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Timekeeping Before Clocks

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Re: Timekeeping Before Clocks

#51

Post by creeble »

jrockway wrote: post #21
dgacmu wrote: post #18

Earlier quoted context omitted.

WWVB is great if you can get the signal -- I have two of those clocks in different rooms, and only one of them synchronizes.

Newer clocks use the phase modulated signal: https://www.nist.gov/system/files/documents/2017/05/09/NIST-... If you have AM-based clocks, you might find that these work better. However, nobody advertises which module they're using, so it's kind of a crapshoot. I specifically bought a phase modulation WWVB receiver and it reliably receives the signal every night. I also have a random $7 clock from Amazon that pretty m…

Thanks for that! Didn't know there were two kinds of radios.

I have one clock that always works perfectly, syncs after DST 100% of the time. Another that always requires manual reset twice a year, defeating it's purpose.

Re: Timekeeping Before Clocks

#52

Post by throw0101d »

SoftTalker wrote: post #50
throw0101d wrote: post #37

Earlier quoted context omitted.

> Are there any available clocks with that precision? Citizens says ±1s/year with their Caliber 0100: * https://www.citizenwatch-global.com/the-citizen/lineup/cal01... * https://www.hodinkee.com/articles/citizen-eco-drive-caliber-... Solar powered as well. It should be noted that Harrison's watches were low-volume productions, so could be tuned very accurately—and their accuracy was a matter of life and death for shi…

> Being 1 minute off in time throws off distance by 15 nautical miles I'm surprised that the accuracy of a hand-held sextant used while standing on a rolling/pitching deck is good enough for that to matter very much.

> […] for that to matter very much.

Life and death at times:

> The Scilly naval disaster of 1707 was the loss of four warships of a Royal Navy fleet off the Isles of Scilly in severe weather on 22 October 1707.[a] Between 1,400 and 2,000 sailors lost their lives aboard the wrecked vessels, making the incident one of the worst maritime disasters in British naval history.[2] The disaster has been attributed to a combination of factors, including the navigators' inability to accurately calculate their positions, errors in the available charts and pilot books, and inadequate compasses.[3]

* https://en.wikipedia.org/wiki/Scilly_naval_disaster_of_1707

When you're trying to find a tiny speck of an island (Pitcairn, Saint Helena, etc) in the middle of an ocean it's also important.

Re: Timekeeping Before Clocks

#53

Post by cvoss »

dgacmu wrote: post #18
WalterBright wrote: post #16

Earlier quoted context omitted.

I used a wall "atomic" clock for a couple decades. It would synchronize itself with a government radio signal.

WWVB is great if you can get the signal -- I have two of those clocks in different rooms, and only one of them synchronizes.

It's an incredible feat to me that a single station can broadcast to the almost the entire US, Mexico, and even parts of South America at the right time of day [0]. (I believe this is why many clocks check for the signal overnight.) It's achieved by using an extremely low frequency, at 60 kHz. The antenna is enormous and suspended between 4 towers.

[0] https://tf.nist.gov/stations/wwvbcoverage.htm

[1] https://www.nist.gov/pml/time-and-frequency-division/time-di...

Re: Timekeeping Before Clocks

#54

Post by ghaff »

cvoss wrote: post #53
dgacmu wrote: post #18

Earlier quoted context omitted.

WWVB is great if you can get the signal -- I have two of those clocks in different rooms, and only one of them synchronizes.

It's an incredible feat to me that a single station can broadcast to the almost the entire US, Mexico, and even parts of South America at the right time of day [0]. (I believe this is why many clocks check for the signal overnight.) It's achieved by using an extremely low frequency, at 60 kHz. The antenna is enormous and suspended between 4 towers. [0] https://tf.nist.gov/stations/wwvbcoverage.htm [1] https://www.nis…

Communication with subs uses ELF/SLF (3-300 Hz) when they're underwater--in the US case from some big communications stations. The coastal VLF stations, like in Cutler Maine are more in the 24 kHz range. As I recall, at one point, there were ecological concerns with the ELF stations but apparently the projects ended up going ahead.

Re: Timekeeping Before Clocks

#55

Post by ghaff »

throw0101d wrote: post #37
vbezhenar wrote: post #8

Earlier quoted context omitted.

> John Harrison was a carpenter by trade who was self-taught in clock making. During the mid-1720s he designed a series of remarkable precision longcase clocks. These clocks achieved an accuracy of one second in a month, far better than any clocks of the time. Wow. I own Tissot and Casio hand clocks and both are significantly worse precision. Are there any available clocks with that precision? Of course with GPS, WiF…

> Are there any available clocks with that precision? Citizens says ±1s/year with their Caliber 0100: * https://www.citizenwatch-global.com/the-citizen/lineup/cal01... * https://www.hodinkee.com/articles/citizen-eco-drive-caliber-... Solar powered as well. It should be noted that Harrison's watches were low-volume productions, so could be tuned very accurately—and their accuracy was a matter of life and death for shi…

Fairly price insensitive.

As I understood the exhibits in Greenwich, the Harrison clocks were largely eclipsed by cheaper versions by the time payment issues were resolved and they made it into widespread production.

Re: Timekeeping Before Clocks

#57

Post by jes5199 »

what, no astrolabe? astrolabes are the direct precursor to mechanical clocks, you can think of them as a slide rules with a inclinometer and a star map, and their primary application was to convert the altitude of visible stars or the sun into the current time

Re: Timekeeping Before Clocks

#58

Post by SoftTalker »

throw0101d wrote: post #52
SoftTalker wrote: post #50

Earlier quoted context omitted.

> Being 1 minute off in time throws off distance by 15 nautical miles I'm surprised that the accuracy of a hand-held sextant used while standing on a rolling/pitching deck is good enough for that to matter very much.

> […] for that to matter very much. Life and death at times: > The Scilly naval disaster of 1707 was the loss of four warships of a Royal Navy fleet off the Isles of Scilly in severe weather on 22 October 1707.[a] Between 1,400 and 2,000 sailors lost their lives aboard the wrecked vessels, making the incident one of the worst maritime disasters in British naval history.[2] The disaster has been attributed to a combin…

Yeah I get that it's important, I just didn't realize that angles could be meaured so accurately by eye at that time (especially on a ship that's moving around on even a moderate sea).

Re: Timekeeping Before Clocks

#59

Post by LeoPanthera »

vbezhenar wrote: post #8
fellerts wrote: post #5

Timekeeping leading up to the marine chronometer is also very interesting. Note that none of the timekeeping devices mentioned in the article would work very well at sea, making it impossible to accurately determine your longitude. Solving that proved to be extremely difficult. https://www.rmg.co.uk/stories/topics/harrisons-clocks-longit...

> John Harrison was a carpenter by trade who was self-taught in clock making. During the mid-1720s he designed a series of remarkable precision longcase clocks. These clocks achieved an accuracy of one second in a month, far better than any clocks of the time. Wow. I own Tissot and Casio hand clocks and both are significantly worse precision. Are there any available clocks with that precision? Of course with GPS, WiF…

> Are there any available clocks with that precision?

Yes! The term you need to type into Google is "High Accuracy Quartz". The most easily available wristwatches with this level of accuracy are the Bulova Precisionist line.

Watchuseek has a subforum about HAQ: https://www.watchuseek.com/forums/high-accuracy-quartz-watch...

Re: Timekeeping Before Clocks

#60

Post by devindotcom »

I was thinking about this while watching an amazing Chinese historical drama, "Longest Day in Chang'an," which has a "24"-like real-time structure. But instead of the beep... beep... beep... you have this one guy in an official building intently watching a water clock and pretty much every episode he bangs a drum on the hour and yells out the exact time and a kind of proverb, like "1 o clock!! The shadows reappear!"

Great show and there are lots of interesting historical details like this. Good post too.

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