Free Mr g by Alan Lightman Page A

atoms of hydrogen bound to one atom of oxygen, was plentiful in at least one planet in every dozen solar systems—covering its surface in liquid oceans and floating above in gaseous vapors. Another common molecule in planetary atmospheres was methane, comprised of one atom of carbon bound to four atoms of hydrogen. And carbon dioxide. And ammonia. Sunlight filtered through these atmospheric gases in a lovely way, causing the air on certain planets to glow in crimson, turquoise, and cadmium yellow.
    Other phenomena were less expected. The atmospheres of a great many planets were repeatedly cracked by jagged bolts of electricity. These spectacular discharges of electricity slammed energy into the primordial atmospheres and formed complex new molecules: sugars and carbohydrates and fats; amino acids and nucleotides.
    Among all the atoms, carbon was supreme at bonding with other atoms. It had four electrons available for pairing, the maximum number for the smaller atoms. As a result, carbon atoms could link together and gather up hundreds of atoms of oxygen, hydrogen, and other elements in long, gangly chains. Or, instead, form hexagonal rings and other elaborate structures. Nitrogen, able to share three electrons with other atoms, was also excellent at bonding. Other elements had different bonding abilities, leading to many patterns. Atoms in molecules formed linear chains, planar triads, tetrahedrons, octahedrons—some folding upon themselves in the most marvelous ways. All of which was caused by the particular electrical attractions and repulsions between atoms, arising, in turn, from the precise orbits of their electrons. These orbits, finally, were rigidly prescribed by the laws of the quantum.
    As with the planets and stars, I had nothing to do with the manufacture of these molecules. They formed by themselves, irresistibly following the creation of matter and the small number of principles with which the universe began. Cause and effect, cause and effect. I was a mere spectator. But I would watch over the progression of events, as Aunt P had suggested, and intervene if things began going awry.
    As soon as large molecules were formed in the planetary atmospheres, they plummeted down through the air and sank into the oceans. And dissolved. Just as carbon is the atom most suitable for forming complex molecules, water is the superior liquid for dissolving other molecules. Owing to the positions of its electrons, water molecules can gently pull apart other molecules, attach themselves by electrical attraction, and escort the guest molecules as they swim about.
    In time, the oceans of quite a few planets became a thick hodgepodge of carbon and nitrogen-based molecules, water, and fragments of other molecules. These bits and pieces proceeded to collide with one another at great frequency as they moved and jostled about in the warm seas. Even on a single planet, there were trillions upon trillions of such molecular collisions every tick of the hydrogen clock. With so many encounters, all kinds of new things occurred. New molecules were created. Some molecules stuck together to form bigger molecules. Some rearranged or tore off pieces of each other. Some extracted energy from other molecules by plucking off their electrons. Various architectural structures formed, such as spherical cavities or solid ellipsoids, held together for a few moments, and then came apart. It was trial and error, trial and error, trial and error. It was trillions of scientific experiments performed every atomic tick. I could hardly wait to see what would happen.
    One of the molecules, a long chain of carbon, hydrogen, oxygen, phosphorous, and nitrogen atoms, had the ability to replicate itself. At each section of the chain, the electrical attractions were just right to snatch a matching section from the jumble of raw material floating around it and duplicate itself. This master molecule could do more than replicate. It also served as an intermediary in