There are many thing I'm interested in, but one in particular is the number of hours in a day. Well. I'm not obsessed with it or anything, but it's always made me wonder how on earth we got everyone on earth to agree to split the day into 24 segments. Splitting the year up into 365 days was easy - everybody knew what a day was, and everybody knew what a year was, so they just counted up how many days there were in a year. This happened all over the world, many times, independently in different cultures. When one group of invaders came along to politely ask another group if they would mind, say, changing their religion, the agressors would say "You've got a day to think about it before we smash you up". It's unlikely these two nations would speak the same language, so this would take a lot of hand waving and pointing at the sun and moon to get across, but across it would nevertheless be gotten. There was no need to go into deep astronomical calculations, because the concept of a day was universal - even newly introduced mortal enemies who didn't have a word or belief in common, would at least have a measurement in common.
But what about hours? Why 24? Why not 10? Why not 60? Time is not naturally split up into 24 anythings, so the division must be totally artificial. After a bit of googling, I found what I thought was the answer:
At which point Bryan crooked his right thumb to touch the base of his right index finger (please follow along and do it, too), and said, in much the same way as a Sumerian might have, 4,000 years ago... "One."
He then moved up a notch - see that? Each of your fingers has three distinct segments. I never really noticed that! - and, touching now the middle segment of his right index finger with his right thumb, he said... "Two."
I think you may sense where this is leading. By the time your right thumb has counted each of the three segments of his neighboring four fingers, you're up to 12.
Long before people were reading with their lips, one imagines, they were counting with their fingers.
So a day was divided into 12 segments, called hours; and, too, the night.
What a lovely story. It was all the ancient Sumerians' fault! The ancient Babylonians inherited this quaint practice, and presumably added their own 60-fetish to divide the hours into 60 minutes, and the minutes into 60 seconds. The Babylonian fascination with the number 60 is interesting in itself - so interesting, in fact, that this page suggests the Babylonians were the ones who split up the day, using geometric series:
... base 12 is more efficient than base 10, as base 10 ignores one of the hand configurations available - to wit:
- Open hand
- One finger folded
- Two fingers folded
- Three fingers folded
- Four fingers folded
- All fingers folded
Clams, naturally, have neither the means nor the necessity for such crude mnemonic devices. As well as being fond of twelve (3 x 4) the Babylonians actually used a base sixty notation (3 x 4 x 5) - hence your hours and minutes. The 360 (3 x 4 x 5 x 6) degrees in a complete revolution also stem back to their childlike fondness for these simple geometric series.
So there's another way of getting the number 12 out of our hands! Even though this explanation comes from the mightily respected "Doctor Clam", who as it happens, is an actual clam, it shows what we probably suspected: these explanations are total guesswork. How are we supposed to know what number a Babylonian saw when he looked at his hand? They don't seem to have written that one down.
Back to Google then. This page here has the world "science" in the URL, but the explanation it gives is still a little shaky:
Division of time into days and hours has gradually changed throughout history. In Babylonia the civil day and astronomical day were different. The civil day was divided up into watches [where] the length of a watch [was] not constant but varied with season. There were four watches during the day - 2 during the day, sunrise to midday and midday to sunset, 2 during the night from sunset to midnight and midnight to sunrise. The number of hours probably came from the use of base 6 as a counting system. It made sense to have each watch lasting 6 hours.
We know that the Babylonians used base 60, not base 6, but they did that because it is easily divisible by lots of other numbers, including 6. So the number 6 may have held a little significance. This explanation boils down to the Babylonians being 60-centric. Is that the real reason then? Did the Sumerians' hands play no part? Perhaps the 12-sectioned hands were a reason for liking base 60 in the first place. Or maybe it was something completely different, as this page suggests. I won't quote the whole thing, as it's quite long. Suffice to say that they've found an astronomical explanation involving stars, and it was the Egyptians, not the Babylonians. It all seems a little convoluted to me, but apparently "significant stages are documented in monuments and tombs" so maybe there's some evidence.
But wait! That's not all! Here we have a slightly different suggestion:
The Babylonians divided the sky into the 12 signs of the Zodiac, and a circle into 360 degrees. They divided the day and night each into 12 hours (although in many time systems the lengths of these varied between summer and winter! Babylon was rather nearer the equator than Liverpool, so they didn't get too confused with this). The hour was split into 60 minutes and a minute into 60 seconds.
Zodiac signs, eh? We're back to the unsubstantiated rumours about Babylon.
None of these solve the problem of getting the whole world to use 24 hours. Did Babylonian (or Egyptian) timekeeping spread naturally across the world in the same way Arabic and Hindu mathematical notation did? Did the Babylonians conquer some rival countries, which went on to conquer others, and so on? Are there, in fact, some countries which still don't use 24 hours? Some isolated island somewhere? Is it just a 'western' concept which has been forced onto the world recently by economic might? Come on! Somebody must know! Sorry for the inconclusive ending... how about I have a guess myself?
I reckon that the Babylonians (or somebody else, but if everyone else gets to blame the Babylonians, I will too) started out with the second as the basic unit of time. It's a nice convenient time interval - if asked to count upwards from one, you'd probably space the numbers about a second apart. Then, using their general love of all things base 60, they must've grouped seconds into groups of 60, and called them minutes. Then, they must've grouped the minutes into groups of 60, and called them hours. Then when they tried to group the hours into a group of 60, they saw that it spanned more than one day. So instead, they stopped naming time intervals, and simply stated that there were 24 hours in a day. Simple as that! It must be true!
If this really was true, they probably started out with something that wasn't quite what we know as a second. Perhaps shorter, perhaps longer. They probably went through the above calculation, and found that there were really 24.145 (or whatever) hours in a day, and to round the number down to exactly 24, they reduced the length of the second. Oh, and the human heart beats roughly once every second when resting, so perhaps that was what they started out with... sadly we'll never know.