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Re: Ballistic Theory and the Sagnac Experiment

Subject: Re: Ballistic Theory and the Sagnac Experiment
From: "Jeff Root"
Date: 25 Mar 2006 11:07:06 -0800
Newsgroups: sci.astro, sci.physics.relativity, sci.physics
George Dishman replied to Jeff Root:

>> Am I correct in understanding that the extremely tiny
>> offset of the two lines in Henry's program is due to a
>> trivially minor rounding error in the calculations?
>> Probably caused by measuring a distance in pixels?
>
> I suspect it is because he changes the direction
> of the beam when it hits the mirror using a test
> of whether it is beyond and then moves off in the
> new direction from that point. To get perfect
> accuracy he would need to calculate the impact
> point which would be between samples.

That's what I meant.  :-)

When I run the program, the lines go through the second
mirror instead of being reflected, which I suspect is due
to the same error.

> Increasing the sample rate reduces the effect but it is
> a side issue anyway, he should be showing an extended
> wavefront, not a point.

That's why I said "lines", not "beams".  He only shows
two lines in the beams which aren't special in any way.

>> I think Henry doesn't realize how easy your version of
>> the experiment is.  Moving the loop is trivial.  I think
>> two people working together-- Henry and an assistant--
>> could put the whole thing together, get the measurements,
>> and take it down inside of eight hours.
>>
>> Do you agree, or have I missed something?
>
> Depends on how he measures the phase difference and
> how long it takes him to make the directional coupler
> but it would take longer as he'd probably have to buy
> the fibre and that would mean finding a source of the
> right stuff. That means first working out what the spec
> of the fibre is that he needs. Then there's a light
> source and some optics and...

I meant, once he has the materials in hand, of course.
Two weeks should cover that.

I'd expect him to buy the coupler rather than attempt to
make it himself.  If it isn't available commercially, I
know he could have one custom made, probably at a very
reasonable price.

> ... a bit of clamping of the fibres to prevent movement.

Duct tape?  On an abandoned or little-used railway track?
Or on the floor of a parking garage on an off day?  Or the
floor of a school hallway on a weekend?  (I just recently
happened to be going by the elementary school I attended
forty-plus years ago, so I stopped to look in the window,
and the floors are exactly as I remembered them: Some very
dense concrete-like material, very hard, smooth and level.
Perfect for physics experiments.  The floors in my high
school hallways were the same.)

> It would take some time and money but it isn't difficult.

Would there be any reason for someone other than Henry to
do it?
 
  -- Jeff, in Minneapolis


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