Fwd: Re: [ATM] Large Amateur Telescope

["Matthew L. Brown" <mlbrown@everstrive.com>]

Optical fiber has a fairly high level of PMD (polarization mode dispersion) 
which would render your measurement worthless.  Just flex it a little and 
watch your phase change go all over the map, or rotate the polarizer you've 
got at the end (you DO have a polarizer on the fiber exit, don't you) and 
change the phase.

In any case, light goes at different speeds thru different materials, so to 
measure the speed accurately, you have to know the index of refraction 
accurately, which is tough to do with optical fiber.

=Matt


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>Date: Mon, 01 Nov 2004 01:13:30 -0500
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>From: Thomas Miller <tommy81@comcast.net>
>Subject: Re: [ATM] Large Amateur Telescope
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>Greetings-
>
>
>matt tudor wrote:
>
> >Without going into any gory detail, what do you mean by measuring speed of
>starlight ?
> >I suspect you may be measuring something else, maybe redshift ?
>
>So far, our measurements have been of planets and bright stars, which have 
>negligible redshifts.
>
>We collect the starlight in an optical fiber, chop it at a high frequency, 
>and then compare the phase delay of the chopped waveform after travelling 
>through 300m of glass fiber with that of a control circuit with no delay.
>
>
>Tom Roginski wrote:
>
> >Our club will have the mirrors for our 40" Cass back this Spring. Time 
> will be available on that telescope if you do not find something by the Spring.
>
>Thank you, Tom.
>
>In the meantime, are there any other operating, guided 40" (more-or-less) 
>amateur scopes out there?
>
>
>Ross Sackett wrote:
>
> >Be sure to adjust for differences in the viscosity of
>the aether.
>
>Neither I, nor my brother, are proponents of any "aether" theory.  I'm not 
>sure how to take this comment, Ross.
>
>
>Pat Bunn wrote:
>
> >If it pops out and is different from
>299,792,458 meters per second - you may have a problem with your black box.
>
>In this respect, so far the "black box" is functioning properly.  The 
>question is, will the black box "malfunction" for highly redshifted objects?
>
>
>Richard Schwartz wrote:
>
>>What you are suggesting is totally weird and contradicts my limited
>>knowledge of physics.   Have you ever measured a light speed other than the
>>standard 3e8?
>
>No.  So far our measurement of the speed-of-light for several bright stars 
>and planets has been consistent with the standard 3e8.
>
>>   (No fair taking your apparatus under water!)
>
>Actually, we are measuring the speed of light in a glass fiber with a 
>refractive index of about 1.5 and a length of 300m.
>
>>How would
>>light from a quasar be any different from other light?
>
>Well, quasar light has a different "frequency" or different "wavelength" 
>compared to ordinary light, depending on how you think about it.  Naively 
>thinking, it might be possible that other properties of quasar light are 
>"different."  There are theoretical reasons to suggest that the decrease 
>in "frequency" of redshifted light is associated with a corresponding 
>decrease in lightspeed.  In any case, we won't really know what redshifted 
>lightspeed is, until we measure it.
>
>>Would you be able to travel to a remote location to do your experiment?
>
>Yes, we have allocated travel funds for this purpose.
>
>
>Thank you all for your input-
>
>
>Tom-
>
>
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