zlacker

Wave function collapse. As far as I can tell there is no discernable difference between a particle whose wave function collapsed (perhaps via measurement with another entangled one) and one that hasn't.

>>phkahl+(OP)
This is super naive but I just think of it as you (or whatever other particle is interacting with the one of interest) have now become part of its system. Like a causal event cone reaching you. Nothing about the particle changed, just your relationship with it (hence locking down the uncertain parameters).

I'm sure you or another physicist could point out the flaws in my mental model.

>>phkahl+(OP)
You can always subscribe to the many worlds interpretation and stop worrying about it.