A team of astronomers from the UK is exploring what might be described as the first astronomical observing tool, potentially used by humans around 4,000 BC.
The view towards the east from the Carregal do Sal megalithic cluster, at dawn at the end of April around 4,000 BC, as reconstructed using a Digital Elevation Model and Stellarium. Aldebaran, the last star to rise before the Sun, is rising directly above Serra da Estrela, the ‘mountain range of the star.’ Image credit: Fabio Silva.
The team, led by Dr. Fabio Silva of the University of Wales Trinity Saint David, suggests that the long, narrow entrance passages to Iberian megalithic tombs from the Middle Neolithic period may have enhanced what early human cultures could see in the night sky.
The team’s idea is to investigate how a simple aperture, for example an opening or doorway, affects the observation of slightly fainter stars.
The scientists focus their study on passage graves, which are a type of megalithic tomb composed of a chamber of large interlocking stones and a long narrow entrance.
These spaces are thought to have been sacred, and the sites may have been used for rites of passage, where the initiate would spend the night inside the tomb, with no natural light apart from that shining down the narrow entrance lined with the remains of the tribe’s ancestors.
These structures could therefore have been the first astronomical tools to support the watching of the skies, millennia before telescopes were invented.
“It is quite a surprise that no one has thoroughly investigated how for example the color of the night sky impacts on what can be seen with the naked eye,” said co-author Kieran Simcox, from Nottingham Trent University.
The team targets how the human eye, without the aid of any telescopic device, can see stars given sky brightness and color.
Photographs of the megalithic cluster of Carregal do Sal: (a) Dolmen da Orca, a typical dolmenic structure in western Iberia; (b) view of the passage and entrance while standing within the dolmens’ chamber: the ‘window of visibility;’ (c) Orca de Santo Tisco, a dolmen with a much smaller passage or corridor. Image credit: Fabio Silva.
The scientists intend to apply these ideas to the case of passage graves, such as the 6,000 year old Seven-Stone Antas in Portugal and Spain.
“The orientations of the tombs may be in alignment with Aldebaran, the brightest star in the constellation of Taurus,” Dr. Silva said.
“To accurately time the first appearance of this star in the season, it is vital to be able to detect stars during twilight.”
“The first sighting in the year of a star after its long absence from the night sky might have been used as a seasonal marker, and could indicate for example the start of a migration to summer grazing grounds,” the astronomers said.
“The timing of this could have been seen as secret knowledge or foresight, only obtained after a night spent in contact with the ancestors in the depths of a passage grave, since the star may not have been observable from outside.”
However, the astronomers suggest it could actually have been the result of the ability of the human eye to spot stars in such twilight conditions, given the small entrance passages of the tombs.
Dr. Silva and his colleagues presented their results today at the National Astronomy Meeting 2016 in Nottingham, UK.
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Fabio Silva et al. Arising and Laying Hidden Stars: their celestial dynamics and role in Neolithic Iberian Cosmology. NAM 2016
