The CRAYFIS project is a novel approach to observing cosmic ray particles at the highest energies.
It uses the world-wide array of existing smartphones instead of building an expensive dedicated detector.
Cosmic rays are particles from space which occasionally possess unfathomably high energies. The most energetic cosmic ray observed to date—dubbed the "Oh-My-God particle"—was found with an energy 20 million times greater than particle colliders on earth can generate.
When these cosmic rays strike the atmosphere, they generate a huge number of lower-energy particles in an an extensive air shower, which can stretch many kilometers across. The most energetic cosmic rays produce the largest showers, but unfortunately they are also the rarest. Only a detector with a large surface area can observe these mysterious particles.
The current state of the art is large-scale arrays of custom-designed dedicated detectors. To see the highest-energy cosmic rays, we need a very large detector array of exisiting commodity hardware: the smartphones in everyone's pockets.
Modern smartphones contain high-resolution cameras with digital sensors which are sensitive to the particles in a cosmic ray shower. They know where they are (GPS) and can upload their data (wi-fi). Most importantly, there are 1.5 billion active smartphones spread across the planet. Essentially, this detector has already been deployed; all that is missing is the app to collect the data.
The CRAYFIS app operates in a manner similar to a screensaver. When the phone is connected to a power source and the screen goes to sleep, the app begins data-taking. No active participation is required on the part of the user after the initial download and installation.
Read the paper.
Observing cosmic rays with a worldwide detector will let us:
In addition to learning about astrophysics, you get to actually be an astrophysicist by joining our collaboration and expanding our detector. Anyone whose phone collects enough data has the option to be made an author of at least one scientific paper.
Cosmic rays and CRAYFIS were featured in an episode of "Physics Girl" on PBS