Easter Island - Rano Kau

Easter Island is the most isolated island on earth. Less than twenty-five kilometers (fifteen miles) across, it is well over 2,000 kilometers (1,300 miles) distant from the nearest habitable land in any direction. Yet when Europeans first chanced across it (Dutchman Jacob Roggeveen arrived there on Easter Sunday in 1722, hence the name), they found it inhabited. In fact, Rapa Nui (which is the Polynesian name for the island) had been colonized well over a millennium earlier, in about C. E. 400. Whether only a single canoe or fleet of canoes ever reached this remotest corner of Polynesia, or whether for a period there was further contact, we shall probably never know. What is certain is that the inhabitants of the island soon lost contact with their forebears and spent many centuries in complete isolation. Both archaeologists and ecologists have been bequeathed an incredibly valuable case study of people interacting with their environment within a closed system, and it is one that has some sobering lessons for the population of the planet as a whole. Certainly environmental disaster loomed toward the end, when the population had increased dramatically and all the forests had been destroyed. 

Among the fascinations of Easter Island are the famous large statues or moai. Several hundred of them came to stand imposingly on platforms (ahu), mostly ringing the island and facing inland, but with a few in other locations. Scores more lie or stand in what resembles a frozen production line in the volcanic crater Rano Raraku, in various stages of production from quarrying to transportation. Why would an isolated population on a small island have put such a significant proportion of its human resources into producing them? One possibility is that they were seen as protective presences, but their full significance for the population of this tiny island remains largely a matter of speculation.

The island has long attracted astronomical attention. As far back as the 1960s, publications appeared describing ahu that were solstitially or equinoctially aligned. But since there are over 250 ahu on the island, the question of bias in selection arose. Were the supposedly astronomically aligned ahu selected on the basis of a preconceived "toolkit" of targets? If so, it is possible that they had no statistical or cultural significance whatso ever. Attempts were made to resolve this question through systematic studies of ahu and moai orientations, both by an archaeologist (the Easter Island specialist William Mulloy) and later by an astronomer, William Liller. They provide only marginal evidence at best of any intentional orientations upon solstitial and equinoctial sunrise and sunset. The overriding tendency is for ahu to be situated close to the coast and oriented parallel to it, with the moai facing inland. Since such platforms are to be found all around the perimeter of the island, their orientations are scattered around the compass, with some falling inevitably within the solstitial and equinoctial ranges. 

Perhaps the most noteworthy ahu from an astronomical point of view is one of a small minority that are not situated on the coast but a good way inland. Ahu Huri a Urenga is situated in a low saddle surrounded-unusually for Easter Island-by a hilly horizon with very little sea visible. Standing upon the platform is a distinctive and imposing moai. This is aligned not only upon the rising sun at the June solstice, but upon a prominent hill summit. Another hilltop marks equinoctial sunset. A number of apparently artificial depressions in boulders adjacent to the platform incorporate several so lar alignments and hence, it has been claimed, could have functioned as a solar-ranging device. All this evidence still falls short of conclusive proof, but it does at least raise the possibility that natural features in the landscape were used to mark the solar rising or setting positions at different times of the year. This is a possibility that has been raised elsewhere in Polynesia, for ex ample in the Nā Pali region of the Hawaiian island of Kaua’i. 

One of the most significant astronomical alignments to the inhabitants of Rapa Nui may actually have been a natural one. The village of Orongo was placed in an extraordinary situation on a knife-edge ridge overlooking the spectacular but treacherous crater of Rano Kau, with its marshy lake on one side and the ocean on the other. This sacred place was the ceremonial base for the extraordinary annual "birdman" ritual in which contestants had to swim two kilometers (over a mile) out to a small rock, wait there for the return of a migratory sea bird, and collect its first egg. As seen from Orongo, the sun rose behind the summit of Poike, a prominent volcanic hill on a far corner of the island, precisely at the winter (June) solstice. As the rising sun moved away from this peak, the spring ceremony approached. It is hard to believe that priests at Orongo could have failed to notice that the peak of Poike marked the limit of the sun's movement along the horizon, especially given that the word poike, according to the anthropologist and Maori scholar Sir Peter Buck (Te Rangi Hiroa), means "to be seen just above the horizon." However, the severe limitations of the topography make it unlikely that this was taken into account when the village was planned. Instead, the solstitial alignment of Poike from the crater-rim village may have been dis covered later. We would see it as a coincidence, but it may well have been taken by the Easter Islanders as something that confirmed and reinforced the already evident sacredness of the place. 

A remnant of Easter Island astronomy of a rather different nature may have been bequeathed to us in the form of Rongorongo script, a system of symbols used on Easter Island that seems to have provided a series of triggers for the reader rather than actual words or syllables. One fragment of Rongorongo has been interpreted as a lunar calendar.

References and further reading Barthel, Thomas. The Eighth Land: The Polynesian Discovery and Settle ment of Easter Island. Honolulu: University Press of Hawai`i, 1978. Fischer, Steven Roger, ed. Easter Island Studies, 122-127. Oxford: Oxbow Books, 1993. Flenley, John, and Paul Bahn. The Enigmas of Easter Island. Oxford: Ox ford University Press, 2003. Liller, William. The Ancient Solar Observatories of Rapanui: The Archaeoastronomy of Easter Island. Old Bridge, NJ: Cloud Mountain Press, 1993. Mulloy, William T. "A Solstice-Oriented Ahu on Easter Island." Archaeology and Physical Anthropology in Oceania 10 (1975), 1-39. Selin, Helaine, ed. Astronomy across Cultures, 148-152. Dordrecht, Neth.: Kluwer, 2000.