For millennia, humans have gazed at the northern lights with wonder, pondering their nature and source. Even today, these once mysterious phenomena still evoke awe, though we understand them a little better now. Still, most of our knowledge about the northern lights has come recently, in the last century or two. Astronomers and meteorologists of the 1800s worked for years to understand the aurora, wondering if they were a feature of Earth’s atmospheric weather, of outer space, or, perhaps, something that straddled the boundary in-between. This centuries-old attempt to understand the northern lights was an immense, international-scale project, and, through fortunate happenstance, it even helped inspire one of the underlying foundations of modern society – time zones.
In the 1870s, the man leading the quest to understand the aurora borealis was Cleveland Abbe. Americans might know Abbe as the father of the National Weather Service, who broadcasted some of the first consistent, reliable, weather reports in the country’s history from his base in Cincinnati, Ohio. But as a meteorologist and astronomer, he was also involved in geophysics research, and a powerful solar storm in April 1874 presented him with a unique opportunity to study the northern lights.
The Aurora Borealis creates stunning displays of dancing light. This particular aurora was captured by Sebastian Kowalski in Norway on March 1, 2017. Credit: Sebastian Kowalski, Wikimedia Commons.
As we know now, auroras are the result of the solar wind interacting with charged particles in the Earth’s magnetosphere. When these particles get bombarded in the upper atmosphere, they shed light energy in spectacular fashion, creating marvelous curtains of green and blue (among other colors). Aurora aficionados will know that solar flares – intense bursts of solar radiation – can dramatically increase the aurora’s vibrancy and color, but also its breadth. Particularly strong solar storms can, on occasion, push the aurora into more southerly latitudes, making them visible across huge swaths of the United States and mid-latitude regions worldwide.
On April 7, 1874, one of these storms caused a particularly memorable display (though it was a moderate storm compared to the famous Carrington event of 1859, at the time still easily within living memory). Abbe jumped at the opportunity to study the aurora, hoping to learn, if possible, its altitude above the Earth, and compare it to concurrent weather phenomena and magnetic observations.
To carry out this task, Abbe needed multiple data points – in other words, he needed observations from multiple sites across the country. Luckily, due to his position as a weather prediction guru, Abbe already maintained a network of contacts across the USA who helped him gather meteorologic data for his weather reports. That night, Abbe put them to work observing the northern lights instead. This team was made up of about 80 public volunteers and 20 expert observers, making this project an early example of a citizen science collaboration (the indirect ancestor, perhaps, of modern citizen science projects like Zooniverse or [email protected]).