I wonder what the actual distance is using current GPS survey processes?
Tom
----- Original Message -----
From: "Jim Lux" <jim...@earthlink.net>
To: <time-nuts@febo.com>
Sent: Monday, June 24, 2013 9:02 PM
Subject: Re: [time-nuts] Measuring speed of light or reproducing a metre
On 6/24/13 4:16 PM, jmfranke wrote:
The tuning fork was used with a clock. The clock was checked against
astronomical measurements.
http://www.schoolphysics.co.uk/age16-19/Wave%20properties/Wave%20properties/text/Speed_of%20light/index.html
http://www.nhn.ou.edu/~johnson/Education/Juniorlab/C_Speed/2007-PhysToday-RefFrame-Michelson.pdf
http://www.loc.gov/item/magbellbib002940 synchronizing two forks, letter
to Bell.
http://www.otherhand.org/home-page/physics/historical-speed-of-light-measurements-in-southern-california/the-mount-wilson-station-1922-1928/
excellent.. and I found on one of those pages the link to the US
Geodetic Survey information
http://www.otherhand.org/wp-content/uploads/2012/03/A-Geodetic-Measurement-Of-Unusually-High-Accuracy.pdf
The "Pasadena" baseline was almost as long as the 22 mile measurement,
and stretched from Pasadena to the east (San Dimas, etc.)
I like the comment that direct measurement of the baseline to 1 part in
500,000 wasn't considered particularly challenging ("routine"), but
transferring that measurement to the "MICHELSON" "ANTONIO" path was
challenging.
Sure.. a few inches in 20 miles isn't particularly challenging...
They measured it with 4 different tapes and came up only 18mm difference
among the measurements. That's some careful chaining. They were using 50
meter invar tapes: that means they had to put that tape out, pull it
straight to the rated tension, etc. about 700 times along the path.
A great picture of the tape going through a house along the baseline, in
one window and out another.
Ultimately, they measured the baseline (down on the flats) to 1 part in
11.6 million, and they estimate the probable error of the
MICHELSON-ANTONIO line was 1 part in 5 million.
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