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
A physical object like the earth spins in a rotation plane around an axis of rotation (Figure 3.17), so its spin on another axis is less than its total spin. If the spin axis is unknown, one must measure spin on three orthogonal axes to get the total spin. So that one can get the total spin of a quantum entity from any axis makes no sense in physical terms.
In quantum realism, a photon gives all its spin on any axis for the same reason that measuring either of Young’s slits gives all the photon. A physical event is an all or nothing restart that gives the entire photon, including all its spin. The spin result for a photon is, as expected, one quantum process in radians, or Planck’s constant in radians.
Imagine a coin spun on a table too fast to see its spin direction so the only way to see if it is clockwise or anti-clockwise is to touch it, after which it spins again, again too fast to see so it could spin either way. Spin is a basic property of every quantum entity because quantum processing spreads not only in linear directions but also in angular directions. Spin is a basic property of every quantum entity because quantum processing spreads not only in linear directions but also in angular directions.