By John Fernando Muñoz | 2026-04-27

Across human history, there has been a persistent fascination with the cosmos. In this three-part series, BlueShift takes a deeper look at the way ancient civilizations in very different parts of the world interpreted the heavens.

In the heart of the Andes, the sky was never a distant abstraction, but a mirror of the Earth.

For decades, a Eurocentric perspective reduced Inca astronomy to a series of religious rituals centered on Inti (the Sun). But recent research has transformed our understanding of the Tahuantinsuyo, the Inca empire that organized Andean territory into four regions converging in Cusco.

This reveals a science applied to survival, as the earliest hunter-gatherers began to accumulate a body of astronomical knowledge in what is now Peru.

Archaeologist Juan Pablo Villanueva, professor at National University of San Marcos in Lima, describes the Incas as not merely observers but specialists who turned the landscape into a masterfully calibrated apparatus.

As Villanueva explained in a recent lecture, "Astronomy, calendars and worldview in the societies of Ancient Peru," there is evidence of systematic observation at sites such as Pacopampa and Chankillo dating back more than 2,500 years.

Pacopampa is a highland ceremonial center in Cajamarca known for monumental stone architecture and tombs, while Chankillo is a coastal desert site.

For Villanueva, an expert in archaeoastronomy and Andean calendars, the turning point lies in Chankillo. This solar observatory, the oldest in the Americas (4th century BCE), predates the Incas by more than 1,000 years.

There, 13 stone towers aligned along a mountain ridge made it possible to measure the solar cycle, solstices and equinoxes with minimal margin of error.

This knowledge was inherited and refined by the Incas, who integrated celestial observation into administrative and religious planning as a tool for economic and social management.

The 'dark constellations'

While Western astronomy focused on connecting bright points, Andean astronomers identified something unique: the Yana Phuyu, or constellations of dark spaces between the stars.

In the Milky Way, which they called Mayu (the Celestial River), they identified shapes within the interstellar dust that were not empty spaces, but living beings responsible for guiding the cycles of life on Earth.

According to Villanueva, this system served as a framework for understanding the behavior of fauna, flora and climate in a geography as complex as the Andes, a mountain range along the continent's western edge.

"In a recent study, I have been able to compile extensive ethnographic and historical information about all these constellations. At least 12 can be observed in this river that is the Milky Way," the archaeologist notes.

Among them are a mother llama and her offspring, a toad, a serpent, and a fox.

These figures had a direct correlation with biological cycles on Earth.

The appearance of the Yacana (llama) at the zenith coincided with the gestation period of camelids, while the emergence of the Hamp’atu (toad) signaled the arrival of the rains.

Inca ethnoastronomy also allowed this ancient people to predict large-scale climatic events.

By observing the clarity of the Pleiades (Qollqa), the Incas could anticipate the El Niño phenomenon: if the stars appeared blurred due to high-altitude clouds, they knew drought was imminent and adjusted their grain reserves accordingly.

The precision of Intimachay

Research in the Machu Picchu National Archaeological Park also has reshaped our understanding of Inca technology by confirming the existence of high-precision astronomical observatories.

According to studies led by Fernando Astete Victoria and specialists from the Polish universities of Warsaw and Wrocław, the sites of Inkaraqay and Intimachay functioned as centers where the Incas studied celestial bodies.

They did this using instruments specifically designed for that purpose.

The findings of these studies demonstrate that celestial observation was not merely contemplative, but enabled the precise determination of phenomena such as the summer and winter solstices.

The observatory of Intimachay stands out for its structure of frontal and lateral windows that acted as astronomical markers.

New measurements carried out this century using 3D laser scanning confirmed this sacred site precisely tracked the movements of the Sun and moon.

Researchers suggest that Inca specialists observed the full lunar cycle, which would have allowed them to determine the dates of lunar eclipses, a technical capability comparable to that of the Maya and Aztec civilizations.

Meanwhile, at Inkaraqay, northeast of Waynapicchu mountain, a wall with trapezoidal niches containing five-centimeter-diameter openings was identified.

High-tech scanning confirmed these openings served as observation points to track the passage of the Sun, functioning as a kind of clock to determine the time and position of the stars.

This enabled ancient farmers establish periods for fallowing and sowing.

According to Villanueva, these advances confirm that Inca astronomy had two clear orientations: one devoted to ceremonial purposes, and another linked to agricultural efficiency.

Today, Inca astronomy survives in high Andean communities that continue to look to the Mayu to determine their planting and harvesting cycles.