Why are the 'Fixed Stars' so FIXED?

On Wed, 24 Oct 2007 21:47:32 -0700, Jerry
wrote:

On Oct 24, 4:14 pm, HW@....(Dr. Henri Wilson) wrote:
On Wed, 24 Oct 2007 02:13:45 -0700, Jerry
wrote:
On Oct 24, 3:10 am, George Dishman wrote:
On 23 Oct, 22:32, HW@....(Clueless Henri Wilson) wrote:

Incidentally, this also tends to suggest that the fringe
production in a sagnac interferometer is something to do
with the phase relationship between INCOMING and OUTGOING
rays rather than the rejoining of the two oppositely moving
rays...I know that sounds impossible...but is it?

Yes, for two reasons. The simpler is that if
you look at the arrangement of the beam
splitter, the remaining light goes back to
the lamp but the more robust is that there
would be a path length difference of nearly
a metre (the loop length) between the originated
light and that which has bone round the loop.
That grossly exceeds the coherence length for
a filament source so there is no way to form
fringes with a detectable contrast ratio.

I think that you have gone -way- over Henri's head with
mention of coherence length.

To Henri:

Early experimentalists such as Michelson and Morley, Sagnac
etc. used monochromatic sources only during the alignment
stages while setting up their interferometers. Actual
experimental runs were always performed with white light.
The reason for this is that white light creates a distinctive
pattern of a central bright white fringe surrounded by a
rapidly fading set of colored fringes. The advantage of this
is that the central fringe of equal path length is always
readily identifiable, whereas monochromatic light produces
uniform fringes in which it is virtually impossible to
determine the central fringe of equal path length.

The distinctive pattern of fringes formed by white light
enabled Michelson and Morley, who recorded their observations
visually, not to "get lost" while figuring out how far their
fringes were displaced from their fiducial marks. In the
Michelson and Gale experiment, which was a giant Sagnac
setup, the central fringe, in the absence of rotation, would
appear precisely midway between the two images of the slit.
This enabled them to calibrate their apparatus for zero
rotational velocity; it was thus not necessary for them to
halt the rotation of the Earth to get a zero reading, which
would have been somewhat impractical in the absence of divine
intervention (Joshua 10:12-15).

Note that I stated that the pattern of colored fringes
surrounding the central bright fringe fades rapidly. This is
because the spacing between the red fringes and the blue
fringes is different. Within a few fringe widths from the
central fringe, the colored fringes overlap until the fringe
pattern is no longer perceptible. Since each fringe represents
a half wave difference in path length to the two images of the
source slit, this means that the path lengths must be
precisely matched, otherwise it would be impossible to see any
fringes at all.

This distance to which the path lengths must be matched,
otherwise fringes are invisible, is known as the "coherence
length". The coherence length for white light is no more
than a handful of microns. Your notion that "fringe
production in a sagnac interferometer is something to do with
the phase relationship between INCOMING and OUTGOING rays
rather than the rejoining of the two oppositely moving rays"
is totally ridiculous to anybody who knows anything at all
about optics.

The sensible thing to do is use monochromatic light and tilt
the top miror slightly in order to produce an 'optical wedge'
effect. That produces a straight line fringe pattern rather
than circles. Straight lines are easier to count than circles
and in the case of gyros, make the direction of an acceleration
easy to determine.

You have COMPLETELY lost the point. Earlier, you made the stupid
and asinine speculation that "fringe production in a sagnac
interferometer [has] something to do with the phase relationship
between INCOMING and OUTGOING rays rather than the rejoining of
the two oppositely moving rays."

George's point was that since white light Sagnac interferometers
are perfectly functional, your speculation is dead in the water.

You didn't read properly. I SAID IT WAS IMPOSSIBLE.


Hasn't it dawned on you yet that you are pontificating on matters
of which you are both ignorant and incompetent?

You are a joke....

see: http://www.users.bigpond.com/hewn/ringgyro.exe

(It doesn't work too well on Vista....will fix)

This shows the difference between your 'moving squiggly line' theory and mine.

The dots represent 'wavelengths'. The two rays meet together at the detector in
both theories...but for different reasons.
You say the phases are the same.
I say the phases are indicated by the 'circle of white teeth'....The arrival
phase for each is (pathlength mod lambda) .
If the phase of one ray is x degrees, then that of the other is 360-x


Henri Wilson. ASTC,BSc,DSc(T)

www.users.bigpond.com/hewn/index.htm