At least one second has a simple origin, and totally wasn’t back-defined in 1967
oh wait
The current and formal definition in the International System of Units (SI) is more precise:
The second […] is defined by taking the fixed numerical value of the caesium (Cs) frequency, ΔνCs, the unperturbed ground-state hyperfine transition frequency of the Cs-133 atom, to be 9192631770 when expressed in the unit hertz, which is equal to s−1.[1]
At least one second has a simple origin, and totally wasn’t back-defined in 1967
oh wait
The second […] is defined by taking the fixed numerical value of the caesium (Cs) frequency, ΔνCs, the unperturbed ground-state hyperfine transition frequency of the Cs-133 atom, to be 9192631770 when expressed in the unit hertz, which is equal to s−1.[1]