Wang / Sagnac Devices [Relativity]

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From: Jonah Thomas on 25 Oct 2009 18:30

Sam <shayiam(a)yahoo.com> wrote:
> Jonah Thomas <jethom...(a)gmail.com> wrote:

> > If a ballistic theory predicts that the speed of light
> > depends on the speed of its source, then in every early
> > Sagnac experiment the light went the same speed in two
> > different directions, according to an inertial observer.
>
> Right, relative to the instantaneous rest frame of the emission point.
> So, relative to the Galilean rest frame of the hub, the light is going
> faster in the direction of rotation than in the opposite direction.

No, the light goes the same speed in all directions if its speed depends
on the speed of its emitter. When you start with one light source, that
light source has a speed. Period.

> > Jonah Thomas <jethom...(a)gmail.com> wrote:
> > The only way to get a change in lightspeed in that experiment
> > comes if somehow mirrors bounce light at different speeds,
> > or a change in direction changes the speed, etc.
>
> There's no change in speed (to the first order). Each pulse has the
> speed c relative to the rest frame of it's emitter at the instant of
> emission, and this is true for each of the successive emissions from
> the mirrors along the path.

There you go, if you figure it's continually re-emitted then its speed
will be c plus the average speed of all the emitters.

To avoid problems for non-ballistic theories the re-emission has to
happen instantaneously. Start with a nonemission theory approach to a
fiber-optic system. The light travels at about 2/3 c. If the other 1/3
of the time the light is being absorbed and re-emitted, then the light
will travel at 2/3 c + 1/3 v in one direction, and 2/3 c - 1/3 v in the
other.

> As a result, relative to the hub frame,
> the forward pulse is always moving faster than the rearward pulse,
> because the mirrors are moving in the forward direction, and the
> pulses are moving at c relative to the mirrors.

This requires a particular emission theory, one that says light is
reflected at c relative to reflectors. Your claim is false for all other
emission theories.

> In addition, relative
> to the hub frame, the forward pulse has a greater distance to travel,
> exactly proportional to its greater speed, so the two pulses arrive at
> the detector simultaneously.

If the speed depends on the original emitter, then all the light travels
at the same speed because it started out with a single emitter
travelling at some speed, and then the beams got split.

> >Jonah Thomas <jethom...(a)gmail.com> wrote:
> > Simple straighforward ballistic theories would say that
> > the light travels at the same speed relative to an inertial
> > observer...
>
> But not just any inertial observer. As I mentioned before, when people
> talk about simple ballistic theory they generally mean a theory based
> on Galilean relativity, and one that says light travels at the same
> speed, c, relative to the inertial rest frame coordinates of the
> emitter at the time of emission. This implies that light does not have
> the speed c in terms of other inertial coordinate systems in Galilean
> spacetime. In particular, for a Sagnac device with the mirrors moving
> at v relative to the hub, light pulses move at c+v and c-v relative to
> the hub, and so arrive simultaneously at the detector.

If the speed of the light depends on the speed of the emitter, then an
inertial observer might think the light travels at c+v or c-v etc. But
the light travels at that speed in both directions.

From: Jonah Thomas on 25 Oct 2009 18:39

HW@..(Henry Wilson DSc). wrote:
> Jonah Thomas <jethomas5(a)gmail.com> wrote:

> >Bear with me on this. I might be wrong, but my argument is simple and
> >ought to be easy to understand.
> >
> >Until we had laser cavities that sent the same light in opposite
> >directions, physicists who did the Sagnac experiment always started
> >with a single light source and then used a beam-splitter etc to
> >convert it into two separate beams of light.
> >
> >If a ballistic theory predicts that the speed of light depends on the
> >speed of its source, then in every early Sagnac experiment the light
> >went the same speed in two different directions, according to an
> >inertial observer.
>
> How did you come to that conclusion?

Single light source. This source emits light at some speed, maybe c-v.
(Note Androcles's diagram of the original Sagnac experiment, in which
the light source faces *against* the direction of travel.)

Once the single light source emits light at a single speed, what will
make the light change speed? Emission theories which predict that light
changes speed regularly might give you light that arrives at the
detector at the same time. But emission simple emission theories will
predict one light speed for the Sagnac experiment, and the light will
arrive at the detector at different times.

> >When the light is emitted it is one light beam
> >emitted in one direction. The only way to get a change in lightspeed
> >in that experiment comes if somehow mirrors bounce light at different
> >speeds, or a change in direction changes the speed, etc. Simple
> >straighforward ballistic theories would say that the light travels at
> >the same speed relative to an inertial observer, so the light in one
> >direction arrives sooner than the light from the other direction, and
> >the difference in arrival time would be essentially the same as that
> >predicted by other theories. Since this class of theories does not
> >predict zero effect it is not refuted by Sagnac.
>
> Either you didn't explain this correctlyor your are plainly wrong.
> BaTh predicts different path lengths and identical travel times. It
> also says light cannot be regarded as a simple oscillator with
> classical 'phase angle'. Interference is caused by different number of
> 'wavelengths' in each path.

Sure, that's your emission theory. But that isn't the only way to do an
emission theory.

> A photon is like a length of ball chain. Do you know what 'ball chain'
> is?
>
> >Now we have lasers that push light in two opposite directions. Align
> >those with the direction of travel and ballistic theories should
> >predict the light will travel at c+v and c-v, relative to an inertial
> >observer. But before those were available -- 60 years? 70 years? --
> >the majority of physicists said that Sagnac refuted ballistic
> >theories when it obviously did not. Why were they so sloppy? Perhaps
> >they were not interested in ballistic theories so they were ready to
> >just slide by them. Perhaps some other experiment really did refute
> >all ballistic theories, and physicists did not care whether Sagnac
> >was falsely claimed to refute them because they were known to be
> >false regardless.
> >
> >> In general, any serious theory that has been called a "ballistic"
> >or> "emission" theory by its proponents is refuted by the Sagnac
> >effect.
> >
> >That used to be false, for the large majority of the years that it
> >was claimed. With fiber optics and lasers that create light that
> >travels in opposite directions and still interferes, it might easily
> >be true now.
>
> The usual argument against Bath is that a rotating Sagnac ring viewed
> in the rotating frame is identical to a nonrotating one viewed in the
> nonrotating frame.

Well, dismiss that argument, it's worthless.

From: Androcles on 25 Oct 2009 18:49

From: Jonah Thomas on 25 Oct 2009 19:31

"Androcles" <Headmaster(a)Hogwarts.physics_p> wrote:
> "Jonah Thomas" <jethomas5(a)gmail.com> wrote
> news:20091025183002.5fbe3867.jethomas5(a)gmail.com...
> > Sam <shayiam(a)yahoo.com> wrote:
> >> Jonah Thomas <jethom...(a)gmail.com> wrote:
> >
> >> > If a ballistic theory predicts that the speed of light
> >> > depends on the speed of its source, then in every early
> >> > Sagnac experiment the light went the same speed in two
> >> > different directions, according to an inertial observer.
> >>
> >> Right, relative to the instantaneous rest frame of the emission
> >point.> So, relative to the Galilean rest frame of the hub, the light
> >is going> faster in the direction of rotation than in the opposite
> >direction.
> >
> > No, the light goes the same speed
>
> No, relative to the Galilean rest frame of the hub, the light is going
> faster in the direction of rotation than in the opposite direction.

Look at your diagram of the original Sagnac experiment. There is one
light source that points in one direction, backward compared to the
direction of motion. The light leaves the source at one speed. It goes
into a beam-splitter and comes out as two beams. Do they travel at
different speeds? Sure, some emission theories say they do, notably the
Ritz version. But not all. They bounce off mirrors.

Do they then travel at different speeds? Sure, some emission theories
say they do. But not all.

If a particular emission theory says they travel at diferent speeds in
different directions in the Sagnac experiment, it is because it says the
beam-splitter nd mirrors change the speed. The light is emitted at one
speed for every theory, emission, classical, relativist, you name it.

From: Inertial on 25 Oct 2009 19:48

"Jonah Thomas" <jethomas5(a)gmail.com> wrote in message
news:20091025183002.5fbe3867.jethomas5(a)gmail.com...
> Sam <shayiam(a)yahoo.com> wrote:
>> Jonah Thomas <jethom...(a)gmail.com> wrote:
>
>> > If a ballistic theory predicts that the speed of light
>> > depends on the speed of its source, then in every early
>> > Sagnac experiment the light went the same speed in two
>> > different directions, according to an inertial observer.
>>
>> Right, relative to the instantaneous rest frame of the emission point.
>> So, relative to the Galilean rest frame of the hub, the light is going
>> faster in the direction of rotation than in the opposite direction.
>
> No, the light goes the same speed in all directions if its speed depends
> on the speed of its emitter.

Relative to the emitter.

> When you start with one light source, that
> light source has a speed. Period.

It has an infinite number of speeds.

>> > Jonah Thomas <jethom...(a)gmail.com> wrote:
>> > The only way to get a change in lightspeed in that experiment
>> > comes if somehow mirrors bounce light at different speeds,
>> > or a change in direction changes the speed, etc.
>>
>> There's no change in speed (to the first order). Each pulse has the
>> speed c relative to the rest frame of it's emitter at the instant of
>> emission, and this is true for each of the successive emissions from
>> the mirrors along the path.
>
> There you go, if you figure it's continually re-emitted then its speed
> will be c plus the average speed of all the emitters.

Yes .. which are in the same direction as one light beam and in the opposite
direction to the other. And so you get two different speeds.

> To avoid problems for non-ballistic theories the re-emission has to
> happen instantaneously.

There is no problem in non-ballistic theories.. they predict the observed
results

> Start with a nonemission theory approach to a
> fiber-optic system. The light travels at about 2/3 c. If the other 1/3
> of the time the light is being absorbed and re-emitted, then the light
> will travel at 2/3 c + 1/3 v in one direction, and 2/3 c - 1/3 v in the
> other.
>
>> As a result, relative to the hub frame,
>> the forward pulse is always moving faster than the rearward pulse,
>> because the mirrors are moving in the forward direction, and the
>> pulses are moving at c relative to the mirrors.
>
> This requires a particular emission theory, one that says light is
> reflected at c relative to reflectors. Your claim is false for all other
> emission theories.
>
>> In addition, relative
>> to the hub frame, the forward pulse has a greater distance to travel,
>> exactly proportional to its greater speed, so the two pulses arrive at
>> the detector simultaneously.
>
> If the speed depends on the original emitter, then all the light travels
> at the same speed because it started out with a single emitter
> travelling at some speed, and then the beams got split.
>
>> >Jonah Thomas <jethom...(a)gmail.com> wrote:
>> > Simple straighforward ballistic theories would say that
>> > the light travels at the same speed relative to an inertial
>> > observer...
>>
>> But not just any inertial observer. As I mentioned before, when people
>> talk about simple ballistic theory they generally mean a theory based
>> on Galilean relativity, and one that says light travels at the same
>> speed, c, relative to the inertial rest frame coordinates of the
>> emitter at the time of emission. This implies that light does not have
>> the speed c in terms of other inertial coordinate systems in Galilean
>> spacetime. In particular, for a Sagnac device with the mirrors moving
>> at v relative to the hub, light pulses move at c+v and c-v relative to
>> the hub, and so arrive simultaneously at the detector.
>
> If the speed of the light depends on the speed of the emitter, then an
> inertial observer might think the light travels at c+v or c-v etc. But
> the light travels at that speed in both directions.

'Might think'? Either it does or does not. 'At that speed' .. at what
speed?