This week, I am at the North American retreat of the Society of Ordained Scientists. Special thanks to Amelia Hagen, chemist and priest, whose reflection this evening inspired this post.
Carbon occupies a special place in the chemistry of biology. Perhaps you have heard that all life on earth is carbon based or perhaps you know that carbon atoms make up the vast majority of all metabolic reactions. The connection is so strong that we have a special name for the type of chemistry that involves carbon-carbon bonds: organic chemistry. Indeed, it was once believed that only living organisms could produce molecules like propane, steroids, and waxes. Throughout the 20th century we came to understand that this was not the case. From the Miller-Urey experiment onwards, chemists have recognized many “abiological organic reactions,” that is chemistry of carbon that takes place outside of organisms. Nonetheless, we recognize a special connection between carbon and life.
The chemical reasons for this are not terribly complex but they are profound and we did not recognize them until recently. Carbon has two important properties: abundance and connectivity. First, due to the peculiarities of nuclear physics, carbon occurs abundantly in the universe. Hydrogen and helium were produced near the beginning of the universe, when things cooled down sufficiently (from the initial explosion) to form matter. They make up 74% and 24% of the atoms in the universe, respectively. The other elements only formed later within the furnaces at the center of stars, where hydrogen and helium fused together. This process uniquely favors carbon, nitrogen, and oxygen as the first stable step in forming larger elements. Consequently, those three elements are the next most abundant. [Nitrogen comes slightly after iron and neon, abundant for slightly different reasons.] Carbon happens to be around, making it an ideal candidate for the chemistry of life.
Second, carbon makes bonds well. A quick glance at a period table will tell you that carbon is element number 6, right in the middle of the second row or “period” of the table. This means, carbon has six protons, which have a positive charge, and frequently attracts six electrons, which have a negative charge. The positive and negative charges balance. More importantly, it means that the second valence shell (corresponding to the second period) is exactly half full of electrons – four out of eight. Each one of those electrons can pair with another electron from another molecule to form a strong “covalent” bond. Carbon pairs well, especially with itself, being capable of making four strong bonds at a time. Like Lego™ blocks, carbon can be added together ad infinitum to form very complex molecules, including proteins (which do chemical work in organisms) and DNA (deoxyribonucleic acid, which stores biological information). Carbon gives life possibilities by allowing it to form complex and intricate structures within our cells.
So carbon is both abundant and connective. Nearby atoms on the periodic table are less successful in both areas. Oxygen occurs more frequently, but only forms two bonds. Nitrogen (3) and sulfur (2) are less abundant. Phosophorus forms a remarkable 5 bonds but, being one period down on the table, these are far weaker. Silicon, like carbon, forms 4 bonds, making it a popular prop for science fiction. Alas, like phosphorus, those bonds are relatively weak. Silicon is at least abundant on rocky planets (like Earth), if not in the universe at large.
Having laid groundwork in chemistry, I would like to add just a note on the subject of morality. I have found two person relationships to be quite common among humans. It can be (relatively) easy to form a strong bond with friends and romantic partners. It can even be (relatively) easy to form strong relationships in small groups, families and clubs. The problem becomes so much more difficult once you expand the group to more people, to 100 or beyond. How do you form the types of social structures that not only last, but continue to be healthy and helpful to their members. I would like to suggest that this takes a special kind of person, a person good at making strong connections. We don’t need everyone to do this, but we need backbones, long chains of people who, like carbon, bind people together into complex structures. I think a big part of Christianity must be devoted to this kind of work, both within and without the “church” proper. Christians should be like carbon.
Biological life provides the best metaphor for spiritual life, and I think chemistry has a role to play in that comparison. This week, with the Society of Ordained Scientists, I am meditating on the relationship between chemical and social bonds. I hope you’ll share that meditation with us. I hope you will reflect on how many bonds you are able to make, whether those bonds get in the way of making other bonds, and what kind of larger structures you are a part of. As humans, we are so much more complicated than atoms and yet, I believe some truth may be found in this kind of comparison.