String Theory has helped teach humankind that more is possible — and probable — than most of us are capable of imagining. Crazy stuff. Like, theoretical physicists with a sense of humor and a talent for writing. Leonard Mlodinow’s “Feynman’s Rainbow,” a breezy memoir about his days as a young scientist at Caltech, is a kind of miracle. The book is about searching for some of the most profound truths in the universe, yet it’s as light and anecdotal as a dish-all about NYU Drama. If you dig eccentric geniuses at work on the mysteries of the cosmos, this is your beach read.