Stony Brook University
7:30 pm
ESS Building, Room 001
Friday, Oct 03, 2025
What's the Matter with ALAN? The Problem of Light Pollution
Prof. Frederick Walter
Prior to the invention of artificial lighting, the night sky was dark. Today, we have lost most of our connection to the night sky. Few people recognize the constellations, because they are obscured by the bright night sky. Ground-based astronomy has retreated to dark sites in Hawaii, Chile, and the Canary Islands, but even there faces limitations as the bright sky outshines the faintest astronomical sources. Furthermore, the rapid proliferation of satellites in low Earth orbit interferes with many kinds of astronomical observations, at both optical and radio wavelengths. Artificial light at night (ALAN) is not just a problem for astronomers. Blue light at night has been shown to disrupt Circadian rhythms and sleep patterns. It suppresses melatonin production, which may inhibit immune system expression. It has been correlated with breast cancers and childhood leukemias. It disrupts avian migrations, nocturnal insects, and the nocturnal predator-prey relations. I shall review what we know about light pollution, and what can, and has, been done to mitigate some of its effects. Link to slides
Prof. Walter, a resident of East Setauket, studies star birth, stellar weather, and star death using the Chandra, XMM-Newton, and Swift X-ray observatories, the Hubble Space Telescope, TESS, and optical telescopes in Arizona, Hawaii and Chile. He has been a professor of Astronomy at Stony Brook since 1989. He will soon be retiring to the darker skies of Colorado.
