As the title says what exactly is the defination of a second?
I am very curios about this.
the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom
taken from wikipedia. but I remember learning it in physics.
Oh, and its the unit of time...
lol why is it that?
Well, I guess cause its something consistent that we can measure. They want something that is universally constant in nature.
Its the same with a meter, being defined by distance traveled by light in absolute vacuum in 1⁄299,792,458 of a second.
But before could they measure the time it took for the radiation or the speed of light?
Well, the first semi-accurate measurement of time came from pendulums. they had second pendumlums and what not. They also had mechanical clocks which showed seconds and minutes and hours like modern clocks. I doubt they were, but they could have beared a resemblance to modern day grandfather clocks. they based there days off of the ascension of stars.
you can read in depth about it here:
Thanks :) Interesting article.
And the one that you could easily check by yourself before asking...
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