Book excerpt: Time surrounds us. It defines our experience of the world; it echoes through our every waking hour. Time is the very foundation of conscious experience. Yet as familiar as it is, time is also deeply mysterious. We cannot see, hear, smell, taste, or touch it. Yet we do feel it—or at least we think we feel it. No wonder poets, writers, philosophers, and scientists have grappled with time for centuries. In his latest book, award-winning science writer Dan Falk chronicles the story of how humans have come to understand time over the millennia, and by drawing from the latest research in physics, psychology, and other fields, Falk shows how that understanding continues to evolve. In Search of Time begins with our earliest ancestors' perception of time and the discoveries that led—with much effort—to the Gregorian calendar, atomic clocks, and "leap seconds." Falk examines the workings of memory, the brain's remarkable "bridge across time," and asks whether humans are unique in their ability to recall the past and imagine the future. He explores the possibility of time travel, and the paradoxes it seems to entail. Falk looks at the quest to comprehend the beginning of time and how time—and the universe—may end. Finally, he examines the puzzle of time's "flow," and the remarkable possibility that the passage of time may be an illusion. Entertaining, illuminating, and ultimately thought provoking, In Search of Time reveals what some of our most insightful thinkers have had to say about time, from Aristotle to Kant, from Newton to Einstein, and continuing with the brightest minds of today.