[frumiousirc]

> it's like a hand - it comes back to itself after 720° of rotation

The analogy is a bit broken in a way that may add confusion. The hand comes back to it's starting configuration after two 360° rotations, each along a different axis. A spinor's symmetry has 720° of rotation along a single axis.

[aap_]

No, around a single axis. if you hold your hand palm up you can rotate in the (vertical) z axis around 360° and get a twist in the arm. another 360° undoes the twist, that's 720° around a single axis.

[frumiousirc]

No. The first rotation is along an axis in the direction in which your fingers point. The second rotation is along an axis normal to your palm.

[aap_]

If you're rotating around your fingers you're doing something else, not what i mean. I'm just talking palm up, rotating in the vertical axis, 720°. like the cup dance.