American Scientist

THE WILD DARK: Finding the Night Sky in the Age of Light. Craig Childs. 212 pp. Torrey House Press, 2025. $24.95.

The Wild Dark: Finding the Night Sky in the Age of Light by Craig Childs is part travelogue, part science writing, and part memoir. Childs is taking a trip to see the closest full-dark sky with his friend and former coworker Irvin Fox-Fernandez, a biologist and “lifer” in the Forest Service. A full-dark sky refers to a sky with no or minimal light pollution. They start from the middle of Las Vegas, NV, one of the brightest places in the United States, and ride mountain bikes northward in search of darker skies.

Childs is passionate about the American Southwest, making Nevada a fitting place for him to explore through the lens of light pollution. He sprinkles a lot of discussion about the negative effects of light pollution throughout the book, giving readers insight into why he is searching for the “wild dark” night skies at which the title hints. A lack of darkness due to light pollution is detrimental to humans and other animals in a variety of ways, but even if there weren’t documented biological impacts, it is clear from the book that Childs thinks that the loss of awe and wonder one feels when looking up at a truly dark sky is reason enough to protect them. Although most readers will likely never be able to take a journey similar to the one about which Childs writes, hopefully many will be inspired to seek out a nearby dark-sky site where they can experience the full splendor of the night sky.

At first glance, the chapters appear to be numbered backwards, but the chapter numbers are actually Bortle scale numbers. The Bortle scale was introduced by amateur astronomer John E. Bortle in a 2001 article for Sky & Telescope magazine and provides a qualitative way of describing the amount of light pollution in a given location. Ranging from a "Class 1: Excellent dark-sky site" to a "Class 9: Inner-city sky," the Bortle scale includes descriptors such as “The sky glows whitish gray or orangish, and you can read newspaper headlines without difficulty” for a "Class 8: City sky," and “The summer Milky Way is highly structured to the unaided eye, and its brightest parts look like veined marble when viewed with ordinary binoculars” for a "Class 2: Typical truly dark site." It is an accessible way for someone to rate the quality of their sky without needing any special detectors or knowledge of limiting magnitudes, just a general familiarity with the night sky.

The Bortle scale also serves to guide the structure of the book, with Childs and Fox-Fernandez riding far enough every day to reach the next darkest level of the scale. When mapping out their journey, Childs realized that walking would be too slow and driving would be too fast, but about a day’s worth of biking would get them to the next Bortle number each evening. After each grueling day of biking in the Nevada desert, Childs and Fox-Fernandez would arrive at their camping spot for the night and set up camp under the stars. Childs uses a device called a Sky Quality Meter (SQM) every night to get a quantitative measure of the light pollution at their camp. On a few of the days, he even finds that his on-the-ground measurements do not match up with satellite observations—with the ground truth always showing more light pollution than reported by the satellites.

The trip itself is quite harrowing: Childs and Fox-Fernandez both got a lot of practice in repairing both their bikes and their punctured tires; much of the terrain they covered was never intended as a bike path and so the bikes took a lot of wear and tear. The weather did not always cooperate, although it only rains one night of the trip, forcing them to sleep in tents instead of directly out under the sky. The narrative is peppered with stories of other dark-sky places Childs has visited, almost as if remembering these previous experiences helps remind him that the end (another truly dark sky) will justify the means (grueling days of riding).

Childs and Fox-Fernandez eventually arrive at their goal, an unnamed "Class 1: Excellent dark-sky site," where they are met by friends who will drive them back to Vegas. The final few nights, they face the same challenge that I do at truly dark sites: There are so many stars in the sky we aren’t used to seeing that it becomes difficult to pick out the familiar bright constellations. Of their Class 1 sky, Childs writes:

What I see tonight, neck craned, following the spilled milk of galactic arms, is enough to reveal a kind of grand clockwork. The mountains are black, bereft of light, causing the sky to blaze and the Milky Way to wave like a banner. The structure is now well-defined, with stellar concentrations putting out radiation and streamers of dirty gas clouds holding it in. Galactic archaeologists would look at this ancient swath of light like studying a fossil, peering into its foramina and socket, understanding how the beast of our galaxy moves and evolves.

The snippets of research and discussions with scientists and dark-sky advocates that Childs weaves throughout the book paint a somewhat dire picture. Light pollution is increasing in both prevalence and its deleterious effects, as we switch from incandescent to LED bulbs: Bluer LED light appears to affect animals, including humans, more negatively than yellow-orange incandescent light. The absence of dark nights affects sleep, reproduction, migration, and general health, among other things. (Indeed, a major thing this book lacks are references for all of the studies that are mentioned. It might have been beneficial if Childs had added a book list for further reading at the end of the book, so that readers could learn more about many of the effects that are mentioned.)

There is, however, hope. As Childs writes, “Light is hungry and has to be told to stop. Human agency is required.” We have that human agency, and the solutions to this problem we have caused are relatively straightforward. Childs speaks with a lighting engineer who described the finesse that is being used in some places to preserve darkness using technology such as timers and dimmers, and clever design to make sure that fixtures are shielded and positioned so they shine only where the light is needed. He speaks with Jenny Ouyang, a professor and ecologist at the University of Nevada, Reno, who is also optimistic. Compared to some of the other pollutants in our modern world, light pollution is one of the easier ones to solve, “a simple matter of turning off a switch, or at least turning one down.” I am not quite as hopeful as they are, and one gets the sense that Childs isn’t either. But at least in this case, there is a possible solution—we just have to implement it.