The Carrington Event
In September 1859, the world experienced its wildest geomagnetic storm in history. These storms were caused due to a huge solar flare that spewed electrified gas and subatomic particles towards Earth. The communication system around the world was wiped out and caused numerous electrical failures and accidents. Fortunately, Earth bounced back after a couple of days of some weird weather and without telegraphs. If such a geomagnetic storm took place now, our electrically connected society would suffer severely and possibly see apocalyptic aftermath.