Astronomical Observatories: from the Prehistory to The
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RMxAA (Serie de Conferencias), 51, 1–8 (2019) ASTRONOMICAL OBSERVATORIES: FROM THE PREHISTORY TO THE XVIII CENTURY M. A. Castro Tirado1,2 ABSTRACT We describe the development of astronomical observatories since the prehistory until the late XVIII century, and how an evolution of several millennia took us from very elementary structures to buildings hosting telescopes and domes in which science was the fundamental, but not the only motivation. RESUMEN Describimos el desarrollo de observatorios astron´omicos desde la prehistoria hasta finales del siglo XVIII, y c´omo la evoluci´on de varios milenios ha pasado de estructuras elementales a edificios albergando telescopios y c´upulas en los cuales la ciencia era fundamental, pero no la ´unica motivaci´on. Key Words: history and philosophy of astronomy — telescopes 1. INTRODUCTION Dreyer (1953), Hall (1983), Magli (2009), Sayili Astronomy originates from the primitive rela- (1960) and Thurston (1994) have been consulted for tionship between man and nature. Especially with the present review. its most unreachable component: the sky. In antiquity, some of the stars were considered 2. STONE AGE gods and the sky was their residence. Therefore The earliest set of recordings in Prehistory to there was a strong connection between astronomy date is the Goseck Circle (Figure 1). It consists of a and religion that only began to diverge a few cen- neolithic structure located in Germany dating about turies ago. In addition to this spiritual sense, the 7000 years old. It is a solar observatory of annu- beginnings of this science point to the instrumental- lar plant, with an inner radius of 48 meters and an ization of the firmament as a system of measurement outer radius of 82. It is composed of four concen- of time periods and as a means of orientation. tric rings, being from outside to inside, the first a Beyond the numerous artistic representations of mound, the second a moat and finally two palisades. the Sun, Moon and stars that have been found, These crowns have three discontinuities aligned ra- or of the written testimonies that have lasted in dially and focused respectively towards the north, time, there is evidence of this astronomical prefer- southeast and southwest. These openings are ori- ence through the incidence of some celestial phenom- ented towards the sunrise and sunset on the winter ena in the arrangement of certain constructions or solstice. archaeological sites. Of a similar chronological period is the megalithic In any case, although certain vestiges of ancient set of Nabta Playa, in Egypt, to the south of Cairo. civilizations evidenced an outstanding impact of as- It presents a circular composition of almost thirty tronomy in its culture through its architecture or perimeter stones marking doors with larger pairs and urbanism, it will be the proto-observatories, under- containing some inner clusters. stood as places conceived exprofeso to be the ones V Workshop on Robotic Autonomous Observatories (Mazagón, Huelva, Spain, October 16-20, 2017) Although this place could accommodate some re- destined, in some way, to the study of the heavens. ligious uses associated with the nomadic cultures of Those that stand out as points of interest to know that context, an archaeoastronomical character is the way in which these people approached the study recognised. Through the study of the firmament the Editors: M. D. Caballero García, S. B. Pandey, & A. J. Castro-Tirado - DOI: http://doi.org/10.22201/ia.14052059p.2019.51.02 of this science. circle would acquire functions of calendar, marking These spaces will be where contemporary as- two of its doors an alignment with the summer sol- tronomical observatories have their deepest roots. stice, and point of orientation in the desert. 1Instituto de Astrof´ısica de Andaluc´ıa (IAA-CSIC), Granada, Spain. 3. PROTOHISTORY 2Departamento de Ingenier´ıa de Sistemas y Autom´atica (Unidad Asociada al CSIC), Escuela de Ingenier´ıa Industrial, Sometime later, around 3000 BC Carahunge (also Universidad de M´alaga, M´alaga, Spain. known as Zorats Karer) can be situated. Located in 1 2 CASTRO TIRADO Fig. 2. Stonehenge. Fig. 1. Reconstruction of Goseck Circle. Armenia is this composition of more than one hun- The outer perimeter was delimited by a series of ver- dred stones arranged as menhirs of between one and tical blocks that supported lintels forming a closed three meters height with plant in form of oval ring. ring. Concentrically there was a circumference of The main singularity of this formation is that smaller monoliths that surrounded five pairs of large part of the rocks that compose it have a perforation stone blocks forming doors. The interior was occu- of between 5 and 20 cm diameter that crosses them pied by a set of menhirs. and that, according to what has been seen, point The alignments that occur in Stonehenge through towards significant events as the Sun at dawn and its gates during the sunrise and sunset during the dusk in the winter solstice. summer and winter solstices are obviously inten- Between 3600 and 2500 BC the megalithic tem- tional. This shows a certain degree of astronomi- ple of Mnajdra is erected, located on the south coast cal knowledge on the part of its constructors and of Malta. The vestiges that have survived until the denotes its function as observatory and calendar be- present day consist of three constructions of lime- yond other ritual or religious uses associated to these stone, that although they are not connected they facts. are grouped around a place between the remains of In any case, the astronomical functions of these a major complex but scarcely conserved. structures were quite limited. It is even possible that Beyond the discovery of signs that point to a re- the scientifically valuable activity can be limited to ligious character of the constructions, there are ar- the determination of the positions and orientation of guments that support the idea that identifies the the elements of the set. A study of the sky is re- southernmost temple as an observatory dedicated quired with systematic and intentional observations to the study of heaven and time. In particular its compared to these reference points that allow to es- orientation and configuration cause the sunrise of tablish a pattern from which to erect these construc- the summer and winter solstices passing through the tions. Once the device is ’calibrated’, using it is not main door and illuminate the megaliths located re- much more scientific than looking at the hands of a spectively left and right of the door. Also, at the watch. spring and autumn equinoxes, at dawn, the Sun en- 4. ANCIENT HISTORY V Workshop on Robotic Autonomous Observatories (Mazagón, Huelva, Spain, October 16-20, 2017) ters through the same door crossing the main nave orthogonally to the altar. The above mentioned cases allude to primitive The famous Stonehenge (Figure 2) is located in civilizations, with a low degree of technification and England, west of London, and its construction ex- even, frequently, with nomadic habits. This makes Editors: M. D. Caballero García, S. B. Pandey, & A. J. Castro-Tirado - DOI: http://doi.org/10.22201/ia.14052059p.2019.51.02 tends from 3100 to 1600 BC. Although an important simple the identification of their constructions. megalithic structure remains, a considerable part of However, the evolution towards more complex the initial composition has been lost. However, the cultures makes this difficult. This is so because the remains are sufficient so that the studies have been more advanced civilizations tend to create settle- able to define its original configuration. ments with multiple buildings in which it is unnec- It displays a circular plant of about 30 meters essary to reach the degree of specialization needed of diameter conformed by concentric constructions. for the function of observation as such. Since no ASTRONOMICAL OBSERVATORIES 3 Fig. 4. The Sun through the Pantheon. Fig. 3. The Pnyx at Athens. Regarding the Roman influence, although its rel- evance is smaller than the one inherited from other scientific instruments had been developed that re- civilizations, it is possible to stand out points of ce- quired demanding conditions, this recognition of the lestial investigation the Field of Mars of Rome, where sky could be carried out with the naked eye in almost the solar clock of Augustus was located, and the any construction or even in the vicinity of these open Pantheon, constructed during the second century, in skies. which, thanks to its oculus, solar studies were car- In the case of Mesopotamian astronomy, al- ried out. Its design and orientation make it possible though there is certainty of its development, there for a beam of light during the zenith of the equinox is little knowledge about the instruments used for to cross the building from the oculus to the portico, the study of the sky, leaving only a few items in mu- through a lattice-work over the main door, indicat- seums. So it is very difficult to clarify where the ob- ing that event (Figure 4). servatories of this civilization were located, although it is possible that these were incorporated as suitable 5. POST-CLASSICAL HISTORY spaces for that objective in other buildings. Or even At the other end of the world is Cheomseong- that certain rooms or areas, such as the terraces of dae, in South Korea. It is the oldest astronomical the ziggurats, were used in a timely manner for this construction of the Asian continent. It consists of a purpose. bottle like shape tower, about ten meters high and Precisely, according to some writers of the antiq- about six meters diameter, composed of granite ma- uity such as Herodoto, Plinio or Diodoro, the Tower sonry (Figure 5).