In quantum mechanics, all elementary entities spin but matter only half-spins. To us, spinning an object 360 degrees in space returns its original state but spinning an electron 360 degrees only half-turns it — it takes 720 degrees of turning to return an electron to its original state! As this applies to all matter, quantum matter entities are said to have a spin of half. Yet again, the quantum world does what the physical world can’t.

Even worse, current physics can’t explain spin in general, let alone half spin, because an electron is a dimensionless point that can’t physically spin, so particle physics has simply given up trying to understand quantum spin:

“We simply have to give up the idea that we can model an electron’s structure at all. How can something with no size have mass? How can something with no structure have spin?” (Oerter, 2006) p95

In contrast, if a photon is a quantum wave that vibrates into an unseen dimension outside space, it has a structure that can really spin (Note 1). In quantum realism, a photon is a two-dimensional structure in quantum space that, like an ideal sheet of paper, is invisible when viewed edge-on.

That our three-dimensional space exists with a four-dimensional quantum space adds three new quantum directions to every point, all at right angles to each other as well as our space (Note 2). The result is that photon structures that are polarized at right angles occupy different spaces that don’t overlap. This explains why horizontal filters stop horizontally polarized light but not vertically polarized light (see 3.7.2).

If an electron is photon structures filling the channels of an axis, only half of them will be visible for any line of view, as the others, like our ideal paper sheets, will be invisible because they are being viewed edge on. If one photon is 100% visible, another at right angles will be 0%, for one that projects 99% there is another that projects only 1%, and so on. If only half an electron’s photons register with us, we can only measure half its spin and so say it half spins.

Quantum space explains why it takes two 360 degrees turn to return an electron to its original state. This is impossible in three dimensions but an electron in four dimensions has two planes to turn into not one. A 360 turn in one dimension only turns half its photons and so another turn is needed to turn the other half. The quantum spin of matter is one half because we are Flatlanders in four-dimensional quantum space.

**Note 1.** For a photon moving in direction X, its quantum amplitude Q vibrates in plane QX, so the structure QX can spin.

**Note 2.** The orthogonal directions X, Y, Z of space give three orthogonal planes XY, YZ and XZ. A fourth dimension Q adds three more orthogonal planes Q_{1}X, Q_{2}Y, Q_{2}Z, where Q_{1}, Q_{2} and Q_{3 }are at right angles.