Seven Brief Lessons on Physics (5 page)

Time sits at the center of the tangle of problems raised by the intersection of gravity, quantum mechanics, and thermodynamics. A tangle of problems where we are still in the dark. If there is something that we are perhaps beginning to understand about quantum gravity that combines two of the three pieces of the puzzle, we do not yet have a theory capable of drawing together all three pieces of our fundamental knowledge of the world.

A small clue toward the solution comes from a calculation completed by Stephen Hawking, the physicist famous for having continued to produce outstanding physics despite a medical condition that keeps him confined to a wheelchair and prevents him from speaking without a mechanical aid.

Using quantum mechanics, Hawking successfully demonstrated that black holes are always “hot.” They emit heat like a stove. It’s the first concrete indication on the nature of “hot space.” No one has ever observed this heat
because it is faint in the actual black holes that have been observed so far—but Hawking’s calculation is convincing, it has been repeated in different ways, and the reality of the heat of black holes is generally accepted.

The heat of black holes is a quantum effect upon an object, the black hole, which is gravitational in nature. It is the individual quanta of space, the elementary grains of space, the vibrating “molecules,” that heat the surface of black holes and generate black hole heat. This phenomenon involves all three sides of the problem: quantum mechanics, general relativity, and thermal science. The heat of black holes is like the Rosetta stone of physics, written in a combination of three languages—quantum, gravitational, and thermodynamic—still awaiting decipherment in order to reveal the true nature of time.

Ourselves

After having journeyed so far, from the structure of deep space to the margins of the known cosmos, I would like to return, before closing this series of lessons, to the subject of ourselves.

What role do we have as human beings who perceive, make decisions, laugh, and cry, in this great fresco of the world as depicted by contemporary physics? If the world is a swarm of ephemeral quanta of space and matter, a great jigsaw puzzle of space and elementary particles, then what are we? Do we also consist only of quanta and particles? If so, then from where do we get that sense of individual existence and unique selfhood to which
we can all testify? And what then are our values, our dreams, our emotions, our individual knowledge? What are we, in this boundless and glowing world?

I cannot even imagine attempting to really answer such a question in these simple pages. It’s a tough question. 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. But to avoid this question or to ignore it would be, I think, to overlook something essential. I’ve set out to show how the world looks in the light of science, and we are a part of that world too.

“We,” human beings, are first and foremost the subjects who do the observing of this world, the collective makers of the photograph of reality that I have tried to compose. We are nodes in a network of exchanges (of which this present book is an example) through which we pass images, tools, information, and knowledge.

But we are also an integral part of the world that we perceive; we are not external observers. We are situated within it. Our view of it is from within its midst. We are made up of the same atoms and the same light signals as are exchanged between pine trees in the mountains and stars in the galaxies.

As our knowledge has grown, we have learned that
our being is only a part of the universe, and a small part at that.

This has been increasingly apparent for centuries, but especially so during the last century. We believed that we were on a planet at the center of the universe, and we are not. We thought that we existed as unique beings, a race apart from the family of animals and plants, and discovered that we are descendants of the same parents as every living thing around us. We have great-grandparents in common with butterflies and larches. We are like an only child who in growing up realizes that the world does not revolve only around himself, as he thought when little. He must learn to be one among others. Mirrored by others, and by other things, we learn who we are.

During the great period of German idealism, Schelling could think that man represented the summit of nature, the highest point where reality becomes conscious of itself. Today, from the point of view provided by our current knowledge of the natural world, this idea raises a smile. If we are special, we are only special in the way that everyone feels themselves to be, like every mother is for her child. Certainly not for the rest of nature.

Within the immense ocean of galaxies and stars we
are in a remote corner; amid the infinite arabesques of forms that constitute reality, we are merely a flourish among innumerably many such flourishes.

The images that we construct of the universe live within us, in the space of our thoughts. Between these images—between what we can reconstruct and understand with our limited means—and the reality of which we are part, there exist countless filters: our ignorance, the limitations of our senses and of our intelligence. The very same conditions that our nature as subjects, and particular subjects, imposes upon experience.

These conditions, nevertheless, are not, as Kant imagined, universal—deducing from this (with obvious error) that the nature of Euclidian space and even of Newtonian mechanics must therefore be true a priori. They are a posteriori to the mental evolution of our species and are in continuous evolution. We not only learn, but we also learn to gradually change our conceptual framework and to adapt it to what we learn. And what we are learning to recognize, albeit slowly and hesitantly, is the nature of the real world of which we are part. The images that we construct of the universe may live inside us, in conceptual space, but they also describe more or less well the real world to which we belong. We follow leads in order to better describe this world.

When we talk about the big bang or the fabric of space, what we are doing is not a continuation of the free and fantastic stories that humans have told nightly around campfires for hundreds of thousands of years. It is the continuation of something else: of the gaze of those same men in the first light of day looking at tracks left by antelope in the dust of the savannah—scrutinizing and deducting from the details of reality in order to pursue something that we can’t see directly but can follow the traces of. In the awareness that we can always be wrong, and therefore ready at any moment to change direction if a new track appears; but knowing also that if we are good enough we will get it right and will find what we are seeking. This is the nature of science.

The confusion between these two diverse human activities—inventing stories and following traces in order to find something—is the origin of the incomprehension and distrust of science shown by a significant part of our contemporary culture. The separation is a subtle one: the antelope hunted at dawn is not far removed from the antelope deity in that night’s storytelling.

The border is porous. Myths nourish science, and science nourishes myth. But the value of knowledge remains. If we find the antelope, we can eat.

Our knowledge consequently reflects the world. It
does this more or less well, but it reflects the world we inhabit. This communication between ourselves and the world is not what distinguishes us from the rest of nature. All things are continually interacting with one another, and in doing so each bears the traces of that with which it has interacted: and in this sense all things continuously exchange information about one another.

The information that one physical system has about another has nothing mental or subjective about it: it’s only the connection that physics determines between the state of something and the state of something else. A raindrop contains information on the presence of a cloud in the sky, a ray of light contains information on the color of the substance from which it came, a clock has information on the time of day, the wind carries information about an approaching storm, a cold virus has information of the vulnerability of my nose, the DNA in our cells contains all the information in our genetic code (on what makes me resemble my father), and my brain teems with information accumulated from my experience. The primal substance of our thoughts is an extremely rich gathering of information that’s accumulated, exchanged, and continually elaborated.

Even the thermostat on my central heating system
“senses” and “knows” the ambient temperature in my home, has information on it, and turns off when it is warm enough. So what then is the difference between the thermostat’s and my own “sensing” and “knowing” that it’s warm and deciding freely to turn off the heating or not—and “knowing” that I exist? How can the continuous exchange of information in nature produce
us
and our thoughts?

The problem is wide-open, with numerous fine solutions currently under discussion. This, I believe, is one of the most interesting frontiers of science, where major progress is about to be made. Today new tools allow us to observe the activity of the brain in action and to map its highly intricate networks with impressive precision. As recently as 2014 the news was announced that the first complete (mesoscopic) detailed mapping of the brain structure of a mammal had been achieved. Specific ideas on how the mathematical form of the structures can correspond to the subjective experience of consciousness are currently being discussed, not only by philosophers but also by neuroscientists.

An intriguing one, for instance, is the mathematical theory being developed by Giulio Tononi—an Italian scientist working in the United States. It’s called
“integrated information theory” and is an attempt to characterize quantitatively the structure that a system must have in order to be conscious: a way, for example, of describing what actually changes on the physical plane between when we are awake (conscious) and when we are asleep but not dreaming (unconscious). It’s still at the developmental phase. We still have no convincing and established solution to the problem of how our consciousness is formed. But it seems to me that the fog is beginning to clear.

There is one issue in particular regarding ourselves that often leaves us perplexed: what does it mean, our being free to make decisions, if our behavior does nothing but follow the predetermined laws of nature? Is there not perhaps a contradiction between our feeling of freedom and the rigor, as we now understand it, with which things operate in the world? Is there perhaps something in us that escapes the regularity of nature and allows us to twist and deviate from it through the power of our freedom to think?

Well, no, there is nothing about us that can escape the norms of nature. If something in us could infringe the laws of nature, we would have discovered it by now. There is nothing in us in violation of the natural behavior
of things. The whole of modern science—from physics to chemistry, and from biology to neuroscience—does nothing but confirm this observation.

The solution to the confusion lies elsewhere. When we say that we are free, and it’s true that we can be, this means that how we behave is determined by what happens within us, within the brain, and not by external factors. To be free doesn’t mean that our behavior is not determined by the laws of nature. It means that it is determined by the laws of nature acting in our brains.

Our free decisions are freely determined by the results of the rich and fleeting interactions among the billion neurons in our brain: they are free to the extent that the interaction of these neurons allows and determines. Does this mean that when I make a decision it’s “I” who decides? Yes, of course, because it would be absurd to ask whether “I” can do something different from what the whole complex of my neurons has decided: the two things, as the Dutch philosopher Baruch Spinoza understood with marvelous lucidity in the seventeenth century, are the same.

There is not an “I”
and
“the neurons in my brain.” They are the same thing. An individual is a process: complex, tightly integrated.

When we say that human behavior is unpredictable, we are right because it is too complex to be predicted, especially by ourselves. Our intense sensation of interior liberty, as Spinoza acutely saw, comes from the fact that the ideas and images that we have of ourselves are much cruder and sketchier than the detailed complexity of what is happening within us. We are the source of amazement in our own eyes.

We have a hundred billion neurons in our brains, as many as there are stars in a galaxy, with an even more astronomical number of links and potential combinations through which they can interact. We are not conscious of all of this. “We” are the process formed by this entire intricacy, not just by the little of it of which we are conscious.

The “I” who decides is that same “I” that is formed (in a way that is still certainly not completely clear, but that we have begun to glimpse) from reflections upon itself, through self-representations in the world, from understanding itself as a variable point of view placed in the context of the world, from that impressive structure that processes information and constructs representations that is our brain. When we have the feeling that “it is I” who decides, we couldn’t be more correct. Who else?

I am, as Spinoza maintained, my body and what happens in my brain and heart, with their immense and, for me, inextricable complexity.

The scientific picture of the world that I have related in these pages is not, then, at odds with our sense of ourselves. It is not at odds with our thinking in moral and psychological terms, or with our emotions and feelings. The world is complex, and we capture it with different languages, each appropriate to the process that we are describing. Every complex process can be addressed and understood in different languages and at different levels. These diverse languages intersect, intertwine, and reciprocally enhance one another, like the processes themselves. The study of our psychology becomes more sophisticated through our understanding of the biochemistry of the brain. The study of theoretical physics is nourished by the passions and emotions that animate our lives.

Our moral values, our emotions, our loves are no less real for being part of nature, for being shared with the animal world, or for being determined by the evolution that our species has undergone over millions of years. Rather, they are more valuable as a result of this: they are real. They are the complex reality of which we are made. Our reality is tears and laughter, gratitude and
altruism, loyalty and betrayal, the past that haunts us and serenity. Our reality is made up of our societies, of the emotion inspired by music, of the rich intertwined networks of the common knowledge that we have constructed together. All of this is part of the self-same “nature” that we are describing. We are an integral part of nature; we
are
nature, in one of its innumerable and infinitely variable expressions. This is what we have learned from our ever-increasing knowledge of the things of this world.

That which makes us specifically human does not signify our separation from nature; it is part of that self-same nature. It’s a form that nature has taken here on our planet, in the infinite play of its combinations, through the reciprocal influencing and exchanging of correlations and information among its parts. Who knows how many and which other extraordinary complexities exist, in forms perhaps impossible for us to imagine, in the endless spaces of the cosmos? There is so much space up there that it is childish to think that in a peripheral corner of an ordinary galaxy there should be something uniquely special. Life on Earth gives only a small taste of what can happen in the universe. Our very soul itself is only one such small example.