Exploring Astronomy Photography Of Outer Space Universe

To understand this interconversion, it is helpful to consider the analogous interconversion of spatial separations along the three spatial dimensions. Consider the two endpoints of a rod of length L. The length can be determined from the differences in the three coordinates Δx, Δy and Δz of the two endpoints in a given reference frame
L2 = Δx2 + Δy2 + Δz2