The Same River Twice

Subtitled "Stenothermal Waters and the Remorseless Flow of Time." Science writer David Quammen, reading Heraclitus, opens with the philosopher's line that "you cannot step twice into the same river" and follows it into a meditation that braids ancient Greek metaphysics with the biology of cold-water trout streams — stenothermal organisms locked into narrow temperature ranges. The result is a characteristically Quammen essay: a scientific particular pulled gently into a much larger reflection on time, change, and persistence.