Lessons and physics are in the title, but don't panic. Although Carlo Rovelli is a high-powered theoretical physicist, he doesn't lecture the reader. He shares his understanding of the strange universe of modern physics as a man steeped in philosophy and with poetry in his soul.

If you met physics in school, you may have found it mathematical, mystifying and mundane. But Seven Brief Lessons on Physics is none of that. It's an interpretation of some of the most important ideas of modern physics, and of our place in this universe. Carlo Rovelli's scientific work is in the field of quantum gravity, but he has also for many years taught general relativity, and the history and philosophy of science at Aix-Marseille University in southern France.

It is brief
The title says brief and that's what you get. It's eighty pages long with a commendably readable typeface. Each chapter is an expansion of an article Rovelli wrote for a Sunday newspaper. He says:
Two splendid theories, but there's a problem
Over half of the book deals with two crowning achievements of the 20th century – Einstein's General Theory of Relativity, and Quantum Mechanics. Relativity deals with the grand structure of the cosmos, while quantum mechanics dives into the Alice in Wonderland world of the tiniest bits of what everything is made of.

General Theory of Relativity
The great Russian physicist Lev Landau called the General Theory of Relativity the “most beautiful of theories” and Rovelli concrurs.

For Isaac Newton, space was empty except for the objects in it, such as stars and planets. These objects affected each other through the force of gravity. Newton himself wasn't happy with a force that acted instantaneously even at great distances, but his equations worked, and no one knew how to take it further. Until Einstein.

Einstein's brilliant insight led him to the conclusion that space isn't nothing and gravity isn't a force. Space has substance and it's warped by the presence of matter. When matter curves space, things move through space along the curvature as something might on a fairground track. The bending of space around a star is summarized in the only equation in the book.

Mercifully, Rovelli invites us merely to admire the equation's elegant simplicity without being required to understand it. However I would have to disagree with his assertion that it takes less commitment and effort to “master the technique to read and use this equation” than “to come to appreciate the rarefied beauty of a late Beethoven string quartet.” I think I'd appreciate Beethoven long before I could make any use of Einstein's equation.

Quantum mechanics and particles
The fundamental particles that make up everything exist in a strange quantum world. These fundamental components are described by the Standard Model. It contains “a handful of types of elementary particles, which vibrate and fluctuate constantly between existence and non-existence and swarm in space even when it seems that there is nothing there.”

They pop into existence only when they interact with something else. Yow! Rovelli goes on to explain it nicely, but admits that no one really understands what's going on at this level. (That is comforting to his readers.)

Conflict
Danish physicist Niels Bohr was one of the great leaders of the exposition of quantum physics. He and Einstein admired each other, but their opinions differed about the reality of existence. Einstein thought there was an underlying reality in which the quantum effects made sense even though we haven't perceived it. Bohr didn't.

The conflict between relativity and quantum physics isn't philosophical. There is a point at which they contradict each other. However this isn't a practical problem. General relativity has been tested many times and always passed the tests. Your GPS only works accurately because it takes general relativity into account. And even though quantum mechanics seems crazy, it works. You wouldn't have a computer without it.

So how can they both be right almost all the time, yet at some point contradict each other? That is something that keeps theoretical physicists like Rovelli hard at work.

Ourselves
Rovelli devotes one lesson to how our view of the cosmos has evolved over millennia from a small Earth-centered universe to an enormous expanding one. But the Universe isn't something from which we are apart, and in the final lesson he considers our place in the Universe. This is more speculative than the other chapters, but, of course, we're always interested in ourselves.

Worth reading?
The book is well written, thoughtful and stimulating. Rovelli wrote it in Italian, and it has been a best seller in a number of languages. I must also commend the translators (Simon Carnell and Erica Segre) for the very readable English version. And taking a look at some websites with reader reviews, it appears that people are actually reading the book. They're also getting something out of it. It might make a nice present for someone you know.

Carlo Rovelli, Seven Brief Lessons on Physics, Penguin Books Ltd, 2016

Note: A copy of the book was given to me as a gift.