In 1859, the Carrington solar storm sent currents surging through telegraph wires, shocking operators, igniting telegraph paper and allowing some lines to transmit with their batteries disconnected. A comparable storm today could cause widespread blackouts—and one influential worst-case assessment warned that full recovery might take four to ten years, although experts remain divided over how severe the damage would actually be.

In 1859, the Carrington solar storm sent currents surging through telegraph wires, shocking operators, igniting telegraph paper and allowing some lines to transmit with their batteries disconnected. A comparable storm today could cause widespread blackouts—and one influential worst-case assessment warned that full recovery might take four to ten years, although experts remain divided over how severe the damage would actually be.

In late August and early September 1859, the Sun threw a burst of charged particles at Earth that lit up the sky with auroras seen as far south as the Caribbean and drove the world’s only electrical network, the telegraph, into chaos. Sparks jumped from the keys. Operators were shocked, in at least one case knocked out of a chair. Paper tape caught fire in the stations. And on some lines, operators disconnected their batteries and found they cou…