We began this book with the viewpoint of a newcomer to the universe. What would he see, and how would he interpret it? The stars would be seen to consist mostly of hydrogen and helium, and the heavier elements would be most apparent in the colder planets that surround some stars. As our visitor approached closer and closer, he would discover first the lightest two elements, and then the rest of the inorganic elements. But if he came close enough to Earth (and probably to some other planets here and there around the galaxy), he would encounter a new kind of chemical organization. In the midrange of size, and under mild conditions of temperature and pressure, there exists a diverse and varied chemistry based on carbon atoms. These atoms can form strong CC bonds in chains of apparently limitless length. Rather than ions and electrons in a plasma, or single and paired atoms in a gas, or ions in crystalline arrays, our observer would find connected groupings of large numbers of atoms into stable units: molecules.

In the midst of this molecular carbon chemistry, and arising from it, highly organized collections of chemical reactions would be detected, which are isolated from the general environment by semipermeable barriers. These living entities show a degree of order and organization not yet encountered elsewhere in the universe, and a state of unusually low entropy. Entropy, as we saw in Chapter 13, is a measure of the degree of disorder. Maintenance of this state of order, or of low entropy, requires the production of specific molecules whose synthesis is not thermodynamically spontaneous.