User:WalkingRadiance/SI unit definitions

Unit
second	"The metre, symbol m, is the SI unit of length. It is defined by taking the fixed numerical value of the speed of light in vacuum, $\mathrm {c}$, to be $299\ 792\ 458$ when expressed in the unit $\mathrm {m\ s^{-1}}$, where the second is defined in terms of the caesium frequency $\mathrm {\Delta \nu _{Cs}}$."