Discovering that the number 1 has n nth roots, eg there are three cube roots of 1. Blew my 16 year old mind and pushed me to go to university from a very working class background where people didnt do such things.

Sadly, I then graduated into a horrible recession so the math degree was useless and i became a librarian. However, in the basement they had these mysterious computers they called roadrunners* and I learned UNIX. which led to my entire career.

*They were weird. Looked like tower PCs but ran some variant of SunOS on i386. I never saw them again.