Category: Non-Fiction. Rating: 4 out of 5. Tags: Cosmology, Physics, Quantum Physics, Relativity
Cosmological Koans is a book about the nature of physical reality, explored through a series of chapters modelled after Zen koans. Not to be confused with the elementary particles called kaons, a koan is a riddle meant to provoke enlightenment. The chapters also follow an unnamed character – “You” – on a journey across southern Eurasia. The author, Anthony Aguirre, has a knack for finding concrete analogies to help explain abstract concepts, and the experiences of the book’s traveller provide a starting point for introducing various topics in physics.
An arrow flies toward the traveller, opening a discussion of Zeno’s paradox and the nature of time. Is time infinitely divisible into smaller and smaller segments? If so, how does anything move? If not, what determines the smallest division?
A sailing boat moves, and balls of light are tossed back and forth between gondolas in Venice. The laws of motion as discovered by Galileo and Newton are thus introduced, as well as the paradoxical differences in the behaviour of light compared to everyday objects.
General relativity, the curvature of space-time by massive objects, and quantum physics are similarly illustrated with analogies to everyday experiences. One of my favourites is about the weird results seen in the double slit experiment: some imagined monks enter a monastery through two gates, their spinning prayer wheels showing the effect of phase differences in creating interference patterns.
Other topics include entropy, the arrow of time, the nature of information, the origin of consciousness, and the many worlds theory. To prove or disprove the many worlds theory, there’s a fun thought-experiment involving a strange form of Russian roulette. It’s like you’re the cat in the Shrödinger’s cat experiment, only you’re the observer, too.
The wide-ranging discussion eventually boils down to some suggestions about the nature of reality. There is no clear separation between the probabilistic world of quantum mechanics and the deterministic world of everyday life. We think there must be a true state of the universe at any point in time, but fundamentally, not only is there uncertainty about that state, there is no instant we can call “now” that applies throughout the universe. Matter isn’t solid. An electron is “an excitation of the electron field, which pervades space-time.” If you want to know what an electron field is, it’s “an entity able to create and destroy electrons!” As Aguirre admits, “This is a rather displeasingly circular response.” Another way of looking at it is that an electron is something that gives a specific set of answers when observed in experiments. When we get those answers, we say we’ve observed an electron. In quantum theory, there’s nothing more to it; it’s just information.
As with koans, the book provides lots of food for thought, but doesn’t always have the answers. It does, however, provide comprehensive coverage of many of the big questions.
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