The h Bar

12:51 AM

@dmckee well, this got out of hand =/

note that OP is not asking about spin-orbit or electron-spin-to-nuclear-spin coupling (fine and hyperfine structure resp.), but rather the electron-spin-to-electron-spin magnetic interaction, which is weaker than both of the above

unless I missed something huge, this is because (i) spin-spin coupling doesn't have any clear qualitative effects on the spectrum (say, splitting degeneracies the way FS and HFS do), and more importantly (ii) because it's weak, it's overwhelmed by the electrostatic structure, which separates spin and orbit, and when you couple this with the coupled spin-spatial structure of the coupling, it essentially averages out to zero once you start taking matrix elements

there's probably an interesting question to be asked there in terms of why spin-spin interactions are so damned weak

(for starters: the Bohr magneton is larger than the nuclear magneton -- so why is electron-electron spin-spin coupling less important than the HFS electron-spin-to-nuclear-spin coupling?)

almost certainly with an answer along the lines I just outlined, but it'd be nice to get a solid grounding in the literature for it

if it exists, though -- it's very likely that the precision-spectroscopy-theory literature just kinda moved on, say, to the Foldy-Wouthuysen manipulations here, without ever bothering to stop and explain why this was happening

Still, I suspect asking such a question is beyond OP's powers

Emilio Pisanty

1:19 AM

oh, and also: apologies if anybody is put off by the sometimes-slightly-rough tone. But frankly, this site's tolerance of the repeated posting of misinformation by that OP, and the abuse of this site that it represents, is beyond my understanding.

PM 2Ring

2:46 AM

@EmilioPisanty Nice answer. IMHO, that OP certainly deserves a slap (or several), I just hope that your actions aren't seen as bullying, or arrogant.

FWIW, here is a neglected recent question about angular momentum and Hawking radiation.

Aaron Stevens

4:18 AM

@EmilioPisanty I think your language in that answer is perfectly acceptable. People who come to this site looking for help in understanding physics should be ready to accept that help. This is not a site for people to be reassured about their faulty understanding.

John Rennie

4:48 AM

Objects falling into a black hole explode because the exceed the local speed of light

2

Emilio Pisanty

7:45 AM

@PM2Ring @AaronStevens Well, whaddayaknow, straight accept by OP without even a comment.

Maybe this does mark a turning point and we won't see the same misinformation getting re-posted?

I'm not particularly hopeful though

PM 2Ring

7:59 AM

@EmilioPisanty Me neither, but let's be optimistic. ;) At least he's prepared to accept correction when his misinformation is pointed out. So while I agree he's annoying, he's not beyond redemption.

John Rennie

@PM2Ring unlike some other members of the site

PM 2Ring

@JohnRennie Exactly. And I'm not just talking about JD.

@JohnRennie Speaking of whom, how does he reconcile his "clocks stop at the EH" with "stuff explodes into gamma rays at the EH"?

John Rennie

@PM2Ring even for him that's a bold claim.

It just shows a complete failure to understand the basic principles of differential geometry.

How can anybody boldly make claims that contradict all work in GR back to Einstein. It's a cognitive position that just seems incomprehensible.

"Every GR textbook ever published is wrong and I'm right"

PM 2Ring

It's downright delusional.