To an extent, this is a kind of dictionary of scientific concepts and terms, but it goes, well beyond the brief or limits, of a mere dictionary. There are lengthy passages, virtually essays in themselves, which explain the phenomenon called "The Big Bang", on stars and supernovas, quarks and quasars, the behaviour of light.
Potted biographies of the great scientists, past and present, are added, and there is a section called "Timelines" which relates events in science to the broader events of history.