Probable Impossibilities: Physicist Alan Lightman on Beginnings, Endings, and What Makes Life Worth Living

In Probable Impossibilities: Musings on Beginnings and Endings, 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.

Building on his lifelong passion for harmonizing for absolutes in a relative world, our yearning for permanence in a universe of constant change — Lightman 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 — 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.

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:

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:

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:

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 — and gives voice to that fundamental humanity with uncommon splendor of sentiment:

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.

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 […], 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.”