That's the thing that always confuses me: "...until their spins are measured..." I'm sure I'm misunderstanding, but measured to me means measured by somebody. Why in the world would these high falutin' theories depend on there being an observer. What am I missing?
An Introduction to quantum mechanics
That Wiki article is a reasonable short introduction to the subject. Of particular significance to your question are the bits about the relationship of the essential uncertainty of measurements in the world of the very small, an essential 'fuzziness', and the accuracy of a particular measurement. Both light (photons) and matter (nucleons) are both waves and particles depending on how you measure them. Do an experiment that asks the question, "Is this a particle?" and the answer comes back, "Yes", do an experiment that asks, "Is this same 'object' a wave" and the answer comes back, "Yes", sometimes even when you do both experiments at the same time!
In the Copenhagen Interpretation the observer is required to 'collapse the wave function', and in the case above, that would be to collapse it either into a wave or a particle as appropriate.You missed my point entirely. You're still talking about "experiments" and "observations" and "measurements". Those are human things (or living thing things). Are you saying QM depends on there being a sentient being? What was the universe like before there were beings to experiment, observe, and measure?
Physics is all about
"experiments" and "observations" and "measurements,"
that is all we can deal with. The intellectual constructs we make to understand those results are all too human, "the map is not the territory", however according to the Copenhagen Interpretation (not my interpretation) it does depend on a sentient being to collapse the wave function, in the absence of such beings the universe exists only as a wave function that describes all possible states and assigns a probability to each of them.