Every now and then, I run into a historical fact I'm astonished I didn't already know. Yesterday, while reading Penrose's The Road to Reality
, I came across Noether's Theorem, which, roughly, says that every symmetry of a physical system corresponds to a conservation law.
Well, here's the odd thing. I knew perfectly well who Noether was - I did several algebra courses as an undergraduate, and Noetherian rings are very important. And I knew about the correspondence between symmetries and conservation laws, which is absolutely basic to modern physics; for example, the whole of Woit's Not Even Wrong
, which I read a couple of years ago, is presented from this point of view. Somehow, though, I'd received the idea that the link between symmetries and conservation laws was just kind of obvious, and no one had actually discovered it.
I suppose the fact that Emmy Noether was a woman is a coincidence. I poked around to see if I could find a biography. This is it, and people say it's good, but it's also incredibly obscure and hard to get hold of - the cheapest one I could find cost $90.00 plus postage. No doubt another coincidence.
Before I spark off any feminist conspiracy theories, it might also be wise to consider the possibility that the book just isn't any good. At least, this review
rather makes it look that way. But I'm still surprised I didn't know about Noether's Theorem already. It should be something that everyone just automatically knows.