What intrigues me i that in this model a singular event is now accurately locked into history at two different time points. If we push the velocity of the train to very fast speeds we may have both Presidents agreeing that they signed at 12.00. But the observers are equally convinced that one signed at 11.59 and one signed at 12.01. The same universe now has historically accurate dates that differ, from which point in time future events may be measured, thereby propagating more differences, e.g. the ceremony of the signing reenactment every year. That’s just weird, but also cool.