Wasn’t sure if posting my not-very-considered answers was in the spirit of the exercise, but since you’re hoping for more answers, here are mine. (And despite taking a QM class that discussed the Stern-Gerlach experiment, I’d somehow forgotten that S-G used an inhomogeneous magnetic field. So I might as well solicit some schoolin’ from LW on this topic.)
Q1. If “When exactly does the atom align itself?” means “When does the atom start changing trajectory in response to the magnetic field?”, I’d say it does that as soon as it enters the field. If it means “When can we say the atom has a single, unambiguous spin direction?”, I’d say that’s not until the atom hits the screen — before then it’s in a superposition of spin up and spin down states.
Q2. As the atoms all travel unimpeded through the first S-G field, through the holes, and then through the reverse field, I guess they’d remain in a 50⁄50 superposition the whole way along. So they’re just as “unaligned” or “aligned” as they were when they started. Presumably most of us would say the silver atoms were originally “unaligned” when they came flying out of the furnace, in which case we’d have to say they’re still “unaligned”.
Q3. I’d see two equally bright blobs, like those I’d have seen on the original screen, only further apart (because the two groups of atoms move further apart as they propagate, since the spin down particles have downward velocity relative to the spin up particles).
Q4. I’d observe either an atom continuously accelerating upwards or an atom continuously accelerating downwards. Once the atom enters the S-G apparatus and I see the accelerometer needle start moving, it’s no longer in a superposition; it’s either spin up or spin down, and I observe it accelerate accordingly.
Wasn’t sure if posting my not-very-considered answers was in the spirit of the exercise, but since you’re hoping for more answers, here are mine. (And despite taking a QM class that discussed the Stern-Gerlach experiment, I’d somehow forgotten that S-G used an inhomogeneous magnetic field. So I might as well solicit some schoolin’ from LW on this topic.)
Q1. If “When exactly does the atom align itself?” means “When does the atom start changing trajectory in response to the magnetic field?”, I’d say it does that as soon as it enters the field. If it means “When can we say the atom has a single, unambiguous spin direction?”, I’d say that’s not until the atom hits the screen — before then it’s in a superposition of spin up and spin down states.
Q2. As the atoms all travel unimpeded through the first S-G field, through the holes, and then through the reverse field, I guess they’d remain in a 50⁄50 superposition the whole way along. So they’re just as “unaligned” or “aligned” as they were when they started. Presumably most of us would say the silver atoms were originally “unaligned” when they came flying out of the furnace, in which case we’d have to say they’re still “unaligned”.
Q3. I’d see two equally bright blobs, like those I’d have seen on the original screen, only further apart (because the two groups of atoms move further apart as they propagate, since the spin down particles have downward velocity relative to the spin up particles).
Q4. I’d observe either an atom continuously accelerating upwards or an atom continuously accelerating downwards. Once the atom enters the S-G apparatus and I see the accelerometer needle start moving, it’s no longer in a superposition; it’s either spin up or spin down, and I observe it accelerate accordingly.