MEDITATIONS AT SUNSET: A SCIENTIST IN THE ATMOSPHERE by James Trefil (Scribner’s: $16.95; 240 pp.).

“There’s as much good physics in a thunderstorm as in a synchrotron,” writes James Trefil. This is the third in a series of books in which Trefil demonstrates that the working of natural laws are as apparent in nature as in the laboratory.

He starts by answering a question dreaded by all parents of inquisitive youngsters: Why is the sky blue? In lucid prose, he explains that light from the sun has in it all the colors of the spectrum, but oxygen and nitrogen in the atmosphere scatter the blue portion to the side, leaving a yellowish orb in the center.

He goes on to explain why smog enhances the beauty of sunsets (a mixed blessing if there ever were one), how clouds form, why there will never be a Hurricane Zelda, and why you can’t get a tan through a window. He’s at his best in two fascinating chapters on sunspots, and on the difficulty of proving that they run in 11-year cycles.

He’s at his worst in a rather pedestrian discussion of the invention of clocks and calendars. And I recommend that the airline traveler avoid reading the chapter called “When Clouds Go Bad,” at least until the plane is safely on the ground. It contains a discuss1768910368for a 1985 crash in Dallas that killed 133 people, and which are still almost totally unpredictable.