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Timekeeping Before Clocks

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Re: Timekeeping Before Clocks

#71

Post by Terr_ »

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...

If you ever find yourself stranded back in time at that spot, skip over the fancy clocks and invent a radio transmitter that can send out a powerful pulse for "it's noon in $city" once a day.

Then sailing ships can manage with simple receiver plus clock just good enough to measure 12 hours. The time delta between receiving the land-broadcast and their own observed noon will tell them their relative longitude.

Since you aren't trying to encode any other information in this pulse, that makes the job a lot easier than if you were trying to make a wireless telegraph.

If you want to restrict who can benefit (e.g. to support a particular military that happened to recognize your time-traveler genius) plan random offsets for when you will be triggering it, and give authorized users a copy of the offsets.

Re: Timekeeping Before Clocks

#72

Post by 0xcg »

Great article that covers some fantastic examples of sun-based time. If you want to read about two more, Seiko has a great article [1] about a traditional Japanese clock (Wadokei) which had moving indices based on the seasons.

The local time we keep today is supremely useful for global synchronization, but is disconnected from the natural world. I came across this example (Wadokei) after making an app for myself to track the moon above and below the horizon and doing some research after creating a similar style clock which uses the sun as the anchor of the clock (high noon is the top of the clock, instead of 12 noon). This one is a full-day clock that shows the hours of the “local time” day as well as the positioning of the sun and moon. The hours shift dramatically during the peak of summer and depths of winter, especially at extreme latitudes [2]. You can really get a sense of the length of the daylight and how it changes by using any of these sun-based clocks.

[1] https://museum.seiko.co.jp/en/knowledge/relation_15/

[2] https://apps.apple.com/us/app/moontime-lunar-clock-widget/id...

Re: Timekeeping Before Clocks

#73

Post by zen_of_prog »

kej wrote: post #14
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.

I’m reading and so far enjoying “A Brief History of Timekeeping” by Chad Orzel.

Not to discount Harrison’s achievements, but there are other interesting navigational approaches - using Tobias Mayer’s Lunar tables:

> Mayer is far less celebrated than Harrison, but his method was in many ways the more immediately successful of the two

Or, if society were to collapse and rebuild, Lewis Dartnell proposes a radio in “The Knowledge”, since a radio transmitter is probably simpler to build than an accurate chronometer.

Re: Timekeeping Before Clocks

#75

Post by teleforce »

Toward the end of the article there are descriptions of Al-Jazari water clocks but did not mention about the infamous Alhambra Palace lions water clock, and most likely it was based on Al-Jazari inventions. Since Alhambra Palace construction was started in the same century of Al-Jazari death (13th century AD) it's very plausible that it's based on his work.

Al-Jazari invented hundreds of inventions including mechanical robots that were said to be copied by later scientist and engineers including Leonardo da Vinci, and we know that good artists copy but great artists steal [1].

During a visit to Alhambra Spain it was claimed the water will gush out from each of the lion figure's mouth fountain for every hour, in sequence of turns not unlike our clock now but it all based on water. Perhaps this is possible due to the Al-Jazari water clock invention but no one know how it was originally working [2].

It's a shame that indispensable knowledge like this has been lost forever and this also happened to the earliest earthquake sensor instrument invented by Zhang Heng back in 132 A.D. He called his seismoscope Houfeng Didong Yi, meaning an "instrument for measuring the seasonal winds and the movements of the Earth." Now the working replica has been recreated but only until very recently they had managed to recreate the functioning replica but knowledge regarding the actual original working mechanism has been lost forever [3]. Ironically after more than 2000 years later and USD1 Billion spent for the earthquake sensors system installations, the latest system with 15K sensor stations throughout China, it still cannot predict the earthquakes but only provide alerts to the authority after the main earthquake has happened somewhere in China [4],[5].

[1] The Relation between Al-Jazari of the East and Leonardo da Vinci of the West:

https://dergipark.org.tr/en/pub/oad/issue/78379/1264652

[2] Invention or Solving the Mystery of Water Clock of the Lion Court Fountain in Alhambra palace (Granada):

https://ijisrt.com/assets/upload/files/IJISRT22JAN498.pdf

[3] The ancient earthquake detector that puzzled modern historians:

https://www.engadget.com/2018-09-28-backlog-zhang-heng-seism...

[4] Innovative earthquake alarm system in China:

https://ibtekr.org/en/cases/innovative-earthquake-alarm-syst...

[5] Chinese Nationwide Earthquake Early Warning System and Its Performance in the 2022 Lushan M6.1 Earthquake:

https://www.mdpi.com/2072-4292/14/17/4269

Re: Timekeeping Before Clocks

#76

Post by eternityforest »

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 rubidium standards show up on eBay a lot for much less, but I don't know if they're still accurate and reliable after being used for years, I would imagine they're replaced for a reason

Re: Timekeeping Before Clocks

#77

Post by pavel_lishin »

Terr_ wrote: post #71
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...

If you ever find yourself stranded back in time at that spot, skip over the fancy clocks and invent a radio transmitter that can send out a powerful pulse for "it's noon in $city" once a day. Then sailing ships can manage with simple receiver plus clock just good enough to measure 12 hours. The time delta between receiving the land-broadcast and their own observed noon will tell them their relative longitude. Since y…

How difficult is it to determine local noon at sea? I assume that on a rocking ship, it's probably not a trivial task...

Re: Timekeeping Before Clocks

#78

Post by Terr_ »

pavel_lishin wrote: post #77
Terr_ wrote: post #71

Earlier quoted context omitted.

If you ever find yourself stranded back in time at that spot, skip over the fancy clocks and invent a radio transmitter that can send out a powerful pulse for "it's noon in $city" once a day. Then sailing ships can manage with simple receiver plus clock just good enough to measure 12 hours. The time delta between receiving the land-broadcast and their own observed noon will tell them their relative longitude. Since y…

How difficult is it to determine local noon at sea? I assume that on a rocking ship, it's probably not a trivial task...

IANAMariner, but I'm assuming the sextant would already be invented, since it would also be important for determining latitudes.

The goal is to figure out when the sun is as-close-as-possible to the reference vector "straight up". On land, we might determine that vector using gravity and a plumb-bob, which is indeed going to be a lot harder on a rolling ship.

However way out at sea, a new option exists: The horizon is no longer an arbitrary mishmash of mountains and hills, but instead self-leveling water in every direction [0], meaning you can safely assume "straight up" is 90 degrees [1] from all points on the horizon.

So you'd measure the angle between the sun and the nearest horizon, and then noon would be when that angle hits its minimum.

[0] Tides exist, but I assume they aren't likely to cause one direction to be significantly higher than the other.

[1] Unless you're measuring from very high up above sea-level, but if the civilization can make ships that big then you probably don't need much navigational help.

Re: Timekeeping Before Clocks

#79

Post by Terr_ »

Terr_ wrote: post #78
pavel_lishin wrote: post #77

Earlier quoted context omitted.

How difficult is it to determine local noon at sea? I assume that on a rocking ship, it's probably not a trivial task...

IANAMariner, but I'm assuming the sextant would already be invented, since it would also be important for determining latitudes. The goal is to figure out when the sun is as-close-as-possible to the reference vector "straight up". On land, we might determine that vector using gravity and a plumb-bob, which is indeed going to be a lot harder on a rolling ship. However way out at sea, a new option exists: The horizon i…

> and then noon would be when that angle hits its minimum.

*Maximum, but yannowhatimean.

Re: Timekeeping Before Clocks

#80

Post by dredmorbius »

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.

It was good enough for the Boeing 747:

https://virginflightdeck.blogspot.com/2010_09_01_archive.htm...>

(Something of a stealth favourite amongst HN commenters: https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...>)

And not the only plane to make use of this option: https://news.ycombinator.com/item?id=9549245>

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