speed of light event Minkowski diagram Lorentz transformations Lorentz transformation
Fig. 3-1d. Since the speed of light is an invariant, the worldlines of two photons passing through the origin at time 




t
′

=
0


{\displaystyle t'=0}

 still plot as 45° diagonal lines. The primed coordinates of 




A



{\displaystyle {\text{A}}}

 and 




B



{\displaystyle {\text{B}}}

 are related to the unprimed coordinates through the Lorentz transformations and could be approximately measured from the graph (assuming that it has been plotted accurately enough), but the real merit of a Minkowski diagram is its granting us a geometric view of the scenario. For example, in this figure, we observe that the two timelike-separated events that had different x-coordinates in the unprimed frame are now at the same position in space.
