Dark Sky Week Starts

International Dark Sky Week begins Sunday, April 13, and runs through April 20 as organizers push a weeklong campaign to cut light pollution and protect darker night skies. (darksky.org) DarkSky International calls it a global event focused on “discovering the night together” and taking practical steps such as switching off unnecessary outdoor lights and reducing glare. EarthSky’s 2026 guide says this year’s theme is “Go Dark.” (darksky.org) (earthsky.org) Light pollution is the human-made brightening of the night, from porch lights, parking lots, billboards, and streetlights that spill upward or sideways instead of only where people need it. DarkSky says the problem affects sleep, wildlife, energy use, scientific observing, and the visibility of stars. (darksky.org 1) (darksky.org 2) The week arrives as dark-sky groups and public agencies keep pressing the same basic fix: use light only when it is needed, point it downward, keep it dim, use warmer-colored bulbs, and turn it off when it is not required. DarkSky and the Illuminating Engineering Society published those five principles jointly, and the National Park Service says similar standards guide its work on outdoor lighting. (darksky.org) (nps.gov) The push is not only about astronomy. DarkSky says darkness supports human wellness and wildlife, and the United States Fish and Wildlife Service says scattered city light can turn a black sky gray and degrade habitat conditions even in protected areas. (darksky.org) (fws.gov) Researchers and advocates also track the problem from space and from the ground. NASA uses nighttime lights data to study urban growth and the biological effects of artificial light, while Globe at Night asks people to submit local sky-brightness observations from a phone or computer. (earthdata.nasa.gov) (globeatnight.org) The campaign has roots going back more than two decades. Flagstaff Dark Skies Coalition says International Dark Sky Week has been observed worldwide since 2003, after Jennifer Barlow proposed the idea as a teenager in Virginia. (flagstaffdarkskies.org) Events this week range from local proclamations to public star parties and citizen-science projects. In Flagstaff, Arizona, partners scheduled nightly stargazing programs during April 13–20, and DarkSky is urging supporters elsewhere to post activities on its world map. (flagstaffarizona.org) (idsw.darksky.org) The week ends April 20, but the pitch behind it is simpler and longer-lasting: fewer wasted lumens, lower glare, and more places where the Milky Way is still visible after sunset. (earthsky.org)