Earth's two lasting radiation belts reach from about 640 to 58,000 km above the surface. A third one did not last. On 28 February 2013 the Van Allen Probes reported a transient belt of high-energy ultrarelativistic charged particles. It persisted for four weeks. Nobody had seen a third belt before, and nothing of it is left now. The belts give off no light. They are clouds of particles trapped by Earth's magnetic field, and this one simply thinned away. #Astronomy #ThirdBelt #Space