Quantum spin is so strange that when Pauli first proposed it, he wasn’t believed:
“… the spin of a fundamental particle has the curious feature that its magnitude always has the same value, although the direction of its spin axis can vary…” (Penrose, 1994), p270.
If a particle spins in a rotation plane around an axis (Figure 3.17), that axis must be known to measure its spin. Measuring spin on any other axis doesn’t give the total spin, so if its spin axis unknown, one must measure spin on three perpendicular axes to get the total spin. In contrast, the spin of a quantum entity measured on any axis is always the same, so quantum spin doesn’t work like physical spin.
In this model, detecting a photon’s spin on any axis gives all its spin for the same reason that it gives all its energy. In both cases, a physical event is an all or nothing photon restart that gives all its energy or spin, so this is expected.
Physics measures quantum spin in units of Planck’s constant in radians (Note 1). If Planck’s constant represents the basic unit of energy transfer, as proposed earlier, Planck’s constant in radians will represent the basic unit of angular transfer, or spin, so this is also expected.
Finally, quantum theory lets quantum spin occur in both directions at once, but measuring it gives only one direction, randomly. Just as a photon can go through two slits at the same time but is only observed in one, so it can also spin both ways but is only observed in one. Essentially, the same principle applies to both linear and rotational movement, so a photon can rotate both ways at once just as it goes through both slits at once. The spin direction measured is then random because it depends on server access, again as expected.
Quantum entities that are just points in our space actually vibrate in a quantum space that extends outside it, and these structures spread in angular as well as linear directions to give the observed properties of quantum spin.
Note 1. Quantum spin is defined as Plank’s reduced constant ħ = h/2p (in angular radians).