Besides a general human fascination for visual representation in different media, petroglyphs can answer not only anthropological questions, but also questions about past environmental conditions.
Quoting from the illuminating article by Sluijs, Marinus Anthony Van Der and Peratt, Anthony.L. Astronomical Petroglyphs, Expedition Magazine 52, no. 2 (July, 2010):
Petroglyph carvers were often more interested in depicting unusual or extraordinary phenomena rather than trivial subjects. These could be of a psychological nature, such as curious hybrid forms of animals and human beings seen during hallucinations, which were interpreted as “spirits” or “mythical people.” Or they could represent rare and striking aspects of the natural environment. Both repositories, psychological and celestial anomalies or curiosities, can be described in terms of globally recurrent factors, setting them apart from the local determinants considered by anthropologists and archaeologists.
Historical documents indicate that eclipses and comets such as Halley’s have caught the attention of ancient peoples for thousands of years, albeit only at certain points in time. Similarly, the auroras (or the Northern and Southern Lights) have been regularly commented upon. In general, it seems likely that other astronomical phenomena, especially rarities like far off supernovae, might have attracted the attention of stargazers the world over. Such transient events have been recorded worldwide in oral traditions and literature. It is reasonable to suppose that astronomical phenomena were also recorded in rock art.
For archaeologists and anthropologists, petroglyphs are not simply representations of the visual world of people in the past, they are depictions of things that had meaning for the artists who made them and the audiences by whom they were viewed. Their decipherment by archaeologists and anthropologists, therefore, is akin to attempting to read a foreign language to gain an understanding of the speakers of that language. As a “dictionary” is not available in most cases, this often leads to a circular method, where information about a local culture colors the interpretation of the rock art in some cases, and the rock art feeds back into the understanding of that culture in other cases. For example, a petroglyph that looks like a wheel can be interpreted as a chariot wheel if the local culture is known to have had chariots. Conversely, a petroglyph that looks like a sheep can be interpreted as evidence that the local culture tended sheep even if such is not otherwise known. In either case there is no systematic method to interpret larger sets of petroglyphs.
In contrast, we approach petroglyphs as the possible man-made evidence generated after the occurrence of a few major environmental events. Just like a meteorite striking the Earth might leave a crater and a spray of debris that could be sampled thousands of years later by geologists looking for evidence of an impact, we consider petroglyphs as possible evidence for a series of major atmospheric events that may have occurred in the past and that were witnessed provoking artists to depict these astronomical phenomena in their rock art. Rather than study the rock art for what it might tell us about past peoples, we study rock art for what it might tell us about past astronomical events.
There is no contradiction between these different approaches, as information about local cultural settings remains important: people will always have interpreted environmental and astronomical events from their own local perspective and based on their own cultural background. While archaeologists and anthropologists quite rightly point out that our interpretation of petroglyphs should be refined for each individual cultural context based on local information, their studies will benefit from our practice to consider the orientation to the sky of each rock art site individually—something that has simply never been considered in the rock art literature (though it has been in archaeoastronomy).
In contrast to geologists or other environmental scientists, who study the physical effects of astronomical phenomena such as meteorites (e.g. craters and debris layers) or increased radiation from space (e.g. higher ozone levels captured in glacial ice deposits), we are interested in identifying astronomical phenomena that may not have left any physical primary evidence on the Earth’s surface, but only the secondary recorded impressions of those who witnessed them visually. After all, we only know about Halley’s Comet and its flyby every 76 years because we have seen it and recorded it. There is no physical evidence on the Earth’s surface to indicate that this has occurred, unless, of course, you count the depictions and descriptions of this comet—the secondary evidence—as recorded by people through the ages. Just so, we are looking for the eyewitness accounts of similar astronomical phenomena that would have been visually noteworthy but left no physical trace.
Our survey of rock art images over the past decade has taken us to 139 countries, where we have recorded over 4 million individual rock art images—bearing in mind that one location with rock art imagery can include thousands of individual rock art images. For each location we visited, we recorded the site’s latitude, longitude, and altitude, and determined the inclination to the horizon and the direction the artist was most likely looking. Besides providing a detailed geographic location that can be mapped globally, these data allowed us to determine which parts of the sky were visible from the location where the rock art was created.
A tentative analysis of the data suggests that all of the mapped locations provided at least one field-of-view toward the sky over the rotational/geographic South Pole. This is not to say that all the sites were south-facing or that all the images were on south-facing surfaces, but just that all the sites allowed for the rock artist to look to the South Pole of the sky (as well as any other parts of the sky that might have been visible from that particular place). If rock artists worldwide were interested in places where they could observe this part of the sky while producing their art, at what sort of astronomical phenomena may they have been looking?
If we exclude from consideration those petroglyphs which seem clearly to represent recognizable phenomena (animals, plants, etc.) and focus exclusively on those enigmatic abstract shapes that few comfortably interpret, we find ourselves presented with 84 types of abstract images. Assuming that these images were indeed meant to depict phenomena seen in the skies, we propose, based on our experience of auroras seen at polar latitudes and plasmas (ionized gases) modeled and photographed in laboratory settings, that these “abstractions” may actually be visual representations of intense auroral storms. Auroras are centered on the poles. In this case, our observations suggest that an auroral storm of unprecedented proportions may have occurred over the South Pole. The light associated with such storms is unbearably bright and is called synchrotron radiation light. We have found that people carved the images exclusively from locations where the brightest parts of the formations were hidden from view by local features such as rocks and distant mountains that may have served as shields.
On very rare occasions, extreme auroral storms can even be seen in areas closer to the equator. The most famous example is the so-called Carrington Event of 1859. A feature article posted May 6, 2008 on the SCIENCE@NASA website describes how on the morning of September 1, 1859, the English astronomer Richard Carrington witnessed a massive solar flare during his normal recording of sunspots.
In the intervention on the picture by Marcin Zajac, together with animator Karl Sandzen, we have tried to use the image as a tableaux vivant and make the petroglyphs shine under the lighting power of the Milky Way, hinting the amount of time the rock carver has spent carving the sky representation through a time lapse. Applying animation to the photograph Marcin Zajac took, we want to enhance the liveliness of the dark environment and how much darkness mattered and was actually lit up. I wanted to underline the effort and the fact that there is no need to be afraid, on the contrary there was guidance and guidance was offered through representation.
Besides, I hope that one of the figures, carved into stone by rock carvers, might be a firefly.
Just before dawn the next day, skies all over planet Earth erupted in red, green, and purple auroras so brilliant that newspapers could be read as easily as in daylight. Indeed, stunning auroras pulsated even at near tropical latitudes over Cuba, the Bahamas, Jamaica, El Salvador, and Hawaii.
What would the sky look like if the solar wind was further increased by one to two orders of magnitude? Although we have no scientific proof that this has ever happened, the American astronomer, Thomas Gold (1920–2004), proposed that such an event did happen within the past 12,000 years. Unfortunately, we have no visual depictions of what such an event would have looked like, but thanks to the affiliation of one of the authors with the Los Alamos National Laboratory, it was possible to use the world’s fastest computer, Roadrunner, to simulate the evolution of an aurora under the influence of such a massive solar wind. Apparently, the aurora would assume different shapes than the familiar frivolous waves, rays, and ripples and take on a less scattered, more concentrated form. As its height profile is altered, a column forms that joins the magnetosphere of the earth to the solar wind. Expected structures include pinched ropes of a “sausage” type, helices, concentric circles, filamentary “rays” that intertwine and merge, and the emergence of “plasmoids” shaped like orbs or eggs. As such a configuration achieves a degree of semi-stability, moreover, the event would last considerably longer than ordinary auroral outbursts, allowing petroglyph carvers to depict aspects, depending on their own point of view on earth. The snapshot results of the different stages of the simulated aurora appear to match closely many of the so-called abstract petroglyphs seen around the world.
So, could these enigmatic petroglyphs be evidence that humans witnessed intense auroral storms in the past? We believe this is the case and have reason to postulate three episodes of auroral activity of this type, accompanied by rock art carving, which occurred between roughly 10,000 and 3,000 BCE. Although it is wise to keep one’s feet on the ground at all times, it is also clear that archaeologists could benefit much from lifting their gaze up to the heavens. The sky was as much a part of the ancients’ environment as the earth.
