quantumspin

if a beam of spin-up-along-vertical particles are put through a horizontally aligned stern-gerlach apparatus, a left horizontal beam and a right horizontal beam are produced. On either of these paths, if the vertical spin in measured, 50% of them will be found to be spin down-along-vertical. If on the other hand, no measurement at all is made until after the point where the two paths are joined, none of them are found to be spin down along vertical at all. question: what happens if one path is made longer than the other but the paths are kept joined? If the long path is made greater than c/t (where t is the measured transit time and c is the speed of light), then the particle couldn't possibly have come via the long path. If no measurement at all is made until after the point where the two paths are joined, do they still all come out spin up-along-vertical in this case, even though the can be distinguished via the different transit times? what if the long path is slightly shorter that c/t?

spin, chirality and helicity are all different. firstly spin is not 'spin', its just called that as a hangover from the early days of qm when the the magnetism associated with particles was thought to be due to particles 'spinning' on their own axes (since moving electric fields produce magnetic fields). Besides, a mathematical point particle cannot 'spin', since rotation isnt defined for a mathematical point. The helicity of a particle may change depending on your velocity relative to it, but its chirality is independent of your relative velocity. the difference between chirality and helicity is this: imagine you had a right handed glove and you throw it such that the palm of the glove is always facing the direction of the gloves forward trajectory. The glove can also be rotating about the forward-trajectory-axis, if it rotates clockwise as it moves forward, the glove has right helicity, if anti-clockwise, it has left helicity. But either way it is still a chirally right-handed glove. If you move parallel to the right helical rotating glove, but faster than it, relative to you the glove will be moving in the backwards direction, and therefore, relative to this backward direction as an axis, it will be seen to be rotating anticlockwise, in other words left helical. The notions of 'chirality' and 'helicity' are fundamentally geometric concepts and not specifically only 'properties' of particles. The polarity of the electron is not related to chirality, the mass basis electron is a mixture of both left and right electrons. see the video: link to commercial site removed by moderator per rule 2.7 and like and comment. I will answer if I can.