[monster_group]

That's not the correct analogy. In classical case, the color of the ball is fixed even before you open the box (you just don't know it). But in quantum entanglement case, the spin is not fixed until it is measured (because the wave function hasn't collapsed). But as soon as you measure the spin you get either up or down value. If you get up, then the other entangled particle will necessarily have down value when measured, If you get the spin down, the other particle will necessarily have the spin up. Now you may say that, the spin of the first particle was fixed all along and we just didn't know it. This argument is called "hidden variables theory". But it is proven by Bell's inequality that such a theory cannot exist, so the spin of particle 1 is indeed a random outcome. What's "spooky" is that in spite of it being random, it instantaneously fixes the spin of the other particle.

[astrange]

> But it is proven by Bell's inequality that such a theory cannot exist, so the spin of particle 1 is indeed a random outcome.

It's still allowed so long as a) the theory is nonlocal b) the outcome was not actually independent of the observer or c) superdeterminism.

[eszed]

Yeah, but I didn't "get" (to the extent that I can without grokking maths) quantum entanglement until I had it explained with this analogy, and then the "but that's not exactly what's happening here" real explanation. Leading with the complicated (albeit correct) wave form collapse explanation spun my head around and got me nowhere.

Good pedagogy (like, you know, science itself) starts simple and adds complexity as you dive deeper into the subject.