It may seem trivial to ask, but why is the day divided into 24 hourseach hour is made up of 60 minutes and every minute from 60 seconds (except for the occasional 61-second minute)? In the metric system, physical quantities (such as mass and length) are measured in multiples of 10, while time is an exception and it is measured with seemingly strange units of measurement: seconds, minutes, hours… How did we arrive at this measurement of time?
The answer is to be found in antiquity, starting from the Ancient Egyptians in 2000 BC, who adopted the numbering duodecimaland it has to do with the Moon, but also with the mathematical properties of the number 12.
Why is the day divided into 24 hours?
The origin of the division of the day into 24 equal parts should be sought not so much in the number 24, but in 12. This number has always had a certain importance, so much so that it is also one of the few quantities to have its own name: the dozen. Already the ancient Egyptians around 2000 BC had begun to use the duodecimal numbering (i.e. in base 12) dividing the daytime hours into 12 equal parts, and so also those of the night. This is where the practice of dividing the day into 24 hours comes from. But why? The reasons behind this choice are astronomical, mathematical and practical.
That it lasted about a year 365 days It was already observed in ancient times starting from the apparent motion of the Sun. But not only that: in the same period of time it was possible to count approximately 12 cycles of the lunar phases. Already at the time of the Sumerians this determined the division of the year into 12 months.
The fortuitous coincidence is that the number 12 has several mathematical properties. One of them is that It has numerous dividers: 1, 2, 3, 4, 6, 12. This fact makes it easily divisiblethat is, divisible into equal parts of different sizes. Another possible reason why 12 has historically been useful on a practical level is that through the phalanges of the fingers You can count up to 12 using just one hand. Considering the thumb as a counter, in fact, it is possible to assign values from 1 to 12 to the phalanges of the index, middle, ring and little fingers.
Using two hands, then, it is possible to even reach up to 60: one hand is used to count to 12, while the other indicates how many times 12 should be considered (in fact 12 5 = 60). Here are some elements that can help explain why the choice of 12 was imposed as the quantity to divide the length of the day and night.
Why are hours divided into 60 minutes and minutes into 60 seconds?
We now come to the second question: why does each hour last 60 minutes and not 50 or 100? The answer lies here too in the properties of a number, this time – precisely – 60. Already the Sumerians by 2000 BC they had introduced a system of sexagesimal numbering (i.e. in base 60) which provided for 60 different symbols. Of course, it may seem bizarre to us and much more complex than our use of the decimal system, which provides for only 10 symbols.
The number 60, like the number 12, has many dividers (ironically, there are 12 of them). This makes 60 a number that can be easily divided, and for this reason an hour made up of 60 minutes is to be considered particularly practical: there are in fact many ways to divide 60 into equal parts, which makes it preferable to a division into hundredths. For example, I can easily take 1/6 of an hour divided into sixtieths (that’s 10 minutes), but I couldn’t do that if the hour were divided into hundredths (that would give me a non-integer number of “minutes”).
