Like all languages, sign language evolves organically. There is no central office inventing or approving new signs. While there’s something beautiful about that, it’s also a huge pain in the ass to hearing-impaired science students, because there is a lack of agreed-upon signs for complicated terms like “photosynthesis” — or even simple ones like “mass.” This leads to a lot of improvisation and finger spelling, which only adds to the frustration deaf students already feel in the classroom. Now, with the rise of the Internet and particularly Web video, hearing-impaired scientists are creating online forums and even wikis to try to agree on some useful signs. The story is here, but be sure to check out the gorgeous multimedia page that goes with it, starring N.Y.C.’s favorite interpreter, Lydia Callis.