The great megalithic monuments
The discipline which, through the analysis of finds such as stone engravings, astronomically oriented monuments or ancient codes and annals, studies the astronomical knowledge of ancient peoples is commonly called "archaeoastronomy". Archaeoastronomy is a young science as only around the 16th and 17th centuries did people begin to evaluate the possibility that some ancient monuments (such as the megalithic ones scattered throughout Europe rather than the pyramids) could have been built according to rules linked to the main celestial phenomena.
Lockyer, one of the leading scholars of this subject, completed a series of research on the Egyptian pyramids and European megalithic monuments around the middle of the 19th century which demonstrated their astronomical orientation. However, the scientific society of the time was not willing to recognize that ancient populations or even prehistoric communities had developed decidedly advanced mathematical and astronomical knowledge, so Lockyer's theories on prehistoric astronomy remained in the shadows for about fifty years. Only around 1960 did scholars such as Hawkins and Thom give new life to this discipline with the support of new archaeological discoveries and new methods of investigation, which led to the official recognition of archaeoastronomy and the legitimation of the theory on the existence of an astronomical culture near ancient civilizations since the Neolithic and Eneolithic eras.
Archaeoastronomy is a science with a typically interdisciplinary character, as it is founded on the collaboration of different disciplines such as mathematics, anthropology and physics, and has led to the birth of ethnoastronomy, which is based on the study of the astronomical meaning of artefacts, of ritual practices, folklore and oral traditions of prehistoric and protohistoric civilizations. Archaeoastronomy is also able to provide useful information on still open problems of modern astronomy, such as the value of the slowing down of the Earth's rotation, the passages of comets, the explosions of supernovae.
Archaeoastronomy aims to determine what astronomical knowledge ancient civilizations possessed. Many populations of the more or less remote past, in fact, developed an intense relationship with natural phenomena and in particular with celestial ones. Their social, religious and artistic life was strongly influenced by astronomical phenomena, and in particular by those characterized by clear and evident periodicity.
Archaeoastronomy bases its investigation on three main lines of research:
- the analysis of megalithic structures (temples and circles) which have in common the fact of having been built using large stones driven into the ground and arranged according to alignments or circular structures;
- the study of the symbols engraved on stone slabs (connected to megalithic monuments, tombs or even isolated stones), found in caves or on rock walls;
- the deciphering of artefacts, such as calendars and almanacs, which are testimony both to the mathematical and astronomical knowledge possessed by these peoples, and to the attention with which they recorded extraordinary celestial events such as the passage of comets or the appearance of stella novae.
What are megalithic monuments
The megalithic monuments were erected in different historical eras by numerous populations. Evidence of such monuments can be found in various geographical areas, from Europe to Africa, from the Middle to the Far East. The term megalithic derives from the Greek 'mega', large, and 'lithos', stone, and it identifies all those structures made up of large stones placed vertically in the ground and arranged in such a way as to create circles, alignments or particular constructions. In Europe there are sites of megalithic monuments from Sweden to the Iberian Peninsula, from the British Isles to France. They were erected, depending on the geographical region, between the mid-5th and 2nd millennium BC. They, therefore, predate the Egyptian and Mesopotamian civilization, given that the first monuments date back to the Neolithic.
The Neolithic, a term used to indicate the period of time from 9000 BC to 6000 BC, is a particularly important period in human history. This is, in fact, the historical age during which man developed the techniques of agriculture and livestock farming, two practices that had fundamental consequences on the evolution of societies. This real revolution began in the Middle East and reached Europe, around the fifth millennium. The oldest megalithic constructions (found in Portugal and Atlantic France) date back to this period and mark the beginning of funerary gigantism.
The origin of megalithism is still little known today and is the basis of a large amount of studies. The most accredited interpretation by scholars is that the phenomenon of megalithism was born simultaneously in different geographical regions and originated from the development of the practice of burial of the dead. In particular, the economic revolution modified the needs of Neolithic communities by introducing fundamental changes in the cult of the dead and in fertility rites. Thus the first signs of the connection between the observation of celestial bodies, such as the Sun and the Moon, and the main ritual practices began to appear. For example, the profound relationship existing between the cult of the dead and the observation of the motion of the Sun is evidenced by the fact that many skeletons found, belonging to the Upper Neolithic and the Bronze Age, are oriented with their heads facing the cardinal points.
Furthermore, following the development of the first settled societies, there arose the need to regulate life in synergy with nature which is characterized by precise rhythms. With repeated observations, primitive populations realized that these rhythms could be correlated with the motion on the celestial sphere of some astronomical objects such as the Sun and the Moon. An astronomical science therefore developed, understood as observation of the sky and its phenomena and with the aim of learning to understand its secrets and use them to the advantage of the whole community to organize social and agricultural life.
The dolmens
A dolmen (which means stone table) generally consists of a megalithic chamber delimited by straight vertical slabs or pillars and by dry stone walls that support one or more stone slabs.
There are three basic types of dolmens:
- the corridor dolmens, whose chamber can have different shapes and extend outwards through a more or less long corridor. These are the oldest dolmens, dating back to the 5th millennium BC;
- the covered gallery dolmens, which made their appearance at the end of the 4th millennium BC, i.e. in the late Neolithic. They differ from the previous ones in that the length of the parallel-walled chamber is greater than the width. Furthermore, the corridor with which they communicate with the outside is covered with slabs. The Giants' Tombs found in Sardinia fall into this type of dolmen;
- the simple dolmens, equipped with a chamber that opens directly towards the outside.
Along with these three basic types it is also possible to include megalithic sarcophagi, from which the dolmens probably derived and which can be accessed simply by moving the covering slab.
Dolmens are usually located inside a stone mound (the cairn) which envelops them almost completely and which can be circular, polygonal or quadrangular, sometimes very elongated and delimited by a dry stone wall or erected slabs. Dolmens are funerary monuments: inhumed or cremated human remains were placed in their chambers depending on the customs of the region. They had the function of collective tombs: in fact, in the mortuary chambers one often finds the remains of several bodies which may appear entire, lying on the ground in a folded position on their sides, or limited to a few bones. In the gallery dolmens, which are the most recent, several hundred bodies have sometimes been discovered. These dolmens were therefore used several times; they were opened and closed and then permanently buried or dismantled to reuse the stones in the construction of other funerary monuments.
Many dolmens are decorated with carvings or even simple staking of the stone slabs. The depictions, however, are often difficult to interpret and do not seem to have a defined organization. Such carvings mainly consist of concentric circles, dotted circles, lozenges, zigzag lines, U-patterns and spirals. All these symbols, which are also found in petroglyphs, indicate propitiatory prayers for hunting or war, solar symbols but also representations of important celestial events, such as eclipses of the Sun and Moon, passages of comets or appearances of stella novae.
Both the majesty of the construction, the decorations and the preciousness of the objects kept indicate how a religious function was added to the purely funerary function of the dolmens. This religious aspect is not only found in the presence of objects that were supposed to guarantee a peaceful journey into the afterlife but, above all, in the evident orientation of the axis of the monument towards certain positions on the horizon connected to the rising and setting of the Sun and in particular along the directions of the winter and summer solstices. This was in fact a custom also adopted in previous and subsequent eras. There are numerous examples of simple tombs in which bodies were turned with their heads towards the north cardinal point or along the equinoctial (east-west). Furthermore, orientations towards very bright stars can also be detected, given that the heliacal rising of some of them marked the beginning of the years for many civilizations. A well-known example is that of the heliacal rising of Sirius, which among the Egyptians corresponded to the beginning of the year and on which occasion the Nile overflowed, making the surrounding land fertile.
A classic example of a dolmen with a mound is the one found in Newgrange (County Meath) in Ireland. From the main entrance during the winter solstice the sun's rays penetrate the mortuary chamber, whose walls are engraved with spirals, classic solar symbols.
The menhirs
The word menhir means "long stone". These megaliths are made up of more or less rough stones of various sizes embedded in the ground. They are sometimes engraved along the entire length with decorative or, as more often happens, symbolic motifs.
Menhirs are found both isolated and in groups of two, three or more; they can be erected along a different number of parallel rows in arrangements known as alignments. They are often part of geometric, quadrangular, elliptical, ovaloid and, above all, circular figures. These structures highlight how the people who built them possessed simple but basic geometric notions such as the properties of the circle and Pythagorean triples.
According to the English scholar Thom, who analyzed several ring constructions in Scotland and southern England and the alignments of menhirs in the Carnac area in Brittany, the measurements of these structures would be multiples of the same linear unit called "megalithic yard", with a value equal to 0.829 meters. Many menhirs are from the Neolithic era, but their construction continued until the Bronze Age and even in times closer to us (up to the threshold of the Middle Ages).
The largest menhir built in the Neolithic, that of Er-Grah, in Locmariaquer in France, exceeded 20 meters in length and its weight was approximately 350 tons. It currently lies on the ground in four pieces; its breakage dates back to the Neolithic era.
Although much has been ascertained both regarding the profound motivations behind the construction of these structures and their meaning and use, important questions still remain open: were they commemorative monuments? did they constitute territorial limits? Were they stones erected for religious purposes or, for example, for fertility rites? Were they linked to the solar and lunar cult?
Various evidence acquired from archaeoastronomical studies demonstrates that a large part of these menhirs were erected with the clear purpose of using them as targets to mark the rising or setting on the celestial sphere of particular astronomical objects such as the Sun at the solstices, the Moon at the lunistices and the main stars in heliacal rising or along the local meridian. From the analysis of many temples it has been possible to demonstrate that the Neolithic populations were able, with good probability, to calculate the equinoctial line, the meridian line and to notice the precession of the equinoxes. It was possible to discover all this by studying the shadow cast by a menhir.
Nowadays, scholars have come to the conclusion that menhirs were not only and exclusively structures made of stone but, in regions where it was rare to find that type of raw material, they were also built in wood. Obviously in these cases not many specimens have survived due to the easy perishability of the material used.
The alignments and circles of standing stones
Very often the menhirs (made up of stones stuck in the ground) are grouped together to form elliptical, ovaloid, quadrangular and, especially, circular geometric figures. Other times, however, they are arranged in such a way as to create long alignments, as in the case of Carnac in Morbihan (France).
The latter is composed of seven main rows of 1029 standing stones of decreasing height and distributed over 1128 metres. To the west, where the tallest stones are located, there was a circle which has now been destroyed. These complexes show how the populations who built them were in possession of some basic rules of geometry. In fact, very often, the relationships between the distances of some stones are Pythagorean triples or, as the Englishman Thom discovered, they are multiples of a basic linear unit called "megalithic yard" equal to 0.829 metres.
One of the first questions that arises when observing a megalithic monument is how men without particularly sophisticated knowledge of engineering could erect such large stones and transport them along the lengths chosen for construction. The single stone slab, whose weight can reach several tons, was probably detached from the quarry by the action of fire and then made to proceed on two parallel rails obtained from oak trunks and its movement controlled by means of laces made of vegetable fibre. Sometimes they were transported along rivers or the sea using special boats. Certainly dragging these stones for kilometers and erecting them required the presence of hundreds of men, so it is likely that entire villages, if not even inhabitants of different territories, cooperated under the guidance of a leader.
The most famous of the circular complexes is Stonehenge in the heart of the Salisbury plain (southern England). Stonehenge is the result of successive reorganizations that took place between 3000 and 1500 BC. Initially it was a henge, that is, a circular area 100 meters in diameter delimited by a moat, in which 56 aubrey holes were distributed in circle. While it is likely that these holes served as funerary urns, some scholars, including Sir Hawkins who was the first to study Stonehenge from an archaeoastronomical point of view, have hypothesized that they could have been used to reconstruct the motion of the Sun and Moon in order to predict the eclipses.
This first circle was later abandoned and was only resumed around 2100 BC to be completely remodeled. 80 bluestones from the Prescelly Mountains in south-west Wales were brought in and placed in the center to form an incomplete double circle. A central access road was built with heel stones marking the entrance; the latter was oriented towards the summer solstice, as archaeoastronomical findings show.
The third construction phase took place around 2000 BC with the addition of the sarsens stones distributed in a circle and connected to each other by stones arranged like lintels next to each other. Internally, 5 trilithons were placed in a horseshoe-shaped structure, the remains of which can still be seen today. The axis of the monument was turned towards the summer solstice and marked externally by a single heel stone placed inside a circular ditch. This new rearrangement of Stonehenge highlights the skill of the builders, as these stones are dug in such a way as to create perfect joints capable of supporting the stones placed as architraves.
The last period occurred around 1500 BC when the bluestones were redistributed in a horseshoe and circle shape (some traces of these structures are still clearly visible). The largest of the bluestones, called the altar stone, probably stood erect as a column in line with the axis of the monument. Around 1500 BC, two circles of holes were dug that could have been used for other rows of stones which, however, were never erected.
Stonehenge remained in use until 1000 BC but we don't know for how long before it was abandoned. A mistake that is often made is to believe that it was the Druids (the priestly class of the Celtic populations) who built this type of monument. The Celts inhabited precisely the regions, such as England and France, where many remains of circles are found, but during the Iron Age. Therefore it is probable that the Celtic civilizations of Indo-European origin merged with the native populations who built these monuments, assimilating their culture and astronomical knowledge. In fact, there is evidence of temples built by the Celts using menhirs that date back to the Iron Age.
