The Order of Time by Carlo Rovelli
The Order of Time by Carlo Rovelli
What is time?
Poetry tells us that time “passes”, it moves like a river, inexorably dragging us with it, and, in the end, washes us up on its shore while it continues. Metaphor tells us time is money, a commodity for us to budget, invest, spend, or waste. Language tells us time has volition: it flies, drags, stands still. The verbs alone suggest that we have always understood time as subjective, something experienced according to individual circumstance.
Yet, between past and future, cause and effect, memory and hope, regret and intention … in the physics elementary laws that describe the mechanism of the world, apparently there is no such difference.
Clock time, is an illusion…according to Einstein.
This concept boggled my mind. No difference from the general crowd, I conventionally think of time as something fundamental that flows uniformly, from the past to the future, measured by clocks. In the course of time, the events of the universe succeed each other in an orderly way. Yet, the author, Rovelli, illustrated that all of this has turned out to be false.
This concept is hardly new, scientists have written primers on the concept of time for a general audience, yet Einstein’s notion that time and space are essentially one, is the stuff of abstract poetry. Fortunately, Rovelli was able to convey warped time and other tentative physics with incisive clarity.
The Order of Time is a deep, abstruse meditation, elucidates some of the key developments in the philosophy and physics of time. Fortified with quotations from Proust, Anaximander, and the Grateful Dead, the book continues a tradition of jargon-free scientific writing from Galileo to Darwin that disappeared in the academic specialisation of the last century.
In Einstein’s general theory of relativity, he predicted that time passes more quickly in higher altitudes compared to lower altitudes, which are closer to the center of gravity. Thus, if a man who has lived at sea-level meets his twin who has lived in the mount Himalaya, he will find that his sibling is slightly older. Analogously, a clock placed on the floor runs a little more slowly than one on a table. So what is the real time? The question permeates throughout the book.
To answer that question: At the deepest level of mathematical physics, time does not exist at all. There is, according to Rovelli, just one basic equation that points to an arrow of time: the second principle of thermodynamics, which says that entropy is always increasing, that the journey from order to disorder is down a one-way street. We observe this journey because heat flows towards the cold things and one day all the heat will have dissipated, and we will experience neither past nor future. What makes the world go round are not sources of energy, but sources of low entropy. That suggests we can be sure of a before and an after, but that is only because we see the world as an approximation, and not as a buzz of its ultimate constituents, a ferment of atoms, and beyond the atoms, a fizzing of subatomic particles that in turn may be thought of as quivering fields embedded in yet more gravitational and electromagnetic fields.
So is there anything that is real? What exists? Einstein’s observation that time passes at different speeds in different places unsettled not just the anti-Jewish physicists of the Third Reich but the Roman Catholic church. Can it really be a sin to know?
The book opens with a discussion of Newton’s idea of absolute true time, ticking relentlessly across the universe. This is how most of us still imagine time, though Einstein showed that there is no single “now” but rather a multitude of “nows”. Rovelli goes on to consider Aristotle’s belief that what we call “time” is simply the measurement of change: if nothing changed, time would not exist. Newton chose to disagree. If the universe was to be frozen, time would tick on regardless. Impishly, Einstein asserted that both Aristotle and Newton were right. Aristotle correctly explained that time flows in relation to a before and after; and Newton’s absolute time does indeed exist – but as a special case in Einstein’s “spacetime” theory of gravity, which treated space and time as one and the same.
The book also depicted how Aristotle and St Augustine both wrestled with the protean question of time, and Rovelli takes his title from the only words written by Anaximander known to have survived the last 26 centuries. There is a paradox of course: even fundamental physicists count the days and contemplate the years. Time, Rovelli suggests, is not to be considered a fundamental entity of creation, but rather a property that emerges from a set of variables, and a special perspective, in the way a hockey team emerges from a group of kids who have decided to play hockey. We can consider our local circumstances as a special subset of the universe where entropy “is low in the past, the second law of thermodynamics obtains; memories exist, traces are left – and there can be evolution, life and thought”. Time, as evidenced by our language for it, becomes more easily appreciated as a set of layers, a complex collection of structures, and our use of the word “when” becomes a matter of social and personal convenience. In a sense, we make time.
In a nutshell, this book illustrates that the notion that time is merely a function of our “blurred” human perception. We see the world only through a glass, darkly; we are watching Plato’s shadow-play in the cave. In lucid pages, Rovelli manages to bring difficult ideas down a level that the general readers can understand and enjoy. I highly recommend this book.
