Re: Precision: the measure of all things
I should add: Didn't someone say that the oldest sundial known was a Chinese Equatorial Dial marked for Equal Hours? Anyway, in Europe, equal hours have been in use for, what, around 700 years? But, if I correctly remember what i read, Temporary Hours were in use in classical and ancient times, for more like 2700 years or more. On Mon, Jul 27, 2015 at 11:45 PM, Roger Bailey rtbai...@telus.net wrote: Hi Dan, Don't worry, 60 is well represented in time and angular measurements. We have 60 minutes in an hour, 60 seconds in a minute, 6 x 60 degrees in a circle and again 60 minutes in a degree and sixty seconds in a minute. Why? Being highly divisible is only part of the story. Other parts include our year of 365.25 days, very close to 360 and six equilateral triangles in a circle indicating that pi was close to 3 but greater as the arc is longer that the cord. If a circle is 360, equilateral triangles are 60 and a quadrant is 90. My preference for angular measurement is degrees and decimal minutes as opposed to degrees, minutes seconds or decimal degrees, From navigation experience, I recognize a minute of latitude is a nautical mile. I can easily handle decimal miles. I hate grads using 100 rather that 90 in a quadrant. Some French topo maps still use the Paris meridian for longitude and grads for latitudes. This is as ridiculous as republican time, 10 hours in a day, 100 minutes in a hour and 100 minutes in an hour. Get over it as the French did with time. The Babylonians were onto something when they defined our base 60 units of measurement. Regards, Roger Bailey *From:* Dan Uza cerculdest...@gmail.com *Sent:* Monday, July 27, 2015 2:59 PM *To:* sundial@uni-koeln.de *Subject:* Precision: the measure of all things Hi everyone, If you haven't already, you might want to check out the first part of the documentary Precision: the measure of all things. It's about the measurement of time and length, featuring the topic of sundials. There's an interesting theory about how the day got split into 12 hours because this number is highly divisible (but why not 60?). I just watched it on Da Vinci Learning. Dan Uza Romania -- --- https://lists.uni-koeln.de/mailman/listinfo/sundial -- No virus found in this message. Checked by AVG - www.avg.com Version: 2015.0.6081 / Virus Database: 4392/10318 - Release Date: 07/27/15 --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Precision: the measure of all things
(I should clarify again that, for clarity, I like to capitalize _kinds_ of whatever sort of thing I'm talking about...such as kinds of sundials or hour-systems, though I realize that that capitalization is probably not officially correct.) Another closely-related interesting question is the matter of what _kind_ of hours are used. Of course every book or article on sundials points out that, before mechanical clocks became widespread, civil time was measured in Temporary Hours, which divided the day, from sunrise to sunset, into 12 equal parts, and likewise divided the night, from sunset to sunrise, into 12 equal parts. Those books and articles nearly always imply or say that equal hours was a new invention when it was adopted--that someone invented a new way to designate time, and so it was adopted. Another frequent, and related, statement or implication is that the Horizontal Dial was an innovation that was came into use upon its invention because, before that, its possibility was there, but just hadn't occurred to anyone. But I read different. I read that Equal Hours were in use by astronomers and astrologers long before they were adopted for civil time, and so they were hardly a new invention at the time of their adoption for civil time. In fact, look at a Hemispherium or Hemicyclium. Designed to read in Temporary Hours, its hour-line, for a particular hour, crosses a different Equal-Hours line, according to the declination. Whether those Temporary Hours were drawn by calculation, or by empirical observation, it's plain that it would have been obvious to the dial-maker that he was making the 3 p.m. hour-line cross different Equal-Hours lines at different solar declinations. One thing that I'm objecting to is that many of those books imply that Temporary Hours are more primitive, and Equal Hours are something more advanced that therefore, when invented, immediately replaced Temporary Hours. Primitive? Rather, a lot more complicated and laborious to make. For sundials, and likewise for water-clocks. People should be impressed by the ingenuity and determination of early makers of sundials and water-clocks, who devised Temporary Hours markings and mechanisms for them. As for the Horizontal Dial, of course it's for Equal Hours. That's what it's convenient for. Sure, Flat Dials, including Horizontal Dials, and Polar Dials, and Equatorial Dials, and others, could have likewise been made for Temporary Hours, but they wouldn't have been easier to mark than a Hemicyclium. So it isn't surprising if the Horizontal Dial came into use around the same time as Equal Hours. What I read was that, though Equal Hours were well known and used by astronomers and astrologers, no one wanted them for civil timekeeping. Hence the effort and ingenuity used to devise Temporary Hours sundials and water-clocks. But, when the mechanical clock was invented, and came into relatively wide use (as tower-clocks, and in some homes), it was so much simpler to make clocks for Equal Hours, that, as a result, Equal Hours replaced Temporary Hours, for that reason of pure manufacturing-practicality. (By the way, were the early mechanical clocks, the Folliet Balance intertially-slowed clocks, without the fusee compensation, any more accurate than water-clocks, which were much cheaper and easier to build?) Temporary Hours surely made a lot of sense in agricultural societies, where it must have been very important and practical for farmers to know what percentage of the day remained. I don't advocate a return to Temporary Hours, because, speaking for myself, it seems to me that finding what percentage of the day is over, and how much or how little remains, seems a bit pessimistic, and maybe not a good way to name the time of day. ...but I realize that it had practical importance in agricultural societies. Michael Ossipoff On Mon, Jul 27, 2015 at 5:59 PM, Dan Uza cerculdest...@gmail.com wrote: Hi everyone, If you haven't already, you might want to check out the first part of the documentary Precision: the measure of all things. It's about the measurement of time and length, featuring the topic of sundials. There's an interesting theory about how the day got split into 12 hours because this number is highly divisible (but why not 60?). I just watched it on Da Vinci Learning. Dan Uza Romania --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Precision: the measure of all things
Hi Dan, Don't worry, 60 is well represented in time and angular measurements. We have 60 minutes in an hour, 60 seconds in a minute, 6 x 60 degrees in a circle and again 60 minutes in a degree and sixty seconds in a minute. Why? Being highly divisible is only part of the story. Other parts include our year of 365.25 days, very close to 360 and six equilateral triangles in a circle indicating that pi was close to 3 but greater as the arc is longer that the cord. If a circle is 360, equilateral triangles are 60 and a quadrant is 90. My preference for angular measurement is degrees and decimal minutes as opposed to degrees, minutes seconds or decimal degrees, From navigation experience, I recognize a minute of latitude is a nautical mile. I can easily handle decimal miles. I hate grads using 100 rather that 90 in a quadrant. Some French topo maps still use the Paris meridian for longitude and grads for latitudes. This is as ridiculous as republican time, 10 hours in a day, 100 minutes in a hour and 100 minutes in an hour. Get over it as the French did with time. The Babylonians were onto something when they defined our base 60 units of measurement. Regards, Roger Bailey From: Dan Uza Sent: Monday, July 27, 2015 2:59 PM To: sundial@uni-koeln.de Subject: Precision: the measure of all things Hi everyone, If you haven't already, you might want to check out the first part of the documentary Precision: the measure of all things. It's about the measurement of time and length, featuring the topic of sundials. There's an interesting theory about how the day got split into 12 hours because this number is highly divisible (but why not 60?). I just watched it on Da Vinci Learning. Dan Uza Romania --- https://lists.uni-koeln.de/mailman/listinfo/sundial No virus found in this message. Checked by AVG - www.avg.com Version: 2015.0.6081 / Virus Database: 4392/10318 - Release Date: 07/27/15 --- https://lists.uni-koeln.de/mailman/listinfo/sundial
