Light pollution is the presence of excessive or misdirected artificial light in the environment, altering natural patterns of darkness. While humans have used simple lamps for millennia, light pollution itself is a modern development. The historical timeline reveals that the shift from localized light to pervasive skyglow is closely tied to specific technological innovations. This marks the point when artificial illumination transitioned from a localized convenience to an environmental concern impacting the global night sky.
Defining the Pre-Industrial Baseline
Before modern lighting, the night was defined by natural darkness. Early artificial light sources, relying on materials like tallow, oil, and wax, were extremely limited in intensity and reach. Sources such as simple oil lamps and candles produced a weak, localized glow sufficient only for close-range tasks indoors. Since the cost was prohibitively high, light was used sparingly and extinguished promptly, preventing any accumulated atmospheric effect. This established the natural baseline against which modern light pollution is measured.
The Technological Tipping Point
The first major break from the baseline occurred in the early 1800s with the introduction of public gas lighting, marking the beginning of organized, fixed-location street illumination. William Murdoch’s successful experiments with coal gas led to London’s Pall Mall becoming the first street lit this way in 1807, followed by Paris in 1820. Gas lamps provided light that was significantly brighter—at least 20 times more intense than earlier sources—creating the first sense of ambient urban light and localized skyglow.
This change was followed by a dramatic leap in intensity with the advent of electric arc lighting, which began commercial application in the 1870s. The arc lamp, pioneered by Charles Brush, was an intensely brilliant light source, sometimes measured as 200 times more powerful than contemporary filament lamps. These lights were initially used for large spaces like factories and city streets, such as those in Paris starting in 1878. Their harsh, bright output pushed the boundaries of illumination further into the night sky.
A broader, more pervasive change came with the development of the incandescent light bulb, which was commercialized by Thomas Edison in the 1880s. While not as powerful as the arc lamp, the incandescent bulb was far more practical, safer, and cheaper for both indoor and widespread outdoor use. This allowed electric lighting to become ubiquitous in homes, businesses, and streets. This accelerated the saturation of urban areas with light, making light pollution commonplace by the turn of the 20th century. The combination of gas, arc, and incandescent technologies created the necessary conditions for light pollution to emerge as a sustained, city-wide phenomenon.
From Localized Glow to Global Phenomenon
After the initial technological shift, the problem of light pollution scaled rapidly, especially following World War II. The post-war era saw massive increases in urban development, suburban expansion, and highway construction, all requiring extensive, round-the-clock illumination. This expansion was fueled by the introduction of cheaper and more powerful light sources, such as high-intensity discharge lamps like mercury and sodium vapor lamps, which became the standard for street lighting.
The growth rate of light intensity increased discontinuously after 1943, marking a departure from the incremental progress of previous centuries. By the 1960s and 1970s, astronomers and biologists began to formally recognize and document the negative effects of this expanding light dome, particularly the obscuring of the night sky, known as skyglow. This is the period when the term “light pollution” entered the scientific and public lexicon, signifying the point where artificial light became a measurable environmental problem and transitioned to a global phenomenon.