Such non-uniformities of time can seem strange and unexpected, but they come to feel like minor oddities compared to what follows, as Rovelli next dismantles our view of time as necessarily having a flow, from the past of the future. Perhaps more strangely, it turns out that there is no single now throughout the universe – the now we experience at any given moment on Earth does not have an equivalent now-moment on a distant star, on another planet in our solar system, or even on the other side of a room, though the difference becomes more and more insignificant at such close range. We learn for example that time doesn’t pass at a uniform rate throughout the universe: the closer one is to a large mass the slower, in fact, time passes – for someone on top of a mountain, time passes more quickly than for someone down in a valley. Fortunately, despite the inherent complexity of the terrain he covers, Rovelli’s captivating prose helps guide us through the intricacies of the mind-blowing discoveries that have overturned our intuitive expectations about time. He demonstrates, however, that these beliefs about time do not align at all with the understandings scientists have developed and, particularly over the past century, validated through experiment. Together these could be summarized as that our intuition tells us that time is an independent scale, around which everything in the universe aligns itself. These include our impression that time: passes at a uniform rate everywhere flows from the past, through the present, to the future has a single now or present applicable across the universe is independent of physical events and so represents a fundamental measure for everything in the universe and, is continuous even at the smallest scales. In each, he presents a particular expectation we have about time, one that seems unimpeachable based on our daily experience but which he goes on to quite thoroughly eviscerate.

Rovelli opens his book with a sequence of five chapters grouped under the appropriately ominous section heading The Crumbling of Time.

In a richly lyrical account, Rovelli employs an engaging mix of science, philosophy, history, music and literature to make his case for how we should think about time. This observation from Max Tegmark could have served as an appropriate epigraph for his fellow physicist Carlo Rovelli’s wonderful new book, The Order of Time, which explores how physicists’ current thinking about the concept of time calls into question our intuitive understanding of it based on millennia of interactions with the physical world. Max Tegmark, Our Mathematical Universe (363)

Carlo rovelli the order of time review