In 1859 a Solar Storm Set Telegraph Offices on Fire

On the morning of September 1, 1859, an English amateur named Richard Carrington was sketching sunspots through a projected telescope image at his home observatory in Surrey when two patches of intense white light flared up across the spot group. He shouted for a witness, watched the flare for about five minutes, and timed it carefully. A few hundred miles north, Richard Hodgson saw the same thing. Their two notes are the first recorded observation of a solar flare.

The coronal mass ejection it threw off crossed the 150 million kilometers between the Sun and Earth in roughly 17.6 hours. Most CMEs take several days. By the early hours of September 2, the geomagnetic storm was tearing through Earth's field. Compasses in mining towns swung uselessly. Auroras lit the sky as far south as central Mexico, Cuba, Honolulu, Queensland, and Colombia, low enough that gold miners in Australia tried to start their breakfast by the light. The Baltimore American compared it to a full moon "with an indescribable softness and delicacy."

The telegraph network — the only electrical infrastructure that mattered yet — went haywire. Frederick Royce, an operator in Washington, D.C., grazed a ground wire with his forehead and was thrown by an arc of sparks. Other offices reported insulation smoldering and printing paper catching fire. In one famous exchange on September 2, the operators in Boston and Portland disconnected their batteries and discovered they could send messages for two hours on the auroral current alone.

No one had ever seen anything like it, and as far as instrumental records go, no one has since. A 2013 Lloyd's of London study estimated that a Carrington-class event hitting today's grid would cost the United States economy somewhere between $600 billion and $2.6 trillion before the lights came back on.