travels at c - constant w.r.t the ether. ... You must understand that those who write text books have to get their ...
    (sci.physics.relativity)