On September 1-2, 1859, the most powerful geomagnetic storm in recorded history struck Earth. British astronomer Richard Carrington had observed an enormous solar flare the day before - the first solar flare ever observed. When the resulting coronal mass ejection reached Earth, it created auroras visible as far south as the Caribbean and Hawaii. Telegraph systems failed worldwide. Some telegraph operators received shocks. Some telegraph paper caught fire. This was the Carrington Event, and if a storm of equal magnitude struck today - with our dependence on satellites, power grids, and electronics - the results could be catastrophic.
On the morning of September 1, 1859, British amateur astronomer Richard Carrington was sketching sunspots through his telescope when he witnessed something unprecedented: a brilliant white flash erupting from the sun. Another observer, Richard Hodgson, independently witnessed the same event.
Carrington had observed the first recorded solar flare - a massive explosion on the sun's surface that releases enormous amounts of energy. The flare lasted about five minutes. Carrington noted the time and position, uncertain what he had seen but knowing it was significant. About 17 hours later, Earth found out.
On September 2, the coronal mass ejection - a billion tons of solar plasma - struck Earth's magnetosphere. The geomagnetic storm that resulted was unprecedented in intensity. The aurora borealis, normally visible only at high latitudes, was seen as far south as Colombia, Hawaii, and the Caribbean.
People in the northeastern United States could read newspapers by the light of the aurora. The sky glowed red over the Rocky Mountains. Gold miners in Colorado woke in the night, believing it was dawn. Ships at sea reported brilliant displays of light in all directions.
The storm's most dramatic effects were on the telegraph system - the internet of the 19th century. The induced currents from the geomagnetic storm caused telegraph systems worldwide to fail. Operators received electric shocks. Telegraph pylons threw sparks. In some cases, telegraph paper caught fire.
Paradoxically, some telegraph systems worked better with their batteries disconnected - the induced current was sufficient to power the instruments. Operators in Boston and Portland reported sending messages for two hours without any electrical supply, powered entirely by the auroral current.
A Carrington-level event today would be catastrophic. Our civilization depends on technologies that didn't exist in 1859: satellites, power grids, computers, GPS. A severe geomagnetic storm could destroy satellites, damage transformers, disrupt navigation, and cause widespread blackouts lasting weeks or months.
The damage to the power grid alone could be devastating. Large transformers take years to manufacture and cannot easily be replaced. A National Academy of Sciences study estimated that a modern Carrington Event could cause $1-2 trillion in damage in the first year alone, with full recovery taking 4-10 years.
Scientists estimate that Carrington-level events occur roughly once every 150 years. A near-miss occurred in July 2012, when a massive coronal mass ejection passed through Earth's orbit - missing our planet by about a week. Had it struck Earth, it would have caused damage comparable to 1859.
Space weather monitoring has improved. We now have satellites that can provide 15-60 minutes warning of incoming solar storms. But our defenses remain limited. The Carrington Event is a reminder that our technologically dependent civilization remains vulnerable to the whims of a star 93 million miles away.
The Carrington Event affected the entire Earth. Richard Carrington's observations were made from his private observatory in Redhill, Surrey, England (51.24N, 0.17W). London Gatwick Airport (EGKK) is 20km south. The aurora effects were global. Today, space weather is monitored by facilities worldwide. The event is commemorated in scientific circles as a benchmark for extreme space weather.