In 1859, a solar storm now called the Carrington Event pushed auroras as far south as Cuba and induced currents so strong in North American telegraph lines that operators disconnected their batteries and kept sending messages using only the electricity coming out of the sky

The 1859 Carrington Event pushed auroras to Cuba and induced currents so strong that telegraph operators in Boston and Portland disconnected their batteries and relayed messages for two hours using only electricity from the sky. The storm, triggered by a solar flare observed by Richard Carrington and Richard Hodgson, remains the benchmark for geomagnetic threats to modern infrastructure.