Amazonian Solar Landmarks: What Geoglyphs Reveal About a Forgotten Civilization ✛ ✦
Context
The discovery of thousands of geometric earthworks—geoglyphs—in the Amazon rainforest has been one of the biggest archaeological sensations of recent decades. Built between the 5th century BCE and the 11th century CE, these structures challenge long-held views about the region's prehistoric past, which was considered unsuitable for complex societies. The function of most geoglyphs is still debated: from defensive fortifications to ceremonial centers. Since few artifacts have been found inside, researchers turned to the orientation of the structures—one of the few measurable characteristics that can shed light on the builders' worldview. The movement of the Sun across the sky, governed by Kepler's first law and Kepler's second law, as well as the law of universal gravitation, creates a predictable annual cycle with extreme sunrise points—the solstices. As early as Galileo Galilei observed spots on the Sun, and Johannes Kepler mathematically described planetary orbits, making it possible to precisely calculate sunrise azimuths at any latitude. Later, Cecilia Payne-Gaposchkin determined the chemical composition of the Sun, but for ancient builders, this luminary was more likely a celestial time marker. Thus, if the orientation of the earthworks is non-random and correlates with astronomical directions, a ritual or calendrical purpose can be inferred.
Methods
For the analysis, 326 square and rectangular structures were selected, including slightly skewed parallelograms with angles deviating from 90° by no more than 2°. Using Google Earth Pro satellite imagery, the researcher manually measured the azimuths of the walls—specifically, the side whose azimuth is closest to the east. This procedure is similar to the approach used in studying Roman cities. The image resolution (about 30 cm) and accurate north alignment allowed data with an error of no more than ±1°. Essentially, we are dealing with remote photometry: the analysis of light reflected from the earth's surface—not to study stars, but to reconstruct anthropogenic landscapes. The method resembles recording transits of the Sun across the horizon on significant dates. To improve reliability, historical images from the program's archive were examined for each object, and discrepancies were averaged—a procedure akin to interferometry in radio astronomy. Although the ground resolution is inferior to the Hubble telescope, it proved sufficient for archaeological purposes. Statistical analysis included estimating the entropy of the azimuth distribution and Gaussian mixture modeling to identify peaks. The null hypothesis of a uniform distribution was rejected using a p-test.
Results
The azimuth distribution (Fig. 2) immediately revealed three pronounced peaks: around 68°, 89.5°, and 115°. The statistical significance of the peaks at 68° and 115° is extremely high (p ≈ 5×10⁻¹⁰); the central peak has borderline significance (p ≈ 0.5), but its alignment with the cardinal east-west direction is noteworthy. All three directions lie within the solar arc (66°–114° for the average latitude of 9°30' S), and beyond it the frequency drops sharply. The 115° peak exactly matches the sunrise azimuth on the summer solstice, directly pointing to the builders' interest in the Sun and possibly the agricultural calendar. The 68° peak is slightly offset from the winter solstice; it corresponds to dates around May 29 and July 14. The author links it to the end of the rainy season in late May, when the Sun rises in that direction, marking the start of the dry season—critical for a double corn harvest. The central peak of 89.5° reflects an orientation toward the equinox and, more likely, a deliberate cardinal orientation, characteristic of many sacred sites from Stonehenge to Maya cities. The low entropy confirms that the choice of directions was not random.
Implications
The results convincingly show for the first time that the creators of Amazonian geoglyphs possessed astronomical knowledge and embedded it into their monumental architecture. This points to a ritual-ceremonial, rather than defensive or utilitarian, purpose for at least the rectangular structures. Perhaps we are looking at shrines or calendrical markers, similar to the Hopewell earthworks in Ohio, where solar orientations have also been identified. The fact that the peaks correspond to extremes and the cardinal direction reinforces the hypothesis of a symbolic quadripartition of the world. Moreover, the link to agricultural dates reminds us that the Sun served as a "clock" for ancient societies, regulating planting and harvest cycles.
Future development
This study opens several avenues. Since many structures are still hidden under the forest canopy, airborne lidar scanning is promising for detecting new objects. Computer algorithms based on machine learning could automatically find and classify geoglyphs over vast areas. Finally, numerical simulation of the ancient horizon, accounting for tree height, will help refine the actual azimuths, as the forest could have shifted sunrise points. Integration with paleoclimatic data and detailed archaeological excavations will likely confirm the calendrical hypothesis.
Impact
The results will impact Amazonian archaeology, prompting a reassessment of the complexity of the region's pre-Columbian societies. The methodology can be applied to analyze similar earthworks worldwide, from Britain to the Mississippi Valley, and to test astronomical hypotheses in other contexts where disturbed landscapes are studied using telescopes and satellites.
Next steps
The immediate next steps include systematically checking the orientation of rhomboidal structures, which may have been oriented diagonally to the cardinal points. It is also necessary to refine the dating of the structures to compare directions with precession and rule out accidental alignment with stellar azimuths.
Key open problems
The study touches on the fundamental problem of reconstructing the worldview of "silent" cultures that left no written records. It also raises the question of how much the environment—specifically, the forest that existed then—influenced the accuracy of sighting celestial bodies. Finally, it remains open how universal the drive was to orient sacred structures toward the Sun and cardinal points.
The knowledge machine's view
This section is addressed to the author of the paper and their colleagues. Neighbouring works were found by meaning-based search across our archive, not by word overlap. We do not review: we show the field around the work.
What the work does
The study measured the azimuths of 326 square and rectangular geoglyphs in the Amazon using satellite imagery. Statistical analysis revealed a non-random orientation that correlates with sunrise and sunset points at solstices and equinoxes. This points to the astronomical and calendrical significance of these structures.
Where its strength is
The strength of this work lies in its systematic approach to measuring the orientation of a large set of archaeological objects and the rigorous statistical testing of the hypothesis about their astronomical alignment. This provides a quantitative basis for further comparisons.
Where it could go next
- There is a related study that applies a similar approach to analyzing the orientation of planetary systems: celestial bodies may retain a 'memory' of early impacts. It might be interesting to see how the methods for finding order in geoglyph architecture relate to the search for patterns in exoplanet orbital architectures.based on: How a Neptune-like planet flipped its star arXiv:2606.11292
- In our archive, there is work that analyzes shadows and transits to search for extraterrestrial artifacts. Although that deals with cosmic scales, the very idea of using shadow geometry to detect artificial structures could offer a fresh perspective for interpreting geoglyphs—for instance, their connection to the play of light on the landscape on specific dates.based on: Earth's Shadow Hunts for Alien Probes arXiv:2510.17907
Worth trying
- Test whether geoglyphs exhibit orientation patterns linked not only to the sun but also to bright stars or planets, using celestial sphere models for the relevant epochs.
- Compare azimuthal peaks with topography and horizon visibility: perhaps builders accounted for local relief when choosing directions, which could be modeled using digital elevation models.
Why this may matter
Understanding the astronomical orientation of the geoglyphs could provide a key to reconstructing the calendrical systems and ritual life of ancient Amazonian societies, as well as reshape our view of their engineering and observational skills.
Nearby works in our archive
- The Magnetic Roots of the Solar Windsimilarity 0.56
- Earth's Shadow Hunts for Alien Probessimilarity 0.54
- Pulsars Catch Ripples from the Early Universesimilarity 0.52
- How a Neptune-like planet flipped its starsimilarity 0.52
- The Universe Turned Out to Be Flat, But Not at Firstsimilarity 0.51
- The Universe Couldn't Have Been Expanding Foreversimilarity 0.51
The archive is sparse around this work: the closest review is only 0.56, against a usual 0.64. It looks like few have drilled nearby.
Original abstract
as written by the authors arXiv:2607.14201
Amazonian earthworks, also called geoglyphs, are thousands of man-made earthen structures, mostly of geometrical shape, which progressively emerged from the tropical forest due to progressive deforestation. They were probably built between the fifth century BC and the end of the first millennium AD, but archaeological investigation on the culture of their builders is yet at the beginning. Nevertheless, a ceremonial rather than practical function seems likely, at least for those having a very regular shape. In the present paper, simple remote-sensing technique, combined with the methodological approach of modern Archaeoastronomy, are applied to study for the first time their orientation. The analysis takes in consideration virtually all known squared and rectangular structures for a total of 326 earthworks. The results show without doubts a non-random choice for their orientation and a clear interest of their builders for the annual cycle of the Sun.
Curiously, the azimuth of 68° nearly matches the direction of the full Moon's set point at its northern extreme (about 61°), but the statistical peak is too narrow for a lunar hypothesis. Likely, the builders ignored the Moon, focusing entirely on the Sun.
The concept of "solar gates" or portals activated on solstices is a staple of science fiction, for example in Arthur C. Clarke's novel "The Light of Other Days," where ancient megaliths serve as keys to other worlds. Amazonian geoglyphs may well have been such ritual thresholds between mundane and sacred time.
Key numbers
- number of analyzed structures: 326
- summer solstice azimuth peak: 115°
- equinox/cardinal azimuth peak: 89.5°
- end of rainy season azimuth peak: 68°
- average latitude of the area: 9°30' S
- solar arc of sunrises: 66°–114°
- measurement error: ±1°