Aurora

Different aurora colors tell you exactly which atmospheric gases are being excited and at what altitude. That iconic green glow? Oxygen molecules about 100-300 km up. Rare red auroras occur above 300 km where oxygen is less dense, while nitrogen gives you blue and purple hues at lower altitudes. You're literally watching a vertical map of Earth's atmospheric chemistry painted in light.

In 1899, Norwegian physicist Kristian Birkeland built a research station on a remote Arctic mountain to study auroras in -40°C conditions, nearly dying multiple times. He correctly theorized that electrical currents from the sun caused the lights—a radical idea that was widely mocked for 70 years. NASA finally confirmed his "Birkeland currents" in the 1960s using satellites, vindicating a man who performed some of science's most extreme fieldwork.

The same solar wind that creates beautiful auroras can be catastrophic for our technology-dependent civilization. The 1989 Quebec blackout knocked out power for 6 million people when aurora-inducing currents overloaded transformers, and the 2022 SpaceX incident lost 40 satellites worth $50 million when a geomagnetic storm increased atmospheric drag. Auroras are essentially the visible warning light of invisible space weather that can cripple GPS, communications, and power grids.

Jupiter's auroras are hundreds of times more powerful than Earth's and never turn off—they're permanent fixtures at both poles. Unlike Earth's auroras driven primarily by solar wind, Jupiter's are powered mainly by its volcanic moon Io, which spews charged particles into Jupiter's magnetic field. The Hubble telescope captured these auroras in ultraviolet light, revealing storms larger than Earth itself, reminding us that auroras are a universal phenomenon wherever magnetic fields meet charged particles.

For centuries, people reported hearing auroras—crackling, whooshing sounds—but scientists dismissed these accounts since auroras occur too high up for sound to travel down. In 2012, Finnish researcher Unto Laine finally recorded the sounds and traced them to electrical discharges just 70 meters above ground, created when temperature inversions trap charged particles during auroral activity. Some auroras are genuinely audible, vindicating generations of witnesses who were told they were imagining things.

You can now get aurora predictions on your phone with remarkable accuracy, thanks to networks of satellites monitoring solar wind in real-time. Apps track the KP-index (planetary magnetic activity on a 0-9 scale) and send alerts when auroras might be visible at your latitude—a KP of 7+ can bring them as far south as Colorado or France. This democratization of space weather forecasting means anyone can plan an aurora chase with better odds than trying to spot a celebrity.