johnct

Thanks, but I still do not get it. There is certainly a particle property called spin the units of which are joule s. There is another property called spin axis, the units of which are degrees or radons. Does up mean right?

I am studying an on-line course, called Quantum Mechanics Concepts from DrPhysicsA. I am on the 3rd lecture on electron spin. The lecturer is very good and quite precise in his language, but I am hung up on the meaning of some terms and a concept. He describes axis of spin as indicated by a line in some direction and rotation around that axis by an arrowhead, according to the corkscrew rule. Fine. He goes on, though, to speak of spin up and spin down states. What is meant by this-- axis or rotational direction? I SEEM TO BE CONFLATING THE TWO PARAMETERS. The results (and predictions) of experiments based on alignment of AXIS of measuring devices relative to AXIS of spin show that spin can be either up or down. For instance, if for the prepared electrons, the arrow indicates clockwise spin, and the axis line is indicating some angle [relative to a measuring device that will only register vertical (z) direction] then some electrons measured collapse to "up" and some to "down". The down arrow would then indicate anti-clockwise spin for some electrons. How does AXIS direction take on a meaning of ROTATIONAL direction or does it? John thompsjc@gmail.com

I have read recently that it is believed that special relativity comes into play in very large atoms, because the "orbital speed" of electrons gets close to the speed of light. I have not thought of electrons in orbit since grammar school, their positions (as particles) being a kind of a smear of probabilities within a given orbital and the corresponding waves as standing closed cycle waves with discreet wavelengths fitting within the cycles. By what is meant orbital speed? I am a new member. If it is possible to include my email in the reply, it would be appreciated. By the way, this is the only website including physics which I could find that was at all possible to register for. Either the image verifications were illegible, or I got rejected as a spammer, or the verification application instructions made zero sense. John