The definition of the second has changed between the 8th edition of the SI Brochure last updated in 2014, with which Wikipedia agrees: > The second is the dura

The definition of the second has changed between the 8th edition of the SI Brochure last updated in 2014, with which Wikipedia agrees: > The second is 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. and the draft 9th edition: > The second, symbol s, is the SI unit of time. It is defined by taking the fixed numerical value of the caesium frequency ∆νCs, the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be 9 192 631 770 when expressed in the unit Hz, which is equal to s−1 . The draft 9th edition incorporates the work to redefine several of the base units in terms of fundamental physical constants and dispenses with the last remaining reference artefact. The changes come up for a vote next month. * https://www.bipm.org/en/measurement-units/rev-si/#when https://www.bipm.org/en/measurement-units/rev-si/#when So Wikipedia could include the concrete wording of what the redefinitions are currently intended to be. And it does. * https://en.wikipedia.org/wiki/Proposed_redefinition_of_SI_base_units#Second https://en.wikipedia.org/wiki/Proposed_redefinition_of_SI_ba...