*On the Works of Pierre Curie on Symmetry* -- one of my favorite papers

This paper describes an amazingly deep principle underlying a lot of physics. The paper might be a little tricky if you're not familiar with group theory, but it's got some pretty good illustrations that help a lot.

The one-line takeaway is:

It is only the absence of some symmetry elements, which is obligatory. It is this property – dissymmetry – which makes phenomena

Essentially, if you can find a broken symmetry in some effect, you know that you'll also find that broken symmetry in (the superposition of) it's causes. You can't necessarily say anything about the set of symmetries of the causes, but you can about their dissymmetries.

The reason I love this paper so much is because it's part of a line of mathematical thinking about science that eventually lead to Emmy Noether's famous theorem, where she was able to prove that wherever we find a conserved quantity (e.g. energy, momentum, etc) it is due to an underlying continuous symmetry in the system. (This isn't the same thing as this paper is discussing, but her result uses this same application of ideas from group theory to physics.)

Note: This paper should be available as part of an open archive but sometimes it's hard for me to tell, since I have institutional access; lmk if you can't access the paper