When Carlo Rovelli was a university student, he painted a poster with Planck’s length on it in red and hung it on the wall of his bedroom. Planck length is 1.6 x 10-35 metres, about 10-20 times the size of a proton, essentially an unperceivable dimension for a non-physicist. Rovelli’s goal in life was to understand what happens at the level. “Then I spent the rest of my life actually trying to achieve this,” he claims.
While chasing this goal, physicist Rovelli has taken on himself another difficult yet laudable task, which is to help us understand the true mechanics of the universe. His previous works, including Seven Brief Lessons on Physics and Reality Is Not What It Seems ,have been worthy contributions in this pursuit. Now comes his new work The Order of Time (translated by Erica Segre and Simon Carnell ) aiming to deconstruct the notion of time.
Doing so requires breaking apart conventional understanding about time. “The difference between the past and the future refers only to our blurred vision of the world," he writes. From Einstein’s work on relativity, we know that ‘clock time’ is a misconception. For instance, a clock at a higher altitude runs faster than a clock at sea-level. So which one shows real time, and more importantly, what’s the unfaltering passing of minutes that we experience in the ticking of a clock? To explain his concepts Rovelli seeks refuge in philosophy and mythology — Greek and Indian primarily. The title of the book itself is borrowed from Rovelli’s favourite 600 BC Greek philosopher Anaximander’s only surviving fragment of writing.
There is no ‘present’ moment and no ‘absolute’ time according to Rovelli. He is also taken up with the Aristotelian view of time, that is, time is a measurement of change. Time wouldn’t exist if there weren’t any change. This is a key idea for it denounces the Newtonian rigid scaffolding-like concept of absolute time. Rovelli believes that there is no universal clock that would continue to tick if change ceases to happen. Instead it’s the ‘heat’ that’s central to distinguishing the past from the future. “Only where there is heat is there a distinction between the past and the future,” he writes. Irreversible progress of heat only in one direction is entropy, which never decreases in the world perceived by us. It’s the entropy that drives the world forward and not the energy. “Life is this network of processes for increasing entropy,” Rovelli proposes, and that the Sun should be seen as not a rich source of energy but rather a source of low entropy. “It is the dance of ever-increasing entropy, nourished by the initial low entropy of the universe, that is the real dance of Shiva, the destroyer,” he writes.
But why did the universe start with low entropy, that is, a state neat order in the first place? There is no definite answer to this mystery yet but Rovelli hypothesises that this phenomenon could be explained by “human perspective”. “Perhaps we belong to a particular subset of the world that interacts with the rest of it in such a way that this entropy is lower in one direction…,” writes Rovelli. The narrative in this section of the book, though devoid of any equations, gets tedious and taxes the reader’s brain quite a bit.
But perhaps that’s what Rovelli wants us to go through: to challenge ourselves to think unconventionally. This is a book that is an easy read but browsing through it in a hurry would defeat the purpose.
The Order of Time ; Carlo Rovelli, Allen Lane/ PRH, ₹497.
