Astronomers have long known that interstellar dust—microscopic grains made of carbon and silica—obscures starlight by soaking it up and reradiating it as infrared. They estimated that dust might block about 10 percent of the total light in the universe. It looks like they were way, way off. In a new study, a team of European astronomers exploited the observation that dust builds up in the plane of a galaxy, not its center, meaning it blocks more light when galaxies are viewed edge on. So they tallied the number of galaxies visible either edge on or face on in the 10,000-galaxy-strong Millennium Galaxy Catalogue. Edge-on galaxies were less common than face-on galaxies by a whopping 70 percent, they report in May 10's The Astrophysical Journal Letters. Combined with models of dust distribution, the result suggests that dust blocks nearly half the light in the universe.