Calendrical devices of a megalithic nature are found in many areas where early civilizations took root. These are exemplified by the huge stelae produced by the Mayan people of Mexico and Central America on which were recorded astronomical and mathematical data, such as the Long Count, that covered more than 4,000 years. Indeed, it appears that Mayan buildings even had astronomical orientations directed at celestial risings or settings on the horizon. Others were aligned so that shadows would cast images, such as the serpent on the Castillo at Chichen Itza. This pyramid also has four staircases of 91 steps that, with the top platform, combine to make 365—the number of days in the year. The Egyptian pyramids have remarkably accurate north/south—east/west alignments. Although these may not have been calendrical, they do seem to have been based upon either the rising and setting or vertical alignments of polar stars, and “star clocks” appear to have been painted upon the ceilings of some Egyptian tombs. Star paintings with astronomical alignments also have been found in megalithic tomb mounds in Japan. In China the Imperial Forbidden City is oriented on a north/ south axis with the Temple of Heaven. The Emperor would follow this path on the winter solstice to perform rituals to guarantee the return of longer days. In Kenya a series of stone pillars called Namoratunga and bearing Sudanese Kushite engravings line up with conjunctions of the moon with various stars around 300 BCE. There are many other examples of archeoastronomy to be found, but not all are megalithic in nature. In recent decades, however, research has come to indicate that much more ancient megaliths found in western Europe, long believed by local peasantry to be petrified giants, giants’ tables, beds of legendary heroes, or just ancient curiosities of unknown use to others, may have served as solar or lunar calendars to the prehistoric farming peoples of the Late Stone Age and Early Bronze Age.
In the most literal sense, megalith means very large stone (mega lı0oç) in Ancient Greek. In the archeological sense, megalith refers to massive block-like stones that have been arranged into simple or complex architectural constructions, most often referent to the Neolithic (or “New Stone”) and Bronze Ages of western Europe (although megalithic architecture is known from later periods, also, and is a worldwide phenomenon, as described above). The simplest type of megalith is the upright standing stone, or menhir. The name comes from the Welsh maen, meaning “stone,” and hir, meaning “long,” thus menhir means “long stone,” and it is synonymous with the Breton peulvan (related to pol in Gaeilge, as in Pol na Brone, the Dolman of the Sorrows in the Burren of County Clare, Ireland). Sometimes menhirs are solitary objects; sometimes menhirs are arranged in groupings, or alignments, that range from just a few stones to more than a thousand, set in long rows, as at Carnac in Brittany and Callanish on the island of Lewis in the Scottish Hebrides, which are parts of gigantic alignments that may be calen- drical in nature.
Ogham stones, found in Ireland, are megalithic menhirs that were incised in the Late Iron Age with horizontal or diagonal grooves on the corners in precise patterns that represent letters and numbers. It is believed possible that they also were done in (now decayed) wood, as the names preserved for the “letters” are those of tree species: The Ogham letter |- corresponds to ‘B’ and is called beith in Irish, meaning ‘birch,’ |= corresponds to ‘L’ and is named for rowan (mountain ash); -| corresponds to H and is called after ‘hawthorn;’ =| corresponds to ‘D’ and is named after ‘oak;’ f stands for ‘A’ and represents ‘pines/firs;’ + is ‘O’ and refers to gorse; and ” corresponds to ‘EA’ and is called after ‘aspens,’ to give a few examples (the vertical line down the center of each symbol is the corner of the stone). The stones are believed to have been carved to commemorate people or events, mainly because most of the inscriptions are chiefs’ names and dates. It is likely that the dates carved into these stones are not the dates of erection, however, as that would be anachronistic: the Late Iron Age dates are several millennia after the probably Neolithic times of construction.
A more complex type of structure is the dolman, or stone table (sometime called cromlech). These were burial chambers that consisted of upright megaliths covered by flat capstones, most likely sheltered within earthen mounds (tumuli) in antiquity, although most mounds have eroded away after 4 to 7 thousand years of weathering. Sometimes the chambers are elongated into galleries, and they may have small entry courtyards and transected internal vaults with corbelled ceilings as at Newgrange.
In 1648 English antiquarian John Aubrey (16261697) saw the megaliths around the British countryside as components of a massive prehistoric temple. He proceeded to conduct research at Avebury, Stonehenge, Wayland’s Smithy, and other ancient sites that led him to describe them as Templa Druidum, or Druid temples. This view was seconded in the 18th century by fellow antiquarian William Stukeley (1687-1765) in two books, one about Avebury, the other about Stonehenge, published in the 1740s.
Despite Aubrey’s and Stukeley’s druidic provenance for megalithic constructions, and notwithstanding the popular French cartoon strip Asterix, in which an ancient Gaulish character, Obelix, frequently is shown to be transporting and erecting megaliths, the Celts were not responsible for the creation of the Western European megaliths. Celtic culture is archeologically accepted to have arisen in the first millennium BCE, and the megaliths of Western Europe are considerably older than that— some on the order of 4,000 to 5,000 years. Although the Celts and their priests, the Druids, did not build megalithic structures, according to some classical sources they did worship and sacrifice at them, just as do some modern people, who did not build the megaliths either. Although the people that we call the Celts did not build them, their ancestors may have, as modern DNA analysis has shown a continuous link between the peoples of Western Europe from the Stone Age to today.
In 1955 an engineer and amateur astronomer, Alexander Thom, presented a paper on his statistical analysis of 250 megalithic monuments, most of them in Scotland and Wales, that he believed showed considerable astronomical and geometric understanding on the part of their Neolithic builders. In addition to a celestial map that aligned the monuments with the horizon, Thom found what he believed to be a Middle Bronze Age solar calendar that was divided into 16 parts, or “months,” that included four 22-day months, eleven 23-day months, and one 24-day month. This would divide the four annual quarters between the solstices and equinoxes into four yet smaller quarters per season. These four smaller quarters, or sixteenths, are Thom’s “months.” Although this idea was rubbished by archeologist V. Gordon Childe, it formed a springboard for further inquiry into the calendrical hypothesis.
Perhaps the best-known megalithic site is also the one that best demonstrates the calendrical hypothesis: Stonehenge. Stonehenge is a truly impressive example of Late Neolithic/Early Bronze Age megalithic architecture. Although it began as a simple circular banked ditch in the late 4th millennium BCE when the entrance and the Heel Stone were erected, the bulk of what today is visible at Stonehenge was constructed from approximately 2000 BCE to 1500 BCE. Because Stonehenge was built by an agricultural society, knowledge of solar and lunar aspects is believed to have been considered vital to survival because it provided more or less reliable indicators of when to plow, plant, sow, and reap. The latitude on which Stonehenge rests is the one where the sun and moon form perpendicular aspects, a phenomenon reflected in the shape of the monuments and their surrounding fixtures. The Avenue from the great circle lines up with the 6-meter-high Heel Stone like the sites on a gun barrel, the target being the rising sun on the summer solstice.
During the second phase of construction a series of 56 holes ranging in size from 0.8 to 1.8 meters, called Aubrey Holes after John Aubrey’s mention of them in his Monumenta Britannica, were cut in the chalk bordering the embankment to hold vertical timbers. In the third phase the bluestones, weighing between 1 and 1.5 tons, were brought to the site from the Prescelly Mountains of Wales 225 kilometers distant and raised in the center of the circle. The gigantic sarsen trilithons (sets of three stones estimated at about 30 tons each, forming huge upside down U’s) were raised in the fourth phase of construction in the Early Bronze Age. The solar connection associated with Stonehenge is significant here in that it is in the Bronze Age that Welsh Celtic specialist Miranda Green sees the rise of a sun cult based upon solar symbols found on art and artifacts from this time.
In 1961, astronomy professor Gerald Hawkins used an IBM 704 computer to plot 120 pair of points against celestial positions to investigate what he believed to be the purpose of the monument: an astronomical computer to calculate, among other things, the solstices and lunar eclipses. Hawkins had expected to find solar alignments at Stonehenge, but the lunar alignments came as a surprise to him. Hawkins concluded that Stonehenge formed an astronomical observatory designed to predict lunar eclipses in a 56-year cycle that included two segments of 19 years and one of 18 years, based on the original Stonehenge’s 56 Aubrey holes and the 19 bluestones of the horseshoe. The two smaller circles of holes, the Y and Z holes within the ring of Aubrey Holes, add up to 59 holes, or two lunar months of 29.5 days each. Continuing the 29.5-day lunar month theme, the ring of 30 Sarsen stones contains one that is quite a bit smaller than the rest, making the number essentially 29.5—once again a lunar month, and this pattern is repeated in the Bluestone Circle. Although some archeologists, notably Richard Atkinson, who was known for his work at Stonehenge, strongly disagreed with Hawkins, it is ironic that astronomers such as Fred Hoyle found his work to be the impetus for even further calculations. Brian M. Fagan argues that Stonehenge never was a device for calculating eclipses, but that it only implies the idea of time as reflected in the celestial cycles observable to its builders. To put it somewhat simplistically, following the publication of Hawkins’s Stonehenge Decoded, the archeologists tended to side against him, while the astronomers tended to side with him.
Although it usually is the summer solstice sunrise above the Heel Stone that gets much of the commentary when discussing the astronomical nature of Stonehenge, Julian Richards argued on his BBC television archeology series, Meet the Ancestors, that it was the winter solstice, not the summer solstice, that may have been more important to the builders. According to Richards, the Avenue is just that—an avenue to the site from which to view the winter solstice, not a sight down which one would view the summer solstice sunrise. Rather than looking down the avenue to the Heel Stone, we should be looking in the opposite direction, through the largest trilithon, at the winter solstice sunrise when the image between the uprights is split like a window, and the sun rises through the upper part of the image as in the window, or Roof Box, at Newgrange in Ireland.
Newgrange, Knowth, and Dowth are the three megalithic passage tombs, or fairy mounds (sidh), found on Newgrange Farm in the Boyne valley, or Bru na Boinne (Palace or Mansion of the Boyne), north of Dublin and about 8 kilometers west of the town of Drogheda, near Slane, in County Louth. At Knowth, one of the slabs is carved with an intricate scalloped design resembling a zodiac and is known as a “sundial.” The best known of the three megalithic monuments is Newgrange, built in the late 4th millennium BCE. The massive mound covers an area of over one acre and is surrounded by 97 carved curb stones. The mound had eroded badly until it was reconstructed forensically through trial and error by its excavator, Michael J. O’Kelly, between 1962 and 1975. Surrounding the mound were a series of white quartz stones that were believed by some to have been a ceremonial road. O’Kelly noted their locations and, suspecting that they formed part of a wall, reconstructed the wall repeatedly, tearing it down each time until the stones fell into the positions where they were found to begin with. This, he decided, was the original design, which he then reconstructed.
Germane to the subject being discussed here, the great entry stone at Newgrange is carved with a number of spirals reminiscent of Vincent Van Gogh’s painting Starry Night, and indeed this is known as a “celestial motif,” although the spirals may represent the sun’s passage across the heavens, not stars. Behind the stone is an entrance surmounted by a window, or “Roof Box.” Normally the corbelled, cruciform vault at the end of the upward-sloping 19-meter-long passage is completely dark. However, for 2 days on either side of the winter solstice the interior is illuminated just before nine a.m. for about 17 minutes by a shaft of sunlight that enters the Roof Box and travels up the passage as far as the basin stone in the corbelled vault (a parallel phenomenon can be observed in the Sun Dagger at Chaco Canyon, New Mexico). Designs similar to Newgrange, complete with carved upright stones, can be observed at Loughcrew in County Meath, Ireland, and at Gavrinis in Brittany, France, built nearly a millennium earlier. Not far from Gavrinis is Carnac, an immense site in Brittany consisting of row upon parallel row of menhirs that seem to be aligned to both the sun and the moon, although whether or not they represent anything of a calen- drical nature is unclear.
See also Anthropology; Archaeology; Chaco Canyon; Eclipses; Observatories; Solstices; Stonehenge; Measurements of Time
Childe, V. G. (1980). Prehistoric communities of the British Isles. New York: Arno Press.
Daniel, G. (1963). The Megalith builders of western Europe. Baltimore, MD: Penguin.
Fagan, B. M. (2000). Ancient lives: An introduction to archeology. Saddle River, NJ: Prentice Hall.
Hawkins, G. S., & White, J. B. (1965). Stonehenge decoded. New York: Doubleday.
McMann, J. (1993). Loughcrew: The cairns. Ireland: After Hours Books.
Mohen, J.-P. (1999). Megaliths: Stones of memory. New York: Harry N. Abrams.
Piggott, S. (1965). Ancient Europe: From the beginnings of agriculture to classical antiquity. Chicago: Aldine.
Ruggles, C. (1999). Astronomy in prehistoric Britain and Ireland. New Haven, CT: Yale University Press.
Thom, A. (2003). Megalithic sites in Britain. Oxford, UK: Oxford University Press.
Wernick, R. (1973). The monument builders. New York: Time-Life Books.