By Our Powers Combined

15 October 2014

An illustration of cosmic rays. CREDO
An illustration of cosmic rays.

If you have a smartphone, you are carrying around a supercomputing sensor array. Modern phones don’t just make calls, they are also constantly aware of their environment. They know where they are using GPS and mobile telemetry. They know their orientation and motion using gyroscopes and accelerometers. Many measure barometric pressure. They can record images and sound, and can communicate with the global internet. And there are about 1.5 billion of them.

With all those sensors across the globe, there’s a lot of interesting studies you can do. You can use mobile data to analyze traffic flow in major cities. You can study weather with barometer measurements from phones. You can also do some interesting astrophysics, because even though phones aren’t designed to take astronomical data, they still do.

Take a selfie! Brian Koberlein
Take a selfie!

For example, your phone can detect cosmic rays. Not directly, but it can detect muons produced in the shower of particles caused by cosmic rays. It does this through the phone’s camera. Digital cameras work through what is known as the photoelectric effect. When light strikes a charged silicon wafer, electrons are released, which creates a current. This is then recorded in your phone’s data. If you block the light coming into the camera, there shouldn’t be any generated currents. But muons from cosmic rays can penetrate the camera and strike the silicon wafer, producing a current. So with the right setup you can detect cosmic rays with your phone.

As the saying goes, there’s an app for that. Actually a couple. One is called DECO, and it works on Android phones. Another is known as CRAYFIS. Both of these apps are part of larger projects trying to crowdsource cosmic ray data gathering. If you like playing with your phone a bit, and want do participate in high-energy astrophysics, they are worth checking out.

Projects such as these are only going to get more common. As phones get smarter and more common, there will be more data available to be analyzed. It will be interesting to see what we can learn with our powers combined.