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
We started out defining the second as a division of the day. In 1967, the definition was shifted to cesium atomic clocks, which is much more precise. From that time, it’s been obvious just how variable the rotation of the earth is. If you damn a river flowing toward the equator, you hold more mass closer to the poles (and therefore closer to the axis of rotation). Like when a spinning skater pulling in their arms, the earth speeds up. There are a bunch of other factors that effect earths rotation and it’s not fully understood, but we’ve had leap seconds about three dozen times since we went to the atomic clock standard.
Leap seconds tend to play havoc with the internet though, because a bunch of servers suddenly find themselves a second off from others during the transition. It was recently decided to stop the practice and just let solar time drift off of UTC. It’s not like you’ll notice though. The drift is about a minute per century.
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