The arrow of time


Paul Davies

Arizona State University, Beyond Center for Fundamental Concepts in Science, P.O. Box 871504, Tempe, AZ 85287-1504 USA


Euresis Journal, volume 7 (2014), pages 47-60

The arrow of time is often conflated with the popular but hopelessly muddled concept of the "flow" or "passage" of time. I argue that the latter is at best an illusion with its roots in neuroscience, at worst a meaningless concept. However, what is beyond dispute is that physical states of the universe evolve in time with an objective and readily-observable directionality. The ultimate origins of this asymmetry in time, which is most famously captured by the second law of thermodynamics and the irreversible rise of entropy, rests with cosmology and the state of the universe at its origin. I trace the various physical processes that contribute to the growth of entropy, and conclude that gravitation holds the key to providing a comprehensive explanation of the elusive arrow.