Offbeat Adventure

This Stone Monument in the Bighorn Mountains Is an Ancient Astronomical Calendar

Every year, the sun, moon, stars, and planets trace a predictable path across the universe. As they've traveled Earth's skies, those cosmic bodies have crossed over the exact same landmarks every year. Some time several centuries (or millennia) ago, people in the Bighorn Mountains created a massive monument of stones to bear witness to that eternal dance.

Rocks of Ages

Even in modern times, Medicine Wheel (formerly known as Bighorn Medicine Wheel) is hard to get to. Set 10,000 feet (3 kilometers) above sea level on Medicine Mountain in Wyoming's Bighorn Mountains, it can only be reached at the height of summer when the snows have melted away. Of course, when it was built, the journey to get there was a bit longer than a 1.5-mile (2.4-kilometer) hike from the parking lot. At some point in history, an unknown group of people covered a mountain clearing with a massive, 80-foot (24-meter) "wheel" of stone cairns, or piles, with 28 distinct spokes. It's survived for several centuries at least — and perhaps even several millennia.

There's a fair amount of debate about the exact age of Medicine Wheel, and a fair amount of conflicting evidence to muddy the issue. It's thought that the wheel was created between 300 and 800 years ago. The most compelling piece of evidence? That's the period of time during which it would have best worked as an astronomical calendar. There's also the fact that samples from wood that had been incorporated into the western cairn were definitively dated to 1760 C.E. However, other archaeological evidence at the site suggests that it had been highly trafficked since approximately 7,000 years ago, and wheels very much like this one have been found dating back to that era.

Unfortunately, getting an accurate historical read of this particular configuration of stones won't tell us much about the actual age of the monument. The spokes and nodes of the wheel are cairns of loose stones, so they could pretty easily be moved as the sky slowly shifts. Furthermore, those clues that at least part of the monument is about 300 years old would place its construction during the time when the Crow tribe controlled the area, but oral traditions of many people that came before the Crow include mention of the Medicine Wheel. It's not likely that we'll ever know the true origins of the circle.

A Compass to the Stars

As we mentioned, there were and are many other medicine wheels — as many as 200 survive to this day. But Medicine Wheel is different in two key ways: It's the southernmost example of its type in the world, and it's very difficult to reach. It's special but not unique in another way, as well: The seven cairns and 28 spokes can be used to track not just the summer solstice, but also the motion of the stars. While other medicine wheels, such as those found at Majorville in Alberta and Moose Mountain in Saskatchewan, line up with astronomical observations, those of Wyoming's Medicine Wheel would only be visible at the height of summer.

The fact that many medicine wheels lined up with recurring astronomical phenomenon went unnoticed by archaeologists for many years, until an astronomer named Jack Eddy put two and two together about the alignment of Medicine Wheel in 1974. He found that not only did the cairns line up with the sunrise and sunset of the summer solstice but, using other cairns and the small spokes of the wheel, a person could watch the star-rises of Aldebaran, Rigel, and Sirius at key intervals of 28 days surrounding the solstice, marking key points such as the end of summer — and time to leave the mountain.

Medicine wheels play a central role in many Native American spiritual traditions, including as sites for vision quests. If the Medicine Wheel in the Bighorn Mountains was used for a similar purpose, it might have been created as a sort of astronomical timer in order to prevent people from being exposed to the most severe elements. Whatever it was used for, it was clearly created by somebody with a firm grasp of the night sky's movements.

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There's only one thing left to do, and that's hike the Bighorns yourself. Bring your Kindle and you'll have a handy guide in "Hiking Wyoming's Bighorn Mountains" by Ken Keffer. We handpick reading recommendations we think you may like. If you choose to make a purchase through that link, Curiosity will get a share of the sale.

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Written by Reuben Westmaas July 31, 2018