Around 2016, “Night mode” or “night shift”—a screen display option that features a light-on-dark color scheme—began cropping up all over our devices. That year, Apple and Twitter released their own versions of the feature. Google and others soon followed, all of them promising to mitigate the harms of blue light exposure. They aimed to address new concerns about the impact of screens on circadian rhythms and preempt a full-blown movement against late-night screen use. Eventually, the setting promised a much vaguer set of around-the-clock benefits, including improved focus, energy savings, and reduced eye strain. Accordingly, “night mode” became “dark mode.” 

There’s no empirical explanation for dark mode’s rise. For the majority of users, dark text on a light background is harder to read, presumably because the human eye has largely evolved to spot dark figures against the bright background of the sky. Ironically, the reason the light-on-dark color scheme of traditional CRT monitors was phased out in the first place was because most people were used to reading ink on paper and therefore experienced a dark-on-light computer screen as more natural. There’s little evidence that dark mode improves focus. What’s more, unless the mode is set to true black and people use certain types of screens, such as OLEDs, the amount of light emitted in light and dark mode is practically the same, which means that the promise of energy savings is void, too.

Where sleep is concerned, there are very real signs that bright light at night is harmful, but the impact of screen light in particular is likely overstated. According to Russell Foster, a professor of circadian neuroscience, the degree to which light exposure impacts sleep depends on the wavelengths, duration, and intensity of the light and the age and sensitivity of the person, plus the precise makeup of their eye. He added that there is “practically nonexistent” evidence to support the efficacy of turning a blue-hued screen red in the hours before bed (as sunset shift applications like F.lux do). It seems that what one is actually doing with a screen late at night will affect how one sleeps afterward far more than the brightness or color of the screen light. 

And yet bright screen light has become almost superstitiously linked to technology’s ills. When circadian rhythm science began to enter popular discourse in the mid-2010s, it seemed to corroborate the fear that digital devices were somehow making our lives less natural, impacting sleep, mood, and concentration. The strength of our attachment to dark mode lies in a deep conviction that our world is overilluminated and overstimulated, and that by approximating natural rhythms, darkness might help us reverse the influence of the digital age on our bodies and minds.

On the internet, the sun never rises and never sets. (It is 11 pm in the Southern Hemisphere, where I am now reading a tweet that wishes New Yorkers good morning.) Like the inside of an airplane, it glows an unnatural blue and straddles time zones, throwing its inhabitants into a kind of perpetual digital jet lag. Its apparent timelessness was once framed as a source of liberation. “The internet is absent of both night and day,” boasted MIT Media Lab cofounder (and former WIRED columnist) Nicholas Negroponte in 1999. He was speaking at the launch of “Internet Time,” a new universal time measurement that accompanied a range of Swatch Beat watches. Now, however, this estrangement from natural patterns is seen as a problem to be fixed—perhaps with a new set of technical interventions. 

Given that our social interactions tend to shape our experience of time, perhaps it makes sense that devices would mess with our sense of rhythm and place. But pundits who go on about night mode, SAD lamps (for seasonal affective disorder), and the impact of technology use on the body tend to dwell more on biological factors than social or cultural ones. Usually, they invoke the relatively recent science of the body clock, the idea that time is lodged in our bodies on a cellular level. In doing so, they tie the issue of digital light to an emerging body of ecological research on the effect of light pollution on animals: migratory birds that are lured to their deaths by the bright lights of the city, turtles drawn away from the safety of the ocean by fake LED moonlight emanating from beachside resorts, flowers opening to a false sun.