O.K. This question shows just how ignorant I am about things academic, but what do people working on a PhD do? And how long does it take to get your PhD? I'm mainly interested in knowing about a PhD in mathematics. Here are my questions: 1)Do you take only classes that relate to math (or whatever your field is)? Do you ever take courses that are outside your field? And if not, can't this eventually lead to a sort of mental tunnel vision? 2)Do you spend most of your time in classes? I know you have to write a dissertation, and then present it to a panel or something... But is that what you spend most of your time on? If so, does that mean you spend most of your time flying solo? 3)How long does it take to get your PhD? 4)If you get a PhD in one field, is it usually easier and faster to get a 2nd PhD in another field? Well, I guess that's enough questions for now. Thanks.