Re: [time-nuts] Measuring speed of light or reproducing a metre
The tuning fork was used with a clock. The clock was checked against
astronomical measurements.
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.
John WA4WDL
From: "Jim Lux" jimlux@earthlink.net
Sent: Monday, June 24, 2013 4:55 PM
To: time-nuts@febo.com
Subject: Re: [time-nuts] Measuring speed of light or reproducing a metre
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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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.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.
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.
I wonder what the actual distance is using current GPS survey processes?
Tom
----- Original Message -----
From: "Jim Lux" jimlux@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.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.
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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and follow the instructions there.
On 6/24/13 6:48 PM, Tom Miller wrote:
I wonder what the actual distance is using current GPS survey processes?
Tom
SLightly different, because there are some faults running across there
and there have been some earthquakes with displacement.
Earthquakes, yes that range is one of the most active in the world. They
measure an uplift of as much as 2 inches per year, those mountains are
still getting taller.
On Tue, Jun 25, 2013 at 3:54 AM, Jim Lux jimlux@earthlink.net wrote:
On 6/24/13 6:48 PM, Tom Miller wrote:
I wonder what the actual distance is using current GPS survey processes?
Tom
SLightly different, because there are some faults running across there and
there have been some earthquakes with displacement.
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--
Chris Albertson
Redondo Beach, California