The Invisible Shield Four Hundred Miles Above Your Head

Every second of every day, a violent stream of charged particles races from the sun toward Earth at over a million miles per hour. This solar wind carries enough energy to strip away our atmosphere and sterilize the planet's surface. Yet you slept soundly last night. Your children played outside this afternoon. You never gave it a single thought. Four hundred miles above you, Earth's magnetosphere — an invisible magnetic field generated deep in the planet's molten core — deflects that deadly barrage around us like water parting around a stone.…