I graduated with a first class honors undergraduate in experimental Physics from the top university in my country - the degree was plainly called Physics but the university does offer a Theoretical Physics course too. After a year of unemployment and not knowing what to do in life, I enrolled for a taught MSc in Computer Science / Software Engineering, being where "all" the jobs are. I graduated with a first class honors degree and I've been working for two and a half years now in a major international technology corporation as a software engineer. So far so good. Don't get me wrong, I find the engineering very enjoyable - apart from the stress, but I always find myself yearning to understand more physics and mathematics. I'm the type that enjoys sitting in an armchair reading or discussing deep, fundamental physics and the nature of the world. From time to time I'll try read up on mathematics or physics from a textbook, or dig out my old college notes for a refresher or to try really learn it this time (I've forgotten a lot of it). There's almost this deep sense of guilt/regret that I'm not pursuing the path that really intellectually thrills and excites me - fundamental physics and the nature of reality. Would it be possible to gain entry to a Theoretical/Mathematical Physics PhD with an undergraduate in experimental physics? Is this unheard of? I have this vague idea that maybe if I self-study mathematics and theoretical physics that in a few years time (I'm in my late 20s now) when I feel ready I could enter a program and be very well prepared...(wishful thinking?) And yet having said all this, there is something that scares me about a PhD. The years of "being a poor student again". The cut-throat culture I hear of where only the best and brightest make it. Being an older student. The constant public speaking demands. The 7-days a week commitments to a heavy workload. The stress. Am I being too sensational, too paranoid? I guess I just wanted to reach out and see if anyone else ever found themselves in a similar situation to mine. How did things work out? Did you feel the same as me?