Probable Impossibilities: Physicist Alan Lightman on Beginnings, Endings, and What Makes Life Worth Living
How our cosmic improbability confers dignity and meaning upon our shared existence.
By Maria Popova
“What exists, exists so that it can be lost and become precious,” Lisel Mueller, who lived to nearly 100, wrote in her gorgeous poem “Immortality” a century and a half after a young artist pointed the world’s largest telescope at the cosmos to capture the first surviving photograph of the Moon and the first-ever photograph of a star: Vega — an emissary of spacetime, reaching its rays across twenty-five lightyears to imprint the photographic plate with a image of the star as it had been twenty-five years earlier, immortalizing a moment already long gone.
And yet in a cosmological sense, what exists is precious not because it will one day be lost but because it has overcome the staggering odds of never having existed at all: Within the fraction of matter in the universe that is not dark matter, a fraction of atoms cohered into the elements necessary to form the complex structures necessary for life, of which a tiny portion cohered into the seething cauldron of complexity we call consciousness — the tiny, improbable fraction of a fraction of a fraction with which we have the perishable privilege of contemplating the universe in our poetry and our physics.
In Probable Impossibilities: Musings on Beginnings and Endings (public library), the poetic physicist Alan Lightman sieves four centuries of scientific breakthroughs, from Kepler’s revolutionary laws of planetary motion to the thousands of habitable exoplanets discovered by NASA’s Kepler mission, to estimate that even with habitable planets orbiting one tenth of all stars, the faction of living matter in the universe is about one-billionth of one-billionth: If all the matter in the universe were the Gobi desert, life would be but a single grain of sand.
Along the way, Lightman draws delicate lines of figuring from Hindu cosmology to quantum gravity, from Pascal to inflation theory, from Lucretius to Henrietta Leavitt and Edwin Hubble — lines contouring the most elemental questions that have always animated humanity, questions that are themselves the answer to what it means to be human.
Building on his lifelong passion for harmonizing our touching human partialities with the fundamental reality of an impartial universe — our hunger for absolutes in a relative world, our yearning for permanence in a universe of constant change — he writes:
As we have struggled through the ages to fathom this strange and wondrous cosmos in which we find ourselves, few ideas have been richer than the concept of nothingness. For to understand anything, as Aristotle argued, we must understand what it is not. To understand matter, said the ancient Greeks, we must understand the “void,” or the absence of matter.
Because we are self-referential creatures — the consequence of being creatures with selves, itself the consequence of consciousness and the ceaseless electrical storm of neural firings that gives rise to our sense of self — no void troubles us more than that of our own mortality: the notion of our absence from the scene of life. It is difficult enough to grasp how somethingness could have arisen from nothingness — how the universe can exist at all. It savages the mind and its animating selfhood to consider that everything — including the subset constituting the particular something of us — could dissolve to nothingness.
It is a discomposing notion — even for a physicist without delusion about the materiality of life, with a soulful reverence for the poetry of existence. Lightman closes his essay on the science of nothingness with a sentiment of touching, inescapable humanity:
What I feel and I know is that I am here now, at this moment in the grand sweep of time. I am not part of the void. I am not a fluctuation in the quantum vacuum. Even though I understand that someday my atoms will be scattered in soil and in air, that I will no longer exist, I am alive now. I am feeling this moment. I can see my hand on my writing desk. I can feel the warmth of the Sun through the window. And looking out, I can see a pine-needled path that goes down to the sea.
Another essay, titled “Immortality,” explores this irreconcilable dissonance between the creaturely and the cosmic — the dissonance from which we make our most symphonic art as we try to fathom our existence. Lying in his hammock one summer day, Lightman observes:
A hundred years from now, I’ll be gone, but many of these spruce and cedars will still be here. The wind going through them will still sound like a distant waterfall. The curve of the land will be the same as it is now. The paths that I wander may still be here, although probably covered with new vegetation. The rocks and ledges on the shore will be here, including a particular ledge I’m quite fond of, shaped like the knuckled back of a large animal. Sometimes, I sit on that ledge and wonder if it will remember me. Even my house might still be here, or at least the concrete posts of its footing, crumbling in the salt air. But eventually, of course, even this land will shift and change and dissolve. Nothing persists in the material world. All of it changes and passes away.
And yet, in an echo of one of the book’s subtlest yet profoundest undertones, Lightman challenges our binary view of life and death. With an eye to consciousness — “the seemingly strange experience” that furnishes “the most profound and troubling aspect of human existence” — he argues that death is not the life-switch in the off position but the gradual dimming of consciousness, of our experience of aliveness, through the deterioration of its physical infrastructure.
Ever since Cecilia Payne discovered the chemical fingerprint of the universe, we have known that the atoms we are made of — seven thousand trillion trillion atoms in each of us, on average — were forged in the furnace of faraway stars. We know, too, that every cell in our bodies — the tendons that stiffen our fists and the cortices that kindle our tenderness — is made of atoms. Lightman writes:
To an alien intelligence, each of us human beings would appear to be an assemblage of atoms, humming with our various electrical and chemical energies. To be sure, it is a special assemblage. A rock does not behave like a person… When we die, this special assemblage disassembles. The atoms remain, only scattered about.
That special assemblage is what we call consciousness. A century after Virginia Woolf observed that “one can’t write directly about the soul [for] looked at, it vanishes,” Lightman writes:
The soul, as commonly understood, we cannot discuss scientifically. Not so with consciousness, and the closely related Self. Isn’t the experience of consciousness and Self an illusion caused by those trillions of neuronal connections and electrical and chemical flows? If you don’t like the word illusion, then you can stick with the sensation itself. You can say that what we call the Self is a name we give to the mental sensation of certain electrical and chemical flows in our neurons. That sensation is rooted in the material brain. And I do not mean to diminish the brain in any way by affirming its materiality. The human brain is capable of all of the wondrous feats of imagination and self-reflection and thought that we ascribe to our highest existence. But I do claim that it’s all atoms and molecules. If the alien intelligence examined a human being in detail, he/she/it would see fluids flowing, sodium and potassium gates opening and closing as electricity races through nerve cells, acetylcholine molecules migrating between synapses. But he/she/it would not find a Self. The Self and consciousness, I think, are names we give to the sensations produced by all of those electrical and chemical flows.
If someone began disassembling my brain one neuron at a time, depending on where the process began I might first lose a few motor skills, then some memories, then perhaps the ability to find particular words to make sentences, the ability to recognize faces, the ability to know where I was. During this slow taking apart of my brain, I would become more and more disoriented. Everything I associate with my ego and Self would gradually dissolve away into a bog of confusion and minimal existence. The doctors in their blue and green scrub suits could drop the removed neurons, one by one, into a metal bowl. Each a tiny gray gelatinous blob. Stringy with the axons and dendrites. Soft, so you would not hear the little thuds as each plopped in the bowl.
An understanding of death as “the name that we give to a collection of atoms that once had the special arrangement of a functioning neuronal network and now no longer does so” renders the boundary between life and death more like a shoreline redrawn by the receding tide pool than like a coastal cliff dropping off into the abyss. And yet even as a scientific materialist with no mystical inclinations and no belief in an afterlife, Lightman remains what we all are — fundamentally human in our special assemblage of atoms — and gives voice to that fundamental humanity with uncommon splendor of sentiment:
Despite my belief that I am only a collection of atoms, that my awareness is passing away neuron by neuron, I am content with the illusion of consciousness. I’ll take it. And I find a pleasure in knowing that a hundred years from now, even a thousand years from now, some of my atoms will remain in this place where I now lie in my hammock. Those atoms will not know where they came from, but they will have been mine. Some of them will once have been part of the memory of my mother dancing the bossa nova. Some will once have been part of the memory of the vinegary smell of my first apartment. Some will once have been part of my hand. If I could label each of my atoms at this moment, imprint each with my Social Security number, someone could follow them for the next thousand years as they floated in air, mixed with the soil, became parts of particular plants and trees, dissolved in the ocean and then floated again to the air. Some will undoubtedly become parts of other people, particular people. Some will become parts of other lives, other memories. That might be a kind of immortality.
As if it were not staggering enough how tiny a fraction of space life animates, Lightman observes that it also animates a fraction of time — not merely in terms of the transience of any one life, but in terms of all life occupying only a slender slice of the totality of time in the universe, as the discovery of cosmic acceleration has revealed. The cosmic brevity of “the era of life” is bookended on one end by the slow condensation of colossal gas clouds into the first stars that forged the first atoms large enough to form complex structures, after the universe had already existed for about one billion years, and bookended on the other by the eventual death of all stars when they burn out in several thousand billion years, leaving behind a dark lifeless expanse of pure spacetime.
Here we each are, each existence a summer day suspended in the hammock of spacetime.
And yet even in these cold unfeeling cosmic facts, Lightman finds reason to swell the brevity of existence with the warm feeling of kinship that makes life worth living. With an eye to his grain-of-Gobi-sand analogy, he writes:
Life in our universe is a flash in the pan, a few moments in the vast unfolding of time and space in the cosmos… A realization of the scarcity of life makes me feel some ineffable connection to other living things… a kinship in being among those few grains of sand in the desert, or present during the relatively brief era of life in the vast temporal sprawl of the universe.
We share something in the vast corridors of this cosmos we find ourselves in. What exactly is it we share? Certainly, the mundane attributes of “life”: the ability to separate ourselves from our surroundings, to utilize energy sources, to grow, to reproduce, to evolve. I would argue that we “conscious” beings share something more during our relatively brief moment in the “era of life”: the ability to witness and reflect on the spectacle of existence, a spectacle that is at once mysterious, joyous, tragic, trembling, majestic, confusing, comic, nurturing, unpredictable and predictable, ecstatic, beautiful, cruel, sacred, devastating, exhilarating. The cosmos will grind on for eternity long after we’re gone, cold and unobserved. But for these few powers of ten, we have been. We have seen, we have felt, we have lived.
Complement these fragments of Lightman’s altogether luminous Probable Impossibilities with physicist Brian Greene’s Rilke-inspired reflection on how to fill our transience with maximal aliveness and Maya Angelou’s Sagan-inspired ode to the cosmic specialness of our humanity, then revisit a Borges-inspired meditation on chance, the universe, and what makes us who we are.
Published June 13, 2021