[time-nuts] Measuring speed of light or reproducing a metre

[Jean-Louis Oneto]

Hi list !
Searching for "newton jupiter moons speed of light" I found this very 
nice page:
http://galileoandeinstein.physics.virginia.edu/lectures/spedlite.html
A lot of the early measurements of c are described, with the accuracies 
reached.
But most of the older methods are rather difficult to demonstrate to 
kids, as they need long series of observations...
Best regards,
Jean-Louis

On 24/06/2013 21:26, Chris Albertson wrote:
> On Mon, Jun 24, 2013 at 1:55 PM, Jim Lux <jimlux at earthlink.net> wrote:
>
>> On 6/24/13 10:08 AM, Chris Albertson wrote:
>>
>>> Isn't that the Fizeau technique, which antedates Michelson's?
>   Michelson got the precision good enough that it finally put the question
> to rest.  We used a miles-long baseline of very clear and still air.
>
>> You need to know the rotation rate of the toothed cog or rotating mirror,
>> don't you?
>
> I think you have to count the number of rotations over a larger time
> interval.  And at the same time make sure the spin rate is constant.  They
> used a large hexagon with mirrors on all the faces and spun it up using
> some kind of clock work.
>
> You can see if the wheel is speeding up or slowing down because the slit of
> returned light should have constant offset.  So the experiment has a
> built-in check on the rate remaining constant.  And then you count the
> turns over some long interval using gears or what not.   They built a shed
> to house this thing on the side or Mt. Wilson.  All that is left no is the
> concrete foundation and concrete pier for the instrument.  This was a not
> small scale lab experiment.  It must have been well funded to be able to
> pour tons of concrete at a remote location like that.
>
> I think the harder part is knowing what the long baseline is.  How to
> measure 5 miles distance with the required accuracy in 1900?  Yes they have
> survey equipment back them put how good was it?   I I don't think they
> needed to know the exact length, just that it was a long constant length.
>   They were only trying to show the "C" was not constant.  But of course the
> experiment "failed"

-- 
Jean-Louis Oneto
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