A database of paper airplanes with easy to follow folding instructions.
what’s there instead, as you say, is “a world of happenings, not of things.”
MR. ROVELLI: Yes, a thing is something which remains equal to itself. A stone is a thing because I can ask where the stone is tomorrow, while a happening is something that is limited in space and time. A kiss is not a thing, because I cannot ask, where is a kiss, tomorrow; “Where is this kiss?” tomorrow. I mean, it’s just happened now.
MS. TIPPETT: I see.
MR. ROVELLI: And I think that we don’t understand the world as made by stones, by things. We understand the world made by kisses, or things like kisses — [laughs] happenings. In other words, the elementary quantities or ingredients for describing the world are not things which remain through time; they are just limited in space and time. And I think which remain through time are processes that repeat themselves. A stone is just a common flickering of electrons and things and stuff, which remains together — not even forever, of course, because it goes into powder for a long time, for a while. So to better understand the world, I think, we shouldn’t reduce it to things. We should reduce it to happenings; and the happenings are always between different systems, always relations, or always like a kiss, which is something that happens between two persons.
MS. TIPPETT: So even, for you, a stone is a happening — seen with a long expanse of time and an understanding of how it became what it is, it’s a happening, not a thing.
MR. ROVELLI: We live 100 years, but suppose we lived a billion years. A stone would be just a moment in which some sand gets together and then it disaggregates, so it’s just a momentary getting-together of sand. The permanence of things is — it’s a matter of the — we look at them for a short time, with respect to their own staying-together.
MS. TIPPETT: I want to read another passage from your writing: “A handful of types of elementary particles, which vibrate and fluctuate constantly between existence and non-existence and swarm in space, even when it seems that nothing is there, combine together to infinity like the letters of a cosmic alphabet to tell the immense history of galaxies, of the innumerable stars, of sunlight, of mountain, woods, and fields of grain, of the smiling faces of the young at parties, and of the night sky studded with stars.” [laughs]
.. But let me tell you something which I think is central. You quoted a sentence by — a phrase by Einstein in which he says that time is a sort of stubborn, persistent illusion, and it doesn’t exist. Einstein wrote that, but he wrote that in a letter addressed to the sister in the family of his best friend, Michele Besso, who had just died.
MS. TIPPETT: I did not know that.
MR. ROVELLI: Yes, so this is not in a text to physicists or to philosophers. It’s in a letter to a sister who has just lost her brother, a family who has just lost a member of the family. So the content is not a discussion about the structure of reality. It’s a letter to console. It’s a letter in which Einstein expresses his love of Michele, who has been his companion. And in that phrase, Einstein writes, “For people like Michele and me, time is.” So he’s talking about his relationship with Michele, and he’s talking, clearly, about his own loss of Michele and his own being in front of death, because Einstein died one month and a little bit after Michele. So it’s very close to Einstein’s death, and when he’s saying, “There is something illusory in time,” I think he’s talking about emotions, and he’s talking about something, in a sense, deeper and more important than the physical nature of time. He’s talking about the illusion of life, of our experiences. I don’t think that phrase by Einstein should be taken too literally.
MS. TIPPETT: So in a sense, what you’re saying, also, is that it’s partly Einstein pointing at this challenge of working with time as we understand it scientifically, and time as we understand it as human beings? Or simply being — are you saying he’s really just — he’s being a human being there? [laughs]
MR. ROVELLI: I think he’s, in that phrase, is deeply being a human being and talking about his love with Michele and also, implicitly, talking about his own attitude towards death, which was coming; a month later, he’s dead. But certainly, time is something which touches us in death, profoundly, because it’s a — thinking about time is thinking about our finitude. We’re not going to live forever, and what is this time in which we are immersed? There’s no time on a fundamental level, and nevertheless, we human beings live in time. We live in time like fish in the water. For us, it’s impossible to think of ourselves without time. So I do think there is more to understand there, and I do think it’s a different question — what is time, in the fundamental level of physics? — from the question, what is time, for us? And for us, it touches a lot of things, including emotional things.
.. MS. TIPPETT: I wonder how — if it’s possible to briefly just describe what time is, for you, as a physicist.
MR. ROVELLI: A fantastic problem to work upon. [laughs] It’s something which — first of all, it’s not a single notion. It’s not “either there is time, or there is no time.” It’s what we mean by “time.” When we think about time, for instance, we think time is the same for everybody. And we know it’s not true, Time passes a little bit faster in the mountain and a little bit slower near the sea; the more high you go, the more time passes fast. So it’s relative to how we move, where we are, and so on. I think that, in the fundamental equation of the world as we have understood so far, we can forget about time. They’re not about how things evolve in time. It is about relations between — within variables. I think, that, more or less, we can understand.
.. So here’s one very intriguing thing you say — again, as a physicist — to the question of what explains that, for us, time seems to pass, or to “flow.” And you say, you believe this is connected to the “connection between time and heat” — that the “difference between past and future exists only when there is heat.” That is such a baffling and fascinating idea. Can you just explain that a little bit?
MR. ROVELLI: Oh, yes. Oh, this is something that, curiously, has not been said enough, and the known physicists don’t know it; but it’s not something new, and it’s something well-established. In fact, since not the last century but the previous century, every time we give a description of the world, of phenomena where there is no heat, we cannot distinguish the past from the future. Every time there is something that distinguishes the past from the future, there is heat.
So take a movie or something, and you run it backward. Imagine you take a movie of the moon going around the earth. You run it backwards, and you see a moon going around the earth the other way. It’s completely consistent with the laws of physics, and there’s no heat there. But if you throw a pen on the table, and it stops, and you take a movie of that, if you run the movie backward, you see something totally absurd — a pen that starts moving from nothing; and in fact, when the pen stops, it heats the table because there’s friction, and there is heat. So only when there is some heat around, the phenomena are different in one direction of time from the other. So the direction of time is deeply connected to the existence of heat. That doesn’t explain the direction of time but is a first step toward understanding it. The direction of time has to do with the presence of heat.
.. MR. ROVELLI: I think our own experience of the world — our thinking, our being, our emotions — are so much produced by our brain, our body, which are full of heat, [laughs] a deeply thermodynamical thing, so we cannot get out from this presence of heat when we think about our experience. When you think, your brain produces heat. When you wake up in the morning, your body produces heat. When you have an emotion, there is heat producing. And so we, in our experience, are children of the presence of heat in the world. I think that in a world completely without heat, we wouldn’t make sense. We wouldn’t be able to think. We wouldn’t have memory. Memory requires heat.
.. Physics struggles to give an objective picture of reality, as much as possible, which is very fine, very good. So it’s reality as seen from the — as much as possible, from the outside. But if you look from the outside, you always miss something, which is the perspective from the inside.
If you have a map of a region, and you want to use it, you want to know where you are in the map. So you need extra information, which is where you are. And there are words like “here,” like “me,” that have a meaning that depends on who says it. If I say, “I’m Carlo,” it’s true, but if you say, “I’m Carlo,” it’s false; so, the same sentence depends on who’s saying. So I think there is an aspect of reality which is strongly connected to its relational aspect. We perceive reality not from the outside, but from the inside. And there is a little difference between each one of us, obviously, and we have to keep this into account. And I think, keeping this into account, it’s one of the ingredients for making sense of what time is — and maybe, also, one of the ingredients [laughs] of learning how to deal with one another a little bit better — by remembering that we always have perspective on things, and everybody has a slightly different perspective than everybody else.
.. I don’t think that I, as a person, exist without the rest. I am my friends, my love, my enemies — everything that I interact with. All my ideas come from things I’ve read, I’ve talked, which are all interactions. And all of what I do is interacting with the rest. And the same is true for communities. Communities are what they are because they’ve been strongly influenced by different communities, [laughs] and they’re going to influence other communities, and so on and so forth. This, I think, is not proof of anything, but this, I think, it’s going to help us if we digest that instead of going in the direction of defending us from the others.
.. The world is much more complex than what it looks at first sight. I look at this glass of water, and it’s just quite transparent, but I know that, in fact, it’s a crazy zig-zagging of molecules down there, which do all sorts of stuff, and how fast they move the temperature, and so on and so forth. And this complexity, which is at all levels, guards us from being driven by too-simple-minded things.
Nobel physicist Frank Wilczek sees beauty as a compass for truth, discovery, and meaning. His book A Beautiful Question: Finding Nature’s Deep Design is a long meditation on the question: “Does the world embody beautiful ideas?” He’s the unusual scientist willing to analogize his discoveries about the deep structure of reality with deep meaning in the human everyday.
.. “Each of us is born to become an accomplished, if unconscious, practitioner of projective geometry.”
.. That’s right. That’s one of our most impressive abilities that humans, children, do routinely without thinking about it — although they have to learn it, or parts of it — and yet, we have not been able to teach sophisticated computers to do it. That is, humans do an astonishing feat, routinely and very quickly. That is, they interpret the messages coming through little, little openings in their eyes and project it on a two-dimensional screen, the retina at the back, which then, the light gets turned into electrical signals. And from that crazy, scrambled encoding, we reconstruct an external world of three-dimensional objects in space. We recognize that if we move our head, they’re still the same objects, and we determine these effortlessly. We do a job which is — it literally is impossible. We use all kinds of tricks and rules of thumb to guess what the external world is, and sometimes it’s wrong, with optical illusions, but basically, in most circumstances, we do this remarkable feat of reconstructing a three-dimensional world from two-dimensional information that’s all scrambled up with things on top of each other
MR. WILCZEK: We take it for granted, but nature has equipped us with extraordinary abilities in geometry. I knew this abstractly, but in preparing the book I decided I should actually learn something about [laughs] perspective and projective geometry. And it was a real revelation. I’m terrible at drawing, just terrible — the worst person I’ve ever met. But I [laughs] learned some of the rules of perspective that artists use, and they are just so beautiful. They’re so elegant. And using them, I was empowered to create accurate buildings and town squares and so forth. I just astonish myself. And I wasn’t able to reproduce it consciously, but now, with knowledge, I was able to do it. And it was just magic to suddenly see these things emerging from geometric constructions, and it looks like the external world. And it had a tremendous effect, historically and psychologically, when these rules were discovered in the Italian Renaissance. It’s one of the things that really powered the Renaissance — the artists took enormous joy in their sudden ability to render the world the way it actually looked.
.. Yes. And people who started to work on artificial intelligence thought at the beginning that would all be trivial, because it’s so easy, [laughs] we don’t have to work very hard. They thought that would be very easy, whereas, say, teaching a computer to play chess would be very difficult. But it’s turned out to be just the opposite. The things that we do unconsciously and are part of our daily lives and are important for survival are things we’re really, really good at.
.. But in science, we need to have a more precise concept. And the concept that we use that’s more precise, that has something in common with the common usage but is a special case of it and gets amplified in different directions, is that symmetry in physics and mathematics means change without change.
Now, that seems kind of mysterious and mystical, but it means something very concrete. Einstein’s theory of relativity, it says that if you ride by the world at a constant velocity, any constant velocity, although things will look different — so some things will be coming at you, other things will be moving away, faster — that the same physical laws will apply to this new configuration of the world. So, you can make a change in the way everything looks, [laughs] but you don’t change the laws.
A simpler example might be helpful here. We’re used to the idea that a circle is a very symmetrical object. What does that have to do with change without change? Well, a circle is an object that you can rotate around its center by any angle, and although it might have changed, and every point, in fact, moves, the circle as a whole does not move, and that’s what makes it symmetric. If you take a more lopsided shape and you rotate it, there’s no way — it won’t come back to itself until you go all the way around. So if you take an equilateral triangle, it’ll come around after you turn it one-third of the way. So it has some symmetry, but much less than a circle. So that’s a concept, change without change — things that might have changed, but don’t — that picks out special kinds of objects, like circles.
.. It turns out that very symmetric laws seem to be the laws that nature likes. Nature likes laws and likes equations that support enormous possibilities for transformation, where things look different, get different names, and different situations are described, but the same equations apply.
.. “Deep propositions have a meaning that goes beyond their surface.” This is so interesting. “You can recognize a deep truth by the feature that its opposite is also a deep truth.”
.. MS. TIPPETT: So one of the conflicts was, is light a particle or wave? And, in fact, it is both.
MR. WILCZEK: It’s both, and…
MS. TIPPETT: It’s both, right.
MR. WILCZEK: …sometimes it’s useful to think of it one way, sometimes it’s useful to think of it another way. Both can be informative in different circumstances, but it’s very difficult — in fact, impossible — to apply them both at once.
MS. TIPPETT: To apply them both at the same time.
MR. WILCZEK: And I think that’s the essence of complementarity, that you have to view the world in different ways to do it justice, and the different ways can each be very rich, can each be internally consistent, can each have its own language and rules, but they may be mutually incompatible. And to do full justice to reality, you have to take both of them into account.
MS. TIPPETT: Somewhere you say, “Complementarity is both a feature of physical reality and a lesson in wisdom.” And I think just what you just said about reality is equally true of — and I know you have to be careful to do too much of this stretching these things, but it’s equally true of the human condition.
MR. WILCZEK: Oh, very much so. [laughs] Oh, I think so. When people ask me what my religion is, I say I’m a complementarian.
MS. TIPPETT: [laughs] That’s right.
MR. WILCZEK: I believe that it’s really interesting and really fun and really informative, and the right thing to do, to be able to look at things in different ways and appreciate their different ways of looking at things that each have their own validity. And they may conflict if you try to apply them both at once, but OK, that’s fine. You apply one at a time [laughs] and try to appreciate both.
MS. TIPPETT: And in terms of this — I have spoken with physicists who will say: Of course, they take their daily perceptions seriously on some level; they understand that, essentially, what we perceive to be reality is full of illusion, and including the perception that we have freedom and choice. But you also present this as another piece of complementarity — two things that, in fact, are true, but hard to speak about in the same moment — that you, as a human being, are nothing but a collection of particles and light; and you are a thinking, feeling human being. [laughs]
MR. WILCZEK: Yes. I think those are both true. [laughs] And they are different ways of organizing our experience of the world, and each one tells us important things. Each one can be very useful in certain applications. But they’re very difficult to apply simultaneously, because they’re just from different worlds.
.. “All colors are one thing.” This is what we learned: “All colors are one thing, seen in different states of motion. And that is science’s brilliantly poetic answer to Keats’ complaint that science unweaves a rainbow.”
.. I’m saying that by understanding the world better that you gain a new perspective on what you are and a different feeling about your place in reality that’s more realistic; also, richer. And there’s good news, and there’s bad news, but in any case… [laughs]
MS. TIPPETT: Right, it’s challenging.
MR. WILCZEK: …it’s something you can — by understanding it deeply, you can certainly enrich your experience of the life you’re given.
MS. TIPPETT: You also cite somewhere what you say is, for you, one of the most beautiful passages in literature, from the 20th-century physicist, Hermann…
MR. WILCZEK: Hermann Weyl, yes.
MS. TIPPETT: …Weyl on spacetime. He’s talking about spacetime from a “God’s-eye view”: “The objective world simply is, it does not happen. Only to the gaze of my consciousness, crawling along the lifeline of my body does a section of this world come to life as a fleeting image in space which continually changes in time.” That’s a very — it’s almost a mystical image. That the world is, it does not happen, is quite a remarkable thing to try to take in.
MR. WILCZEK: Yes, but it’s really, I think, very much what the theory of relativity suggests. It’s really basic, to think of spacetime as a whole, because there are relationships between things that happen in different parts of space and at different times that are significant in forming the laws and the regularities of the world that are very, very difficult and awkward to express if you carve the world into time slices, as we experience…
MS. TIPPETT: Right — past, present, future.
MR. WILCZEK: …and regard them as separate and unrelated, or as snapshots, each a thing in itself.
Relativity teaches us to think of spacetime as a whole and that it’s very unnatural to divide them. So it leads, I think, very much to the worldview that Hermann Weyl was alluding to there, that the world — that is, spacetime — it simply is. It does not happen. It already encompasses all times.
.. “I know not how I appear to the world, but to myself I appear like a boy on a beach who came upon some particularly beautiful pebbles, while the great ocean of the unknown lay before me.”
So he realized that he understood some things very well, and he understood what it meant to really understand something, but part of that is realizing that you don’t understand a lot of things. And there’s a profound humility that comes from really understanding something, because then you understand what it means to really understand something. [laughs] And you realize how much is missing that is different.
MS. TIPPETT: [laughs] And you feel that way as a physicist at this juncture in physics, which is so far from what Newton could have imagined, also.
MR. WILCZEK: Yes. We’ve done very, very well. Physics is pretty good. [laughs] Physics, we’ve attained a high level, although there are certainly big holes in our understanding. But when it comes to the mind, when it comes to understanding society, our understanding is much, much less satisfactory and, I’m fully aware of that.
Believe it or not, a Roman Catholic priest first proposed the Big Bang theory of the origin of the universe. In 1927, Georges Lemaître, a Belgian priest, astronomer, and physics professor, suggested that the expanding universe might be traced back to a single point of origin, a singularity. As Ilia Delio describes, “[It] appeared like a little quantum size blip on the screen [creatio ex nihilo] and inflated rapidly like a balloon and since that time, it has been expanding.”  I’ll let Delio, a scientist, explain the implications for this cosmology—our story of the universe:
Every human person desires to love and to be loved, to belong to another, because we come from another. We are born social and relational. We yearn to belong, to be part of a larger whole that includes not only friends and family but neighbors, community, trees, flowers, sun, Earth, stars. We are born of nature and are part of nature; that is, we are born into a web of life and are part of a web of life. We cannot know what this means, however, without seeing ourselves within the story of the Big Bang universe. Human life must be traced back to the time when life was deeply one, a Singularity, whereby the intensity of mass-energy exploded into consciousness. Deep in our DNA we belong to the stars, the trees, and the galaxies.
Deep within we long for unity because, at the most fundamental level, we are already one. We belong to one another because we have the same source of love; the love that flows through the trees is the same love that flows through my being