[Alamo-Girl]

Thanks for your reply!

Please let me know if the following sheds any light on the question: How is spin in quantum systems a direct result of special relativity

[GregoryFul]

I still protest. It seems to me that it must be a presumption that a quantum parameter's value is indefinite until measured. If an electron has spin UP when measured, could it not have had spin UP prior to its being measured.

I mean, the ironic statement physicists make about quantum states: "you don't know the value of a quantum parameter until you measure it." -- well, duh? What is the evidence that the state is not a characteristic property of an individual particle before it is measured?

Any interaction that reveals this characteristic is a measurement. Otherwise the characteristic remains unknown, not necessarily indefinite -- or is there a clear argument that convinces physicists that it is indefinite, not merely unknown?