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Why and when was the hour divided into exactly 60 minutes (and not for example 70 or 80)?

Big Brother
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Ubiquitous Student
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1 Answers1

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It comes from the ancient Babylonian numeration system which had base 60. (The reason for the choice of such a base is simplicity of calculation: 60 is divisible by 2,3,4,5,6,10,12,15,20,30. Much more convenient than base 10, whose only justification is the number of fingers on both hands).

It was used mainly in astronomy (ancient people had little need in dividing an hour into smaller parts, and if necessary they used 1/2 or 1/4 of an hour). Then with the spread of clocks, it started to be used in daily life.

Alexandre Eremenko
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    It should be emphasised that measurement of angle was historically far more refined than the measurement of time, and that time has merely inherited approaches that were originally devised for the measurement of angle. – Steve Feb 21 '21 at 00:16
  • I don't know what is the ground for your assertion that measuring angles precedes measuring time, historically. In early astronomy, these two tings are inseparable. – Alexandre Eremenko Feb 21 '21 at 03:34
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    Babylonians are over a 1000 years late for this. This was the Sumerian number system. The Babylonians inherited it, just as we have today for measuring time and angles. – Paul Sinclair Feb 21 '21 at 04:43
  • @Eremenko: The base 60 system is also based on the fingers, but in a different way. See Wikipedia on the sexagesimal number system. – Jonathan Rosenne Feb 21 '21 at 10:42
  • @AlexandreEremenko, I didn't say measuring angle precedes measuring time, I said the measurement of angle was far more refined, and that it is in angles unrelated to timekeeping (such as latitude and longitude calculations) where the minute has first come into widespread use, only later to be transferred over as a unit of timekeeping also. (1/2) – Steve Feb 21 '21 at 12:34
  • Another thing is that although the practice of using base 60 for some purpose can be traced back at least as far as the Sumerians, there's little evidence of actual continuity, and it appears to have been independently readopted - on best guess, as you say, because it can be seen to have a large number of divisors (which includes every divisor between 1 and 6, as well as tens and dozens).(2/2) – Steve Feb 21 '21 at 12:46
  • @Steve: I don't believe that Sumerians (or Babylonians) had any idea of latitude or longitude:-) – Alexandre Eremenko Feb 21 '21 at 14:35
  • @AlexandreEremenko, exactly my point. Rather than tracing it back to the Babylonians or Sumerians, my previous reading suggests that use of the modern minute became established in navigation (and its use of angle measures), and simply transferred to timekeeping from there (as a division of the first class unit). As to why 60 minutes per degree became established, it was likely not based on an old Babylonian tradition or influence, but on a straightforward analysis that it has a desirable set of factors for use with arithmetic involving angles. – Steve Feb 21 '21 at 15:33