Experimenting with Tucson Night Lights

Since the invention and spread of artificial light, few locations on Earth appear entirely dark after sundown anymore. Even in a place like Tucson, Arizona dark-sky locations for astronomers the night sky is illuminated to a certain extent by artificial light sources.

Using satellites, scientists are starting to better understand the specific sources of this light pollution.

In a 2020 study led by Christopher Kyba of the German Research Center for Geosciences, scientists conducted an experiment with Tucson’s lights. They brightened then dimmed some streetlights for a few nights and used satellite images to observe changes in Tucson’s radiance. The results are not what you might expect.

Kyba and colleagues found that streetlights accounted for just 13 percent of the city’s total light visible after midnight. That number would jump to 18 percent if the city did not dim the lights. This means most of the light is coming from other types of artificial lighting.