By Lorentz transformation $t^{\prime}=\frac{1}{\sqrt{1-\frac{v^{2}}{c^{2}}}}\left(t-\frac{v x}{c^{2}}\right)$
$\mathbf{1 7 3}$
So at time $\quad t=0, t^{\prime}=\frac{v x}{c^{2}} \frac{1}{\sqrt{1-v^{2} / c^{2}}}$
If $x>0 t^{\prime}<0$, if $x<0, t^{\prime}>0$ and we get the diagram given below "in terms of the $K$ -clock".
The situation in terms of the $K^{\prime}$ clock is reversed.