Salvage the following posts from SDMB:

https://boards.straightdope.com/t/macro-quantum-effect-witnessed-implies-time-travel-multiple-universes/535583/41?u=indistinguishable

https://boards.straightdope.com/t/entanglement-question-how-to-prove-that-before-one-of-a-pair-is-measured-its-not-well-defined/546047/11