Wikipedia:Reference desk/Archives/Miscellaneous/2016 September 22

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September 22

Why do (most) clocks and watches have 12 hour dials when sundials have 24 hour dials?

I see no logic behind the 12 hour dial, since sundials have 24 hour dials. What is the origin of the 12 hour dial?--Leon (talk) 09:27, 22 September 2016 (UTC)

See Impatience. I remember seating sometimes idle watching at the clock for seemingly unending periods of time during my youth. A 24-hour dial would have broken my patience often much earlier after my impression. Breaking vows being the first step to most deliquescent failures I'm satisfied with the shortcuts the system took. Things went differently after the digital display, information then seemed to behave differently. --Askedonty (talk) 09:57, 22 September 2016 (UTC)

Any evidence for this? Warofdreams talk 10:48, 22 September 2016 (UTC)

Which this ? I was not trying to suggest it explained what you're stating just below, the change which happened during the 14th- and 15th-centuries, although that might be it, together with the satisfaction for the prometers of the trick, of packing two half-days in one single display. I was just reviewing the question of a "lack of logic" ( although you might in fact be right, I could have found myself only uninterested if they had been 24-hour dialed clocks). --Askedonty (talk -- 11:24, 22 September 2016 (UTC)

In fact as stated in 12-hour_clock there was, beside an established 24-hour counting usage, an other established usage of counting twice twelve hours already before the time of viable mechanical clocks. There must be a number of various reasons that have been converging for imposing a 12-hour sheme. Eccentric and popular, vs elitist for example. A moralist/didactic suggestion implying that "things were not so simple", and implied, science was always on some other side. The cost of foundry could have played a role (MTBF) too, as bells and carillons were to be associated with in a widely extended public usage. Those really did not come cheap. --Askedonty (talk) 16:36, 23 September 2016 (UTC)

Did you really mean "deliquescent failures", Askedonty? I have an image of a pile of zinc chloride getting distracted by a cute copper sulphate crystal and forgetting to absorb water from the atmosphere. Maybe you meant delinquent. -- Jack of Oz ^{[pleasantries]} 22:25, 22 September 2016 (UTC)

Well, something like "spiritual decay" was more like my intention, I was missing some kind of grammatical articulation for introducing failures... there exists "deliquescent" used with the meaning I intended, though I agree, it must be a bit rare. --Askedonty (talk) 16:17, 23 September 2016 (UTC)

Thanks. That's something new I've learned today. -- Jack of Oz ^{[pleasantries]} 21:17, 23 September 2016 (UTC)

You'd better check your driver's license for your name, in case that's what you forgot, to make room. :-) StuRat (talk) 00:58, 25 September 2016 (UTC)

Our article on the 24-hour analog dial states that the earliest mechanical clocks did have 24-hour dials, but were supplanted by 12-hour dials during the 14th- and 15th-centuries. It doesn't give a reason, and I can't easily find one. Warofdreams talk 10:48, 22 September 2016 (UTC)

What sundial has a 24 hour face? They aren't going to work at night, so you typically have 12 to 16 hours marked. Here is an example sundial with a 12-hour face. More to the point, you are really asking why we use a 12-hour clock. That article says that all the way back in Ancient Egpyt they used a 12 hour sundial for daytime and a 12 hour water clock for night. The fashion of dividing a 24-hour day into two 12 hour pieces is thus ancient though its popularity has waxed and waned and varied with different cultures. Dragons flight (talk) 11:04, 22 September 2016 (UTC)

Sundials imply a 24-hour face, even if they aren't marked. Sundials typically include 12 hours over 180 degrees, which would imply a full circle = 24 hours. No sundial has 12 hours over 360 degrees, that would be wrong. Most of the sundials here are not fully marked for 24 divisions of the day, but they all imply 24 divisions, even if most are numbered for 2 sets of 12. --Jayron32 11:54, 22 September 2016 (UTC)

• Some boring possibilities - a 24 hour clock is harder to read from a distance. It's also harder to read minutes from, since 24 doesn't divide neatly into 60 (each interval therefore represents 2 and a half minutes) - the minute hand was introduced in the seventeenth century, according to our article, so maybe that's a bit late. Numbers like XVIII and XXIII are long and ugly and throw off the aesthetic balance (famously, many clocks use IIII for 4 instead of IV, because then it balances VIII for 8). Smurrayinchester 00:37, 24 September 2016 (UTC)

FWIW, you can build a fully working 24 hour sundial - you just have to place it sufficiently close to the north or south pole. SteveBaker (talk) 01:56, 24 September 2016 (UTC)

Thinking more about this - I wonder if compactness was an issue. The gear train you need to divide the output of a 1-second pendulum by 86,400 in order to get one revolution every 24 hours would necessarily require twice as many teeth as one that only had to divide by 43,200 to get one revolution every 12 hours. Hence a 12 hour dial ought to result in a smaller/lighter clock than one with a 24 hour dial. SteveBaker (talk) 17:27, 27 September 2016 (UTC)