Translated from Italian by Erica Segre and Simon Carnell
Published by Penguin, 2018, 214 pages. Original version published in 2017.

What is time? The idea that there is a “now” throughout the cosmos, that the past is behind us and the future is open: these are ways in which we think of time. But the reality is far more complex.                        

What physicist Carlo Rovelli does in this book is to take time apart and prove that everything we know and believe about time is false.

Time is not universal—that is, it does not move at the same pace throughout the world. Time is affected by location and speed: it moves faster in the mountains than on the plains, it moves faster when you’re in motion than when you are standing still. On the plains, it is not just time that is slower, all processes are too—whether it is the rate at which plants grow or people age. The differences may be infinitesimal, but nevertheless, they exist. This means that there is no correct time, time works differently depending on where you are, and all these times are relative to each other. 

Rovelli then takes on the supposed linearity of time (his explanation involves entropy and the second law of thermodynamics). One by one, he explains why all the things we assume about time do not stand up to scrutiny.

The book is divided into three sections: The Crumbling of Time, in which Rovelli, using modern physics, takes apart all our conceptions of time; The World Without Time, where he looks at what it means for time to not exist; and The Sources of Time, where he goes back on what he calls “the return journey”, to understand how and why time works for us.

This is a book that explains complex concepts in relatively simple terms—at least, most of the time. I admit that I did not understand everything and, in my summary, may have got something wrong. If I did, my apologies. Rovelli uses literature, music, and popular culture (some of the diagrams involve Smurfs) to make his point.

I have always been fascinated by time. One of the reasons I love Christopher Nolan’s films is because he plays with time. In his films, time stretches, condenses, loops back onto itself, giving the story another dimension of reality.

So it is no surprise that I picked up this book.

It is intriguing and has not only given me plenty to think about, but also made me reassess the way in which I perceive the world. And time.