As the bus pulled farther away from its stop, the houses would become fewer and fewer until they were left behind; the olive groves where I would ride my bike would look less familiar; the coast line would no longer be the one with the beaches where I would spend time swimming and playing with friends. That’s when I would recall the moment I jumped out of the buss when it arrived at the village, the welcoming of my uncles, aunts and cousins, and the anticipation of the pleasures of a whole summer ahead of me. All that would come to an end two months later. I would try to relive those first moments of arrival but it was hard to really “live” them. I could not replay my summer vacation. That was then my personal struggle with time.
We all struggle with time. We want time to stay still, or the duration of something we enjoy to remain endless. Other times we wish something lasts as little as possible. So, given our human fascination and struggle with time, I read with great interest Carlo Rovelli’s short book The Order of Time. Rovelli is an Italian physicist, specializing in quantum gravity. But don’t assume he is a story teller of cold scientific facts. His book is informative and poetic, close to science but never far from our human essence.
In this book, we learn that time as a physical variable is anything but stable, single, or always present. Time passes faster if you live at the top rather than the ground floor of the Empire State building. Time passes more slowly if you keep moving than staying still. The rambunctious kids that run around in the ground floor age more slowly than the old folks who spend hours watching TV in the top floor. The present, the now, is also not the same for all of us. When my cousin in Greece hears my voice on the phone, I have already moved into the future because my voice does not reach my cousin instantaneously. There is a multitude of “presents” in our universe. In the world of quantum physics, that is, the world of the very, very tiny things we call particles, time, as a variable, is absent. Processes can be played forth and back without upsetting the laws and equations of quantum mechanics. In this infinitesimally small world, the very foundation of our universe, there is no past, present or future.
By the end of that part of the book, we realize that time is not what we think it is. That line we divide into past, present and future along which we believe our lives unfold. But after Rovelli has destroyed our everyday notions of time, he starts to reconstruct time as we humans experience it. Our ability to perceive the world in its smallest scale, the quantum scale, has not been selected by nature as a trait necessary for our survival. That’s why we do not sense all these peculiarities about time. What is necessary for us to survive and thrive is just enough (actually a coarse) perception of the world as a three-dimensional space plus a fourth dimension we experience as a single time, ordered from past to future.
Our human sense of time, as far as the outside world is concerned, starts with our incomplete perception of the world as a physical system that moves from low entropy to higher entropy. Entropy measures how well- arranged things are. The leaves on the tree are ordered in some arrangement. Then the fall wind blows them to the ground where they lie in a less ordered arrangement. Later the wind scatters them into greater disorder. The leaves on the tree had lower entropy than the leaves scattered around the yard. Thus, in our human eyes, the world moves from low (greater order) entropy to higher (greater disorder) entropy. Entropy cannot move backwards, that is, entropy does not go from high to low.* Entropy, that is, the order of the world as we perceive it, is the closest thing we have in relation to nature that can sustain our sense of a past, present and future.
If it is so difficult to find time in the physical world, how does it emerge in our human lives? Rovelli argues that time emerges in our brains as memory (a sense there is a past) and anticipation (a sense there is a future). The clock is in our brain. It helps us organize our lives along a line from past to future and give us a sense of personal identity and makes us conscious of our interactions with the external world.
Here Rovelli starts to sound like the French philosopher Henri Bergson (An Introduction to Metaphysics) for whom consciousness means memory. Our memory is the repository of the past so that the past lives in the present. But the present is elusive like the flow of a river. “We cannot step into the same river twice,” is how the Ionian philosopher Heraclitus (6th century BCE) put it. We sense time as duration not as a string of still moments. Bergson writes “Without this survival of the past into the present there would be no duration, but only instantaneity.” Therefore, the becoming not the being is true reality.
Once we start to accept that becoming (the change) not the being (the stillness) is what the world is all about and what we intuitively sense, then we can start coming to better terms with time. We recognize that our sense of time, despite the load of past unpleasant or sad moments it carries, is what makes us live fuller lives with consciousness of who we are. That, to quote Rovelli, makes time a source of anguish but in the end a tremendous gift.
Those years I spent my summers in the village, I knew nothing about Rovelli or Bergson. I knew nothing about time in the external or our internal world. All I wanted, as the bus pulled away, was to take one more glimpse of what I was leaving behind, anything that would keep me tied to the summer moments. The moments that were now becoming melancholy memories relieved only by the anticipation that another summer would arrive again next year. This is what time is all about.
* Entropy moves in one direction from low to high because of the second law of thermodynamics which states that the total entropy of an isolated system can never decrease over time.
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