It's a quantum number required to get agreement with experiment. But in reality, no one knows exactly what it means except for the case of polarized photons, which is rather unlike spin anyway. Spin is more important for fermions than bosons like photons anyway. Most important for electrons. Electrons of opposite spin can occupy the same space without being entangled. Photons with opposite spin annihilate each other because they are anti-particles of each other. But electrons with opposite spin are happy together, and in fact are not anti-particle pairs.



You must know what a network is, like in electrical wotk. It's just a sequence of electrical components. So a spin network is a sequence of particles with spin- could be 2-d or 3-d.

• Thank You - carefuluniverse - January 11, 2005 - 22:22 UTC