Is there a "convenient fiction" that explains why the angle of an electron's spin axis affects the probability of it being observed in a spin up or spin down state?
By "convenient fiction", I mean a story or image that provides useful intuition to novices, even though it may not be technically accurate. For example the analogy of water flowing through a pipe is a convenient fiction used to introduce the concepts of current and voltage.
I imagine the electron being sent through a Stern-Gerlach device. It makes sense that the closer the spin axis is to vertical, the more strongly the electron is drawn up or down. But, I don't see what would induce the electron to ever move in the "unexpected" direction. For example, if the axis is 5 degrees off vertical, what ever induces it to move down?
Watching this Veritasium2 video leads me to imagine that the electron is constantly flipping its spin axis; but, that doesn't seem to explain how the angle of the axis affects the probability of being measured in the up or down position.