NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
One second of time
From: J Cora
Date: 2008 May 15, 08:14 -0700
From: J Cora
Date: 2008 May 15, 08:14 -0700
Greetings,
I have asked on navlist in the past about the time unit, a second, and was able to find one of the recommended books Revolution in Time, by David S. Landes. The author mentions that perhaps before there was even a second hand on the early clocks, Astronomers would count the teeth of the gears to measure times of less than a minute. It wasn't expected that the clocks could keep time over any long interval.
The thing I can't quite understand though, is what standard the clockmakers used to decide on the length of a second, in building their timepieces.
Here is my first guess, the solar day length on the equinoxes along with the suns meridian transit set the day length standard.
Then build a gear train dividing the day into 24 by 60 by 60 parts. Recalling that Harrison used sidereal time to calibrate his clocks, it must have been well known by his time ( or much earlier ?) The "exact" difference in time
between the solar day and the sidereal day so the clock needed to run slower by about 4 minutes. Wikipedia says 86164.1 seconds. If the exact difference in time was well known and transit times could be measured to tight accuracy this would seem to be the best option.
In thinking about Galileo's experiments with pendulums and the length of the string, he must have had some standard to decide what the length of the string ought to be for accuracy to a second. Going to look into this further as this seems to have set a new standard for clockmaking in general.
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Navigation List archive: www.fer3.com/arc
To post, email NavList@fer3.com
To , email NavList-@fer3.com
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I have asked on navlist in the past about the time unit, a second, and was able to find one of the recommended books Revolution in Time, by David S. Landes. The author mentions that perhaps before there was even a second hand on the early clocks, Astronomers would count the teeth of the gears to measure times of less than a minute. It wasn't expected that the clocks could keep time over any long interval.
The thing I can't quite understand though, is what standard the clockmakers used to decide on the length of a second, in building their timepieces.
Here is my first guess, the solar day length on the equinoxes along with the suns meridian transit set the day length standard.
Then build a gear train dividing the day into 24 by 60 by 60 parts. Recalling that Harrison used sidereal time to calibrate his clocks, it must have been well known by his time ( or much earlier ?) The "exact" difference in time
between the solar day and the sidereal day so the clock needed to run slower by about 4 minutes. Wikipedia says 86164.1 seconds. If the exact difference in time was well known and transit times could be measured to tight accuracy this would seem to be the best option.
In thinking about Galileo's experiments with pendulums and the length of the string, he must have had some standard to decide what the length of the string ought to be for accuracy to a second. Going to look into this further as this seems to have set a new standard for clockmaking in general.
--~--~---------~--~----~------------~-------~--~----~
Navigation List archive: www.fer3.com/arc
To post, email NavList@fer3.com
To , email NavList-@fer3.com
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