@mcnees It's great to see a thread about this because it's something that's often skimmed over, and/or is unclear, in pop-sci articles.

I've explained it to people in person (and mentioned it in brief social media replies) a fair bit... but I always like how you put your threads together, and they have far greater reach than any I post! 😀

@mcnees I just saw that the original series is available on YouTube. But I'm wondering if anyone knows the easiest way to stream the new series in Australia.

@mcnees Even cooler!

@mcnees I just hope you don't edit the post because:

(a) Then my comment won't make sense, and;

(b) I prefer your spelling, and;

(c) It made me look it up and learn that it's apparently (at least officially) now called the Willis Tower... a name change which people are clearly ignoring. 😀

@mcnees One can use it to look into the future?

@mcnees Yes. This is interesting because it's usually presented at a high school level as Bohr using de Broglie's hypothesis. I mean, I present it this way, but I DO mention that' I'm simplifying the story (as we usually do in teaching) for time / ease of learning.

Bohr "quantised" the angular momentum rather than "fitting" waves into orbits.

However, IMO, it's a great example of what "semi-classical" means and, more generally, a great example of transitioning from one "paradigm" to another.

@mcnees I did something vaguely analogous with my high school students the other day... showing them how the relativistic expression for kinetic energy reduces to the Newtonian expression by using a series expansion where smaller terms can be ignored for v << c (low energy) - Newtonian mechanics, "an EFT".

I'm currently struggling to get students through the curriculum, otherwise, If I had students who were at a more sophisticated level, I would take them through your tweet... love it!

@mcnees Is it good, or sad, that I double-checked your indices? 😀

@mcnees @drskyskull I had "classes" (fairly elementary) on both but I did not really pay much attention / understand much at the time.

Have since got my head around GR... still working on particle physics / QFT.

@mcnees Did you sell your soul... again!?

Which reminds me of George Parker "selling the Brooklyn Bridge", and stories of others doing similar things.

https://en.wikipedia.org/wiki/George_C._Parker

@mcnees I liked Strange & Norrell too and I'm looking for my next read. Sounds like I should give this a go.

@mcnees And, no doubt, it looks even more entrancing/calming IRL.

[Though, seemingly, no alt text... grumble grumble.]

@mcnees But does that mean if they fix one bug (chop one head off) two more take it's place?

@rjme @mcnees I was assuming he meant she was the first one to use it in relation to Cepheid variables... but I could be wrong.

@mcnees Clearly from eating too many pancakes.

[This being the moral to get kids to eat more "greens"? 😀 ]

@mcnees No one expects the... Mexican mariachi?

@mcnees Kind of similar to... a bright, young, slender, cheery(ish) Einstein in 1905 having explained special relativity to the world vs an older, more sombre, world-weary, slightly portly Einstein in 1915, having grappled with general relativity for 10 years!

@mcnees For those not wanting to read all 2814 posts 😉 😀, a much shorter derivation of the Klein-Nishina formula can be found in Weinberg's "The Quantum Theory of Fields" Vol I, p 362.

@mcnees Nice!... urge to resist... leaving it at that... and... making the... following comment... failing...

C standing for complex, wouldn't it make more sense the other way around?

[Arghhhhh!]