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Timekeeping Before Clocks

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Re: Timekeeping Before Clocks

#11

Post by [deleted] »

loppink wrote: post #7
keiferski wrote: post #3

Another interesting thing is how Western clock technology was adapted to fit traditional Japanese notions of time, in the pre-Meiji era (after which, Japan adopted Western time.) A Japanese clock (和時計, wadokei) is a mechanical clock that has been made to tell traditional Japanese time, a system in which daytime and nighttime are always divided into six periods whose lengths consequently change with the season. Mechan…

There is a scene in that recent shogun series where a team performs a raid. The leader sends the team in in small waves and “times” each groups entrance by counting rhythmic taps on his shoulder. I thought it was such a great detail to include. Of course rhythm would be the measure of time without a watch to look at.

[deleted]

Re: Timekeeping Before Clocks

#12

Post by [deleted] »

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...

[deleted]

Re: Timekeeping Before Clocks

#13

Post by dgacmu »

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…

A cheap watch or clock will use an off-the-shelf crystal oscillator, where you'll be lucky if it's accurate to 20 seconds in a month.

A temperature compensated crystal oscillator (TCXO) can do better than one second per month, but probably not better than a second every 2 months.

An oven controlled crystal oscillator (OCXO) or a double ovenized crystal oscillator can get an order of magnitude better than that, But they start costing between $50 and $1,000. Beyond that you get into funky stuff like rubidium or cesium atomic clocks. There are, notably, miniaturized atomic clocks these days - about 2" x 2" - So you could technically put one into a wall clock, although they cost about $2,000.

These days it's usually cheaper to use GPS to control a temperature compensated oscillator, which we call a GPSDO (gps disciplined oscillator).

Re: Timekeeping Before Clocks

#14

Post by kej »

complaintdept wrote: post #6

I'd just like to throw out a recommendation here for the book Longitude by Dava Sobel. It's about the invention of the marine chronometer by a self-taught carpenter. Fascinating read, and a real page turner too.

Seconding this, and I'd add that Sobel's Galileo's Daughter was also a good read for anyone interested in the history of science.

Re: Timekeeping Before Clocks

#16

Post by WalterBright »

dgacmu wrote: post #13
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…

A cheap watch or clock will use an off-the-shelf crystal oscillator, where you'll be lucky if it's accurate to 20 seconds in a month. A temperature compensated crystal oscillator (TCXO) can do better than one second per month, but probably not better than a second every 2 months. An oven controlled crystal oscillator (OCXO) or a double ovenized crystal oscillator can get an order of magnitude better than that, But th…

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

Re: Timekeeping Before Clocks

#17

Post by WalterBright »

I sometimes watch those TV shows about ancient civilizations. They often talk about "astonishing" astronomy they used.

In reality, all they did was track the sun. This can be done simply by putting a vertical stick in the ground, and marking the path the tip of the stick traces in the ground. This way, the calendar and solstices can be accurately determined.

The shows will also talk about the "amazing" technology that enabled, say, a hole in a wall to shine on a statue for one special day a year. Again, rather simple to do using the same idea as the stick in the ground.

The third thing that annoyed me was their "incredible" astronomical knowledge in predicting eclipses. All that is is collecting observations over decades and then recognizing the pattern. There is no astronomical knowledge involved. They still had no idea what the sun, moon, and planets were, nor even the layout of the solar system.

Re: Timekeeping Before Clocks

#18

Post by dgacmu »

WalterBright wrote: post #16
dgacmu wrote: post #13

Earlier quoted context omitted.

A cheap watch or clock will use an off-the-shelf crystal oscillator, where you'll be lucky if it's accurate to 20 seconds in a month. A temperature compensated crystal oscillator (TCXO) can do better than one second per month, but probably not better than a second every 2 months. An oven controlled crystal oscillator (OCXO) or a double ovenized crystal oscillator can get an order of magnitude better than that, But th…

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.

Re: Timekeeping Before Clocks

#19

Post by russdill »

dgacmu wrote: post #13
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…

A cheap watch or clock will use an off-the-shelf crystal oscillator, where you'll be lucky if it's accurate to 20 seconds in a month. A temperature compensated crystal oscillator (TCXO) can do better than one second per month, but probably not better than a second every 2 months. An oven controlled crystal oscillator (OCXO) or a double ovenized crystal oscillator can get an order of magnitude better than that, But th…

The mems temperature controlled oscillators are also very good, 0.05ppm range (about a second every 8 months). They are tiny and low power, but still >$79.

Re: Timekeeping Before Clocks

#20

Post by antognini »

WalterBright wrote: post #17

I sometimes watch those TV shows about ancient civilizations. They often talk about "astonishing" astronomy they used. In reality, all they did was track the sun. This can be done simply by putting a vertical stick in the ground, and marking the path the tip of the stick traces in the ground. This way, the calendar and solstices can be accurately determined. The shows will also talk about the "amazing" technology tha…

Those kinds of shows can be sensationalized and shallow, but if you're interested in learning more in depth about ancient astronomy (shameless plug) I have been doing a podcast on the subject. So far I've covered the astronomy of the Babylon, Greece, Rome, India, prehistoric Europe, Subsaharan Africa, and am currently five episodes into the astronomy of premodern China.

https://songofurania.com

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