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Timekeeping Before Clocks

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Re: Timekeeping Before Clocks

#21

Post by jrockway »

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.

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 much synchronizes every night. Living in NYC, this is truly amazing to me; I never ever got the AM signal here.

Re: Timekeeping Before Clocks

#22

Post by HelloMcFly »

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…

I think you're underselling the accomplishment of determining some of these things, particularly predicting eclipses. And I think there's quite a bit to be said about novel applications that emerge out of tracking the sun, like announcing seasons for citizens to help know when to plant, reap, store, etc. to manage agriculture across empire. Often they amazing thing was taking a small thing and spinning into a massive, society-impacting solution.

Re: Timekeeping Before Clocks

#23

Post by sandworm101 »

russfink wrote: post #15

Often we wonder what distinguishes humans from other animals. Measurement and optimization. Do other species measure, and optimize? Others use tools, but do they optimize?

>> Do other species measure, and optimize? Others use tools, but do they optimize?

They all do. Think of locomotion. Most every animal that can move has a few different ways of doing it. We can walk, or run. An eagle can fly direct or take a circuitous route between updrafts. A whale has sprint mode or easy cruise mode. We are all constantly optimizing how we move in order to minimize expended energy to accomplish a given task.

Re: Timekeeping Before Clocks

#24

Post by kjkjadksj »

russfink wrote: post #15

Often we wonder what distinguishes humans from other animals. Measurement and optimization. Do other species measure, and optimize? Others use tools, but do they optimize?

How would you define optimization? As in time management? Making some process take less effort perhaps? I’d say my cat fits the bill. She seems to have a better sense of time and keeping to her schedule than I do. She has also figured out many optimizations for her life that make sense to her. For example her path routing ability while running full speed is pretty amazing, she manages to figure out routes that keep her on a vector enabling full tilt acceleration vs turning and walking around furniture like us humans do with our poorly optimize walking.

Re: Timekeeping Before Clocks

#25

Post by kjkjadksj »

johnlk wrote: post #2

Fascinating article. This has inspired me to make a sundial that works inside my NYC apartment. Ideally, there's some reflective device pointed outside and some warping that happens to allow the sundial to work inside.

Why not just install one on the outside window sill?

Re: Timekeeping Before Clocks

#26

Post by shagie »

russfink wrote: post #15

Often we wonder what distinguishes humans from other animals. Measurement and optimization. Do other species measure, and optimize? Others use tools, but do they optimize?

I wonder why we limit measurement and optimization to animals when examples of it have been observed in plants.

https://en.wikipedia.org/wiki/Plant_arithmetic

> When an insect or spider crawling along the leaves contacts a hair, the trap prepares to close, snapping shut only if a second contact occurs within approximately twenty seconds of the first strike.

> ...

> The mechanism is so highly specialized that it can distinguish between living prey and non-prey stimuli, such as falling raindrops; two trigger hairs must be touched in succession within 20 seconds of each other or one hair touched twice in rapid succession, whereupon the lobes of the trap will snap shut, typically in about one-tenth of a second.

> ...

> Most plants accumulate starch by day, then metabolize it at a fixed rate during night time. However, if the onset of darkness is unusually early, Arabidopsis thaliana reduces its use of starch by an amount that effectively requires division. wever, there are alternative explanations, such as feedback control by sensing the amount of soluble sugars left. As of 2015, open questions remain.

Re: Timekeeping Before Clocks

#27

Post by antognini »

There is a really nice surviving water clock from the early Imperial era in China that was discovered in the 1970s [1]. The Imperial bureaucracy was sophisticated enough at this point that official timekeeping equipment like this was carefully tracked. The water clock has an inscription that details where it was made (Qianzhang), when it was made (27 BC), and how heavy it is 32 "Jin").

There is a text written a few decades after this water clock was made that provides enough detail to approximately reconstruct how astronomers used it for their measurements. In essence they would calibrate the water clock against the motion of the Sun so that they could correspond some volume of water to a 24 hour period. Then they would measure the amount of water that flowed from the transit of one star to another to figure out the separation of those stars in right ascension. The measurements were sophisticated enough that they apparently took into account factors like humidity and temperature when using the water clock.

[1]: https://www.reddit.com/r/ArtefactPorn/comments/150024l/the_z...

Re: Timekeeping Before Clocks

#28

Post by antognini »

HelloMcFly wrote: post #22
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…

I think you're underselling the accomplishment of determining some of these things, particularly predicting eclipses. And I think there's quite a bit to be said about novel applications that emerge out of tracking the sun, like announcing seasons for citizens to help know when to plant, reap, store, etc. to manage agriculture across empire. Often they amazing thing was taking a small thing and spinning into a massive…

One of the most impressive aspects of Babylonian and Chinese eclipse predictions was simply the social organization that was required to collect the necessary data. These records were collected almost continuously over centuries. The Babylonian astronomical records which span around seven centuries and are arguably the longest continuous scientific program any civilization has produced.

Re: Timekeeping Before Clocks

#29

Post by dekhn »

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…

https://en.wikipedia.org/wiki/Shortt%E2%80%93Synchronome_clo...

technically it's "electromechanical" but does not use GPS, WiFi, quartz, or atomic methods. To make thigns this accurate you need extremely good temperature compensation, close-to-frictionless bearings, run in a vacuum, use a pair of pendulums, etc.

When you reach that level of accuracy, you end up basically building a sensitive measurement device that is influenced by second and third order terms like subtle changes in the shape of the earth.

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