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

Jim Lux jimlux at earthlink.net
Mon Jun 24 16:55:36 EDT 2013


On 6/24/13 10:08 AM, Chris Albertson wrote:
> Using only "moderately" accurate equipment, like mechanical clocks and
> meter sticks Albert Michelson has able to measure the speed of light and
> determine it was a constant in all directions.   It was this work the
> prompted Albert Einstein to think about what t means for C to be constant.
>
> They were working at about the turn of the last century or before 1890 to
> about 1905 and did not have lasers or HP universal contours.   They used
> sunlight.
>
> One experiment was done here where I live up at the Mt. Wilson Observatory.
> They put light from a slit onto to a rotating mirror and then bounced it
> off a fixed mirror back to the rotating one.  If the speed were infinate
> the light would go right back up the slit.  But in reality the light misses
> because the rotating mirror moves a little while the beam is in flight.

Isn't that the Fizeau technique, which antedates Michelson's?

>
> The advantage of this is that it is a direct measurement of the speed of
> light that does not depend on many assumptions and can be done with
> technology that was available in the late 1800's   One big limitation is
> the atmosphere.  You need very stable air over the long path length

You need to know the rotation rate of the toothed cog or rotating 
mirror, don't you?

You could get that by matching against something like a tuning fork, but 
how do you measure the frequency of the tuning fork.

>
> This was the experiment that got Einstein thinking.  He said he started at
> age 16 to think about how the light from a moving lamp could be the same
> speed as one from a stationary lamp.  It was total non-sense and impossible
> at the time.   We have to remember that those experiments at the time were
> are considered to be "Failed Experiments" because "C" could not be constant.
>
>


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