The Oldest Solar Observatory In The Americas

“Shine out, fair sun, till I have bought a glass, / That I may see my shadow as I pass.” —William Shakespeare, Richard III

In A Nutshell

Running along a ridge in Peru are 13 towers whose purpose has long baffled researchers. Now, it’s been discovered that when viewed from designated observation points, the towers mark the positions of the rising and setting sun throughout the year, making the ruins the oldest known solar observatory in the Americas, as well as one of the oldest structures credited to an ancient sun cult.

The Whole Bushel

Chankillo is an ancient ruin in Peru that’s long been a mystery to researchers and archaeologists. It’s been dated to about the fourth century B.C. The structures show signs of having been briefly inhabited around the first century A.D. but were probably abandoned after a relatively short period of time. The odd-shaped ruin has been thought to be a site of religious ceremonies or a fortress of some sort, but the decoding of a particularly strange set of structures has revealed that it’s much, much more interesting than that.

Lying along the top of a ridge is a 300-meter-long (984 ft), slightly curved row of 13 identical towers. The towers themselves are all between 17 and 125 square meters (180 and 1,345 sq ft) in size, and each has only two staircases leading to the top. With no real defensive purpose or clear religious significance, the point of the towers had long proved elusive.

That is, until the discovery of two other observation platforms, one to the west of the wall of towers, one to the east. When professors from the National Institute of Peru started taking measurements, they found something startling.

It was the oldest solar calendar ever found in the Americas. Observers standing on one of the platforms would mark the tower (or towers), and the gaps between them over which the sun rose, using the movement of the sun to mark off the days of the year. When standing on the opposite platform, they could measure where the sun was setting. The rising and setting suns on the summer and winter solstices are in line with the northernmost and the southernmost towers.

Article Continued Below

The implications of the discovery are staggering. The religious significance of the sun is well established in Incan and Mayan culture, but many of the records we have talk about solar calendars in the context of the Europeans who observed their use in the 16th century. The 13 Towers site pre-dates those written records by centuries, and it even pre-dates similar Mayan structures found in Central America by about 500 years. The towers provide proof that sun worship dates much, much farther back than originally thought.

Later Incan kings considered themselves born of the Sun, and it’s thought that priests who had been taught how to track the position of the Sun were high up in their civilization’s political power scale, privy to this sacred and divine information. Chankillo suggests that it’s a hierarchy that dates back not just centuries, but millennia.

Plus, Chankillo is unique even among solar observatories because of the year-long cycle. Many other solar observatories have been discovered, but most of them only mark important dates such as the solstices. The precision with which the towers were positioned, carefully spaced and curved, would have allowed observers to keep precise track of the entire calender year. Information would have been invaluable, not just for the practice of religious festivals and ceremonies (nearby artifacts have shown that the site was a highly ceremonial one as well), but also for the planting of crops and preparations for the different seasons.

Show Me The Proof

Featured image photo credit: David Edgar
Yale Bulletin and Calendar: Scientists determine ancient Peruvian citadel was earliest solar observatory in the Americas
BBC News:Towers point to ancient Sun cult Ancient Solar Observatory Discovered
NASA EarthObservatory: Chankillo

Looking for our newsletter? Subscribe here!