I'm currently looking to major in theoretical physics/astrophysics for my undergraduate studies next year and I have a few questions about it that I'd like cleared up. At the moment, I'm a year 12 Australian high school student and I'm trying to decide exactly where and what I want to study at tertiary level. My main areas of interest are theoretical particle physics (mathematically rigorous areas of study like string theory) and various aspects of astrophysics, in particular research into physical cosmology. Dark matter/energy and topics pertaining to large celestial bodies like collapsing stars, black holes, etc interest me a lot. I also love the prospect of learning and using very advanced mathematics. Is the mathematics used in advanced theoretical physics (in particular, stuff like supersymmetric string theory, etc) more applied or pure maths? I haven't actually done any higher level physics studies, so my motivation to do the subject is mainly from pure interest, with what I know mostly derived from wikipedia reading. I'm also curious how 'research' in theoretical physics works both on an undergraduate level and in graduate studies and beyond (i.e. academic research). Am I right in assuming that since it's theoretical, I don't actually have to use any research facilities, etc. to conduct experiments? My impression of theoretical physics is that its mainly thinking, maths and computational calculations, etc. I hate actually doing anything practical, so this is quite important to me. Continuing that point, are studies in theoretical astrophysics/cosmology similar to theoretical physics? Is it the same line of work but in a different context? What are the main differences between the two? Being that I haven't had much opportunity to delve deeply into these topics, I figure that I should probably take both during my BS and decide my specialization during honors. If all these questions have been answered somewhere, a quick reference would be appreciated; I've been doing a lot of searching but haven't really found any information to iron out the finer details. I also have a few more questions but I notice the volume of this post is starting to become excessive, so thanks in advance for reading my questions.