I have a PhD [DPhil] in physics from the university of Oxford in the UK. I signed up for a course in interdisciplinary science, and ended up working on somethin

I have a PhD [DPhil] in physics from the university of Oxford in the UK. I signed up for a course in interdisciplinary science, and ended up working on something I never new existed –– a technique (called dynamic nuclear polarisation [1]) that uses low-temperature nuclear physics, quantum mechanics and condensed matter physics of the variety you learn at university, but ultimately ends up being applied for medical imaging. People are alive because of the work I did, and I find this deeply meaningful. I loved learning about lots of new things that were genuinely very different, and applying them through the lens of physics, for very real applications – and liked being in a supportive environment that gave you the ability to choose what you were interested in and follow it through. The thing I would say though is that 1) the supervisor or supervisors you end up working with are incredibly important and are really the make or break decision for the whole programme of study; 2) you are in a surprisingly powerful position if you are a good undergrad student (the world is your oyster! You can go anywhere and do almost anything!); and 3) think beyond the PhD: it is little more than an apprenticeship. Where are you going later – do you want to work broadly in the area of $PHD_SUBJECT for the next few years? Will you learn the skills you want to let that happen? If you don't enjoy your subject of study, you may well come to resent being cheap labour for a rich institution, at a point in your life when you can do almost anything and go almost anywhere – and see your friends earn real money and get on with life (marriage, children, houses, etc). Full disclaimer: just today I have advertised a PhD place for a bright mathematical scientist, at Aarhus University in Denmark [1]. I am biased, but I would encourage you to go elsewhere. There are many great institutions in europe (switzerland and the UK included) and the other thing is that you do a PhD in 3-4 years on a real salary in most places – e.g. the starting point for total compensation for a student in Aarhus is ~428500 dkk per year (~$60k/year, ~€57k/year, ~£47k/year, from which tax & compulsory pension contributions are deducted, but no health insurance) and it is expected that this is enough to live on. This is a very reasonable salary, comparable to many graduate jobs. If anyone would like to talk to me about it, I'd love to chat (see profile). [1] https://physicsworld.com/a/dynamic-nuclear-polarization-how-a-technique-from-particle-physics-is-transforming-medical-imaging/ https://physicsworld.com/a/dynamic-nuclear-polarization-how-... [2] https://phd.health.au.dk/application/opencalls/multimodal-medical-imaging-ai-and-quantum-physics-for-diagnostics https://phd.health.au.dk/application/opencalls/multimodal-me...