The dark sky is a natural resource, and too much light is polluting it

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• When private space venture company SpaceX’s Starlink constellation of small satellites began to obscure the view of ground-based telescopes around the Earth, the idea of the sky as a natural resource capable of being polluted became popular. These incidents also rendered the absence of a global treaty to reduce light pollution more conspicuous

• satellites are unable to ‘sense’ blue light emitted by LEDs and to study light that is emitted parallel to the ground.

• Visible light emitted by many sources is divergent, so light emitted insufficiently downward could find its way into the sky.

• The researchers recommend light sources that cast light at an angle below the plane of the horizon, capping the emissions of these sources and calibrating their output according to the total brightness at the spot being lit.

• A 2016 study reported that 19.5% of India’s population — the lowest fraction among G20 countries — experiences a level of skyglow that would at least keep the Milky Way galaxy out of sight and at most render “dark adaptation for human eyes” impossible. The effects include stimulating the cone cells in human eyes, which is possible only when an environment is considered to be well-lit.

• lit beaches deter sea turtles from coming ashore to nest.

• skyglow keeps trees from sensing seasonal variations.

• young burrow-nesting seabirds don’t take flight unless the nesting site becomes dark

• clownfish eggs don’t hatch when exposed to artificial light at night, killing the offspring.

• t skyglow interferes with multiple aspects of insect life and allows insect predators to hunt for longer.

• . By disrupting the circadian rhythm, artificial light at night can hamper the production of melatonin, an influential hormone in the human body which affects sleep, moods and cognition.

• “silvery cloud” at night. It became evident later that they were really seeing the Milky Way.

• “The erasure of the night sky acts to erase Indigenous connection to the stars, acting as a form of ongoing cultural and ecological genocide.”