Carlo Rovelli's Seven Brief Lessons on Physics, originally published as a series of essays in an Italian newspaper, was just released in book form in the U.S. on March 1. I read the book by the noted physicist in a single sitting with pleasure and mounting excitement.
It is a very clear book and it is likely to provoke in readers, as it provoked in me, a desire to learn more about space, time, quantum reality, the nature of the gravity, our universe and, finally, about ourselves.
Seven Brief Lessons does not shy away from philosophy and it is an admirable testament, I think, to the fact that philosophy and natural science, although perhaps never one and the same, must grapple with each other.
None of Rovelli's "lessons" left me satisfied. But in a good way. They all left me wanting more. For example, when the author explains that the "Earth does not turn around [the sun] because of a mysterious force [gravity] but because it is racing directly in a space that inclines, like a marble that rolls in a funnel," I found myself wishing he would then cash out this funnel metaphor in a way that doesn't take gravity for granted. This is less a criticism than an appreciation that this lovely little book, which I plan to give to my 11-year-old, is as much an expression of curiosity as it is an attempt to set out the answers.
On one point, though, I think the book deserves to be challenged.
If you open a balloon it will shoot hither and thither; it is impossible to say where it will land. This is not, the author rightly points out, because the action of the released balloon is truly random — but simply because we, given our knowledge or, as he puts it, "the limited sets of properties [of the balloon] with which we interact," are unable to predict which way the balloon will travel. An all-knowing or super-sensible creature, in contrast, he suggests, would be able simply to see what the balloon was going to do when opened, for such an all-knower would directly appreciate the exact positions of the molecules within the balloon and out of which it is composed. Such a super-intelligent being would perceive that there is no balloon, that there are only atoms obeying entirely fixed, independent laws of nature, laws which it is in position to comprehend.
The same point can be made, argues Rovelli, about time. Time seems to flow. There seems to be beforeand after, past, present and future. But this, as with the balloon, is an illusion that is produced in us as a result of our parochial limitations, of the "profoundly relational nature of the concepts we use to organize the world... ." He explains:
"For a hypothetically super-sensible being, there would be no 'flowing' of time: the universe would be a single block of past, present, and future. But due to the limitations of our consciousness we perceive only a blurred vision of the world and live in time."
But we must ask: Are there not phenomena whose essential irreversibility seems to require of us that we think of them as unfolding in time, that is, as captured by time's flow?
Even if we grant that statistical thermodynamics can explain why heat dissipates and chicks don't turn into eggs (as Rovelli explains), one can wonder whether we can make sense of the phenomena of consciousness itself without time. Melodies, for example, are creatures of time — and does it make any sense to imagine that one might think backwards?
Which leads me to wonder: Would Rovelli's super-sensible being, far from having discovered the unreality of time and balloons, be rather in the position of one who could not think and was deaf to music?
Rovelli, whose book is not dogmatic, appreciates that consciousness is still poorly understood. (He speaks of "limitations of consciousness" in the quotation above.) And moreover he says: "In the big picture of contemporary science, there are many things that we do not understand, and one of the things that we understand least about is ourselves."
And he is also admirably insistent that science has no business overlooking or ignoring this question. "I've set out to show how the world looks in the light of science, and we are part of that world, too."
But Rovelli remains hopeful; I worry that his hopefulness is misplaced.
The scientific picture of the world, Rovelli says, lives within us, in the space of our thoughts, and our relation to the world is constrained by our ignorance, our senses, our intelligence. But these limitations, he insists, are not fixed. They are set by the "mental evolution of our species and are in continuous evolution." Moreover, he believes, our knowledge, such as it is, frequently reflects the world as it really is, in itself. There really was a Big Bang. We really have come to understand the fabric of space. And, in part, this is because we "learn to gradually change our conceptual framework and to adapt it to what we learn."
But who is this "we" that succeeds in modifying the very limitations of our relation to the world around us? And is there some reason, beyond a brute optimism, for thinking that evolution, a natural process itself, would have the effect of letting us, as he puts it, get it right and find what we are seeking?
Rovelli wants to resist the thought that we somehow stand outside of nature when we describe it. We, like everything else, are in continuous transaction with the world around us. We carry information about the world in our brains, just as a raindrop carries information about the presence of a cloud in the sky and a footprint carries information about the one who made it. But the raindrop and the footprint, for all they are packed with information, have no knowledge. Why think the brain is any different?
Rovelli seems to appreciate this unbridged gulf, for he resorts to highly poetic language when he addresses exactly this issue: "The primal substance of our thought is an extremely rich gathering of information that's accumulated, exchanged, and continually elaborated." Indeed! But neither Rovelli, nor anyone else, has yet explained how that process of continual elaboration is a physical process or how it is a process unfolding in our brains.
Rovelli's is a beautiful book and I recommend it. But I warn the reader, and I warn him: If he is right that we belong to the very same nature it is the project of physics to understand, then it may be that there is something incomplete or not yet adequate in our physics itself. For we have nothing like an adequate account of ourselves in the natural world.
Alva Noë is a philosopher at the University of California, Berkeley, where he writes and teaches about perception, consciousness and art. He is the author of several books, including his latest, Strange Tools: Art and Human Nature (Farrar Straus and Giroux, 2015). You can keep up with more of what Alva is thinking on Facebook and on Twitter: @alvanoe