Space-time symmetry is broken

Space-time intervals corresponding to different events on the worldline of any ponderable object (for example a clock) are time-like. In consequence, in the analysis of any space-time experiment involving clocks only the region for $c\mathrm{\Delta }t\ge 0$ between the line $\mathrm{\Delta }x=0$ and the light cone projection $c\mathrm{\Delta }t=\mathrm{\Delta }x$ of the $c\mathrm{\Delta }t$ versus $\mathrm{\Delta }x$ Minkowski plot is physically relevant. This breaks the manifest space-time symmetry of the plot. A further consequence is the unphysical nature of the relativity of simultaneity' and length contraction’ effects of conventional special relativity theory. The only modification of space-time transformation laws in passing from Galilean to special relativity is then the replacement of universal Newtonian time by a universal (position independent) time dilation effect for moving clocks.