Arguably the three most important atoms on Earth are carbon, oxygen, and hydrogen. Carbon provides the fundamental chemical base of every life-form on the planet, past and present. When fuels derived from the decomposed and fossilized life of the past—such as coal or gasoline—burn, they release carbon into the air. Oxygen is vital to keeping carbon-based life forms alive, barring a few odd creatures like anaerobic bacteria. And if two hydrogen atoms attach to a single oxygen atom, the result—H2O—is that gloriously necessary liquid called water.
