Possible Duplicate:
How does one experimentally determine chirality, helicity and spin?
This is a rough quite from Hawking:
"An elementary particle with 0 spin looks the same no matter what direction. A particle with spin-1 looks the same only after a full revolution (360degrees) in spin. A particle with spin-2 looks the same after a half revolution (180degrees)."
How do we know this when we can't even see the particles? How do we measure spin?
