Mediocre though it may be, carbon is the stuff of life

Mediocre though it may be, carbon is the stuff of life

Photo by Nick Nice on Unsplash

Originally published 1 December 1997

Dia­monds are for­ev­er” say the De Beers ads.

Well, yes and no. Depends on what you mean by forever.

Dia­monds are pure car­bon. Car­bon atoms in a dia­mond crys­tal are linked in a three-dimen­sion­al lat­tice, like the steel frame of a sky­scraper. The lat­tice gives hard­ness, rigid­i­ty. The reg­u­lar­i­ty lets the dia­mond shine, form facets, glim­mer with a deep light.

But let car­bon atoms join in anoth­er fash­ion, with dif­fer­ent bonds, then instead of glit­ter­ing dia­mond they become black graphite, flat sheets of atoms that slip and slide one across the oth­er. Or car­bon atoms can roll them­selves into tubes, or sphere-like poly­he­drons called fullerenes, after Buck­min­ster Fuller, the inven­tor of the geo­des­ic dome.

Car­bon is the wiz­ard ele­ment, the arch­ma­gi­cian. No oth­er atom is so ver­sa­tile in its arrange­ments with itself. And oth­er atom is so flu­ent in the speech of oth­er ele­ments; it forms alliances with ease and grace.

The British chemist P. W. Atkins says: “Car­bon’s king­li­ness as an ele­ment stems from its medi­oc­rity.” It is not so anx­ious to give up elec­trons as, say, hydro­gen or cal­ci­um. Nor is it so ready to receive elec­trons from its neigh­bors as, say, oxy­gen or chlo­rine. It is a giv­er and a tak­er in mod­er­a­tion, nature’s ful­crum. If ele­ments can be thought of as hav­ing per­son­al­i­ties, car­bon is steady, bal­anced, reli­able — wel­com­ing friend­ships, but con­tent with its own com­pa­ny. In medio stat vir­tus—in the mid­dle stands virtue, the gold­en mean.

These qual­i­ties of car­bon make it the arma­ture of life. Chains, trees and rings of car­bon atoms are the skele­ton of all liv­ing mat­ter. The mol­e­cules that account for the mus­cles of the heart, the stink of a skunk, the col­or of car­rots, the hor­mones of sex, the taste of vanil­la, the hot pun­gency of pep­pers, have a back­bone of car­bon. All life on Earth is a flour­ish on the theme of carbon.

Every car­bon atom that ever was, still exists (with the excep­tion of radioac­tive car­bon-14 atoms, with two extra neu­trons in their nucle­us). The car­bon atoms that were squeezed and cooked in the depths of the Earth to make nat­ur­al dia­monds had pre­vi­ous lives, per­haps as parts of the plan­et’s soft wrap of air. The car­bon atoms in dia­monds may them­selves abrade into the air to become part of a but­ter­fly­’s wing. Con­trary to the De Beers mot­to, dia­monds come and go; it’s their atoms that are forever.

Cos­mol­o­gists tell us that at the only ele­ments cre­at­ed in the Big Bang were hydro­gen and heli­um. The first gen­er­a­tions of stars and plan­ets con­tained no car­bon, oxy­gen, sil­i­con, or iron. All of the heavy ele­ments in the uni­verse today were cre­at­ed in stars as they burned, fused togeth­er from hydro­gen and heli­um, and cast into inter­stel­lar space at the end of a star’s life. Stars die vio­lent­ly, and when they go they spew into space a breath of heavy atoms, car­bon among them. Every dying star adds a whiff of car­bon to the universe.

The Hub­ble Space Tele­scope has pro­vid­ed us with remark­able images of dying stars. We see them puff­ing off their out­er lay­ers into the inter­stel­lar medi­um, like insects shed­ding chitin shells, or explod­ing swirling mass­es of their sub­stance away from their col­laps­ing cores. The pho­tographs are spec­tac­u­lar­ly beau­ti­ful. These events are the most vio­lent we know about in the uni­verse. And with each beau­ti­ful, vio­lent star death the uni­verse gains atoms of car­bon, oxy­gen, sil­i­con, and iron.

Count­less gen­er­a­tions of stars lived and died in the uni­verse before our solar sys­tem was born, and every star added heavy atoms to the inter­stel­lar medi­um. Slow­ly, the pri­mor­dial hydro­gen and heli­um was spiced with car­bon. When our solar sys­tem formed about 4.5 bil­lion years ago, there were enough heavy ele­ments in the par­ent neb­u­la, includ­ing car­bon, to make a few tiny sol­id-sur­face planets.

The Earth is a smidgen of col­lect­ed stardust.

We take our own atoms from the Earth as we grow. Every car­bon atom in our bod­ies was once blast­ed from a star. Even dur­ing our lives, our atoms are tem­po­rary; they come and go, in and out of our bod­ies like a slow breath, in con­stant replace­ment. Our abid­ing selves are not atoms, but infor­ma­tion, con­tained in the DNA, and in the intri­cate­ly woven neur­al net­works of our brains. Car­bon atoms blow in and out of us like a wind, orches­trat­ed by that exquis­ite score called life.

When we die our atoms will recir­cu­late, becom­ing part of earth, or air, or anoth­er liv­ing thing. What goes around, comes around, star­dust giv­en and tak­en, car­bon atoms form­ing alliances with hydro­gen, oxy­gen, nitro­gen, phos­pho­rus, sul­fur, as only car­bon atoms do with such facil­i­ty, such won­drous vari­ety of form.

All things flow,” said Her­a­cli­tus. We can­not step in the same riv­er twice, he said. The flow is even more per­va­sive than he imag­ined. Even the foot that steps in the riv­er is in con­stant flux. What flows are atoms, in a con­stant shuf­fle, in and out of stars, of neb­u­las, of plan­ets. Of all these atoms, it is car­bon that pro­vides the frame upon which life weaves its woof and warp of variation.

Car­bon is the back­bone, flow­ing, in and out, like an endur­ing flame. Forever.

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