Book review: ‘The Order of Time’ by Carlo Rovelli

It’s a great time to be a non-physicist who enjoys a spot of string theory or thermodynamics in their spare time. There is a growing mountain of well-written popular science books exploring particles, parallel universes and everything in between, often penned by renowned physicists. What makes The Order of Time stand out is its brevity and its unapologetically poetic style.

Its author, Carlo Rovelli, is a founder of the theory of loop quantum gravity: a theory which unifies gravity and quantum physics in a common framework. He is best known to non-academics for his previous book, Seven Brief Lessons on Physics, which takes the reader on a similarly elegant and accessible approach to introducing the weirdness of modern physics.

And if there’s one thing you’ll be thinking at the end of The Order of the Time (Penguin, £12.99, ISBN 9780735216105) it may well be: “Modern physics is weird”. The Order of Time is a guide to time as physicists understand it today: how discoveries have washed away the familiar notion of clock time and how physicists have been rebuilding the concept of time ever since.

We experience time as something that ticks by steadily, as something that can be divided up into slots and dedicated to different tasks, as something fleeting and directional. This concept serves us well on our little planet and at the leisurely pace that we, as macroscopic objects, live - but it is wrong. The revelations contained just in the first half of The Order of Time may sound shocking, but told in Rovelli’s clear-headed style, they make perfect sense. There is no such thing as the present. Time is experienced differently for different people. The division between past and future only arises due to our unique perspective of the universe. So what is left of time?

This is what Rovelli tackles in the second part of his book as time is rebuilt as something alien to non-physicists (and probably most physicists, too). Although this short book could easily be read in a single sitting, you may well find yourself needing to re-read pages and take short head-scratching breaks as you deal with the implications of what Rovelli has shared. Perhaps most challenging is the idea that we – or at least physicists – need to stop thinking of the universe as being full of ‘things’.

“The world is not a collection of things, it is a collection of events,” Rovelli writes. “The difference between things and events is that things persist in time, events have a limited duration. A stone is a prototypical ‘thing’: we can ask ourselves where it will be tomorrow. The world is made up of networks of kisses, not of stones.”

Even we humans are events; multitudes of events in which air, food, water, information and culture is consumed, transformed and emitted. Only by looking at the world as wildly complex networks of events can we understand it. This is the basis on which physicists can build a new understanding of time.

Even when time is reconstructed as an unrecognisable concept, Rovelli never loses sight of humanity and what time means to us. He ends The Order of Time with a short, exquisite chapter about time and human mortality which is as far from technical diagrams and jargon as you could imagine.

The Order of Time may be a book about science, but Rovelli is deeply poetic in his approach to his writing (a style well conveyed by his English translators Erica Segre and Simon Carnell). He weaves together physics with world mythology, ancient poetry and moving personal stories – both about himself and other scientists – with a balance of sincerity and lightness of touch. If almost any other writer attempted this, it would feel dithering and self-indulgent.

It is tempting to compare The Order of Time to Stephen Hawking’s A Brief History of Time, which is a similarly well-written and concise introduction to the weirdness of time from the perspective of a theoretical physicist. However, I would be most inclined to compare it to Alan Lightman’s Einstein’s Dreams, a short work of fiction flitting between universes in which time behaves differently, giving rise to alternate human societies.

Although The Order of Time is short and constructed with a light touch, the subject matter is complex and it could not be called an easy read. Many passages will require the reader to take time out to think before re-visiting. This is not to say that it is flawed in any regard; deconstructing and reconstructing the concept of time was never going to read like a gossip magazine. Instead, it reads like a short work of literature, combining science and art in a manner that feels natural, heartfelt and perhaps even profound.