As of right now I'm a rising sophomore, math and physics double major. It's hard to say whether I'm gonna be pursuing a PhD in one of these disciplines or whether I'll be switching to something more employable later, as I haven't had many upper division classes. I do, however, strongly suspect that I'll certainly enjoy and feel challenged by them. Secondly, the prospect of researching in Theoretical or Mathematical Physics, especially for a TOE seems highly attractive to me. So chances are I will be pursuing a PhD in one of these fields. However, the prospect of being in school for 5+ years AFTER undergraduate studies seems undesirable to me, and highly undesirable to my family who have certain expectations from me (which I want to meet). So I'm looking for certain routes, if any, which will allow me to remove a year or two from that 5-6 year number. I've heard that at certain places in Europe or the UK a PhD is doable in 3 years. Can someone expand upon the accuracy of that? Going to the UK is something I'll consider if that happens to be the case. Also what are the differences between someone who does his PhD in 4 versus someone who does it in 5? Is it a matter of preparation and talent? Does it have to do with the research project? Will taking graduate classes as an undergrad help me shorten the amount of time? What other possibilities are there? Any insights to these questions, I'll certainly appreciate. I'm not looking for shortcuts and easy way outs and I certainly understand that getting a PhD is tough and requires extreme dedication. I'm just trying to explore my options. Note that the number of years I'm talking about are the years after getting a bachelors, not a masters. I don't necessarily want a masters.