The asymmetry of natural phenomena under time reversal isstriking. Here Zehinvestigates the most important classesof physical phenomena that characterize the arrow of time, discussing their interrelations as well as striving touncover a cosmological common root of the phenomena, such asthe time-independent wave function of the universe. Thedescription of irreversible phenomena is shown to befundamentally "observer-related". Both physicists andphilosophers of science who reviewed the first editionconsidered this book a magnificent survey, a concise, technically sophisticated, up-to-date discussion of thesubject, showing fine sensivity to some of the crucialphilosophicalsubtleties. This new and expanded edition willbe welcomed by both students and specialists.