What's electron spin ?

http://www.youtube.com/v/Lk-i7vPi7Ok?version=3&autohide=1&showinfo=1&feature=share&autohide=1&attribution_tag=s-klKPYGGW6m4HHCHbfgZQ&autoplay=1

Escudo Invisivel da Terra Campo Magnetico 46

 

http://www.youtube.com/v/af_qS3q0p_c?autohide=1&version=3&autohide=1&feature=share&attribution_tag=l0o8hJmqIE1JlqAbRM82zw&showinfo=1&autoplay=1