The atoms we share

An individual contains roughly 6 × 10²⁶ carbon atoms, which make up about 18–20% of the body. With every breath throughout a human life, carbon atoms leave the body and enter the atmosphere. There they wait to be reabsorbed—into the air, the soil, or underground water—continuing the cycle for as long as time itself can be treated as a simple, continuous process. After drifting for thousands of years, these atoms eventually join the global active carbon pool of roughly 1.9 × 10⁴¹ atoms, mixing into the same reservoir that cycles through every other person, each of whom also contains about 6 × 10²⁶ carbon atoms.

By analogy and recursion, the probability that any carbon atom once part of you has also, at some point, been part of any other individual approaches 1. In a literal sense, Pythagoras, Newton, and Einstein were once me, and parts of them remain in me; their carbon atoms help form my body and sustain my will. If something like metempsychosis exists, then you will become anyone, and we are all anyone. We continually become one another and, from time to time, reunite. We share this world, burning and reforming through endless cycles of samsara. We are aggregates of carbon atoms, aggregates of countless lives, aggregates of history.

As Poincaré recurrence suggests, in a closed and finite system whose dynamics are deterministic and reversible, and whose particles remain confined to a finite region of spacetime, the system will almost surely return arbitrarily close to its initial state given enough time. On this view, everything we long for, are reluctant to leave, or wish to rebuild will reappear after an eternity. Life itself is finite—scarcely a hundred years—yet civilization is infinite. Rather than only looking back at a distant, lost past, we may look forward to a reunion after billions of years. By then, you will still be you, and I will still be me.

When we look back at the stars shining in the long flow of history, we are, in a sense, looking at another possible version of ourselves.