Who owns the night?and what is lost as we flood it with light, worldwide? Darkness has become legible?and contested. Blending archival narrative with on-the-ground ethnography, Sara B. Pritchard traces how four fields?astronomy, remote sensing, conservation science, and ecology?have investigated artificial light at night, turning a ubiquitous convenience into a category of harm. From observatories chasing ever-receding darkness to the satellite images that first rendered a nocturnal planet from space and recent ?Black Marble? maps, Pritchard shows how methods, instruments, and field sites shape what scientists can know about night and light?and what remains unseen. Across these encounters, night emerges not as a backdrop but as an environment in its own right?one transformed by rapidly expanding, brightening illumination in the Anthropocene. Transforming Night chronicles the ascent of ?light pollution,? as well as the new challenge of space-based brightness from satellite constellations, even as dark-sky advocates fight to preserve the starry firmament. Attentive to politics as much as photons, Pritchard brings environmental justice to the fore?highlighting tensions among light poverty, forced illumination, and surveillance and calls for ?beneficial darkness.? She takes seriously Indigenous astronomers? critiques of dispossession and ?astro-colonialism,? asking what it means to site world-class telescopes on sacred land. Sweeping from local parks to planetary vistas, Transforming Night reframes a familiar story of modern light as a history of changing nights?past, present, and possible. It will engage readers in environmental history and humanities, science and technology studies, and the sciences themselves, along with dark-sky activists and anyone drawn to the beauty and politics of the world after nightfall.