On 4 August 1972, a burst of solar plasma rocked Earth’s magnetic field after hurtling through space for about 14.6 hours—the fastest sun-to-Earth plasma journey ever recorded. The resulting space storm, one of several that occurred from 2 to 11 August, triggered widespread disturbances to electrical and communication grids and likely caused accidental detonations of U.S. undersea naval mines in North Vietnam.