Okay, I really wanted to get a Ph.D on either mathematics or physics. I have current knowledge all the way up to differential equations for mathematics, and just classical mechanics and Principia for physics. I will go for the doctoral degree after six years (after the Navy). If I want to get a Ph.D sooner, then should I choose mathematics or physics for doctoral degree? Also, I've heard that physics takes a bit longer to problem solving than mathematics does, but anyways, any helpful replies will be appreciated.