Lenny Curry @lennycurry
A fun educational 5 minute video. One second is defined as 9,192,631,770 (billion) periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom — PolitiTweet.org
Aeon+Psyche @aeonmag
Measuring the length of a second might seem simple, but this history of the time unit from TED-Ed (@TED_ED) shows h… https://t.co/14o8fUsVqt