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Like an enthusiastic old man explaining the ways of the world to a wide-eyed grandson, he guides the reader through complex ideas and theories, all the while populating his books with personal anecdotes and cultural references ranging from Lewis Carroll’s Alice, to Lennon and McCartney’s Fool on the Hill. There is, of course, no scientific evidence for this, and Rovelli is sure to emphasise this: “I’m not sure if we are dealing with a plausible story, but I do not know of any better ones.” It is, however, an intriguing and seductive idea that we must look within ourselves to find the key to unlock this mystery.Īs in his bestselling Seven Brief Lessons on Physics and Reality is Not What it Seems, it is Rovelli’s idiosyncratic tone that sets his books apart from similar titles. It is, he suggests, the fact that from our perspective of the Universe, entropy increases with our thermal time, that allows us to distinguish past from future. More precisely, it is the fact that this interaction is partial, given our limited sensory capacities, combined with quantum indeterminacy that gives rise to a variable he calls ‘thermal time’. What Rovelli proposes is an idea that focuses on our interaction with the world around us. This remains one of the greatest mysteries of time: why does its onward passage seem so utterly inexorable to us, when all of these fundamental laws work just as well if time is reversed? For, as Rovelli notes, past and future are not differentiated in the elementary equations of the likes of Newton, Einstein and Maxwell, that dictate the events of the world. It is then left to the second half of the book to explain why we perceive the flow of time as we do.

Both seem equally implausible, but as with all of the material in this half of the book, they can, and have, been verified through scientific thought and experimentation.

However, that is not to say that, locally, the passage of time does not fluctuate: the speed at which we move, as well as our proximity to a mass, affects the rhythm of this passing of time. Instead, the present is a localised phenomenon. For example, through getting the reader to imagine the temporal experience of their sister who happens to be on Proxima b(a planet around four light years from Earth), Rovelli debunks the idea of ‘now’ common throughout the Universe. The first half of the book gives an overview of what we know to be true about the nature of time. In his new book The Order of Time, theoretical physicist Carlo Rovelli challenges these understandings, while also offering suggestions as to how they might have come about. Our common understandings of time are so ingrained within us that to suggest anything else seems ridiculous. Bruno Reynell reviews the mind-bending and revelatory new work by renowned physicist Carlo Rovelli.īefore today was yesterday.