In the latter part of high school, and in my early years in college as a computer engineer, I found physics and the philosophy of it really interesting. I remember the first time, in 9th grade, that our teacher showed us how to predict the bounce-height of a ball using some basic algebra. I was immediately in love with physics, and it was the first time that I realized math could be fun.

In my senior year, AP Physics C: E&M would become one of my favorite courses of my entire scholastic career (largely thanks to my teacher). While Calc 3 wasn't required for the AP test, he introduced the concepts so that he could properly walk us through the history of the field from the perspective of its founders, up to and concluding with Maxwell's equations. We read a lot of the original papers that introduced certain operators and equations, including works from Newton, Leibniz, Heaviside, Maxwell, Einstein, and Dirac. Ironically, I failed the AP exam (2/5) but had a very easy time with Calc III, linear algebra, and diff eq in college thanks to that course.

I really miss the feeling of wonder and astonishment I had when I was first exposed to these concepts -- it's been long enough that my memory of them is fuzzy now, but I don't get the same satisfaction from re-reading them.