Work Reviewed: Rovelli, Carlo. The Order of Time.* Riverhead Books, 2018.
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Introduction
Carlo Rovelli’s The Order of Time is a challenging but rewarding take on the physics behind time. Follow Rovelli as he first unravels our understanding of time, then rebuilds it according to his findings. In all, this was a profound read. Rovelli draws not just from his work as a scientist, but from the humanities as well. The author takes inspiration from Aristotle, Beethoven, and Hildegard of Bingen alike to craft an awe-inspiring journey through time. Each chapter opens with a few lines of poetry, usually Horace, a tactic that invites the reader to consider the philosophical implications of his arguments.
Five Key Points from Rovelli’s The Order of Time
Time flows differently in different parts of the universe due to the influence of gravity.
It is a strange quality of time that the closer one is to a large mass, the slower time moves. So, a person high above sea level will experience time differently than someone in a deep valley. On a similar note, the speed at which you are moving also influences the passage of time. Moving at a slower speed means time will move more quickly, and vice versa. You may have heard of Einstein’s thought experiment on simultaneity. Check out the video to review the concept or learn more about it.
At the quantum level, time doesn’t exist in the way we typically understand it.
If we zoom in to the quantum level, time still does not behave as we might expect. While we think we can distinguish the past from the present based on our fuzzy view of the world, at a quantum level, there is no such distinction. There is no constant time variable, or constant flow of events. Instead, quantum physicists often think about probabilities and particle relationships.
The concept of “now” varies from place to place, especially on a cosmic scale.
The inevitable conclusion of the first two points is that “The present is a localized rather than a global phenomenon” (Rovelli 194). Time flows differently due to speed and gravity on a larger scale. It does not appear to exist on a quantum level. Therefore, the concept of “now” is unstable, and only helpful on a human scale. In fact, humans have long looked to the sun, the stars, and later on, water clocks and mechanical watches to measure time in terms of change, as Aristotle discusses. If you want to meet a friend for lunch, or even sign on to video call with someone across the world, we can roughly agree on when. But this is only because we exist in a context that provides us with enough common observations to help us track time on a similar scale.
Time is a human invention that relies on memory, consciousness, and emotion.
Although now is not universal, and time does not flow in reality as we assume it does, it is still full of meaning. When we observe change, we are comparing. Imagine waking up from a nap. The light is glancing in the window at a steep angle. The cup of tea you left on the end table is cold. Perhaps you dreamed, and felt as though events unfolded all around you over some period in your mind. You must recall all of these things in order to understand that time has passed.
You may also have experienced time ebb and flow differently depending on your mood. A lecture seems to drag on, while a roller coaster ride is over before you know it.
The distinction between the past, present, and future is not inherent in the fabric of the universe. Rather, it is something we interpret based on our experience of entropy.
Rovelli’s The Order of Time gets more specific about the variables we can look at when interpreting the passage of time. Heat and entropy are both crucial. Consider the first two laws of thermodynamics, summarized below:
- Energy cannot be created or destroyed.
- Entropy increases over time; heat always moves from hotter to colder objects.
Our perception of increasing entropy, or disorder, is the basis for our understanding of time, as in the example of the tea cup above. It is through this lens that we experience the flow of time around us, and the beauty, ugliness, growth, change, and loss that make up our lives.