As an inside tip, you might want to adjust away from M theory; I've got a fair few friends (and a sister) in physics, and aparently it's looking a lot less compelling. Publications have been declining, and more physicists are beginning to speak out against the untestable nature of string and its related theories. Fortunately, the Large Hadron Collider comes online next month, and that might give us some clues either confirming or refuting it.
Ironically, she actually wants to teach when she gets over to the US (as well as to breed herps).
These are exactly the big questions that are, I think, the most fun. They likely can't be solved, but IMHO, how we each reason about them can serve to not only hone our minds, but to give insight into ourselves and how each of our minds work.
Henry