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 second was originally based on the earth’s rotation but that turned out to be less regular that we thought, which is why we occasionally have to add leap seconds.
Nowadays we base it on quantum stuff. We measured how often a certain atoms vibrates per second and then used that to redefine the second.
It turns out the length of the day if measured exactly varies quite a bit. It might be either a tiny amount longer or shorter and over a period of years the extra time can add up to a whole second necessitating the addition of a leap second.
in the 70s we needed to add a leap second almost every year, but nowadays we haven’t had to need to since 2016 and if current trends continue we might actually need to subtract a second at some point.
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