The 24th collection of Asimov's essays, these culled from recent monthly columns in The Magazine of Fantasy and Science Fiction. The essays are grouped into three parts: "Isotopes and Elements"; "The Solar System"; and "Beyond the Solar System." Expect lots of chemistry and chemical history in Part I, including personal bits about Asimov's tiff with Harold Urey, who was not willing to admit someone who had not taken physical chemistry into Columbia's graduate chemistry program and made it very tough indeed. Here find essays on naturally radioactive substances and artificial radiation; the charms and dangers of carbon 14 in the body ("The Enemy Within"): and discourses on sulfur, phosphorus, and early matches, ending with an essay on the importance of phosphorus as the energy store of cells and as the calcium phosphate of bone. Asimov's fascination with size, distance, brightness, and other measurables is a familiar refrain seen in essays like "The Incredible Shrinking Planet." This is a neat exercise in logic and discovery that finally establishes Pluto as a small and icy "mesoplanet" (A's coinage for a planet between major and minor), accompanied by an even smaller moon, Charon. Or in an essay on novas, which led to a controversy over whether the Andromeda nebula, in which a nova had been spotted, was a far distant "island universe" or a nearby solar system in the making. Revelation comes in a succeeding essay on super-exploding stars: the star in Andromeda was a supernova 2.3 million light years away in the Andromeda galaxy. Concluding essays deal with matter and antimatter, star voyages, and, finally, the title piece, in which Asimov knocks the idea that right and wrong are absolutes. The point is that some things are wronger (or righter) than other things and we all got off on the wrong foot with the spelling, arithmetic drills, and short-answer tests of grade school. "Good" scientific concepts get refined over time, that's all. And written about by upbeat, postive-thinking, righter-than-most Asimov.