Is it something we just made up? Or is it something that was discovered?
In: 1
We defined a second
A day was chosen to be 24 hours long ago. The first small part (pars minuta prima in latin) of an hour was called the minute and it was decided there should be 60 in an hour. They repeated the splitting to create the second small part (pars minuta secunda) with the same 60 seconds per minute. The latin is how we ended up with the words for minute and second.
Wayyyy after all this was defined relative to a day on Earth we realized it’d be really handy if you could define things without any Earth reference. That’s how we ended up with definitions based off hyperfine transitions of a Caesium-133 atom. You may not have a 24 hour system to measure and then divide by 86,400 to figure out a second, but if you’re off Earth you probably have a way to find a caesium atom and measure things. You did cross space after all.
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