That one‘s gold too, but for me it was the other way round - needed Hartley to fully grasp Alpha Phoenix.

Understanding waves feels a bit like the bell curve meme for me: you start with the mental water model, and eventually end up with it again.

Or Feynman: you hear him helpfully talk about bouncy rubber balls, then learn a bunch of stuff over the next decade, and randomly listen to the same lecture again, and suddenly all sorts of „aaaah, that’s what he meant“ lightbulbs go off.