"What would we do with time off our backs?
We would make this world a perfect place.
We would make our lives a perfect thing, if not for time.
But I tell you now, time is an illusion.
Time is an illusion. Time is not real.
Time is the dividing line between what is true and what is not true."
— "I Love My Life," Nearly Human, Todd Rundgren, 1989.
One day in the future, time travel will be scientifically possible long ago.
I like books by scientists. I read and review them regularly:
- A Brief History of Time
- Surely You're Joking, Mr. Feynman
- The Last Lecture
- The Grand Design
- War of Worldviews
I also like Jessica Hagy's This is Indexed site where she shares pithy insights via index cards. I have often combined these two likes in my book reviews: Only Humans Need Apply, FLOW, Codermetrics, Shutting Up, The Infinite Resource, High-Tech, High-Touch Customer Service, SPIN Sucks, and Junkyard Planet. In this fine tradition, I thought I'd once again try my hand at being a Jessica Hagy by providing an index card for each chapter of The Order of Time. Hopefully, it's interesting in a unique way.
Perhaps Time Is the Greatest Mystery
"The book is divided into three unequal parts. In the first, I summarize what modern physics has understood about time... The second part describes ... an empty, windswept landscape almost devoid of temporality... The third part of the book is ... the return journey, back toward the time lost in the first part of the book when pursuing the elementary grammar of the world. As a crime novel, we are going in search of the guilty party: the culprit who created time." [pages 1-5]
Loss of Unity
"It has long been the convention to indicate time in [physics] equations with the letter t (the word for 'time' begins with t in Italian, French, and Spanish, but not in German, Russian, or Mandarin). What does this t stand for? It stands for the number measured by a clock. The equations tell us how things change as the time measured by a clock passes." [page 15]
Loss of Direction
"Why, to us, is the past so different from the future? Nineteenth- and twentieth-century physics engaged with [this question] and ran into something unexpected and disconcerting — much more so than the relatively marginal fact that time passes at different speeds in different places. The difference between past and future, between cause and effect, between memory and hope, between regret and intention ... in the elementary laws that describe the mechanisms of the world, there is no such difference." [page 21]
The End of the Present
"What is happening 'now' in a distant place? Imagine for example, that your sister has gone to Proxima b, the recently discovered planet that orbits a star at approximately 4 light-years' distance from us. What is your sister doing now on Proxima b?... If you ask what your sister, who is in the room with you, is doing now... you can look at her, and you can tell... If your sister is on Proxima b, however, light takes 4 years to reach you from there. Hence, if you look at her through a telescope, or receive a radio communication from her, you know what she was doing 4 years ago rather than what she is doing now." [pages 41-42]
"A present that is common throughout the whole universe does not exist." [page 194]
Loss of Independence
Aristotle: Time is the measurement of change. [page 63]
Newton: Time exists that measures days and movements (like the one defined by Aristotle) but also contends that "true" time passes regardless, independently of things and their changes. [page 65]
"The synthesis between Aristotle's time and Newton's is the most valuable achievement made by Einstein." Time and space are real phenomena, but they are in no way absolute. They are not at all independent from what happens. They are not as different from other substances of the world. Time and space are the canvas on which the world is drawn, but this canvas is made of the same stuff that everything else in the world is made of, the same substance that constitutes stone, light, and air. It is made of fields. [page 74]
Quanta of Time
"The time measured by a clock is 'quantified,' that is to say, it acquires only certain values and not others. It is as if time were granular rather than continuous. Granularity is the most characteristic feature of quantum mechanics, which takes its name from... 'quanta' [which] are elementary grains. [page 83]
"In the elementary grammar of the world, there is neither space nor time — only processes that transform physical quantities from one to another, from which it is possible to calculate probabilities and relations. We do not register quantum fluctuations.". [page 195]
The World Is Made of Events, Not Things
"We can think of the world as made up of things. Of substances. Of entities. Of something that is. Or we can think of it as made up of events. Of happenings. Of processes. Of something that occurs. [page 97]
"Our world is a world of events, not things." [page 195]
The Inadequacy of Grammar
"People like us who believe in physics, know that the distinction between past, present, and future is only a stubbornly persistent illusion."
— Albert Einstein [page 109]
Dynamics as Relation
"There is nothing mysterious about the absence of time in the fundamental equation of quantum gravity. It is only the consequence of the fact that, at the fundamental level, no special variable exists. The theory does not describe how things evolve in time. The theory describes how things change one in respect to the others, how things happen in the world in relation to each other. That's all there is to it. [page 120]
Time is Ignorance
To define a macroscopic state of the world, we first need to know the energy, and to define energy, we need to know what is time. In this logic, time comes first and is independent from the rest. But there is another way of thinking about this same relationship by reading it in reverse. That is, to observe that a macroscopic state, which is to say a blurred vision of the world, may be interpreted as a mingling that preserves an energy, and this in its turn generates a time. Hence, a macroscopic state (which ignores the details) chooses a particular variable that has some of the characteristics of time. In other words, time becomes defined simply as an effect of blurring. [pages 135-136]
"The entire difference between past and future may be attributed solely to the fact that the entropy[definition] of the world was low in the past." [pages 143]
Take a pack of 12 cards, 6 red and 6 black. Arrange it so that the red cards are all at the front. Shuffle the pack a little and then look for the black cards that have ended up among the red ones. Before shuffling, there are none; after, some. This is a basic example of the growth of entropy. At the start of the game, the number of black cards among the red in the first half of the pack is zero (the entropy is low) because it started in a special configuration. This same process can be repeated with the cards even in any random order where cards get mixed. The same may be true for the entropy of the universe: perhaps it was in no particular configuration. [page 148]
What Emerges from a Particularity
"At school I was told that it is energy that makes the world go round... But there is something that does not add up. Energy is conserved. It is neither created nor destroyed. If it is conserved, why do we have to constantly resupply it? Why can't we keep using the same energy? It's not energy that the world needs to keep going. What it needs is low entropy." [pages 159-160]
The Scent of the Madeleine
There are different ingredients that combine to produce our identity: Point of view — reflect the world and elaborate the information in an integrated way; Organization of our reflections of the world into entities; Memory — our present swarms with traces of our past, histories of ourselves, narratives. [pages 174-178]
Each one of us is a unified being because we reflect the world, because we have formed an image of a unified entity by interacting with our kind, and because it is a perspective on the world unified by memory. [pages 197]
The Source of Time
"The rhythms at which time flows are determined by the gravitational field, a real entity with its own dynamic that is described in the equations of Einstein. If we overlook quantum effects, time and space are aspects of a great jelly in which we are immersed. But the world is a quantum one, and gelatinous space-time is also an approximation. In the elementary grammar of the world, there is neither space nor time — only processes that transform physical quantities from one to another, from which it is possible to calculate probabilities and relations. [page 195]
The Sister of Sleep
"And it seems to me that life, this brief life, is nothing other than this: the incessant cry of these emotions that drive us, that we sometimes attempt to channel in the name of a god, a political faith, in a ritual that reassures us that, fundamentally, everything is in order, in a great and boundless love — and the cry is beautiful. Sometimes it is a cry of pain. Sometimes it is a song. [page 212]
When I read each chapter of Stephen Hawking's A Brief History of Time, I would often have to put the book down to reflect upon what I had read to try to understand it. Carlo Rovelli's The Order of Time is not like that at all. Rovelli writes in a clear, direct way that makes these complex topics easy to digest. The book did not take long to read. (Do you see what I did there?) I recommend this book for anyone curious about the physics of time.
Given that the past, present, and future occur simultaneously, what will we do when we discover how to navigate time? As mentioned in the Todd Rundgren quote, will we go back in time and make our world a perfect place? The Autodesk vision is to help everyone imagine, design, and make a better world. Until time travel is upon us, we'll keep striving for better in pursuit of perfect.
The study of time is alive in the lab.