Seven Brief Lessons on Physics
This one took an evening. It is under a hundred pages, the English translation of a series of newspaper articles, and it reads more like an essay than a textbook. I am not sure I learned many facts from it. I am sure it changed how I picture a few things.
The lessons
The seven pieces cover general relativity, quantum mechanics, the large-scale structure of the universe, elementary particles, quantum gravity, heat and time, and finally where we humans fit in all this.
The first lesson is the strongest. Rovelli calls general relativity the most beautiful theory he knows, and he makes you see why: gravity is not a force pulling across space, it is the shape of space and time itself. The image of space as something that bends, ripples and can be stretched, not as an empty stage, is old by now, but he puts it more vividly than anyone I have read.
Grains of space
The fifth lesson is where his own research comes in. In loop quantum gravity, space itself is made of discrete pieces, tiny grains linked to each other, and there is no continuous background underneath. I won’t pretend I understood how this is supposed to work, and the book doesn’t really try to tell you. But it is honest that this is one approach among several, unconfirmed by experiment.
Heat and time
The sixth lesson connects heat, probability and the direction of time. The basic laws of physics don’t care which way time runs; the difference between past and future seems to come from heat flowing and from our blurry, statistical view of the world. Rovelli pushes this further than most popular writers, toward the idea that the flow of time may partly be a product of our perspective. I found this the most provocative part, and the part I trust least, simply because it is so far from settled.
What bothered me
The poetic style is the book’s selling point and its weakness. Sentences like his work well in a newspaper and less well when you want to know why something is true. A few times I closed the book with a lovely feeling and no idea how to explain the idea to someone else.
Verdict
Read it as an invitation, not an explanation. It sent me back to things I thought I understood, and it made me want a longer, more careful book on time. Rovelli’s own The Order of Time is next on the list.