An representation of Earth astatine nighttime arsenic seen from abstraction appeared connected my laptop surface during an net search. The captivating representation with a vague title—“Global Map”—drew maine successful similar an insect mesmerized by the lukewarm glow of a streetlamp astatine night.
Initially, the representation reminded maine of flying astatine nighttime nether wide skies, with illuminated cities, suburbs, and roads below, often reaching toward the horizon, but it was evidently astatine a overmuch bigger scale. Yet, contempt the immense distance, it was inactive imaginable to place galore locales by their artificial lightprint. The agleam nodes of large metropoles: Paris, Delhi, Johannesburg, Mexico City, and the dazzling sprawl of Cairo and illuminated “snake” of the Nile River. I was struck by the map’s elemental yet arresting aesthetic: shades of acheronian bluish and yellow, some contrasting and complementary.
What does it mean, I wondered, to observe and visualize Earth lone by day, fixed that daytime is fractional of the planet’s clip and place? This representation showed determination is different fractional to the story: night, often forgotten oregon ignored due to the fact that of what I present telephone an implicit daytime bias.
Night is defined by the lack of sunlight, yet the representation revealed a nocturnal satellite that was not wholly dark. Sure, ample swaths of terrestrial Earth were inactive the deepest shades of navy blue, indicating immoderate illumination by the satellite but small artificial light. But portion of what made the representation truthful remarkable, adjacent stunning, was the grade and strength of illumination—so overmuch artificial airy that it was disposable from space.
This representation showed determination is different fractional to the story: night, often forgotten oregon ignored due to the fact that of what I present telephone an implicit daytime bias.
Some scientists person characterized specified illumination arsenic light pollution. One salient idiosyncratic has defined airy contamination simply arsenic adverse artificial airy astatine night, owed to its detrimental scientific, ecological, quality health, aesthetic, and different effects. However, not each scientists studying nocturnal artificial airy hold connected what precisely “adverse” means.
Other scientists connection a method explanation of airy pollution: “an accrued measurement attraction of photons successful the nocturnal situation supra people expected values.” This utile but adust mentation fails to seizure the affective powerfulness of the map—its illustration of quality beingness connected the satellite and the resulting proliferation of artificial light. Part of the map’s powerfulness is that we often deliberation of nighttime arsenic obscuring what is readily disposable by day. The hypervisibility of nocturnal illumination made by radical undermines this assumption. As the representation shows, nighttime is peculiarly effectual astatine illuminating artificial light.
This planetary representation captured a snapshot of nocturnal Earth successful 2012, but, arsenic a historian, I started pondering what the representation would person looked similar if it had been made in, say, 1912 oregon 1812. In short, I realized that nighttime has a history.
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Several years aft unexpectedly glimpsing the nocturnal map, I decided to constitute a publication astir the past of artificial airy astatine nighttime and however scientists came to beryllium acrophobic astir it.
In Transforming Night, my travel begins with the archetypal scientists who raised questions astir nocturnal artificial light: astronomers. Many observatories had been built successful oregon adjacent metropolis centers earlier extended nighttime illumination. But arsenic artificial airy arsenic good arsenic aerial contamination and vibrations from caller transit systems, similar streetcars, accrued successful municipality areas, galore of these observatories closed, the buildings repurposed for non-observational work, and caller technological facilities constructed successful much distant locales successful an effort to flight the problematic caller qualities of municipality nightscapes. Such was the signifier astatine Mexico’s Observatorio Astronómico Nacional, which was founded successful Mexico City and past moved 4 times betwixt 1867 and 1969.
The past of Mexico’s observatory suggests however nighttime and associated acheronian person changed. It illustrates 3 of the ways artificial airy has transformed night. Human-made illumination has gotten some bigger and brighter, accelerating since the nineteenth period and particularly since the aboriginal twenty-first century.
Scientists person identified a 4th mode human-made illumination is altering night. Different lighting technologies nutrient otherwise colored light. The caller adoption of light-emitting diodes (LEDs) has made galore cities’ lightprint whiter.
Data for this representation was acquired implicit 9 days successful April 2012 and 13 days successful October 2012. It took outer 312 orbits and 2.5 terabytes of information to get a wide changeable of each parcel of Earth’s onshore aboveground and islands. (Download Map Views—NASA Earth Observatory and NOAA National Geophysical Data Center).
Some scientists and activists acrophobic astir nocturnal artificial airy person argued that modern nightscapes person go inverted: from constituent sources of illumination scattered crossed the entity amid an different acheronian nightscape to agleam lights dotting the Earth’s aboveground with luminous haze from those lights rising above. They person suggested that earthly lights person go terrestrial stars blocking celestial illumination, including existent stars.
In galore parts of the world, the regular experiences of nighttime are becoming little night-like. In dense, highly illuminated cities similar Hong Kong, inhabitants walk their nights successful what scientists telephone perpetual “artificial twilight”: a luminous hinterland wherever daylight is ne'er wholly replaced by nocturnal darkness. This improvement raises the question, Is nighttime without earthy acheronian inactive night?
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When I began probe for my book, I wasn’t definite wherever the communicative would end. That changed with SpaceX.
On May 23, 2019, the now-public spaceflight, telecommunications, and AI institution launched by Elon Musk deployed sixty Starlink trial satellites into low-Earth orbit to supply low-cost net to agrarian and distant communities. The adjacent day, Marco Langbroek, a Dutch amateur astronomer, was 1 of the archetypal radical to people a video showing the satellites traversing the nighttime entity specified hours aft launch. He described a “spectacular view” implicit northwestern Europe: “a ‘train’ of agleam satellites, each moving adjacent unneurotic successful a line, moved crossed the sky.”
“Global Map” besides demonstrates that we request to see not lone the past of nocturnal artificial illumination but besides its future.
“It started with 2 faint flashing objects,” Langbroek explained. “Then, a fewer tens of seconds later, my jaw dropped arsenic the ‘train’ entered the tract of view.” By bare eye, the satellites look arsenic moving “stars” from the Earth’s surface, but successful astronomical images, they look arsenic parallel streaks interfering with the reflection of celestial phenomena. Given what helium was seeing, “I could not assistance shouting ‘oaaaaah!’”—followed by a fewer expletives, Langbroek added.
At the time, I happened to beryllium successful Colorado doing fieldwork. I watched astronomy and light-pollution Twitter (now X) stroke up online, arsenic these 2 overlapping communities abruptly realized what was happening earlier their eyes, cameras, and telescopes.
They didn’t expect what has occurred since. More satellites were deployed betwixt 2019 and mid-2024 than successful the erstwhile sixty years combined. As of June 15, 2026, implicit 16,000 progressive satellites are presently orbiting Earth (of those, 10,634 are Starlink satellites), but this fig includes lone operational spacecraft. It doesn’t see immoderate abstraction debris, besides called “space junk”—or the 1 cardinal further satellites SpaceX unsocial hopes to deploy.
Ground-based artificial illumination since the precocious nineteenth period had already altered nightscapes. Space-based airy is present extending the geography of nocturnal artificial illumination into extraterrestrial territory, rapidly and dramatically expanding the spatial scope of wherever human-made airy is located and yet its impacts connected nighttime crossed astir the full planet, unless it is addressed—and quickly. Transformations of nighttime owed to some ground- and space-based airy are momentous successful the discourse of quality history, fixed each cultures’ connections with nightscapes.
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Ultimately, I decided to extremity my publication wherever it began—with the representation that started it all, though I don’t look astatine it the aforesaid mode anymore. “Global Map” is astatine erstwhile an representation of artificial airy astatine night, airy pollution, and airy poverty. Composed from information collected successful 2011, it is simply a humanities artifact, already retired of date.
“Global Map” besides demonstrates that we request to see not lone the past of nocturnal artificial illumination but besides its future. That aboriginal includes which environmentalism champion addresses coming challenges. Since 2020, the caller question astir airy justice, rooted successful principles of biology justice, offers the astir compelling motivation and governmental model for addressing the benefits and costs of some artificial airy and darkness, for some humans and nonhumans alike. The adjacent measurement is simply a combat for much equitable, conscionable entree to light—and night.
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From Transforming Night: The History and Science of Light Pollution by Sara B. Pritchard. Copyright © 2026. Available from University of Washington Press.
English (US) ·