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Timekeeping Before Clocks

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Re: Timekeeping Before Clocks

#61

Post by storyinmemo »

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.

> Modern sextants can read the angle to a 0.1 minute level of accuracy, i.e. one-600th of a degree or one-tenth of a mile. In practice, actual accuracy to one-half mile is acceptable and quite good. The usual standard is accuracy to within five miles. The sextant (or octant) is meant to get the ship across the ocean. Once near the coast (20-100 miles) the more accurate techniques of piloting are relied upon for a safe landfall. The sextant is still the standard instrument for taking the observations required for celestial navigation.

https://www.ion.org/Museum/item_view.cfm?cid=2&scid=14&iid=2...

One thing that helps with a pitching deck is that the horizon and object remain the same angle. Like a camera following race car, the objects move together.

Re: Timekeeping Before Clocks

#62

Post by jes5199 »

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…

traditionally, every culture used seasonal/unequal hours! just, in Europe, the advantage of mechanical clocks was so great that the culture changed to fit the technology

Re: Timekeeping Before Clocks

#63

Post by WalterBright »

swatcoder wrote: post #40
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…

> They still had no idea what the sun, moon, and planets were, The composition of celestial bodies is useless trivia until you have some very modern material and energy sciences that might start turning to them for inspiration. There will almost certainly be a collapse of the modern world, and losing that information will be the very very least of our problems. > nor even the layout of the solar system. Depending on…

Sure they watched the paths. That doesn't tell them what they were, how far away they were, helicentric vs geocentric, etc. Anybody can watch paths and notice they repeat.

> heliocentrism are ultimately just an optimization that wasn't obvious, necessary, or meaningful given what little practical use there was to the paths of those planets until very recently

True, but that wasn't my observation. My observation is it was not advanced, sophisticated, etc.

Re: Timekeeping Before Clocks

#64

Post by WalterBright »

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…

> you're underselling the accomplishment of determining some of these things, particularly predicting eclipses

If you keep records over the decades, you can predict it. It's just a pattern, not an understanding. It wasn't until the last century, however, that the application of math to the precise orbits was able to predict the track of an eclipse very accurately.

Re: Timekeeping Before Clocks

#65

Post by gumby »

A few footnotes:

The “stick” of the sundial is called a gnomon.

Early hours were not uniform in length (they couldn’t be, really, with a sundial). The Babylonians (and the Egyptians after them) divided day (daylight) into twelve equal regions and night (between sunset and dawn) into twelve equal periods, but day and night hours were not the same length, nor were those of successive days or nights.

Parasite was a kind of job: if you were rich you had a parasite or two who would accompany you when you were out and about. You paid for their food and upkeep and in exchange everyone could see how rich and generous you were.

Re: Timekeeping Before Clocks

#66

Post by throw0101c »

SoftTalker wrote: post #58
throw0101d wrote: post #52

Earlier quoted context omitted.

> […] 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).

> I just didn't realize that angles could be meaured so accurately by eye at that time

Sextants have a bit of magnification (usually 4x, but sometimes 7x or higher). Higher mag allows for better accuracy at the cost of more shaking of the view.

Basic explanation:

* https://www.youtube.com/watch?v=30_wEda3ltM

Re: Timekeeping Before Clocks

#67

Post by HelloMcFly »

WalterBright wrote: post #64
HelloMcFly wrote: post #22

Earlier quoted context omitted.

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…

> you're underselling the accomplishment of determining some of these things, particularly predicting eclipses If you keep records over the decades, you can predict it. It's just a pattern, not an understanding. It wasn't until the last century, however, that the application of math to the precise orbits was able to predict the track of an eclipse very accurately.

> If you keep records over the decades, you can predict it.

Of course we know that now, but that level of understanding is hardly trivial to societies at those levels of development. To use our current understanding to be so underwhelmed - and to not be at all impressed by the scale at which they applied it for transforming and modernizing aspects of their growing societies - I don't know man, it honestly kind of shocks me and bums me out in equal measure.

Re: Timekeeping Before Clocks

#68

Post by WalterBright »

HelloMcFly wrote: post #67
WalterBright wrote: post #64

Earlier quoted context omitted.

> you're underselling the accomplishment of determining some of these things, particularly predicting eclipses If you keep records over the decades, you can predict it. It's just a pattern, not an understanding. It wasn't until the last century, however, that the application of math to the precise orbits was able to predict the track of an eclipse very accurately.

> If you keep records over the decades, you can predict it. Of course we know that now , but that level of understanding is hardly trivial to societies at those levels of development. To use our current understanding to be so underwhelmed - and to not be at all impressed by the scale at which they applied it for transforming and modernizing aspects of their growing societies - I don't know man, it honestly kind of sh…

When I was a boy, I had a newspaper route. It required me to deliver the newspapers at around 5AM, when it was still dark. While biking around the neighborhood throwing newspapers at houses, I would also watch the night sky.

It wasn't long before I started noticing patterns.

Ancient people also lived largely outside. They'd see the patterns, too. This isn't amazing or sophisticated or incredible.

Re: Timekeeping Before Clocks

#69

Post by felipeerias »

WalterBright wrote: post #63
swatcoder wrote: post #40

Earlier quoted context omitted.

> They still had no idea what the sun, moon, and planets were, The composition of celestial bodies is useless trivia until you have some very modern material and energy sciences that might start turning to them for inspiration. There will almost certainly be a collapse of the modern world, and losing that information will be the very very least of our problems. > nor even the layout of the solar system. Depending on…

Sure they watched the paths. That doesn't tell them what they were, how far away they were, helicentric vs geocentric, etc. Anybody can watch paths and notice they repeat. > heliocentrism are ultimately just an optimization that wasn't obvious, necessary, or meaningful given what little practical use there was to the paths of those planets until very recently True, but that wasn't my observation. My observation is it…

It was actually extremely complex and sophisticated. Getting accurate measurements was seriously tricky and making sense of them involved doing complex calculations (particularly spherical trigonometry) by hand. Some phenomena, like the precession of the equinoxes, required aggregating observations which had been taken over several centuries.

A good book to get a sense of this complexity is “The Light Ages” by Seb Falk.

Re: Timekeeping Before Clocks

#70

Post by WalterBright »

antognini wrote: post #43
swatcoder wrote: post #40

Earlier quoted context omitted.

> They still had no idea what the sun, moon, and planets were, The composition of celestial bodies is useless trivia until you have some very modern material and energy sciences that might start turning to them for inspiration. There will almost certainly be a collapse of the modern world, and losing that information will be the very very least of our problems. > nor even the layout of the solar system. Depending on…

Also worth noting that pretty much every ancient civilization ended up figuring out the order of the planets, at least relative to earth. (It turns out not to be so difficult since this is directly related to their sidereal periods.)

If you stand at the center of a circle, and have a man walk a circle at radius r from you, and another man walk a circle at radius 2r, it will take the second man twice as long to complete the circle.

It's not a great leap to apply that to the planets.

But it's not proof that the planets were ordered that way.

Science happens when one invents an explanation for observed phenomena, and then the explanation (theory) makes a prediction, then an experiment is devised, and the theory is validated if the prediction matches the theory, or tossed aside if it doesn't. In other words, the scientific method. That appeared fairly recently, and the consequences were an explosion of knowledge.

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