You can do all those things meaningfully: I think it's really about the end product (physical or not) - if you are making something you don't believe is useful to society, or don't have control over how your efforts are being used downstream, then it can easily become inherently meaningless.<p>There are basic needs: clean water, clean air, infrastructure, transportation, logistics, etc., etc. And also "non-tangible ones". You can get much more authentic social respect if you work on products/services that people unambiguously like and need.<p>I recommend, for example:
- Biomedical: signals, images, ... (I've done a bit)
- Anything GIS, urban/transportation planning, geo-spatial analytics, cities, etc. (my chosen specialty, very fulfilling).<p>There's lots of number crunching, but also human-entry string processing (fuzzy matching, etc.). Actually, very versatile programmatically. And then there is fast graphics (OpenGL, etc.) - not my favourite part, actually, but you can outsource it partly.<p>You get to work in very multi-disciplinary groups, so you can really assess where you want to go long-term. I was surrounded by people with very similar training to mine - technologically it was pretty good, but topic-wise it was a bit of an echo-chamber.