^Light year (ly)

It is the distance travelled by light in vacuum (with a speed of 3 x 10⁸ m/s) in one year

(i.e., 365 x 24 x 60 x 60 s).

1 ly = 3 x 10⁸ x (365 x 24 x 60 x 60) » 9.5 x 10¹⁵ m