This question already has an answer here:
- QM without complex numbers 12 answers
- About the complex nature of the wave function? 13 answers
- Why are Only Real Things Measurable? 7 answers
- Where does the $i$ come from in the Schrödinger equation? 5 answers
Coming from someone who knows a tiny bit about the subject but who really wants to learn. I know it's the square root of -1 but I would like some insight as to why it's used at all.