Layzej writes with this quote from Nature: "For a century, scientists have known that charged particles from space constantly bombard Earth. Known as cosmic rays, the particles are mostly protons blasted out of supernovae. As the protons crash through the planet's atmosphere, they can ionize volatile compounds, causing them to condense into airborne droplets, or aerosols. It is hypothesized that clouds might then build up around the droplets — possibly affecting the Earth's climate. To find out, [Jasper] Kirkby and his team are bringing the atmosphere down to Earth in an experiment called Cosmics Leaving Outdoor Droplets (CLOUD). ... Early results seem to indicate that cosmic rays do cause a change (abstract). The high-energy protons seemed to enhance the production of nanometer-sized particles from the gaseous atmosphere by more than a factor of ten. But, Kirkby adds, those particles are far too small to serve as seeds for clouds."