And meter itself is defined as the length of the path traveled by light in vacuum during a time interval of 1/299,792,458 of a second. So it's cyclic and does

And meter itself is defined as the length of the path traveled by light in vacuum during a time interval of 1/299,792,458 of a second. So it's cyclic and doesn't make sense outside the earth reference frame Edit: since 2019, 1 second 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 9192631770 when expressed in the unit Hz, which is equal to s−1 So a second makes sense in the galactic scale at least as long as Caesium-133 is a stable isotope in that environment