If you could enlist your smartphone to become part of an earth-sized telescope searching for the source of cosmic rays, would you? Researchers at University of California are hoping you'd say yes—they've developed an app that will leverage the power of one million smartphone cameras to answer one of the great questions about our universe.
What exactly is a cosmic ray? Basically, it's radiation from far, far away that smashes into our atmosphere and creates something called an "air shower" of particles, like muons. How common are they? Well, CERN says that "one per second passes through a volume the size of a person's head," which is to say that one muon may have just passed through your head while reading this.
The thing is, air showers are hard to detect since they're random and massive—in fact, we've been trying to figure out where they come from for nearly a century. In the early 1900s, a scientist named Theodor Wulf planted the empirical seed that would become the idea of cosmic rays by showing how the air at the tip of the Eiffel Tower contained more radiation than the air at the bottom. A few years later, physicist Victor Hess confirmed Wulf's findings in a hydrogen balloon high above the Earth, and cosmic rays were born.
Victor Hess and his balloon in 1911. Via.
But while theories have proliferated since, it's been tough to prove anything about cosmic rays—because our detection methods are so meagre. That's where an app called CRAYFIS, or Cosmic Rays Found in Smartphones, will come in. The app was designed by a team of physicists at UC Irvine, who want to build a user base of one million phones to create a cosmic ray detector—in essence, a telescope—that's as big as the planet itself.
Here's how their app works: Inside your smartphone's camera, whether a Galaxy S5 or an iPhone 6, are silicon photodiode pixels—the things that detect visible light and turn it into something you can see on your screen. But as the UC team explains in their new paper (PDF), they can also detect high-energy particles. The app is basically a piece of software that records when your camera senses these particles, then records the levels, location, and time of the "shower."
It runs itself automatically and imperceptibly only when your phone is charging, so it doesn't suck up battery life, and it only uploads relevant captures to UC's server when you're connected to Wi-Fi. What about privacy? The data the app is uploading is able to detect the different between shower data and actual photos, and will never upload actual images. The team at UC says they've spent over a year on the beta of the app, all because to achieve the number of users they need for their telescope to function, their app needs to be as invisible and convenient as possible—hence the focus on battery life, data, and privacy.
Another cool detail? If your phone records shower data using the app—which you can request access to here, though it is still in beta at the moment—and the UC team uses in an analysis, you'll be listen as an author in the subsequent paper.
Particle physics has pretty much remained within the purview of multi-national agencies with billion-pound projects since cosmic rays were detected—at least after Wulf first did his controversial experiments atop the Eiffel Tower. As scientists—and smartphone users—get smarter about leveraging the power of the ubiquitous sensors found in billions of devices all over the world, that may be about to change. [CRAYFIS; UCI]
Image: Syda Productions.