Here is the essential guide to physics, an authoritative reference book and timeline that examines the foundations upon which all scientific knowledge rests. Without physics, everything else-from astronomy to zoology-would be a meaningless conjecture. Our journey begins with the first attempts to understand reality, Mother Nature-or as the ancient Greeks called it, physis. Follow the journey through history as great scientists, such as Thales, Galileo, Feynman, and many others, gradually unpick the fabric of the Universe revealing an array of fundamental forces, intangible particles and indestructible energy.