Astronomy of the Incas

The Inca empire was a powerful social organization which amazingly only lasted a century before the Spanish conquest of the New World. It began when a military leader named Pachacuti Inca Yupanqui brought western South America under one rule, following the demise of the earlier Huari and Tiwanaku cultures. The new empire was centered politically and spiritually at the city of Cuzco in the Andes Mountains, but it encompassed over 375,000 square miles. The society was very organized, with strict laws and demarcation of classes.

Astronomy played a key role in their culture, particularly due to the importance of agriculture. 

The city of Cuzco was laid out in a radial plan which mimicked the sky and pointed to specific astronomical events on the horizon. Like Ancient Egypt and India, this was a horizon-based culture. The most important events to the Inca involved certain risings and settings of the Sun, Moon, and stars. For instance, when the Pleiades star cluster rose, it signaled the start of the Incan year. The Pleiades were called the Seven Kids after the seven brightest stars in the cluster, but the Inca were actually able to see 13 stars due to the clear atmosphere at the high altitude of Cuzco.

Astronomy was used extensively for agricultural purposes. The Inca built carefully oriented pillars on hills overlooking Cuzco, and when the Sun rose or set between the pillars, it was time to plant at a specific altitude. A whole range of pillars was employed so that the most accurate time-keeping was possible for the high altitudes, the valley floor, and everywhere in between. The people ritually made sacrafices to the Sun asking him to rise in the proper place for planting.

The astronomers recognized the planet Venus as the same whether it appeared as the morning or evening star. They believed that Venus was a servant of the Sun and was ordered to go ahead of or behind the Sun, but always remain close.

The Inca built observatories where they captured the first and last rays of the Sun through a series of specially placed windows. Their chief observatory was called the Coricancha, or ‘golden enclosure’, and was covered completely in gold. A gold sun disk faced the rising sun. As in the case of so many other New World sites, the gold was pillaged by the invading Spanish. A drawing of an Inca sun ceremony is pictured below.


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Anthony Aveni, Stairways to the Stars, John Wiley & Sons, 1997.

Inca Civilization.

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