Why there isn't "missing information" in QM First of all, can I ask you to be a little patient, because my years of performing quantum calculations are well and truely over. I write computer software for an insurance company now! I have noticed that every so often, a member of the public who is trying to understand quantum physics will ask something about "missing information" and I have also noticed that every time the response from those who do know quantum physics is always "There isn't any missing information". I have slowly got used to this and started to accept this answer without questioning it... The problem I have never removed from the back of my mind is that quantum mechanics does contain unpredictabilty. eg. in the double slits experiment, the sequence that individual electrons will arrive at on different points on the screen is unpredictable. Surely the information about where the individual electrons will arrive is in some sense "missing" (until the measurements are actually made?) I recall that the position of a single electron on the screen can not be calculated beforehand (although the final pattern they make is predictable). Also, it seems to me that this idea of "missing information" is intuitive to the public and I have forgotten why we don't call it "missing information". Sorry if I have posted this before (I couldn't see one), it comes back to haunt me occasionally.