Entangled particles as in glove analogy Just listened to a lecture about entanglement, and they gave an example of right/left glove which is not spooky at all. but then they said that the gloves are never right or left to begin with, and may be right OR left up until you 'open the box' 
in other words, why are they so confident that a pair of entangled particles dont have the property of up/down to begin with?
here's that lecture..
https://youtu.be/IxRfDtaot5U?t=4375
Thank you
 A: The reason that physicists know the entangled particle spins are not like gloves in boxes is because the entangled spins can be measured along different axes. For instance, the spins can be measured along the x-axis, y-axis, or z-axis. Depending on which axis the spatially separated spins are measured along, the probabilities for measuring different results changes. This has no analogy in the glove/box example. If you look closely at the proof of Bell's theorem, you'll see that the ability to measure spins along different axes is the non-trivial thing about quantum mechanics which allows you to prove the theorem.
However, I will say something extra about the glove/box picture. Even though entangled particles are certainly NOT like gloves in boxes, their implications for causality are only as severe as gloves in boxes. The EPR "paradox," which attempted to show that QM was inconsistent with relativity (spooky action and all that) is no longer considered an actual inconsistency. This is because "information" does not travel faster than light, i.e. measuring the spins is no less inconsistent with relativity than opening a box and seeing what handedness the glove is.
A: There is a difference between measuring the right or left glove and measuring the spin orientation of a particle. There are two states for a glove, left glove or right glove. For a particle, the spin can be oriented 360°, but the measuring instrument (e.g. a polarizing foil) has only a 50% probability of letting the particle through.
Having two independent measurements, a coincidence of 25% for two particles points to their entanglement. From this it was concluded that the particles are in quantum superposition and the wave function collapses at the moment of the measurement. Such a point of view is the same as for Schrödinger’s cat.
Your question is the same as asking, wether the wave function of the superposition collapses or our not-knowledge about the states collapses. For the state of the particles between the generation of entangled particles and their measurement both statements are right. Keeping it simple does not change anything for the cat nor for the entangled particles. Only, with Kopenhagens interpretation it is a mystery “which could not be explained” and for your thought, it is simple that the two spin of the two particles are oriented 90° to each other from the beginning and the measurement shows that coincidence.
