I'm about to finish the second semester of the second year of a physics BS (out of 5 years). Next semester I will be taking CM, EM and Optics, so that you have a slight idea of my very limited knowledge (haven't touched to Relativity yet nor any quantum mechanics). Correct me if I'm wrong : String theories and any other theory that want to reconciliate QM and GR suppose the existence of magnetic monopoles, i.e. a symmetry in Maxwell's equations. Although it is probable that some elementary particles behaves this way, they have been searched for long and we never found them yet. So how do you feel about learning a theory that could be wrong at the beginning (its axioms)? I know that Dirac predicted the positron's existence (by making suppositions of symmetry I believe) and it has been confirmed a few years after by chance. He did the same for the existence of magnetic monopoles. I understand that for some physicists the idea of symmetry might result in a beauty, but I don't understand why so many physicists trust in it. My little experience with mathematics has showed me not to always trust my intuition, much less what I'd find beautiful. In my opinion any physicist has a good experience with math and shouldn't fall into many suppositions/speculations. Furthermore, what to think about GR? From what I've read, it cannot explain the speed of rotations of galaxies nor what happened (and what is happening) to Pioneer spacecrafts. Also from what I've heard, if we suppose GR to be accurate at large scale, we have to introduce dark matter and dark energy in order to make the Universe accommodates with the theory (while it should be the opposite, the theory accommodating to the Universe!). Believing in dark matter sounds to me like believing in God, but again, I've no knowledge on the subject and I've a probably biased viewpoint on all this. That's why I'm writing this post, I'd love to hear physicists. My dream is to do a Phd in Physics (I don't know the area yet and I'm opened to all) but I'll have to improve drastically my grades because I have no chance for now. I've expressed my feelings about these theories, a bit sad I must say. Before studying physics I had a much better point of view of these theories. I don't know if I forgot to say something. I hope not. Waiting for your replies.