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
What ancient civilizations meant by second (or whatever name they had for it), was closer to half a minute than one heart beat.
Time keeping in the early time was quite different from today, they didn’t really want to account for each moment like we do. Romans had a calendar that had 10 months same length of ours (30-ish days), and a 2-month long nameless winter time when nothing happened. In the medieval, days were divided to equal amount of hours from sunrise to sunset, regardless of the actual length of the day (as in winter and summer). Consequently, hours were longer in summer than in winter.
In the ancient times there were different kinds of time keepers, like sundials or water clocks (basically a cylinder of water with a small hole on the bottom that lost an amount of water during an amount of time so you could always see where it is). So as you see, having seconds of different length was not a problem for very very long time.
It’s not until the 16th century in Europe when mechanical clocks started to show minutes and hence the hours should have been made to equally long, day and night. It’s another almost hundred years until the minutes were further divided to 60 seconds. This actually had two feasible reasons, one is that you already had a clock face that had 60 units around it so it was kind of practical to have a smallest kind of unit 60 times less than the minute (a full circle within one minute). It also coincided with the time when such short times (roughly equal to one heart beat) became kind of important.
Of course these clocks were rather imprecise. They basically worked by a spring driving a set of intricate cogwheels, in a nonstandard secret way that a clock master cooked up in his chamber, and the parts were manufactured by hand. They were quite imprecise.
The pendulum clock was invented like a hundred years later. They were also hand made You actually needed to tune the pendulum by adjusting the weight and length until a new clock was sellable. But everything was made at small scale so it was doable. A huge pendulum clock was already much more robust and once set, they kept the time quite reliably.
As you see, time keeping developed gradually, and real precise clocks came up in around the 17th century. Ever since the time we needed was going down, like sport events started to require tenths of seconds, science started to need millisecond and less, GPS needs nanoseconds.
And here we are.
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