Cosmic rays spark into life
17 March 1999
Cosmic rays - created when subatomic particles from outer space collide with the atmosphere - are brought to life in this photograph of a large spark chamber at CERN, the European Laboratory for Particle Physics. When a charged particle passes through a spark chamber, its track can be made visible as a series of sparks between metal plates (or planes of parallel wires) several millimetres apart. The charged particle ionises gas between the plates, and if a high voltage is immediately applied across the gaps, sparks fly along the track! Although not used in experiments today, spark chambers were important for detecting particles during the 1960s, and are still used in displays, for example at London's Science Museum and in the Micrcosm visitor centre at CERN.
Credit: CERN Photo
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