The physicist Sidney Nagel delights in solving mysteries of the universe that are hiding in plain sight. Sidney Nagel, pictured in his office at the University of Chicago, concerns himself with coffee stains, traffic jams and “all the ways in which nature works, not just the ones that sound esoteric and deep.” Kristen Norman for Quanta Magazine Introduction A stain drying on the counter. A raindrop splashing onto the sidewalk. A pile of gravel settling. Historically, such phenomena have rarely c...