3 ms·
> There's nothing shocking or spooky about two billiard balls being made to spin in arbitrarily opposing directions, selecting only one, then separating them, a
by mundo 8y ago
> There's nothing shocking or spooky about two billiard balls being made to spin in arbitrarily opposing directions, selecting only one, then separating them, and then noticing the spin of one, in order to reliably grasp that the other is the reversal.
Okay. So now, make two billiard balls so that they're spinning opposite directions, and separate them to opposite sides of the table. Then, go to ball A and do something to it that reverses its spin. Then observe the spins of the two balls. Are they the same?
For billiard balls, yes. If ball A is spinning clockwise and ball B is spinning counter-clockwise, and you reverse the spin of ball A, then you will observe both balls to be spinning counter-clockwise.
For quantum particles, no. If we manufacture two entangled electrons such that observing them will reveal them to have opposite spin, you can reverse the spin of one of them, and then observe them, and they will both still have opposite spin.
- zackmorris 8y agoUnfortunately I don't think this is true. The moment you observe them, they are no longer entangled. So they have opposite spin at that point, but if you reverse one, it behaves classically and both electrons then have the same spin. I'm still trying to wrap my head around why there isn't some hidden variable though which determines which spin they'll have. Like with Bayes' theorum, I keep learning it but for whatever reason my brain won't remember it and I have to look it up again hahah.
- mundo 8y agoCorrect, this only works if you can reverse the particle's spin without observing it. This is a descriptive example - the real experiment is slightly more complicated - but it was experimentally verified by Alain Aspect in 1982. If you want a more detailed explanation I recommend http://scienceblogs.com/principles/2007/02/22/spooky-action-at-a-distance-1/ http://scienceblogs.com/principles/2007/02/22/spooky-action-...