Cosmic rays are not rays, but high-energy particles from space. When they collide with gas molecules in our upper atmosphere, muons and other “secondary rays” are created. These constantly shower down to Earth’s surface.
Dozens of those secondary cosmic rays pass through our bodies every second. We can detect them when they go through a spark chamber and cause electrical disturbances.
How a Spark Chamber Works
A spark chamber detects energetic particles (mostly muons) that pass through it. When these particles encounter the helium and neon gases inside, they ionize the atoms of gas (by stripping electrons away from their atoms). If a particle hits all three sensors, the high-voltage plates become electrified. We see and hear sparks created along the particle’s ionized path where it intersects the plates.