In the course of these lessons, we have seen why and how the analysis of the astronomical content of ancient architecture helps us in understanding several aspects of our past. The approach to Archaeoastronomy I have proposed here is of course the scientific one, but the point of view is cognitive: going beyond materiality and supplying a model of the way objects and environments were perceived, and of the symbolic value that people attached to them. The specific focus of interest of Archaeoastronomy is thus the perception and the contextualisation of the celestial cycles in material objects trough the use of astronomical alignments. It goes without saying, of course, that in the cognitive approach there is the risk of introducing ideas, parallels and interpretations which may come from our own experience and cultural background, and may have little or even nothing to do with the original purposes of the builders. On the other hand in most cases we lack explicit, written sources about the monuments we study. As a consequence, an assertion in Archaeoastronomy can usually be made only within a certain degree of confidence. It is therefore important to have a clear idea of the risks of Archaeoastronomy, and of how to avoid them. The key is always the context: each astronomical interpretation must be backed up whenever possible by all what we know from history and archaeology. Further, we must avoid to select the experimental data in such a way as to favour an interpretation instead of another. Otherwise, we are not making Archaeoastronomy, but what we may rather call pseudo-archaeology or even trash-archaeology. Be careful, therefore, because – unfortunately – the World Wide Web is plenty of such things. For instance, we can still read a crazy idea formulated many years ago about the ancient Bolivian site of Tihuanaco, near the Titikaka lake. Tihuanaco is a wonderful place, rich in megalithic constructions and well dated archaelogically to the 6th century AD. Instead, many books and websites claim that it is as old as the 15th millennium BC! Why? Because the solar alignments of its main building do not match perfectly with the azimuths of the sun at the solstices today; but, due to the slight variation of the obliquity of the ecliptic, they did match 15 millennia ago! What do you think what is it more likely, a slight error of alignment committed by the Tihuanaco architects or 15 millennia of error by the archaeologists? Scores of other examples can be made. For instance, many try to identify the disposition of monuments on the ground as an image of suitably chosen constellations and suitably chosen stars of these constellations in the sky. This should have occurred for monuments built during centuries, such as the Egyptian pyramids, the Khmer temples of Angkor or even the gothic cathedrals of France, which are tens of Kilometers afar from each other – without remembering that the Earth happens to be round and therefore the visible horizon is much limited. There is no cultural or archaeological proof whatsoever that the architects of all these works ever conceived such a kind of mapping of the sky. So far, so good for the risks of Archaeoastronomy. However, if used with due caution, the potential of this discipline is really impressive, since uncountably many architectural masterpieces were linked to the sky, and the discovery of such links can help us in understanding the mind of their builders. Much research remains to be done in this field. A striking feature of Archaeoastronomy is the possibility of rediscovering spectacular appointments – relating in particular to the Sun – which were fixed in ancient times and successively forgotten. This may help in promoting the site in question and is potentially very important for the dissemination of Archaeoastronomy itself among the general public. In this sense we can speak of Astronomical value of cultural heritage or, of astronomical heritage. To conclude then, putting together stars and stones following a strict scientific approach is a challenging, but fascinating enterprise to which I would like to invite you all.
