How Space Shield Protects Earth from "Sledgehammer Blow" of "Killer Electrons"

We live inside a bubble surrounded by a shooting gallery, but we've only realized for a few years how well-designed that bubble is.

The Van Allen radiation belts were detected in 1958 by the Explorer rockets, America's first satellites to orbit the Earth. Since then, physicists have known they shield the Earth from high-energy particles from the sun, but many questions have remained about the belts' structure and physical mechanisms -- especially, how electrons from the solar wind are acceler...