The sun's violent glow powers nearly every movement on the Earth's surface, yet its origin is still incompletely understood. This is Asimov's message; and as in the other 29 books in his "How did we find out?" series, he takes readers on a historical tour of scientific research. In this case, the topic is: "How does the sun shine?"--and from Aristotle's theory of the Ether to Reines' neutrino detector, the author shows, in a nontechnical way, how successive ideas were suggested, studied, discarded or refined. A natural companion volume to Asimov's briefer What Makes the Sun Shine? (1971) or the plethora of other simple introductions to our nearest star. Occasional diagrams and pencil drawings; index.