A sign error in the Minkowski space-time plot and its consequences

A sign error in an angle while drawing the original Minkowski plot has persisted for a century in text books and the pedagogical literature. When it is corrected, the length contraction' effect derived from the geometry of the plot disappears. It is also shown how the relativity of simultaneity’ effect that has been derived from the plot results from a lack of correspondence between certain geometrical projections on the plot and the properties of the physical system --two spatially separated and synchronised clocks in a common inertial frame-- that they are purported to describe.