Don’t think I’ve forgotten about the falling electron question from a while back. Short version: an accelerating charge radiates. So if you let an electron fall in a gravitational field, it should radiate. But a person (or detector) falling along beside it does not perceive the electron as accelerating and so the electron shouldn’t radiate in their frame. How to reconcile the perspectives?
I didn’t know. Still don’t. I got back to the university and asked a few grad student friends of mine. One had an interesting argument involving vacuum polarizability that the electron will radiate EM waves in one frame but not the other. We couldn’t hash out the details because we were in a restaurant, but even if he was right (I am not convinced) from the semi-classical EM wave perspective that still doesn’t reconcile things from the photon perspective. A counter falling beside the electron will either detect photons or it will not. The best my (very, very smart) friend could offer was to say that “quantum fields in curved space are very weird”, but he had no definite conclusion. I’ll try to ask some professors this week. If anyone here is a Ph.D. who knows something about general relativistic quantum electrodynamics, feel free to chime in!
That out of the way, here’s my classes this semester if anyone’s curious. I’m taking two, Classical Mechanics and E&M II (waves, basically). I’m teaching the non-calculus-based intro physics, which is definitely a nice easy assignment. One that’s quite fun to teach, as well. On this site I plan to go over concepts and problems from both the classes I’m teaching and the classes I’m taking.
Off topic and apropos of last Saturday’s post: Yesterday a bunch of grad students and I went to see Death Race. It was about like you’d expect. Anyway, there were posters for upcoming films, and what do you know: both Quantum of Solace and Defiance feature Daniel Craig exercising appropriate trigger discipline! This is a staggering rarity in film posters involving someone carrying a gun. Good for him.
Perfunctory politics: Biden? Ok. Very standard, very safe. Perhaps what he feels he needs. There was exactly one possible interesting choice – a particular senator from New York. Since she was not chosen (assuming the Biden news is accurate), I think McCain can breathe a sigh of relief. If McCain has any political savvy at all, he’ll pick Alaska governor Sarah Palin. I’m not holding my breath.
Have a great weekend! Sunday function is tomorrow, and we’ll be doing an alternate series approximation for a function whose power series fails to converge. Yes, it is EXCITING, darn it!