Seventeen essays from the Magazine of Fantasy and Science Fiction form this latest Asimov anthology. What's neat about the group is that rather than present random reviews, the essays are connected serially, laid out nicely in four major areas: physical chemistry, biochemistry, geochemistry and astronomy. The themes represent an interesting reprise of 19th- and 20th-century science. Physical chemistry focuses on batteries and, naturally, on electricity and magnetism, first from the point of view of the Galvanis and Voltas, the Oersteds, Faradays and Henrys, down to the postwar transistor era and current work on fuel and solar cells. One can imagine 12-year-olds reading these chapters virtually as do-it-yourself recipes for running wires around iron cores or making their own voltaic piles. Biochemistry is a treat for nutritionists. Asimov concentrates on the history of the discovery of vitamins and trace elements necessary for life. He reviews the classic experiment of British surgeon James Lind, who fed oranges and lemons to sailors to prove that the fruits would prevent scurvy (but alas did not live to see his advice heeded), down to the 20th-century stories of beriberi, pellagra and pernicious anemia. Biochemist Asimov is excellent here as he explains how vitamins work and why some need a "coenzyme" to do the job. Geochemistry plays upon the theme of tunneling to the center of the earth. Asimov unravels the mysteries of mass, temperature, and magnetism and how discoveries of radioactivity and devices like the seismograph have built up the present picture of the earth as thin crust atop a mantle over inner solid and liquid cores. Part four, culminating in the title essay--are Asimovian speculations on stars, planets, and space, beginning with a fine historical essay on time measurement, and ending with thoughts on where the universe is headed. To reach that climax, Asimov introduces concepts of "the Void," interstellar molecules and dust, the notion of superstars (not to be confused with supernovae), and the unresolved astronomical problem of the "missing Mass." Asimov presents alternatives (his own, he confesses) that would make it possible for universes to form and reform even if the present mass is insufficient to prevent an endless expansion and recession of galaxies. Here Asimov the scientist and science-fiction writer meet in an artless, seamless way that marks the man as formidable and readable as ever.