How were units of time (second, minute, hours) determined?
The origins of our current measurement system go back to the Sumerian civilization of approximately 2000 BCE. This is known as the Sumerian Sexagesimal System based on the number 60. 60 seconds in a minute, 60 minutes in an hour – and possibly a calendar with 360 (60×6) days in a year (with a few more days added on). Twelve also features prominently, with roughly 12 hours of day and 12 of night, and roughly 12 months in a year (especially in a 360 day year). This method of accounting for time spread to other civilizations. The Babylonians used factors of 60 in their counting system. However, the Babylonians did not subdivide their time units sexagesimally (except for the day). The hour had been defined by the ancient Egyptians as either 1/12 of daytime or 1/12 of nighttime, hence both varied with the seasons. Hellenistic astronomers, including Hipparchus and Ptolemy, defined the hour as 1/24 of a mean solar day. Sexagesimally subdividing this mean solar hour made the second 1/86,400 of
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- How were units of time (second, minute, hours) determined?
