Let me first tell you how the idea for this book came about. Many years ago,
when I was a young assistant professor, I enthusiastically began my college
teaching in a junior-level course that was supposed to cover quantum mechanics.
I was eager to share my recently acquired insights into the intricacies
of this very fundamental and profound subject, which seeks to explain the
structure and behavior of matter and energy. About five minutes into my first
lecture, a student raised his hand and asked, “Sir, what is that funny curly
thing?”