It seems like everything with our calendar is based around 24hr days and the number of 24hr days to revolve around the sun. But a 24hr day can be broken down to 1,440 minutes and in turn 86,400 seconds. How did we (humans) calibrate the second so that exactly 86,400 would be 1 rotation of the earth to the point where we never need something like a “leap second” like we have with leap years?
In: Planetary Science
The day was defined as 24 hours. The hour was defined as 60 minutes. The minute was defined as 60 seconds. This worked out to 86400 seconds. No one defined the day as a certain amount of seconds initially.
Then as measurements got more precise we realised the Earth’s rotation varies slightly so basing a measurement of time off of the rotation of the Earth is not a good idea as it isn’t consistent. It was decided to base the second on vibrations of caesium atoms and a the number of vibrations to use was based off the previous definition of a second.
As we now have a definition of a second that does not change we can see how much the rotation of the Earth varies with great accuracy and sometimes leap seconds are required to keep time synced to the Earth’s rotation (keep midnight actually at midnight).
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