Okay that is indeed very difficult.

Initially because of the history it was thought particles were solid and as you have seen that simply isn't true.

However as you deduced you have energy and the energy itself can move around or spin.

So you need to not think of it like a solid ball spinning but I guess more like a liquid ball in space spinning .. I seem to remember there were some images of water droplets drifting around the space station.

That is why not all spins can be equated to normal momentum spin like spinning a ball for example in a liquid ball you can simple have a vibration backward and forward across the ball of liquid.

So the short answer is a spin is something that is different between two particles and we are now trying to call it quantum information as opposed to spin because it confuses.

So spin = quantum information = energy

Edited by Orac (11/05/13 01:42 PM)
I believe in "Evil, Bad, Ungodly fantasy science and maths", so I am undoubtedly wrong to you.