International Year of Astronomy - Archaeoastronomy and Ancient Astronomy
Archaeoastronomy and Ancient Astronomy
According to Clive Ruggles, emeritus professor at the University of Leicester in the United Kingdom, archaeoastronomy is “the study of beliefs and practices relating to the sky in the past, especially in prehistory.” Archaeoastronomy incorporates the study of the astronomical practices, celestial lore, mythologies, religions and world-views of all ancient cultures. It is often described as the “anthropology of astronomy”, to distinguish it from the “history of astronomy.”
Agricultural societies often related the appearance and movement of celestial objects to meteorological and seasonal phenomena. The ability to predict the motion of the heavens and produce sufficiently accurate calendars was quite useful for harvest and subsistence in general.
In addition, ancient cultures often identified celestial objects with gods and the supernatural. It is generally believed that the first astronomers were priests, and that planetary positions, eclipses, and other celestial phenomena were related to important events in the life of the community or individuals—hence astronomy's ancient connection to what is now called astrology.
Megalithic Site in Nabta Playa, Egypt
One of the world’s earliest archaeoastronomical devices is this megalithic site, located in Nabta Playa, southern Egypt. It was built in the 5th millennium BCE, about a thousand years older but comparable in purpose to Stonehenge. Research suggests that this “calendar circle” may have been used to mark the summer solstice.
The Antikythera mechanism is an ancient mechanical calculator used to calculate, by means of numerous gears, the position of celestial objects. It was found in 1901 near the Greek island of Antikythera and researches believe it was built about 150–100 BCE. Clockwork mechanisms of similar complexity did not reappear until a thousand years later.
Ancient Chinese Astronomy
The ancient Chinese had a long tradition of accurate astronomical observations that began as early as the 4th century BCE. They invented numerous devices, such as armillary spheres and sundials, to measure stellar positions (a field now known as astrometry). Several of these monumental instruments are still on display at the top of the Beijing Ancient Observatory, built in the 15th century. One of the oldest and most complete records of stellar positions is the Dunhuang Star Map made approximately in the year 700 CE during the Tang Dynasty. The whole set of star maps contained about 1,300 stars.
El Caracol in Chichén Itzá, Mexico
El Caracol or “the observatory” in the Mayan site of Chichén Itzá, Mexico, was used to observe the motion of the planet Venus, which had a special significance for the Maya culture. The building is dated between 600 – 850 CE, and was remodeled from 800 CE to 1200 CE. To modern eyes, the rounded dome of El Caracol looks like it could house a telescope, but it is actually the decayed remains of what was a cylindrical structure.
Chaco Canyon, New Mexico
The Ancient Pueblo Peoples, also known as Anasazi, observed and recorded celestial phenomena. Two well-known archaeoastronomical sites are found in Chaco Canyon, New Mexico. The Sun Dagger in Fajada Butte is a celestial calendar that marks the equinoxes and solstices by projecting sunlight on a spiral petroglyph. The 1054 supernova petrograph is thought to record the sighting of the supernova that originated the Crab Nebula in the year 1054 CE (also recorded by the Chinese), as well as the visit of Halley’s Comet a few years later.
An astrolabe is a mechanical device used to measure the position of celestial objects. In the medieval Islamic world, astrolabes were used for finding the Qibla (the direction that should be faced for prayers), as well as for astronomical studies, navigation, surveying, and timekeeping.
Gurkhani Zij Observatory, Uzbekistan
Sextants, along with quadrants and octants, were used for centuries to measure angular positions of celestial objects. One of the largest sextants ever built was the giant Fakhri sextant, with a radius of about 36 meters (118 ft), in the Gurkhani Zij observatory in Samarkand, Uzbekistan. The observatory complex in Samarkand was built in the 15th century by sultan, astronomer, and mathematician Mīrzā Mohammad Tāregh bin Shāhrokh, commonly known as Ulugh Beg.