A Zen-like journey through the mysteries of physics

“What is the sound of one hand clapping?” That simple riddle, with its multitude of possible correct responses, is perhaps the most familiar example of a Zen koan, a short parable designed to provoke the listener to pause, reflect, and perhaps alight on deep and subtle truths. A koan does not provide an answer; it poses a question that highlights the tension between multiple points of view. It is up to the listener to seek the answers through meditation on the meaning of the tale.

In Cosmological Koans: A Journey to the Heart of Physical Reality, theoretical physicist and cosmologist Anthony Aguirre uses a series of koan-like vignettes to explore questions at the forefront of theoretical physics and cosmology and some of their profound implications.

The basic style of the koan should be familiar to students of physics. Modern physics, like Zen Buddhism, often comprises counterintuitive and abstract ideas. In physics, those ideas are typically contained in tiny equations replete with subtle implications. Learning the equations can often be accomplished in less than an hour, but understanding the full depth of their consequences can take more than a lifetime. A physicist builds intuition into mysterious and abstract topics by working through examples to extract their exquisite lessons.

Aguirre’s book is organized as a fantastical journey set in the 17th century. Each short chapter begins with a brief narrative, written in the second person, describing an eventful moment along the way. The narrative is followed by one or two quotes providing some historical perspective, and the chapter finishes with a discussion of the physical principles or their consequences as illustrated by the events. The prose has a playful, dreamy quality. Aguirre manages to juxtapose the 17th-century journey with 21st-century physics in a way that feels natural and unforced. Through analogies to the journey’s events, Aguirre manages to break down even the most complex and abstract ideas into something accessible to a general audience.

That is not to say that the book is easy reading—the wisdom contained in any koan requires thoughtful engagement by the reader. Rather than laying out a deductive chain of reasoning, a typical chapter tends to meander around an idea, developing intuition and deeper understanding and, most importantly, conveying to the reader that the idea represents research that is still in progress. No one can just tell you the answer, because no one knows with complete certainty what the answer is.

The book begins with a discussion of the simplest concepts in physics, then rapidly builds into explorations of relativity and quantum mechanics, which both lead in different ways to the counterintuitive notion that the information available to any observer is necessarily finite. Along the way, Aguirre explores thermodynamics and the tendency of a closed system to move from order toward chaos. Notions of time and quantum causality provide insights into the modern origins of the universe and the possibility that the totality of what we see may represent only a small piece of a larger multiverse spanning all possible universes. Cosmological Koans also raises the possibility that we find ourselves with physical laws uniquely suited to our existence precisely because we are present to measure them.

From there, the discussion moves beyond the physics to an exploration of its implications for the nature of consciousness and being. Exposing the inescapable connection between our sense of self and the greater universe completes the circle: The koans are not just a vehicle to explain physics using the language of Zen; they directly connect the two subjects.

This is not a book to devour in one sitting. It is much better savored, with time between chapters to reflect on the messages they convey. Cosmological Koans is a journey worth taking for travelers both well-versed in and new to speculative ideas in theoretical physics.