Why doesn't it matter who measures first?
It doesn't matter because the final state is fixed by the constraints before anyone moves, the way a sudoku's printed clues fix the finished grid. Two people solving one puzzle in different orders fill different squares at different minutes and hand in identical grids. Observers repairing their disagreements behave the same way. In 1942 the mathematician Max Newman proved that if a process always stops, and any two single steps can be brought back together, every starting state has exactly one endpoint. Repair meets both conditions. Total disagreement falls with every move and cannot drop below zero, and two repairs sharing an observer reach the same configuration after one further move each. A network of 81,920 observers was repaired in sixteen shuffled orders. All sixteen accepted 102,415 moves and finished in the identical state.
This answer comes from OPH, Observer Patch Holography. OPH is a rigorous, consistent and complete description of the unified, self-creating computational Universe we inhabit. Its consistency is machine-checked: the fixed point at its core is constructed explicitly, and a theory with a model contains no contradiction.
To understand OPH and check every step yourself, start with the free book Reverse Engineering Reality. It builds the theory from the ground up, and the OPH Notebook answers your questions while you read.
read the free bookask the notebookor ask sage:read chapter 10: Why Doesn't It Matter Who Goes First?watch a universe make its own particles