$100 Pocket Muon Detector: Students build handheld CosmicWatch; sparks citizen-science network

A device that can detect particles arriving from space does not necessarily require a multimillion-dollar laboratory. A compact detector developed by physicist Spencer Axani began as a low-cost student project and has since grown into a tool used for particle-physics research, education and high-altitude experiments. The University of Delaware detailed its latest developments in September, while earlier accounts in Physics Today and Fermilab/SLAC’s Symmetry documented how the project evolved from Axani’s work at MIT into the CosmicWatch programme.The device, called CosmicWatch, detects muons, short-lived subatomic particles produced when high-energy cosmic rays collide with atoms in Earth’s atmosphere. Those collisions generate cascades of secondary particles, some of which reach the ground and pass through buildings, rock and even the human body. Muons travel extremely close to the speed of light, making them useful messengers of what happens when cosmic radiation interacts with Earth’s atmosphere. Unlike ordinary light, however, they cannot be seen directly. A detector such as CosmicWatch converts their passage into measurable electrical signals.How a $100 device detects particle...