The oldest solar observatory in the Americas has been discovered in coastal Peru, archeologists announced today.
The 2,300-year-old ceremonial complex featured the Towers of Chankillo, 13 towers running north to south along a low ridge and spread across 980 feet (300 meters) to form a toothed horizon that was used for solar observations.
Researchers excavated the solar observatory between 2000 and 2003. They found buildings-in exact mirror position of each other-to the east and west of the towers with observation points for watching the Sun rise and set over the toothed horizon.
How it works
In addition to the daily east to west motion, our Sun appears to move eastward through the stars in a path known as the ecliptic over the course of a year. Also, the Earth’s axis is not perpendicular to the ecliptic but slanted by an angle of a little over 23 degrees. The combinations of these positions determine where the Sun is above our horizon day by day.
At different times of the year one can observe the Sun rise and set in different spots with respect to our horizon and for different lengths of time. For example, in the Northern Hemisphere, around the summer solstice-which falls on June 21-the Sun rises highest in the sky and stays up longer.
As viewed from the two observing points of Chankillo [image], the spread of towers along the horizon corresponds very closely to the range of movement of the rising and setting positions of the Sun over the year, the authors write in the March 2 issue of the journal Science.
Once the Sun started to move away from any of its extreme positions, like the solstices or equinoxes, the towers and gaps between them provided a means to track the progress of the Sun up and down the horizon, to within a couple of days accuracy.
“Chankillo is arguably the oldest solar calendar that can be identified as such with confidence within the Americas,” said lead study author Ivan Ghezzi from Pontificia Universidad Catolica del Peru.
Tree-ring samples dated these structures back to the fourth century B.C.
“Many indigenous American sites have been found to contain one or a few putative solar orientations,” Ghezzi said. “Chankillo, in contrast, provides a complete set of horizon markers and two unique and indisputable observation points.”
How Weather Changed History
At the end of a 131-foot-long corridor in the building to the west of the towers, the researchers found pottery, shells, and stone artifacts in an area possibly for commoners who participated in rituals linked to solar observations.
Previous studies showed that the Incas-South American Indians who established an empire that once ranged from northern Ecuador to central Chile from 1100 to the 1530s-had built sites to mark solar observations by 1500.
In comparison, the earliest portion of Stonehenge-megalithic ruins in southern England purported to correlate with the rising and setting of the Sun and the Moon-is said to have been completed around 3000 B.C.
The new finding, however, puts Sun cults in the Americas at an earlier date than the Incans.
“Chankillo was built approximately 1,700 years before the Incas began their expansion,” Ghezzi said. “Now we know these practices are quite a bit older and were highly developed by Chankillo’s time.”
Beijing Ancient Observatory:
museum looks like a turreted tower set in Beijing’s ancient city walls. It is located on the southeast corner of Jianguomen Street in Beijing. When it was originally built, in the Guo Shoujing (1231-1316) period of the Yuan dynasty, it had a slightly different name but the same intent: to explore the heavens. Over the course of more than five hundred years, through Ming and Qing dynasties and on into the period after the Xinhai Revolution (1911), this location has been used to observe phenomena of the skies. This is the longest historical record of using any such observatory for so long. At present, eight large bronze implements for viewing the heavens are arrayed on the top of the museum’s tower; these date from the Qing dynasty. Under the tower is a hall built between the years 1442 and 1446, during the Ming dynasty. To the east and west are subsidiary rooms and other ancient structures.
The observatory’s platform, rebuilt in recent years, is 17 meters high and holds exhibition rooms inside. If you walk through the door with the three characters for the observatory carved above it, you find a three-level exhibition space devoted to China’s ancient astronomical accomplishments. A stone-carved star map from Suzhou is exhibited here, as well as the ceiling astronomical map from Longfu Temple, two rare treasures. The former was done in the Song dynasty in the year 1247. It depicts 1,434 stars and is recognized as one of the best early star maps in the world. The latter was accomplished in the Ming period, but from the characters carved on the side of the map one can see that the underlying information already existed in the Tang dynasty. In the courtyard of the museum, surrounded by ancient trees, the hall and east gate areas exhibit early astronomical instruments and the methods and changes in making them. In the western chamber some 150 early methods of calculating calendars in China are exhibited. Archaic as well as more recent astronomical water clocks and contemporary astronomical clocks are exhibited. Eight bronze astronomical instruments are arranged on the top of the platform, as per the Qing-dynasty emperor Qianlong’s instructions.
Ancient solar observatory discovered in Peru:
The oldest solar observatory in the Americas may have been uncovered in coastal Peru. The ceremonial site provides evidence of sophisticated ‘cults of the Sun’ operating in South America as early as 2300 years ago.
Other ancient structures around the world – such as Stonehenge, which is estimated to be 5000 years old – are aligned with the rising and setting of the Sun on certain days called the solstices. These occur twice a year, around 21 June and 22 December, when the Sun appears to reach its highest point above or below the equator.
Previously, archaeologists had uncovered 4000-year-old gourd fragments in Peru showing images of a “staff god” with rays emanating from its head, perhaps like the Sun (see America’s oldest religious icon revealed).
Historical records also describe “Sun pillars” suggesting that South America’s Incan civilisation was observing the Sun – possibly to help mark when to plant crops – around 1500 AD, though those pillars have since been destroyed. The Incas also held public rituals to observe the Sun rise or set at marked positions on the horizon, and Incan leaders claimed authority to rule through kinship to the Sun.
Now, Ivan Ghezzi of the Instituto Nacional de Cultura in Lima, Peru, and Clive Ruggles of the University of Leicester, UK, say earlier civilisations in Peru may also have been observing the Sun as early as the fourth century BC.
They base their conclusion on ruins at a walled coastal Peruvian site known as Chankillo. Once thought to be part of a fort, ceremonial centre or fortified temple, the researchers now argue the ruin’s central complex may have actually been used as a solar observatory.
Within Chankillo, 13 regularly spaced rectangular towers run the length of a 300-metre ridge like a spine, creating an artificial horizon from some vantage points.
On either side of the ridge are the remains of a western observatory and, lesser so, an eastern observatory, which scientists say were used to watch the Sun rise or set between those towers. On the summer solstice, the Sun rose between Tower 1 and a nearby mountain, Cerro Mucho Malo, and on the winter solstice, the Sun rose around Tower 13.
The Sun appeared for only one or two days in each gap between towers, taking six months to go from one end of the structure to the other. So it is possible the different towers were meant to divide the year into regular intervals lasting about 10 days – the time it takes for sunrises to occur between adjacent towers in the central part of the structure.
The site may have been a place for public rituals and feasts associated with the seasons and the Sun. Excavations have revealed offerings of pottery, shells and other artifacts near an opening at the western observing point.
Researchers say the inhabitants of this site may have been involved in ritualistic practices of passing through a 40-metre-long exterior corridor and standing at the opening to observe the towers.
The specialists who actually tracked the Sun’s motions likely did their work in private while watching the Sun’s light fall onto a wall or through a window, however. “Entry to the observing points themselves appears to have been highly restricted,” the authors write.
“Individuals with the status to access them and conduct ceremonies would have had the power to regulate time, ideology, and the rituals that bound this society together,” they continue. “Thus, Sun worship and related cosmological beliefs at Chankillo could have helped to legitimise the authority of an elite class, just as they did within the Inca empire two millennia later.”
David Dearborn, a physicist at Lawrence Livermore National Laboratory in California, US, says the study is very interesting.
“With this abundant evidence for Inca interest in astronomy, and for its use in social organisation, archaeologists have long suspected that earlier cultures also may have engaged in such activities,” he told New Scientist. “Finally, in this work, material evidence is presented that strongly supports such suspicions.”