Interesting features of John Harrison's sea clocks
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Interesting features of John Harrison's sea clocks
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Re: Interesting features of John Harrison's sea clocks
#2These old ship clock were the peak of engineering at the time. Accuracy was very much a necessity, being one second off London time means a 4 mile error when determining position IIRC.
Re: Interesting features of John Harrison's sea clocks
#3Thought this was very interesting - https://www.theguardian.com/science/2015/apr/19/clockmaker-j...
It mentions - "scientists revealed that a clock that had been built to the clockmaker’s exact specifications had run for 100 days during official tests and had lost only five-eighths of a second in that period."
While "a typical quartz clock or wristwatch will gain or lose 15 seconds per 30 days" (https://en.wikipedia.org/wiki/Quartz_clock#Accuracy). You can get temperature compensated quartz watches etc. though, which perform better apparently, but found it pretty interesting that a mechanical clock can best standard quartz technology.
Re: Interesting features of John Harrison's sea clocks
#4I wonder if this is the first example of government IT project specification failure?
What the navy wanted was a simple way to calculate a ship's position - which is exactly what they ended up with. What they didn't anticipate is that each device would cost twice as much as the ship it was going on.
Re: Interesting features of John Harrison's sea clocks
#5If you're interested in the subject, the book "Longitude" by Dava Sobel (mentioned in Resources) is a very good read with lots of historical perspective on how these clocks were built.
Re: Interesting features of John Harrison's sea clocks
#6Thought this was very interesting - https://www.theguardian.com/science/2015/apr/19/clockmaker-j... It mentions - "scientists revealed that a clock that had been built to the clockmaker’s exact specifications had run for 100 days during official tests and had lost only five-eighths of a second in that period." While "a typical quartz clock or wristwatch will gain or lose 15 seconds per 30 days" ( https://en.wikipedia…
That's certainly hasn't been my experience, all my watches have kept an accuracy if a few seconds over a year.
Re: Interesting features of John Harrison's sea clocks
#7There is a great Map Men Episode about the Longitude Problem[1]
Re: Interesting features of John Harrison's sea clocks
#8Thought this was very interesting - https://www.theguardian.com/science/2015/apr/19/clockmaker-j... It mentions - "scientists revealed that a clock that had been built to the clockmaker’s exact specifications had run for 100 days during official tests and had lost only five-eighths of a second in that period." While "a typical quartz clock or wristwatch will gain or lose 15 seconds per 30 days" ( https://en.wikipedia…
That greatly undersells the accuracy of quartz watches. An individual unit may gain or lose 15 seconds per month (though that level of inaccuracy would be unusual), but that given unit will consistently gain or lose almost the exact same amount of time every month.
After you have measured the relative speed of a given quartz movement, it becomes trivial to obtain the correct time (for, e.g., navigation purposes).
For what it’s worth, the NBS and US Naval Observatory switched from mechanical (pendulum) clocks to quartz during the Great Depression.
Re: Interesting features of John Harrison's sea clocks
#9I wonder if this is the first example of government IT project specification failure? What the navy wanted was a simple way to calculate a ship's position - which is exactly what they ended up with. What they didn't anticipate is that each device would cost twice as much as the ship it was going on.
That just increases the cost of the ship. It has become part of the ship’s navigation system. Not really a failure, just a justifiably expensive enhancement.
Re: Interesting features of John Harrison's sea clocks
#10If you're interested in the subject, the book "Longitude" by Dava Sobel (mentioned in Resources) is a very good read with lots of historical perspective on how these clocks were built.
Seconded! It is a wonderful book. Also an easy read and not very long.