On the morning of 1 September 1859, the English astronomer Richard Carrington was sketching sunspots, projecting an image of the Sun onto a screen. Suddenly, two patches of intensely bright white light appeared among the spots. They brightened, moved, and faded within about five minutes.

He had seen a solar flare — the first ever recorded.

Within a day, Earth found out what it meant.

The sky catches fire

A huge burst of charged particles from the Sun slammed into Earth's magnetic field, triggering the most intense geomagnetic storm on record.

Auroras — normally seen only near the poles — lit up skies across the world. People saw them in places like Cuba, Hawaii and other tropical regions. In parts of the United States, the light was reportedly bright enough to read a newspaper by at night. Some people thought cities were on fire. Some birds began to sing, thinking it was morning.

The telegraph goes haywire

The storm induced powerful electrical currents in long wires. And in 1859, the world had just built its first great network of long wires: the telegraph.

Telegraph systems failed across Europe and North America. Operators reported sparks leaping from equipment and paper catching fire. Then came the strangest part.

What if it happened today?

In 1859, the most vulnerable technology was the telegraph. Today we have satellites, GPS, long-distance power lines and transformers, undersea cables and a world that runs on electricity.