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No matter how big of a skeptic, everyone has seen a mysterious light at one point or another. Even if you can write it off as something mundane, like an airplane or a flashlight, it's always a little thrilling to consider what else it could have been.

This explains why generations of tourists have flocked to the little town of Marfa, Texas. Though it's now a bit of a hipster artist hub, for a long time the main draw to Marfa was the Marfa lights: mysterious, unexplained, floating orbs that appear next to the highway on the plains just outside of town. The lights have been documented as far back as the 1800s. They're best viewed from a special lookout the town constructed along the U.S. 90 highway.

For a more detailed story behind the Marfa lights, listen to this week's episode of Science Solved It:

Though scientists have now determined where these lights are coming from, and why they look so strange, there are still some sightings they can't explain.

"The Marfa lights that you see every night are not very big as far as you know," explained Karl Stephan, one of the scientists who solved the mystery of the lights. "[They're] much smaller than the size of a fist, it looks almost like a star, maybe—yellowish to white—and they move very slowly, they don't move very fast."

These orbs appear any time it's a clear night, out on the plains that run beside the highway. The plains outside Marfa are already an otherworldly place—located in west Texas, surrounded by desert landscape and mountains, it's on a mountain plain, with an elevation of one mile. The area is dotted with cacti and dry grass, and in the distance are the craggy peaks of the Chinati mountain range.

A tourist photo of one of the lights. Image: Flickr/Nicolas Henderson

"It looks a little bit like the desert, it looks a little bit like the mountains," said Michael Hall, an executive editor at Texas Monthly magazine who has written about the lights. "You're a mile high so the air feels different. It already feels like something strange could be happening here."

There have been some folktales explaining the lights over the years. Some locals claim they're the light from a lantern carried by the ghost of an Apache chief who was murdered on those very plains. But mostly, the lights are just a pleasant detour, and an excuse to go to Marfa—something the town has embraced wholeheartedly.

The tourism from the lights helped support the town after it nearly disappeared due to a failing economy. There's an annual Marfa lights festival, and the town invested $720,000 of federal and state funding into expanding the visitors center where tourists can view the lights, complete with restrooms and a parking lot.

But the tourists might not be so eager to drive all the way out to Marfa if they realized something most locals already know: the lights aren't mysterious at all. They're practically mundane.

"It turns out that they're headlights," Stephan told me. "Headlights on a highway, highway 67, which is some distance, about 15 or 20 miles south of the viewing area."

The Marfa lights viewing center. Image: Flickr/Nicolas Henderson

Stephan and some colleagues published a study about the lights back in 2011 in the Journal of Atmospheric and Solar-Terrestrial Physics. Using sensitive infrared and ultraviolet spectrometers, they found that the atmospheric conditions of the flats outside Marfa were unique, and such that they warped the lights coming from the highway as they travelled across 20 miles of flatland.

By the time the lights reach the eyeballs of tourists at the viewing area, they don't look like car lights at all. They look like weird, white, floating orbs. The temperature, air density, and humidity in the atmosphere of these plains creates a perfect storm that distorts the light in this unusual, and perplexing way.

"When the desert heats up, the air above the ground gets warm and rises in little kind of bubbles after dark," Stephan said. "It's like looking through a wavy piece of glass."

While this conclusion isn't as exciting as the ghost of an Apache chief, there's still some mystery that remains. Stephan told me there have been multiple reports of lights out on the plains that don't match the description of these warped headlights. Lights that move backward, or dance, or disappear suddenly, and so far, he hasn't been able to explain what they could be.

"My colleague Jim Bunnell has actually witnessed these in person, and has taken photographs of them," Stephan said. "Close enough to show that there's some structure inside the unusual lights that aren't just headlights."

Even with scientific investigation, there's something strange out in the desert of west Texas, that hasn't yet been explained.