The City Dark, which airs tonight on PBS’s documentary series POV, is a quiet, reflective, modest movie, but it changed the way I look at the city, the sky, the stars, and night itself. Director Ian Cheney’s premise is simple: For much of the species’ existence, we’ve used the blackness of night to replenish our body’s energy, orient ourselves geographically and psychologically, and develop metaphors that help us understand who we are; but over the last 120 years, the visual din of electric lighting has grown to the point where we can barely see the stars anymore. The damage from this change is still largely unknown but almost certainly devastating. “What do we lose when we lose the dark?” Cheney asks.
Cheney gives us a bit of personal backstory about his migration from rural Maine, where he could see the night sky, to Manhattan, where he’s lucky to see a handful of stars after sundown. But much of The City Dark is a scientific inquiry that explores what it means to lose the night — what it’s costing us as individuals and as a species. It’s a straightforward example of the nonfiction filmmaker’s craft, featuring travelogue footage, animated charts and graphs, interviews with experts (including Neil DeGrasse Tyson). There are discussions of the importance of the stars in navigation, mythology, and religion, and a long section about what the ebb of night means for astronomy (the short answer: astronomers must travel to increasingly remote areas).
Then things get, well, darker, as Cheney talks about how the artificial daylight spawned by electricity is re-ordering and perhaps distorting our physiology. The human body is based around circadian rhythms: twelve hours of sunlight, twelve hours of dark; action, repose; expenditure, replenishment. What happens when more and more people disregard these rhythms, to earn a living or simply because they can? Internal chaos. Maybe sickness, too: One of the most chilling sections of The City Dark asks whether the alarming rise in breast cancer rates might be due to the systematic destruction of our body clocks. (Answer: We’d be fools to bet against it.) There’s a dollars-and-sense factor, too: Every gas station, skyscraper, monument, or mall that keeps its lights on is burning power (and fuel) that should not be so wantonly wasted. Why illuminate everything in creation if we don’t have to? (Part of the motivation, of course, is safety; Cheney points out that the fear of violence has been part of the allure of light ever since cave people huddled around campfires.)
Then there’s hubris. The sight of a city skyline is spectacular and beguiling, an inspiration for music, poetry, painting, and cinema, but it also represents an arrogant reversal of primitive impulses. Instead of gazing up in awe and contemplating our smallness within the greater scheme, we now streak through the heavens in airplanes, look down at constellations of electric lights, and think, How magnificent. Aren’t we an amazing species? The sky has fallen, and it’s so pretty that we don’t seem to mind.