What exactly is the “chemtrails” conspiracy? You’ve probably noticed these white streaks in the sky. They’re clouds of water vapor that form when the warm exhaust of a plane’s engine encounters cold temperatures in the upper atmosphere. But some people think there’s a lot more to the story. Conspiracy theorists call these chemtrails, and believe the government is spraying chemicals into the atmosphere in order to control the weather and population - a practice they call “geoengineering.”