Re: Why SR? (was: Source Independency of Light Speed Without an Aether???????)

On Jul 1, 4:23 pm, John Kennaugh <J...@xxxxxxxxxxxxxxxxxxxxxxxxxx>
wrote:
Bruce Richmond wrote:
On Jun 30, 4:42 am, John Kennaugh <J...@xxxxxxxxxxxxxxxxxxxxxxxxxx>
wrote:
Bruce Richmond wrote:
On Jun 26, 6:43 am, John Kennaugh <J...@xxxxxxxxxxxxxxxxxxxxxxxxxx>
wrote:
Whoever wrote:
"John Kennaugh" <J...@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:u2U9njRCI9QKFwEN@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Whoever wrote:
"John Kennaugh" <J...@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message

[snip] You need to rethink your basics see below.

There is no change at the source itself .. nothing happens to it. As
already pointed out. Similar to when you move away from a sound
source, the longer wavelength of that wave (in your frame of reference)

No No No. If you move away from a sound source the wavelength
does NOT change. The wavelength stays the same but your speed relative
to the wave changes. That is my point. You may know the formula but you
clearly are unable to visualise what is happening.

Sound travels in a definite medium. The wavelength is calculated in
the FoR of that medium. With light if there is a medium its FoR has
not been identified. If you want to assume there is one then in order
to have the laws of physics work in all inertial frames you end up
with LET. SR and LET use the same math, only differing in
interpertation of what the math represents.

SR does not have an interpretation. It is only a principle theory - a
mathematical model - "which puts forward no specific hypothesis" -AE

SR says that light travels at isotropic c in all frames.  LET says
that light travels at c only in the ether frame but moving clocks slow
and rulers shrink in such a way that it is measured to travel at c in
all frames.  Those are two interpertations of the same observations.
Both SR and LET are mathematical models.  The interpertation of what
is happening is what determines how the model is constructed.

LET Hypothesises the existence of a physical aether as a physical
hypothesis to explain causality. SR puts forward no physical hypothesis.
Both emerge from the same basis: That Maxwell's wave in aether theory is
impeccable and that if you assume it to be so then the MMX shows that an
observer's speed relative to Maxwell's aether always appears to be zero.

I don't think the MMX even needed to be considered in developing SR.
We needed Maxwell's waves to travel at c in all frames, and we wanted
to keep the Principal of Relativity. With Galilean relativity having
light travel at c in one frame had it traveling at c+v in other
frames. Since Einstein knew he wanted it to be c in all frames he
just started from that premis and constructed the coordinate systems
of all frames in such a way that the speed of light would be measured
as c in all frames.

Lorentz tried to explain that in terms of a conventional aether by
considering the other property of the aether - that it is responsible
for action at a distance force. He postulated that matter was a matrix
of charges held together (or kept apart?) by action at a distance force
in the form of stress in the aether. He calculated the effect of a
moving aether on the dimensions of the array and found it got sorter in
the direction of travel - as per length contraction. His theory is a lot
more sophisticated that it is given credit for.

Agreed. In fact I accepted LET before SR for the same reasons you
prefer it. I could see how all frames measured the speed of light to
be c even though it seemed contradictory.

Einstein's theory is purely empirical in that he makes no attempt to
explain anything. He simply accepts that the MMX result showed that for
whatever reason an observer is always stationary w.r.t Maxwell's aether.
That is what the second postulate is describing and was the generally
accepted interpretation of the MMX at the time. As the Maths is the same
as Lorentz's and as it is simply empirically based it isn't a different
theory to Lorentz's. Einstein understood this and tried to come up with
an alternative theoretical structure to Lorentz's - or at least to hint
that there was one. He objected to the asymmetry in the theoretical
structure of Lorentz's theory but failed to come up with an alternative.
He suggested that the key was in our understanding of the aether and
suggested an aether "without the immobility of Lorentz's". What he was
hinting at seems to be an aether which every observer will naturally
find himself stationary w.r.t - the only way of achieving symmetry which
requires that all observers must have the same relationship with the
aether. Rather than go there, and rather than go back to Lorentz
physicists changed the nature of physics and declared that a physics
theory did not require a physical structure and that Einstein's theory
was acceptable without one.

I don't claim any knowledge of Einstein's motivations. As I see it
the second postulate is most easily explained with an ether theory,
but that is not proof that there is an ether. Since all that is
needed for SR is the property of all light traveling the same speed
why not just use that property?

Along with that goes the idea that things are what you measure them to
be. I suspect that went a long way in getting SR accepted over LET.
It's got to be a bit disconcerting to know that all your accurate
measurements are just an illusion.



In the ether frame of LET
the light has a fixed wavelength. But there is no way to know which
frame is the rest frame of the ether. Lorentz showed in his 1904
paper that all inertial frames end up measuring the speed of light to
be isotropic c. So it makes sense that we let each FoR use its own
coordinate system when measuring things, and that coordinate system is
constructed based on light being measured to travel at c.
SR just gets rid of the baggage of an ether and starts with the
postulate that light travels at isotropic c in all frames.

A FoR may be a math construction, but they are implimented in the real
physical world. We measure lenghts with rods, mark of distances in
various directions, and sychronize clocks placed at various points.

They are an aid to our concepts of measurement but they do not have
physical properties. The assumption that the speed of light is isotropic
in a FoR is not a physical property of the FoR.

If you have constructed the frame in such a way as to *make* the speed
of light isotropic c then it is a property of that FoR and it is no
longer just an assumption that the speed of light is isotropic c in
that frame, it is a known fact.

Semantic games.


Not really. If the coordinate system is constructed using light
signals that by definition travel at isotropic c then there is no way
you can measure the speed of light to be anything but c. Call it
circular if you like but it is true. And that is a property of the
coordinate system. You could have made it differently if you wanted
to.


One should still ask why
this is so. Physics having denied the existence of anything physical in
the space which a FoR defines it has put itself if a physical impasse. A
mathematical model combined with a dogma that nothing exists which can
possibly bring about what the maths is describing. Maths is the new
religion. It needs nothing other than itself to command the workings of
the universe.

I agree we should still be asking why things happen as they do.  But
for right now we have some math that allows us to make correct
predictions.  When primitive people didn't know how the explain things
like the weather, the rise and fall of the sun and moon, where things
came from, they invented gods to explain them.  Inventing an ether
sounds more like a religion than just admitting we don't know
everything.  If you must have an ether theory check out LET.  In the
end the math is the same as for SR.

I was never keen on the aether but what you have is an aether theory, SR
who's devotees claim is not an aether theory and which makes no sense
without an aether. You stress that it gives correct predictions. So did
the geocentric theory of the solar system.

Beckmann and Mandics for example pointed out that Einstein was one of
the few people who realised explicitly that his theory rests on the
*assumption* that our present Maxwell-Lorentz electrodynamic theory,
experimentally verified only for low velocities of charged matter will
also hold for velocities commensurate with the velocity of light.
"Considering that our present electrodynamics have grown out of a
concept of an elastic ether, whose existence is now disproved beyond
reasonable doubt [??? has it? JK],

I still have doubts.

and that the Maxwell equations do not
satisfy the principle of relativity in its simple form using the Galilei
transformations this assumption is far from self evident ....
Einstein assumed the universal validity of Maxwell-Lorentz
electrodynamics and to make them comply with the principle of relativity
he introduced the Lorentz transforms (drastically changing the classical
concepts of space time and mass) [ditching 3 long established and
apparently sensible axioms of physics - JK]. This is not the only
possibility. One might assume the universal validity of the Galilei
transforms, leave the concepts of  space, time and inertial mass
unmodified and work out electrodynamics that are consistent with all
observations. Except for a single attempt by Ritz (1908) no such
electrodynamics have so far been worked out but there is no reason to
believe that this is inherently impossible."

They suggest the possibility that Lorentz transforms could simply be
equivalence formula, making up for inaccurate electrodynamics by
suitable deforming space and time to achieve the correct result.

That's grasping at straws.

With the dogma that a theory only needs maths capable of correct
prediction there is no need to even look for an alternative. There would
have been no need to look for an alternative to the geocentric theory.

When you change your FoR your old FoR is still there after you leave,
and your new FoR existed before you arrived.
Neither frame noticed
anything different about the frequency of the light when you changed
frames. The meter stick you brought with you will still measure
exactly a meter when compared to a meter stick in your new frame, and
your atomic watch will tick at the same rate as those in your new
frame. That means you should measure things the same as those that
were already in the frame.

Now you are talking like a relativist. You are talking as if a FoR is
separate physical universe where things can be different with impunity
and that the answer "because it is a different FoR" is a valid answer to
a (every) physical question. It is not.

Things look different when you drive down a road than they do when you
stand on the same road.  The tree over there changes position relative
to you when you are moving, but not when you are standing still.

And you can explain why. From that physical understanding you can
construct a mathematical model. That is the correct relationship between
physics and maths as Dingle pointed out. Maths should be the servant of
physics and has become its master.

The
difference is your FoR.  It's not the answer to every question, but it
explains quite a few.

1/ If you have a source and the wavefronts are concentric circles
(spheres in 3 dimensions obviously) then either the source is stationary
w.r.t the propagation medium or light speed is constant w.r.t the source
(emission theory). Mathematically there is no difference.

2/ If the wavefronts are close together at one side and spaced out on
the other then it shows that the source is moving relative to the
propagation medium or the mathematical equivalent.

3/ The mathematics of relativity assume that in an observers FoR the
speed of light is every which way equal to c, arguments about the aether
aside, this is mathematically the same as the observer always being
stationary w.r.t the propagation medium.

4/ If you take the simple case

A S
B->v

Then the maths imply that because S is stationary in A's FoR light is
leaving the source in concentric circles to reach A.
The maths further imply that as the source is moving towards B in B's
FoR the wavefronts leaving S are squashed together in the direction of
AB and spaced out in the other direction.

A FoR does not physically exist so what you have in reality are two
observers at the same point in space observing the same light. It cannot
be spreading through space in two entirely different ways.

It's not,

What do you base that statement on?

The two frames are giving different coordinates to the same points.
It's not hard to make sense of when both frames use the same time, but
when you have different time coordinates due to position it can mess
with your head. But that is what SR is doing. The grid used to
measure the time and place of each point in the wave was constructed
so that the observers measure the same wave to travel at c in both
coordinate systems. Because there times are out of sync they get
different positions for the wave at any given time. LET does the same
thing to come up with the illusion that light is measured to travel at
c in all frames.

but it can certainly look different, and be measured
different from the two different frames.

Why? Forget frames you just have two observers at the same point in
space observing the same light.

Yes, and one of the observers is moving. For a real world experiment
we can show the same thing using sound.

If you see a car traveling from left to right on a road in the
distance the sound emitted by the car seems to come from a point
behind the car, where the car was when it emitted the sound that is
reaching you at a later time.

Go with a friend to an open field when the wind is blowing strong and
steady. Stand well apart from each other in a cross wind and shout
back and forth. Try using a megaphone so you can aim your sound. You
will find that you still hear the sound coming straight to you from
the source, even though the sound gets carried down wind. If you
measure the speed of the sound you will find that it takes longer to
reach you that it would at the same temp and pressure but with no
wind. If you put up a small barrier to block the sound it needs to be
put on the line of sight between you and the source.

It took a while drawing eccentric circles and visualizing them
expanding to figure out how the sound is heard to come straight
across, not from down wind.

Now it doesn't matter whether you are both standing still or both
moving at the same speed, the effect is the same as long as there is
no relative motion. So grab another friend and find a couple of
parallel roads. Position one friend on the side of the road. Have
your other friend drive along the parallel road at the same speed as
you. Just before you reach your friend on the side of the road have
the other friend honk his horn. You will hear the sound coming
straight across from the other car while your stationary friend will
hear it come from behind the car.

The same waves seem to come from two different places for two
observers that are at the same point but in different states of
motion.

Gotta go now. More later.

B sees the light as being
red shifted due to the motion of S relative to him where A did not.

We understand the physical mechanism of producing Doppler in sound. Here
you have two observer's viewing what appears to be a wave like phenomena
and getting a change in frequency - even described as Doppler. The
obvious conclusion is that the same mechanism is involved and that just
as with sound A and B are simply travelling at a different speed
relative to the wave. Superficially this disproves SR.

If you are saying it doesn't disprove SR you need to put forward an
alternative plausible explanation of the result. It is not good enough
to simply say that motion causes Doppler you need to say how motion
effects what is going on so as to produce a frequency shift because the
only known way that relative movement between two observers will cause
Doppler is if their movement means that they are encountering the wave
at different speeds. Use of the term FoR is unnecessary. It is used as a
smokescreen to make a description of the maths sound as if it is a
physical explanation.

In his own FoR B is at rest.

= B

 He is not moving relative to himself.

tautology

If he is not moving and S is getting closer then S must be moving,

Speed is relative. If S isn't moving and they are getting closer B must
be moving

and
the red shift confirms that.

Confirms what? A and B measure different frequencies at the same point
in space. As it is impossible that the same light separates from the
source at two different speeds producing two different wavelengths then
A and B must be travelling at different speeds relative to the same
wavelength in order to get different frequencies - disproving SR.

If you insist that B is moving, not S,
then you are not only throwing out SR but the Principal of Relativity
as presented by Galileo and elaborated on by Newton.

Not at all. The PoR says that speed is purely relative and you are
entitled to assume S is stationary w.r.t B or B is stationary w.r.t S or
both S and B are in relative motion w.r.t C.

You use the phrase "Frame of Reference" as a crutch.

  SR implies that the same light separates from the source at different
speeds to travel to the two observers. That is obvious nonsense. But
rephrase it including the phrase FoR and you accept it because you are
so used to that construction of wording that it seems perfectly
reasonable that in one FoR light separates from the source at one speed
producing one wavelength and that in the other it separates at a
different speed producing a different wavelength. The speed of the wave
is the same in both FoR so the different wavelengths produce different
frequencies.

--
John Kennaugh
"The nature of the physicists' default was their failure to insist sufficiently
strongly on the physical reality of the physical world."  Dr Scott Murray

.

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