I am an undergrad with geophysics major. Well...my course does contain some substantial amount of physics, but it does lack the thrills of quantum mechanics and particle physics(and probably something more). Frankly, i am highly fascinated by the subjects like QM, particle physics. I have a strong inclination towards theoretical physics.. and i do want to pursue my career in this (may be as good professor or working as a scientist). I don't have the provision to shift my majors now...its too late, and we don't have dual majors. At this situation i feel like i have two choices. 1. To do my phd in geophysics(from some good university)...on topic overlapping with QM and particle physics (like the cosmic rays). But i am still not sure whether this will take me to that level(as a good physics professor) or not ?....(help me out on this). 2. To complete my B.S in geophysics and apply for phd in physics(which does seem to be quiet difficult).The problem is that i may not get in good univs. And that would also take a lot of extra work and much more time. Which one do you think is a better option ? and if you have any more suggestions,,,,then you are welcome. I am really curious about option 1......it does to seem to be better but will this actually help me reach my destiny ?