People like you and me, though mortal, of course, like everyone else, do not grow old no matter how long we live. What I mean is that we never cease to stand like curious children before the great Mystery into which we are born. – Albert Einstein

When I was 14, I read Arthur Eddington’s The Nature of the Physical Universe. I remember how excited I was to learn that a desk is not a solid piece of furniture. If you could look closely enough, said Eddington, beyond the power of any microscope, you would see that it is made up of atoms so tiny that we can hardly grasp their tinyness. These atoms are made of even tinier nuclei, and these in turn are made of particles called neutrons and protons, while little electrons whiz around them in orbits like miniature solar systems. “So that is what the world is made of!” I thought, and this was the first step in my eventual decision to make physics my career. Of course it didn’t occur to me then to wonder what electrons, protons and neutrons are made of.

Some time later, as a graduate student, I attended a three-year lecture series at Harvard University by Julian Schwinger. The timing was perfect. Schwinger’s development of Quantum Field Theory (QFT) had matured and he was about to publish a monumental work, “A theory of the fundamental interactions”. I sat mesmerized, as did others.

Attending one of [Schwinger’s] formal lectures was comparable to hearing a new major concert by a very great composer, flawlessly performed by the composer himself… The delivery was magisterial, even, carefully worded, irresistible like a mighty river… Crowds of students and more senior people from both Harvard and MIT attended… I felt privileged – and not a little daunted – to witness physics being made by one of its greatest masters. – Walter Kohn, Nobel laureate (M2000, p. 593-4)

As Schwinger stood at the blackboard, writing ambidextrously and speaking mellifluously in well-formed sentences, it was as if God Himself was handing down the Ten Commandments. The equations were so elegant that it seemed the world couldn’t be built any other way. From the barest of first principles, he derived all of QFT, even including gravity. Not only was the mathematics elegant, but the philosophic concept of a world made of properties of space seemed to me much more satisfying than Eddington’s mysterious particles. I was amazed and delighted to see how all the paradoxes of relativity theory and quantum mechanics that I had earlier found so baffling disappeared or were resolved.

Later on, I must admit, things got more complicated as the number and variety of fundamental fields grew, and quarks entered the scene. But to my knowledge, QFT remains as the true fabric of which the world is made. What’s more, I believe it is the only fabric of which the world could be made.

Unfortunately, Schwinger, once called “the heir-apparent to Einstein’s mantle” by J. Robert Oppenheimer, never had the impact he should have had on the world of physics or on the public at large. Instead, the more colorful and outgoing Richard Feynman came to the fore, especially after his public role in the Challenger disaster. It is his image, not Schwinger’s, that is enshrined on a postage stamp. It is possible that Schwinger’s very elegance was his undoing.

Julian Schwinger was one of the most important and influential scientists of the twentieth century… Yet even among physicists, recognition of his funda­mental contributions remains limited, in part because his dense formal style ultimately proved less accessible than Feynman’s more intuitive approach. However, the structure of modern theoretical physics would be inconceiv­able without Schwinger’s manifold insights. His work underlies much of modern physics, the source of which is often unknown even to the practi­tioners. His legacy lives on not only through his work, but also through his many students, who include leaders in physics and other fields. – J. Mehra and K.A. Milton (M2000, p. v)

In the 50 years that passed since my student days, I have seen very little mention of QFT. Instead I have seen a bombardment of books and articles that keep repeating the paradoxes that people are expected to accept. Physical intuition has disap­peared or, worse yet, is sneered at. Far from bringing to the public an understanding of nature, these popular books and articles have brought confusion and incomprehensibility. This hit me hard one day as I was reading Joseph Heller’s memoir, Now and Then. Heller is the author of Catch 22, one of my all-time favorites. When I read that he tried to understand quantum mechanics and had to give it up, I knew that something was badly wrong. And so I decided to write a book.

My mission soon turned into a labor of love, with emphasis on labor. I had not anticipated the breadth and depth of the subject, or the drama as our greatest minds waged what I think is our greatest battle: to understand the world we find ourselves in (a far more worthy battle than the wars we are so good at waging against each other). By drama, I mean not only the philosophic struggle to wrest nature’s secrets from their most hidden recesses with only the flimsiest of evidence; I also mean the human side of the story – stories that are sometimes tragic, sometimes nettlesome, but always fascinating.

This book is my attempt to bring to the public the same sense of satisfaction that I felt in Schwinger’s courses and to dispel the paradoxes of physics that prevent so many people from understanding the natural world. The book is aimed at two audiences. The primary audience consists of those who, like Heller, have made some attempt to understand modern physics and found it to be incomprehensible. The other audience is those people who have not read much about physics, but who would like to learn about it in a way they can understand. I hope that my efforts will bear fruit and that the reader will come away from the book feeling that nature is not mysterious or paradoxical, but is understandable and indeed makes perfect sense.

Rodney Brooks
Wanaka, New Zealand, 2010


The second edition brings “Fields of Color” fully up-to-date with a description of recent developments in the “Standard Model”, otherwise known as Quantum Chromodynamics (see Chapter 7). Of particular importance is the calculation of hadron masses from basic field equations, which has been called “one of the greatest scientific achievements of all time” – an achievement of which the public is largely unaware! A discussion of dark matter is also included, along with other clarifications and improvements.

Rodney Brooks
Prescott, Arizona, USA
December, 2011


The third edition is a major rewriting.  Among the new features are an explanation of gravity waves and their detection, and solutions to the measurement problem (Schrödinger’s cat), the Ehrenfest paradox, and the mystery of dark matter.

Rodney Brooks
Silver Spring, Maryland, 2016