She writes for The New Yorker, where portions of “Under a White Sky” first appeared. In the Anthropocene era, when humans have fundamentally altered the planet and its environment, she asks, what does nature even mean anymore? As she mentions, the resulting changes could also include turning the color of the sky from blue to white. Yes, she quotes Allison Macfarlane, a former chairwoman of the Nuclear Regulatory Commission, who gives the idea a thumbs down over the unintended consequences. But she also suggests that the world might find its options so narrowed by inaction that it has little choice but to turn the sky white.