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Comment by gumby | Hacker News Reader

Our conception of micro time is also modern. The Babylonians (who came up with the excellent system of 12 hours in a day and 12 in a night) divided the day into equal increments or hours, but the length of a day's hour changed from day to day as the length of the day changed. As far as I know the modern, fixed-length hour was an invention of the English (pre British) navy who used it to manage watches.

When clocks were developed the hour length became fixed, and the modern invention of the divisions of minute ("tiny") and ultimately second ("even more tiny") became first feasible and then, as the Industrial Revolution progressed, became useful. I've always assumed we had RPM and not RPS because of this, although very slow rotations would be easier to work with with a more find-grained denominator.

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The two senses of the word minute ("tiny" and "1/60th of an hour") are etymologically related -- a minute is called a minute because it's a tiny division of an hour.

The one that was more surprising to me is the etymology of "seconds". They're called seconds because they're the second division of an hour (the first being minutes).

Yep. "pars minuta prima" -- first small part, and "pars minuta secunda" -- second small part.

I had never considered whether anyone had continued dividing time beyond "first minute" and "second minute", but apparently yes, there have been partes miniutae tertiae too:

https://simple.wikipedia.org/wiki/Second#Trivia

One natural way of adapting this into English would be "terce" (like the religious service), although I guess we could also just call it a "third" -- about 17 milliseconds.

According to some stuff I was reading last week, this is just about the smallest time interval that a human being can learn to notice in many contexts, or just about the smallest timing accuracy with which a person can learn to react to an anticipated event. For example, it's about the timing accuracy needed for a frame-perfect action in a NES speedrun. So there is a human use for such a small time interval!

Is the convention of 60 frames per second related at all?

Huh, that's certainly a more fundamental reason that the NES frame is that length...!

I wonder if people involved with early film and video had a lot of 60:1 gearing available because of clocks or something (or just thought it was a very intuitive division to use).

well 60 * 17 = 1020 (about as close as you can get to a millisecond with integers), so it lines up pretty well.

Yeah, the ~17 ms frame duration is indeed based on a ~60 fps frame rate.

60 frames per second is because (in the USA) electricity suppliers standardised on 60Hz mains frequency, and in the early days of TV it was easiest to make the refresh rate match the mains supply.

(In the UK the mains frequency is 50Hz, as is the standard TV refresh rate)

BTW, because of choices made for color TV, it's almost never actually 60 fps... it's 59.94. https://www.tvtechnology.com/news/whats-the-difference-betwe...

Ha, I had never thought about "tertia" either. Interesting!

> When clocks were developed the hour length became fixed

... except in Japan! Japan imported Western mechanical clock, and modified it to display unequal hours. More on this at https://en.wikipedia.org/wiki/Japanese_clock.

Cool!

Has anyone here written a 12 hour day, 12 hour night clock as described? I'm fascinated now, it seems like it could be a cool watch face to superimpose fixed length hours over day/night hours.

You should look up the way they measure time in Ethiopia, they have a 12 hour clock - 12-hours of darkness, and 12 when there is daylight.

Written? Well, some have been constructed. Here it is in wristwatch form: https://www.masahirokikuno.jp/watches/temporal-hour-watch/

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