In 1619, after looking up and seeing the night sky streaked with green and purple light, Galileo Galilei coined the term “Aurora Borealis” after the Roman goddess of dawn, Aurora, and Boreas, the Greek god of the north wind. But Galileo was hardly the first human to marvel at the Northern Lights.
Perhaps the earliest depiction of the Northern Lights can be found in a cave in Southwestern France, where 30,000-year-old finger tracings mimic the twists and turns of the starry light show. In 567 BC, a royal astronomer working for Babylon’s King Nebuchadnezzar II inscribed his report of the aurora on a stone tablet. Two thousand years later, a massive display shone over the modern day Czech Republic, where painters depicted it as flaming candles above the clouds.
Just a century later, Galileo trained his eyes on the Northern Lights and wrongly assumed they were the reflection of sunlight on the atmosphere. It would take until the 20th century for scientists to figure out what causes the aurora, but many mysteries about the phenomena remain.
What causes the Northern Lights?
The cause of the Northern Lights begin 94 million miles away with instabilities in the sun’s magnetic field. The resulting coronal mass ejection (CME)—a solar eruption that ejects billions of tons of superheated plasma into space—can travel through the solar system at more than 45 million miles per hour, reaching Earth in less than a day.
When those solar particles smack into the Earth’s magnetic field, they are accelerated up and down our planet’s magnetic field lines toward the North and South Poles. Along the way, they collide with atoms of nitrogen and oxygen in the atmosphere, infusing those atoms with a surplus of energy that is then released in a burst of lights.
The characteristic colors of the Aurora Borealis are dependent on the types of atoms being energized. An interaction between solar particles and oxygen, for example, produces red or green light, while collisions with nitrogen produce green and purple light. Lines of magnetic force affect the pattern of the light display, creating the ripples, pulses, streaks, and swirls we associate with the event.
When and Where Can You See the Northern Lights?
While solar storms are constant, auroras tend to be more dazzling and more frequent during times of high solar activity, which occurs on a roughly 11-year cycle. At the middle of this cycle, the sun goes through a period of intense activity called the solar maximum; the beginning and end of the cycle are characterized by less activity, known as the solar minimum. Our current cycle started in 2019, meaning 2025 will mark the solar maximum and be the best time for viewing the aurora across the widest swath of the planet, including areas near the equator.
But the Northern Lights, as well as their southern counterpart, known as the Aurora Australis, are still visible most nights of most years in the region known as the Aurora Zone, the area that lies within 1,500 miles of the pole. In the north, the zone includes countries like Greenland, Finland, Canada, and Russia. The darkest, clearest skies in those places occur during spring and autumn, when the Northern Lights are generally most vivid on moonless nights between the hours of 10 p.m. and 2 a.m.
The Dark Side of the Lights
Despite hundreds of years of study, scientists are still unlocking the mysteries of the Northern Lights. For example, until very recently, researchers weren’t sure how plasma from a CME reached such remarkable speeds. In a study released in 2021, physicists from UCLA revealed they had solved the mystery, confirming that powerful undulations occuring in plasma, called Alfvén waves, carry the electrons that cause auroras, accelerating them like a speed-up boost in a video game.
In 2018, NASA launched the Parker Solar Probe, which will come closer to the sun than any spacecraft before it, helping scientists understand and predict major space weather events like CMEs. That’s because these events don’t just create beautiful light shows—they can also wreak havoc on the technology society depends on.
In 1859, a severe CME caused telegraph systems around the world to go haywire, delivering electric shocks to operators and setting telegraph paper on fire. In 1989, a violent solar storm that produced a stunning aurora also knocked out power across Quebec, Canada, for more than nine hours. Solar storms can pose a risk to navigational and telecommunication systems as well as satellites.
Today, the National Oceanic and Atmospheric Administration, along with the United States Air Force, oversees the Space Weather Prediction Center, which supplies forecasts to aviation and telecommunication sites. For amateur sky watchers, SWPC also provides a nightly aurora forecast that shows the location and likelihood of a Northern Lights display.
Ashley Stimpson is a freelance journalist who writes most often about science, conservation, and the outdoors. Her work has appeared in the Guardian, WIRED, Nat Geo, Atlas Obscura, and elsewhere. She lives in Columbia, Maryland, with her partner, their greyhound, and a very bad cat.
