Our world is constantly being struck by cosmic rays–mysterious radioactive particles that likely come from supernovae and other distant sources. They interact with the Earth’s atmosphere and break into more benign particles before they reach human bodies, and we rarely ever notice them.

But that doesn’t mean we don’t care about them. There is currently a $2 billion cosmic ray detector on the International Space Station, and scientists and amateurs alike have been tracking them with lower-tech methods for a century. This week, a University of Wisconsin physicist announced an unusual new tool for tracking cosmic rays: mobile phones.

IceCube Particle Astrophysics Center researcher Justin Vandenbroucke and his team created an app that draws data from phones’ camera chips to spot those secondary particles created by cosmic rays interacting with the atmosphere. Smartphone camera chips are made with silicon. When the cosmic ray particles hit it they emit an electric charge, which…