Re: Learning and Teaching Special Relativity
From: John Kennaugh (JKNG_at_kennaugh2435hex.freeserve.co.uk)
Date: 09/13/04
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Date: Mon, 13 Sep 2004 12:08:11 +0100
Bilge writes
> John Kennaugh:
> >Bilge writes
> >> John Kennaugh:
> >> >No 1 'kook' was of course Einstein who was very definitely under the
> >> >impression the HIS theory was about light.
> >>
> >> Oh, really? Please cite a reference in which einstein states that his
> >>theory[1] is about light.
> >
> >His theory is based on two postulates one of which states:
> >
> >"Any ray of light moves in the 'stationary' system of co-ordinates with
> >the determined velocity c, whether the ray be emitted by a stationary or
> >by a moving body."
>
> That doesn't support what you said above. I've also explained to you
>more than once why the speed of light, per se, is irrelevant.
On the contrary you merely split hairs. 'Relativity is a geometric space
time theory'. Space time construction is based upon invariance.
A purely hypothetical construction says that the speed of light in
vacuum is fundamental, that there is something more fundamental named
Invariance which is axiomatic which is responsible for source
independence but acknowledges that other things beside light speed might
travel at c and raises the possibility that if photons have rest mass
then the speed of light might not be quite equal to c. It is rather
academic in that it is a purely hypothetical concept anyway. (an
assumption which Einstein managed without). The likely contenders of
'other things which might travel at c' have been eliminated (those which
can be detected at all that is) and all the evidence is that photons do
not have rest mass which means that for all intents and purposes c is
the speed of light which if you read what Einstein said and do not try
to deliberately misunderstand what he said, is what he based his theory
on.
>
> >I am at a loss to know in what way Einstein's contribution differed from
> >that of Lorentz because all questions relating to what would constitute
> >a difference e.g. 'if ether is not involved what is?' are answered by
> >stating that relativity does not attempt to answer those sorts of
> >question.
>
> Of course you're at a loss. You flat out refuse to try and understand
>the difference because you're hung up on the idea that light is of
>some importance to relativity.
"Any ray of light moves in the 'stationary' system of co-ordinates with
the determined velocity c, whether the ray be emitted by a stationary or
by a moving body." Einstein 1905
Is still the basis of Einstein's theory no matter how much you squirm.
The theory is based on the assumption that light is special in that it
does not obey Newton's laws of motion. Had anyone put it to Einstein
that other things (as yet unthought of) might share this property with
light he might have acknowledged the possibility but would have pointed
out that Maxwell's equations indicate that c is a fundamental constant
relating to the electromagnetic properties of space. Its permittivity
and permeability.
"Certainly, from the standpoint of the special theory of relativity,
the ether hypothesis appears at first to be an empty hypothesis. In
the equations of the electromagnetic field there occur, in addition
to the densities of the electric charge, only the intensities of the
field. The career of electromagnetic processes in vacuo appears to
be completely determined by these equations, uninfluenced by other
physical quantities. The electromagnetic fields appear as ultimate,
irreducible realities, and at first it seems superfluous to
postulate a homogeneous, isotropic ether medium, and to envisage
electromagnetic fields as states of this medium. But on the other hand
there is a weighty argument to be adduced in favour of the ether
hypothesis. To deny the ether is ultimately to assume that empty space
has no physical qualities whatever. The fundamental facts of mechanics
do not harmonize with this view." Einstein Lecture 1920.
You are in denial of what Einstein actually thought, said and based his
theory on. You keep trying to put modern constructs into a historical
context where they simply have no place. Why not simply accept that your
view is fundamentally different Einstein's. That you believe that
Einstein had it wrong as did Lorentz before him. Then at least your
arguments might make some sort of sense.
> I'm not surprised in the least that
>you fail to understand the significance of einstein's contribution vs
>lorentz'.
>
>[...]
> >
> >Do you suggest that MMX had nothing to do with light? That the
> >transforms which Lorentz produced had nothing to do with light either.
>
> There's not much point in suggesting anything either way, since you
>don't understand the reason einstein included the second postulate,
>why it's an historical artifact and why it's irrelevant to relativity.
Usual twaddle. Constant assertion does not make your assertion right.
See Below.
>
>[...]
> >> Wrong again, since my responses to you were about nothing but the
> >>philosophical implications. You understand _nothing_ about relativity,
> >>except perhaps how to apply the lorentz transforms in a limited number
> >>of situations, but that really isn't understanding relativity.
> >
> >"Understanding relativity" in your book is being able to do the maths.
>
> That level of understanding isn't necessary to correct the misconceptions
>you have about a relativity. It's certainly possible to understand what
>the theory is about without understanding it in detail. It's also possible
>to use the formulae from relativity without understanding relativity.
>You've chosen to equate understanding the formulae with understanding
>the theory.
No I try to avoid formulae altogether where possible and to try and
understand the physical concepts the formulae are describing.
>That is why you cannot understand the difference in lorentz'
>theory and relativity beyond the difference of the ether.
I appreciate that there are conceptual differences. For example Lorentz
says that a measuring rod is physically shortened in its direction of
travel in the ether by an amount related to its speed relative to the
ether. SR says that a moving rod is shortened in the stationary FoR but
not in the Moving FoR. The maths is the same.
The fact that the maths is the same and the description widely different
should provide a warning. Modern physics is littered with statements
which say "The maths tells us that ......." followed by some sort of
physical construct e.g. ".... that wormholes in space can exist". Maths
does not tell you that sort of thing nor whether an equation is
physically meaningful. Mathematically you can reverse the direction of
time and derive all sorts of things. If you do not keep a strict
discipline on the origins of the maths you are likely to take what is
derived seriously and worse accept the fanciful concept someone has
thought up as being what the 'maths is describing'. For example we know
that light is bent by gravity. It is perfectly reasonable to conclude
that if you have sufficient mass in one place that any light passing
close to that place will be captured by it. The idea of a 'black hole'
is not contrary to logic. I would however suggest that mathematically
extrapolating knowledge which is limited to justify belief in a
singularity and all the magical distortions of the laws of time and
physics which go with it is a flight of fancy. When it gets to the
effect of what happens if you pass through the centre of a rotating
black hole then physics has ceased to be a science and has simply become
the playground for the fantasies of mathematicians each trying to outdo
the other.
Conceptually Lorenz works better than SR in that different speed
relative to the ether distorts a single reality so that two observers
see things differently. In SR there is no such causality so you have two
realities. The same measuring rod is actually two different lengths. For
two observers in relative motion viewing the same source their realities
differ. Light leaves the source at different speeds relative to the
source, and sets out at different times in the reality of the two
observers. That doesn't bother you, the math is consistent. I don't care
about the math I don't accept that two realities can exist in the same
universe. That is where we differ. Not in a difference of understanding
but in what we are differently prepared to accept. I see faith in a
purely mathematical description as indiscipline. A way of hiding the
underlying absurdity.
>[...]
> >>
> >> >You see you cannot get away from the fact that the second postulate of
> >> >relativity is simply the first postulate + source independence.
> >>
> >> No, it isn't.
> >
> >Yes it is. The first postulate says that any observer in uniform motion
> >will discover the same laws of physics to be true. It does not say
> >anything about what the laws of physics are in general and nothing
> >specific regarding the laws relating to light.
>
> I derived the lorentz transforms for you assuming the first postulate
>and the ``law of physics'' that the length of something is the same
>in any coordinate system. I did not assume that light propagated at
>a fixed velocity, since I never used light at all.
Einstein could not have derived the Lorentz transforms without the
second postulate. The reason you can is that you are using space time
geometry which incorporates the concept of invariance which does the job
the second postulate did for Einstein. Stop playing silly word games.
The first postulate does not distinguish between relativity and
ballistic theory. The second postulate limits it to relativity. Space
time geometry limits it to relativity.
>[...]
> >> No one taught me ``what to believe''. The fact that relativity is a
> >>theory of space time geometry and not a theory about light propagation
> >>is common sense.
> >
> >No it isn't.
> >
> >If A is true then B is true. If B is true C is true. If C is true then A
> >must be true therefore A is true.
>
> Relativity is about coordinate transforms between inertial frames.
>Electromagnetism is about light.
Co-ordinate transforms between inertial frames would be in accordance
with Newton if it were not for the assumed properties of light i.e.
"Any ray of light moves in the 'stationary' system of co-ordinates with
the determined velocity c, whether the ray be emitted by a stationary or
by a moving body." Einstein 1905
c is an electromagnetic constant.
-- John Kennaugh to email convert the number from hex to decimal
- Next message: Dirk Van de moortel: "Re: The speed of light c."
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- In reply to: Bilge: "Re: Learning and Teaching Special Relativity"
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- Reply: Bilge: "Re: Learning and Teaching Special Relativity"
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