The Jacobian conjecture is a mathematical problem in several variables, that was first posed in 1939 by Ott-Heinrich Keller. It is a question in the area of algebraic geometry that requires little beyond a knowledge of calculus to state. It became widely notorious among mathematicians, as all of the attempts to prove it had included subtle errors, and it remained unproven well into the 21st century.
In 1943, Emmett Brown left the class he was teaching at the California Institute of Technology to confront Robert Millikan about getting an interview with the United States Army for the Manhattan Project. He told his students to work on the Jacobian conjecture, stating that, since he didn't teach a math class, they'd be thoroughly occupied.
- Back to the Future (IDW Publishing)