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From: Androcles on 19 Oct 2009 13:22

<tominlaguna(a)yahoo.com> wrote in message
news:snuod5h68j0apkqo99c4vcn4f5lhjtd456(a)4ax.com...
> The re-emission theory claim is that light is c relative to its source
> AND all points of reflection. In other words, a mirror becomes a new
> source. Sagnac disproves that hypothesis.


No it does not.

(4) I'm walking with respect to the ground while watching a man
who is also walking with respect to the ground light a cigarette.
Light from the flame leaves the lighter at c-v with respect to the
ground because he is moving, and it arrives at my eyes at a
speed (c-v)+v with respect to me because I am moving.


From: Darwin123 on 19 Oct 2009 16:29
On Oct 17, 2:08 am, tominlag...(a)yahoo.com wrote:
> On Fri, 16 Oct 2009 09:01:34 -0700 (PDT), "Dono." <sa...(a)comcast.net>
> wrote:
>
>
>
> >On Oct 16, 8:43 am, tominlag...(a)yahoo.com wrote:
> >> On Fri, 16 Oct 2009 08:31:15 -0700 (PDT), "Dono." <sa...(a)comcast.net>
> >> wrote:
>
> >> >On Oct 16, 8:08 am, tominlag...(a)yahoo.com wrote:
>

> First, please let me know which
> Ives experiment you are discussing.  I was not aware of an Ives
> experiment that tested the Sagnac effect.
Charles Ives was a physicist who strongly disblieved in general
relativity. This is Charles Ives the physicist, not Charles Ives the
composer. In any case, he wrote some books on why general relativity
is wrong. Most of his "experiments" were thought experiments. I read
some pages in Ives book relating to the Sagnac effect. I believe Ives
analysis was wrong.
Charles Ives described a thought experiment to show why the
Sagnac effect contradicted relativity. He never actually performed
this experiment, but simply guessed what the results would be based on
symmetry. However, the symmetry that he hypothesized did not exist in
the equivalent real-world systme.
He proposed a Sagnac interferometer consisting of a highly
reflective ring of material. There would not be separate mirror, but a
continuous curve of reflective material. He proposed that the ring was
completely circular, so that the optical system had complete radial
symmetry. A rotation by any angle would not change the system, in his
model, by any amount. Suppose two traveling waves are propagating in
opposite directions in this circular cavity.
His argument was that since the cavity is radially symmetric,
there is no way the light waves can "know" that the cavity was
rotating. The surface of this smooth cavity is smooth and featureless.
Motion can not show itself on a featureless surface. Thus there could
be no beats between the two waves, and thus no Sagnac effect. Since
the Saganc effect is predicted by relativity, the fact there is no
Sagnac effect for such a cavity means relativity is wrong.
Note he didn't make the main error provided by members of the
group. He did not claim the Saganc effect contradicts relativity. His
arguement was that the Sagnac effect couldn't exist under certain
conditions that were consistent with relativity.
First, let me point out that such a system has been made.
Sagnac cavities have been constructed using fibers connected in a
circle. There are no separate mirrors in such a cavity. The reflective
surface is a continuous curve. The Sagnac effect has been observed
with such continuously curved surfaces. So what went wrong with Ives'
analysis?
1) The cavity, though "continuously curved," is made of atoms. Thus,
it did break down.
2) The free electrons on the surface, that cause the reflection of
light, are also discrete up to the limits of quantum mechanics.
3) The light itself consists of nodes and antinodes. Thus, the
illuminated surface is not flat and featureless. There are regions
with oscillating electrons, and these are forced to rotate by the
elastic forces in the cavity.
So his Ives argument is wrong.
Now Ives the composer really made good music!
From: Inertial on 19 Oct 2009 18:18

<tominlaguna(a)yahoo.com> wrote in message
news:snuod5h68j0apkqo99c4vcn4f5lhjtd456(a)4ax.com...
> On Mon, 19 Oct 2009 23:03:57 +1100, "Inertial" <relatively(a)rest.com>
> wrote:
>
>>
>><tominlaguna(a)yahoo.com> wrote in message
>>news:sqfod5hhbbd0o9bg90letn9p4gc8303ffe(a)4ax.com...
>>> On Mon, 19 Oct 2009 19:02:28 +1100, "Inertial" <relatively(a)rest.com>
>>> wrote:
>>>
>>>>
>>>><tominlaguna(a)yahoo.com> wrote in message
>>>>news:e63od5t7bl229oahgcrjfud7ts7f1i113f(a)4ax.com...
>>>>> On Sun, 18 Oct 2009 18:58:18 +0100, "Androcles"
>>>>> <Headmaster(a)Hogwarts.physics_p> wrote:
>>>>>
>>>>>>
>>>>>><tominlaguna(a)yahoo.com> wrote in message
>>>>>>news:lt7md512qegmkrme8hh6h7icq47u302ht4(a)4ax.com...
>>>>>>> On Sat, 17 Oct 2009 12:21:32 +0100, "Androcles"
>>>>>>> <Headmaster(a)Hogwarts.physics_p> wrote:
>>>>[snip]
>>>>>>>>Both contain the same blunder, namely, there are two angles alpha
>>>>>>>>and -alpha not one, as shown here,
>>>>>>>>
>>>>>>>> http://www.androcles01.pwp.blueyonder.co.uk/Sagnac/SagnacIdiocy.htm
>>>>
>>>>There are lots of angles, alpha and -alpha, made by the beams relative
>>>>to
>>>>the start/end point in the rotating frame .. which is what Androcles
>>>>animation in that page shows. Those angles both end up as zero when the
>>>>beams meet at the detector.
>>>>
>>>>Of course, this is not the alpha described in the article. Androcles is
>>>>confused. The article describes alpha as the amount the start/end has
>>>>rotated from its initial position, in the non-rotating frame. Androcles
>>>>doesn't understand that, as is obvious from his irrelevant animation and
>>>>nonsensical questions in red on that page.
>>>
>>> I agree with most all that you have said regarding the analysis of the
>>> Mathpages diagram. I don't understand the Androcles animation.
>>
>>Not surprising .. he doesn't understand Sagnac :)
>>
>>>>In emission theory, there is only one alpha value (ioe one angle through
>>>>whic h the start/end point has rotated in the non-rotating frame) when
>>>>the
>>>>beams arrive back at the start/end location. Because the rays meet
>>>>simultaneously, there is no phase shift.
>>>
>>> I do disagree with your comments about the emission theory. You
>>> appear to be claiming that photons are travelling at c +/- omega*R.
>>
>>They travel in emission theory at c wrt the source ..
>
> Correct.

Good

>>which makes it c+/-v
>>in the non-rotating frame (because the source is travelling at v at the
>>time
>>of emission)
>
> I'm not following you.

Its very simple. Try.

> We are only interested in knowing what is
> happening in the experiment that produces the signal.

That is all I am talking about

> Before
> rotation,

You mean if the whole experiment does not rotate? Then in the non-rotating
frame the source is at rest so the 'v' of the source is 0. c+v=c and c-v=c.

When the entire device rotates, as viewed from the non-rotating frame, at
the point the light is emitted the source has a velocity v. So, according
to emission theory, the light travels at c+v and c-v according to a
non-rotating observer.

There's no magic here .. nothing special about it being light .. you'd get
the same if you're talking about a gun shooting bullets in opposite
directions.

> the light is c relative to the source and during rotation it
> is still c relative to the source.

In the rotating frame .. yes .. and hence when the light arrives back at the
source the two beams arrive at the same time and so with no phase difference
and so no sagnac effect .. hence refuting emission theory

>>How does your pet emission theory differ?
>
> The re-emission theory claim is that light is c relative to its source
> AND all points of reflection. In other words, a mirror becomes a new
> source. Sagnac disproves that hypothesis. I adopt the Stewart (1911)
> definition which says light is reflected at c with respect to the
> mirror image of its source.

So .. if the mirror is moving toward the source, then the reflected light
goes slower wrt the mirror, and if the mirror is moving away from the
source, then the reflected light goes faster wrt the mirror .. how can that
happen .. how can light travelling at c-v when it hits the source reflect at
c+v. How does the mirror or light know that it has to speed up or slow
down.

What happens then with light made to travel around the circular path .. does
its speed stay the same, or does it continually alternate between c+v and
c-v?



From: Jonah Thomas on 19 Oct 2009 20:13
Darwin123 <drosen0000(a)yahoo.com> wrote:

> Charles Ives was a physicist who strongly disblieved in general
> relativity. This is Charles Ives the physicist, not Charles Ives the
> composer. In any case, he wrote some books on why general relativity
> is wrong. Most of his "experiments" were thought experiments. I read
> some pages in Ives book relating to the Sagnac effect. I believe Ives
> analysis was wrong.
> Charles Ives described a thought experiment to show why the
> Sagnac effect contradicted relativity. He never actually performed
> this experiment, but simply guessed what the results would be based on
> symmetry. However, the symmetry that he hypothesized did not exist in
> the equivalent real-world systme.
> He proposed a Sagnac interferometer consisting of a highly
> reflective ring of material. There would not be separate mirror, but a
> continuous curve of reflective material. He proposed that the ring was
> completely circular, so that the optical system had complete radial
> symmetry. A rotation by any angle would not change the system, in his
> model, by any amount. Suppose two traveling waves are propagating in
> opposite directions in this circular cavity.
> His argument was that since the cavity is radially symmetric,
> there is no way the light waves can "know" that the cavity was
> rotating. The surface of this smooth cavity is smooth and featureless.
> Motion can not show itself on a featureless surface. Thus there could
> be no beats between the two waves, and thus no Sagnac effect. Since
> the Saganc effect is predicted by relativity, the fact there is no
> Sagnac effect for such a cavity means relativity is wrong.
> Note he didn't make the main error provided by members of the
> group. He did not claim the Saganc effect contradicts relativity. His
> arguement was that the Sagnac effect couldn't exist under certain
> conditions that were consistent with relativity.
> First, let me point out that such a system has been made.
> Sagnac cavities have been constructed using fibers connected in a
> circle. There are no separate mirrors in such a cavity. The reflective
> surface is a continuous curve. The Sagnac effect has been observed
> with such continuously curved surfaces. So what went wrong with Ives'
> analysis?

If the emitter and the detector move with the mirror, which they had
probably better do, then you get a Sagnac effect because they are
moving. I believe you could get a sagnac effect with the source and
detector moving even if they were bouncing light off mirrors that did
not move. But like Ives I have not done the experiment.

> 1) The cavity, though "continuously curved," is made of atoms. Thus,
> it did break down.
> 2) The free electrons on the surface, that cause the reflection of
> light, are also discrete up to the limits of quantum mechanics.
> 3) The light itself consists of nodes and antinodes. Thus, the
> illuminated surface is not flat and featureless. There are regions
> with oscillating electrons, and these are forced to rotate by the
> elastic forces in the cavity.

I doubt all that matters. Get your detector and emitter moving along the
mirror cylinder and you'll get a Sagnac effect with the mirror not
moving at all. If it doesn't matter whether the mirror moves then it
does not matter abouut the astoms and the free electrons and the
antinodes.

But I could be wrong.
From: Inertial on 19 Oct 2009 20:23

"Jonah Thomas" <jethomas5(a)gmail.com> wrote in message
news:20091019110349.12a07b51.jethomas5(a)gmail.com...
[snip]
> I want to take this opportunity to review my understanding of emission
> theory.
>
> The fundamental tenet of emission theory is that light in vacuum travels
> at speed c relative to its source.

Yes .. just like a bullet out of a gun

> The reason this is important is that
> it could possibly provide a simpler and more intuitive approach to
> derive relativity.

Relativity says the same thing. Light always travels at c relative to its
source.

However, the nature of spacetime and how velocities combine when you change
frames of reference means that c (+) v = c (where (+) is the velocity
composition operator). So when you 'add' the velocity of the source to the
speed of light, you still get c.

> Light sources often appear to produce concentric waves.
> http://i847.photobucket.com/albums/ab31/jehomas/concentric.gif
>
> But when they move they are thought to compress those waves.
> http://i847.photobucket.com/albums/ab31/jehomas/eccentric.gif

Thats right.

Its because the emission point of each successive wavefront is not the same
point as the previous wave front

> If you could tell whether the waves were compressed then you could get a
> handle on absolute motion. But instead special relativity (SR) says that
> time and space are distorted so that everybody sees what they ought to
> see.

What you show in that diagram is what SR says you would see.

> But if the light moved at c+v and c-v etc,

If the + and - are velocity composition, then that is what SR says it does.

> then everybody would see it
> moving the same way without requiring time dilation and length
> contraction.

Why should everyone see the same thing?

> You might still get some time dilation etc, but some of the
> weirdness might vanish. This is why it is an issue on
> sci.physics.relativity. If it was only a question of precisely how light
> works, then it would be more a question for sci.physics.electromag. But
> since it could affect relativity, some of the people who are biased
> against SR want emission theory to be true, while the people who are
> biased in favor of SR categorically deny any possibility that any form
> of emission theory could possibly be true.

Its not a matter of bias.

> The problem I run into is that it appears nobody understands emission
> theory well enough to give a convincing argument what it should do.

Its not the emmission itself, what it is is that emmision theory assumes
reality is simple euclidean goemetry, newtonian physics and galilean
transfroms. Experiment shows reality isn't like that.

> People often use ideas that work well when lightspeed is a constant,
> which do not apply when lightspeed varies.

The net speed light travels through a medium can be less than c, of course.
And then the speed is observer dependant.

> For example, Androcles says that (mostly?) you cannot measure
> wavelength. You can only measure frequency. Well, of course you can
> measure wavelength with an interferometer. Intererence patterns depend
> only on wavelength, not on frequency or speed.

Yeup

> That is, they depend only
> on wavelength when the speed is constant. When you have light that comes
> into the interferometer at different speeds,

Why would you do that?

> then frequency and speed do
> matter and you cannot predict interference patterns knowing only
> wavelength and the phase shift at the entrance.

You use an interferometer on light from a known source.

> For emission theory to have a good effect on relativity, it's necessary
> that the wavelength be the same independent of the lightspeed,

Which experiment shows is not the case

> so that
> the light will look like
> http://i847.photobucket.com/albums/ab31/jehomas/concentric.gif instead
> of http://i847.photobucket.com/albums/ab31/jehomas/eccentric.gif
> If the wavelength is constant, then frequency must vary with speed. So
> OK, your lightbeam has been split into two parts that travel at
> different speeds. (Exactly why emission-theory light should travel at
> different speeds in a Sagnac or Wang apparatus is one of the things we
> don't have clear. Some people say it might not, for one reason or
> another.) The two arrive at the detector at the same time, with
> different speeds

As measure by whom? Speed is relative to the observer.

In sagnac, both the beams arrive at the detector at c relative to the
detector. According to emission theory, relative to the detector, they take
the same time to get there, they have the same wavelength and the same
frequency.

[snip more of the same]

> To construct an emission theory you must specify what light does on
> reflection, what it does on refraction, and how interference works for
> light that travels at different speeds.

Except, of course, there are experiments that show that light from a moving
source does not travel at c+v. Which rules out all emission theories.

But if we ignore that for now (as emmision theory supported do all the
time), and are just looking at how to explain Sagnac, then changing how
light reflects can give you the speeds you require. But how a mirror can
make light that arrives at a lower speed get reflected at a higher speed,
and how light or the mirror knows what speed to reflect at, noone seems to
know.


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