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From: tominlaguna on 28 Oct 2009 09:11
On Fri, 16 Oct 2009 16:08:07 +0100, tominlaguna(a)yahoo.com wrote:

>I missed the opportunity to comment on this subject when a thread was
>started by Jonah Thomas last month. I hope to continue the discussion
>from this new starting point.
>Sue posted a link to a Wang & et al paper which describes their fiber
>optical gyro (FOG) experiments. That paper has been superseded by:
>http://arxiv.org/ftp/physics/papers/0609/0609235.pdf. This latest
>paper provides a more detailed account of that work.
>Figure 3 of the new Wang paper shows that when a linear section of the
>FOG is moved in translation, there is a fringe shift that is
>proportional to the length of that section and the speed of its
>motion. Most people that I have discussed this with believe that Dr.
>Wang has demonstrated that his design can detect translational motion.
>I disagree. They measured the acceleration of the fiber section from
>zero to some constant velocity.
>The Wang paper has lead me to conclude that the "Sagnac effect" is a
>phenomenon peculiar to situations when the source and/or receiver are
>experiencing acceleration. There are "Sagnac devices" that can detect
>that phenomenon, but they should not be confused with the phenomenon
>itself. Examples of the devices are: the passive Sagnac
>interferometer devices of Sagnac, Pogany, Michelson-Gale, and
>Dufour-Prunier; the active Sagnac interferometer devices of
>Macek-Davis, Stedmann, modern laser gyros; and finally the "one-way"
>Sagnac system of devices known as GPS.
>A simple analogy of the phenomenon can be understood by this example:
>Assume you have a long freight car, 100 feet long. There is a dueler
>located at each end with identical guns, ammo and skill. If the car
>is stationary with respect to the rails or moving at a constant
>velocity and both fire their guns at the same time, they both die at
>the same time. But, if the train happens to accelerate forward while
>the bullets are in flight, the guy at the rear of the car dies first.
>The same thing would occur if the car was experiencing acceleration
>throughout the gun fight. That, in my opinion, is the phenomenon of
>Sagnac. Bullets are flying in two directions covering an equal
>distance of 100 feet, but one arrives sooner than the other due to the
>acceleration of the receiver.
>Paul Anderson was describing a type of device while he thought he was
>describing the effect. The generalized Sagnac effect does not deal
>with enclosed areas and angular velocity; several detection devices
>are based on those criteria, but the phenomenon is not exclusive to
>them. Saburi in 1976 demonstrated that there was a radio signal
>transit time difference east-west between two earth-stationary
>receiver/transmitters. The GPS network is corrected each day to
>adjust their clocks so that the one-way transmission of signals is
>accurate due to the Sagnac effect. Paul also suggested the Wang
>experiment was a modified Fizeau experiment. They used both hollow
>fibers and solid cross-section fiber and got the same readings. Others
>in the past, Pogany and Harress, investigated the use of glass prisms
>in the Sagnac set-up to determine if it was a Fizeau effect, and they
>concluded it was not. Post has written about this.
>Tom Roberts erroneously states that the ballistic model cannot explain
>Sagnac. I will acknowledge that the "re-emission" ballistic model is
>denied by the Sagnac results. Tolman (1912) and Panofsky and Phillips
>(1961) describe three ballistic models. Waldron (1977) describes two
>of the three: the ballistic model of Ritz/Waldron and the re-emission
>model. The re-emission model fails in explaining Sagnac and a host of
>other experiments.
>In the Ritz/Waldron model, a mirror is not a new source, and therefore
>light may or may not be reflected at c with respect to it. Its speed
>after reflection is based on any relative motion between the source
>and the mirror. If there is no relative motion, the reflected photon
>will be moving at c; if there is relative motion, v, its speed will be
>c +/- v� all with respect to the mirror.
>Regards,
>Tom Miles

One of the more interesting aspects of the Wang experiment was the
discovery that movement of a straight section of the fibre loop, in
translation, produced a Sagnac signal.

At first, it seems counter-intuitive. The length of the fibre loop
does not change, yet moving part of it changes the optical path
length.

My original comments on the mechanism concluded that acceleration was
the mechanism. Maybe that would be too simplistic as Tom Roberts
pointed out. That would be applicable if the source was illuminated
prior to moving the straight section. But what would happen if the
source was not illuminated until after the translational motion was
linear? Would you not get the same result?

I suspect you would get the same signal.

What I see as happening is illustrated in the two diagrams below. In
the top diagram, there is a straight section of fibre of length L.
There is no translational motion (no relative motion between source,
receiver, or conduit). A photon at location A reflects off the inner
walls of the hollow fibre and eventually arrives at location B; from
there it continues to bounce of the walls until arriving at the
detector located to the right.

In the lower diagram, we have induced translational motion to that
section of the fibre by moving it to the left. Now, instead of
arriving at B, it arrives at B'. Since B' is closer to the detector,
that photon will arrive in a shorter duration of time. The opposite
occurs for the photon going in the opposite direction.


|<---------- L --------->|
__________________
� /\ /\ �
� / \ / \ �
� / \ / \ � --> to detector
� / \/ \ �
���^��������^�����
A B
|<---------- L ---------->|
__________________
� /\ /\ �
� / \ / \ �
� / \ / \ � --> to detector
� / \/ \ �
���^�������^���^��
A B B'

So how do we generalize the phenomenon? How do we best describe what
is happening? I am looking forward comments.

OFF TOPIC COMMENT: I will be travelling to California on Friday for
10 days and will not have much opportunity to participate while away.
I hope there will still be interest in this topic upon my return so I
can provide follow-up comments. I am very behind at this point having
only opened about half of the messages posted so far.


From: Androcles on 28 Oct 2009 09:30

<tominlaguna(a)yahoo.com> wrote in message
news:4uege5hevdieg6gupdcue8hs22hq291e5j(a)4ax.com...
> On Fri, 16 Oct 2009 16:08:07 +0100, tominlaguna(a)yahoo.com wrote:
>
>>I missed the opportunity to comment on this subject when a thread was
>>started by Jonah Thomas last month. I hope to continue the discussion
>>from this new starting point.
>>Sue posted a link to a Wang & et al paper which describes their fiber
>>optical gyro (FOG) experiments. That paper has been superseded by:
>>http://arxiv.org/ftp/physics/papers/0609/0609235.pdf. This latest
>>paper provides a more detailed account of that work.
>>Figure 3 of the new Wang paper shows that when a linear section of the
>>FOG is moved in translation, there is a fringe shift that is
>>proportional to the length of that section and the speed of its
>>motion. Most people that I have discussed this with believe that Dr.
>>Wang has demonstrated that his design can detect translational motion.
>>I disagree. They measured the acceleration of the fiber section from
>>zero to some constant velocity.
>>The Wang paper has lead me to conclude that the "Sagnac effect" is a
>>phenomenon peculiar to situations when the source and/or receiver are
>>experiencing acceleration. There are "Sagnac devices" that can detect
>>that phenomenon, but they should not be confused with the phenomenon
>>itself. Examples of the devices are: the passive Sagnac
>>interferometer devices of Sagnac, Pogany, Michelson-Gale, and
>>Dufour-Prunier; the active Sagnac interferometer devices of
>>Macek-Davis, Stedmann, modern laser gyros; and finally the "one-way"
>>Sagnac system of devices known as GPS.
>>A simple analogy of the phenomenon can be understood by this example:
>>Assume you have a long freight car, 100 feet long. There is a dueler
>>located at each end with identical guns, ammo and skill. If the car
>>is stationary with respect to the rails or moving at a constant
>>velocity and both fire their guns at the same time, they both die at
>>the same time. But, if the train happens to accelerate forward while
>>the bullets are in flight, the guy at the rear of the car dies first.
>>The same thing would occur if the car was experiencing acceleration
>>throughout the gun fight. That, in my opinion, is the phenomenon of
>>Sagnac. Bullets are flying in two directions covering an equal
>>distance of 100 feet, but one arrives sooner than the other due to the
>>acceleration of the receiver.
>>Paul Anderson was describing a type of device while he thought he was
>>describing the effect. The generalized Sagnac effect does not deal
>>with enclosed areas and angular velocity; several detection devices
>>are based on those criteria, but the phenomenon is not exclusive to
>>them. Saburi in 1976 demonstrated that there was a radio signal
>>transit time difference east-west between two earth-stationary
>>receiver/transmitters. The GPS network is corrected each day to
>>adjust their clocks so that the one-way transmission of signals is
>>accurate due to the Sagnac effect. Paul also suggested the Wang
>>experiment was a modified Fizeau experiment. They used both hollow
>>fibers and solid cross-section fiber and got the same readings. Others
>>in the past, Pogany and Harress, investigated the use of glass prisms
>>in the Sagnac set-up to determine if it was a Fizeau effect, and they
>>concluded it was not. Post has written about this.
>>Tom Roberts erroneously states that the ballistic model cannot explain
>>Sagnac. I will acknowledge that the "re-emission" ballistic model is
>>denied by the Sagnac results. Tolman (1912) and Panofsky and Phillips
>>(1961) describe three ballistic models. Waldron (1977) describes two
>>of the three: the ballistic model of Ritz/Waldron and the re-emission
>>model. The re-emission model fails in explaining Sagnac and a host of
>>other experiments.
>>In the Ritz/Waldron model, a mirror is not a new source, and therefore
>>light may or may not be reflected at c with respect to it. Its speed
>>after reflection is based on any relative motion between the source
>>and the mirror. If there is no relative motion, the reflected photon
>>will be moving at c; if there is relative motion, v, its speed will be
>>c +/- v. all with respect to the mirror.
>>Regards,
>>Tom Miles
>
> One of the more interesting aspects of the Wang experiment was the
> discovery that movement of a straight section of the fibre loop, in
> translation, produced a Sagnac signal.
>
> At first, it seems counter-intuitive. The length of the fibre loop
> does not change, yet moving part of it changes the optical path
> length.
>
> My original comments on the mechanism concluded that acceleration was
> the mechanism. Maybe that would be too simplistic as Tom Roberts
> pointed out. That would be applicable if the source was illuminated
> prior to moving the straight section. But what would happen if the
> source was not illuminated until after the translational motion was
> linear? Would you not get the same result?
>
> I suspect you would get the same signal.
>
> What I see as happening is illustrated in the two diagrams below. In
> the top diagram, there is a straight section of fibre of length L.
> There is no translational motion (no relative motion between source,
> receiver, or conduit). A photon at location A reflects off the inner
> walls of the hollow fibre and eventually arrives at location B; from
> there it continues to bounce of the walls until arriving at the
> detector located to the right.
>
> In the lower diagram, we have induced translational motion to that
> section of the fibre by moving it to the left. Now, instead of
> arriving at B, it arrives at B'. Since B' is closer to the detector,
> that photon will arrive in a shorter duration of time. The opposite
> occurs for the photon going in the opposite direction.
>
>
> |<---------- L --------->|
> __________________
> � /\ /\ �
> � / \ / \ �
> � / \ / \ � --> to detector
> � / \/ \ �
> ���^��������^�����
> A B
> |<---------- L ---------->|
> __________________
> � /\ /\ �
> � / \ / \ �
> � / \ / \ � --> to detector
> � / \/ \ �
> ���^�������^���^��
> A B B'
>
> So how do we generalize the phenomenon? How do we best describe what
> is happening? I am looking forward comments.
>

Since is just a short straight part of this, it's nothing remarkable.
http://www.androcles01.pwp.blueyonder.co.uk/Sagnac/MechSagnac.gif
(All three gears are rotating in the same direction.)
http://www.androcles01.pwp.blueyonder.co.uk/Sagnac/Sagnac.htm
and scroll down to "Deception:"





> OFF TOPIC COMMENT: I will be travelling to California on Friday for
> 10 days and will not have much opportunity to participate while away.
> I hope there will still be interest in this topic upon my return so I
> can provide follow-up comments. I am very behind at this point having
> only opened about half of the messages posted so far.
>
>


From: Darwin123 on 29 Oct 2009 16:31
On Oct 28, 2:23 am, "Androcles" <Headmas...(a)Hogwarts.physics_p> wrote:
> "Darwin123" <drosen0...(a)yahoo.com> wrote in message
>
> news:73e81849-45bc-497b-b260-6460f062bc97(a)s31g2000yqs.googlegroups.com...
> On Oct 27, 6:49 pm, "Androcles" <Headmas...(a)Hogwarts.physics_p> wrote:
>
> > "Darwin123" <drosen0...(a)yahoo.com> wrote in message
>
> >news:8726a9ec-2c0d-4d34-a1d5-cedf92ed3415(a)y23g2000yqd.googlegroups.com....
> > On Oct 27, 3:16 pm, "Androcles" <Headmas...(a)Hogwarts.physics_p> wrote:
>
> Michelson interferometers do not output intensity, you idiot.
The output of the Michaelson inteferometer is spectral lines, which
can be described as power collected at different angles. The measured
output is proportional to the power detected at a certain angle. One
can analyze an intensity normalized to the peak values. However, a
more quantitative description can be made of the output.
which are measured in radiant intensity. The units of radiant
intensity are watts per steradian.
Since the radiant intensity is normalized, one can describe the
output in other ways depending on the detector used. The intensity of
the output can be decribed as a radiance (watts/srm^2) or spectral
irradiance (Watts per m^2 per nm^2).
The ouput of a Sagnac interferometer can also be described in
terms of intensity. The common implementation would be proportional to
the radiant flux, which is output power. One would measure the power
output as a function of time. However, The radiant flux can also be
normalized to the peak radiant flux. So again, there are several
different quantities that may describe the output of the Sagnac
cavity.
Regardless, you don't seem to have a clear idea of what is
measured from these interferometers.
From: Androcles on 29 Oct 2009 16:51

"Darwin123" <drosen0000(a)yahoo.com> wrote in message
news:d7ddf893-256c-4aa1-b9a8-b3fa79ce0106(a)y32g2000prd.googlegroups.com...
On Oct 28, 2:23 am, "Androcles" <Headmas...(a)Hogwarts.physics_p> wrote:
> "Darwin123" <drosen0...(a)yahoo.com> wrote in message
>
> news:73e81849-45bc-497b-b260-6460f062bc97(a)s31g2000yqs.googlegroups.com...
> On Oct 27, 6:49 pm, "Androcles" <Headmas...(a)Hogwarts.physics_p> wrote:
>
> > "Darwin123" <drosen0...(a)yahoo.com> wrote in message
>
> >news:8726a9ec-2c0d-4d34-a1d5-cedf92ed3415(a)y23g2000yqd.googlegroups.com...
> > On Oct 27, 3:16 pm, "Androcles" <Headmas...(a)Hogwarts.physics_p> wrote:
>
> Michelson interferometers do not output intensity, you idiot.
The output of the Michaelson inteferometer is spectral lines, which
can be described as power collected at different angles.
=======================================
Learn to spell the man's name, it is "Michelson".
Interference fringes look like this, they are not spectra.
http://upload.wikimedia.org/wikipedia/en/9/90/Michelson_Interferometer_Laser_Interference_Fringes-Red.jpg



From: Darwin123 on 29 Oct 2009 16:56
On Oct 27, 10:02 am, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote:
> Jonah Thomas wrote:
> > I haven't seen an argument yet why there shouldn't be frequency
> > differences in Sagnac.
>
> A light source emits periodic waves, but as I have discussed before, one
> must consider a short light pulse.
One can validly describe the system in terms of wave packets. This
is what you are describing. However, the wave packet will itself have
a spectrum one can find by Fourier analysis. These components can and
are Doppler shifted. The clockwise pulse will have components shifted
differently from the counterclockwise pulse.
I think there is some pedagogical confusion with your
representation because the short pulse has a spectral bandwidth. This
would complicate the analysis. The spectral bandwidth of each pulse is
not effected by Doppler shift. I think this spectral bandwidth is what
you mean by saying the "frequency is not changed." However, the
carrier wave frequency will be changed by Doppler shift. So will the
phase when they meet again. You may mean "wave front" instead of
"short pulse".
I think Jonah's problem is the following: His right brain is
Fourier analyzing that short pulse without telling his left brain that
a Fourier analysis is being performed. His left brain reads your post
that says that the frequency of the pulse doesn't change. His left
brain then asks you how come the Fourier components don't change in
frequency.
Now your problem is that your left brain has Fourier analyzed
that short pulse without telling the right brain that it has done so.
So your right brain still thinks there has been no frequency change.
Your left reads his post that the frequency must change, but delegates
the answer to his question to your right brain. Your right brain tell
him that there is no frequency change, just look at that short pulse.
This is why I have never tried to become a psychologist |:-)
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