They started with algebra and ended up learning about gravitational lensing

Dmitry Khavinson and Genevra Neumann didn’t know anything about astrophysics. They were just doing mathematics, like they always do, following their curiosity. In 2004, they posted a new result, an extension of the fundamental theorem of algebra, on arXiv.org, a preprint server.

Five days later, they received an e-mail. Congratulations, it said. You just proved Sun Hong Rhie’s conjecture on gravitational lensing.

Gravitational what? Khavinson, of the University of South Florida in Tampa, and Neumann, of the University of Northern Iowa in Cedar Falls, had …