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Ancient Astronomers


Astronomy is perhaps one of humankind’s oldest sciences, playing a role in the religious and cultural development of all the great civilizations of the ancient world. In those far-off times, astronomy and the development of agriculture were inextricably linked. Planters and farmers relied on astronomers to predict the seasons for planting and harvesting.

"After the mastery of fire, the greatest economic advances known to humankind came from the deliberate cultivation of cereal plants and the selection, taming, and breeding of animals... Successful farming, however, is dependent on water. Settlements distant from existing waterways therefore required the ability to predict with some degree of accuracy the patterns of local rainfall, seasonal patterns that occur at approximately the same time each year. After years of observing the heavenly bodies - the changes in their appearance, their height in the sky, the light and shadows they cast, and their rising or setting positions as related to fixed objects - various methods were devised to make these predictions." 1

From around 3500 B.C.E, the ancient Sumerians started to record their knowledge on clay tablets using cuneiform writing. From their writings and seals, we know that astronomy was important to them, and that they used the rising and setting of the Pleiades to mark the beginning and end of the agricultural year. The Sumerians were also the first people to divide space and time into units of six. From them, and through the other Mesopotamian civilizations, we have inherited the twelve zodical constellations: Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, Pisces, and Aries.

By 2782 B.C.E the ancient Egyptians had in place an official calendar of 365 days. They divided their year into twelve months, in turn subdivided into three 'weeks' of 10 days each. To the resulting total of 360 days they added five sacred ones. And from their astronomical observations, the Egyptians knew that the inundation of the Nile would begin within hours of Sirius reappearing in the night sky, in late July. This event was of such elemental importance to them that they regarded it as the beginning of a new year. 2

In prehistoric Britain, construction of the site now known as Stonehenge began in around 3100 B.C.E, and continued in stages until about 1600 B.C.E. Since the people who built Stonehenge left no written records, today we can only guess as to what its purpose was.


El Caracol

El Caracol Temple dated to between 600 and 850 C.E.

However, from studying the arrangement of the stones, it is clear to archaeologists that the builders of Stonehenge were influenced by astronomy, and that perhaps one of the uses of the site was to mark astronomical events, such as equinoxes and solstices.


In the Americas, the Maya were keen astronomers who mapped the paths of heavenly objects, including the Moon and Venus. In the building of their temples, they alluded to their knowledge of astronomy by aligning doorways and windows precisely to celestial events.

At El Caracol, the temple shown above, located in Mexico’s Yucatan Peninsula, there are openings which are lined up with the Moon's northern-most and southern-most setting points on the horizon. At the vernal (or spring) equinox, the window in its western wall aligns with the setting sun. From its observation points, the orbit of Venus can be followed 236 days a year in the morning, and 250 days per year at night.

However, although the temple’s rounded tower looks similar in shape to modern observatories, there is no archaeological evidence to suggest that it was used exclusively as an observatory. Rather, such round towers were often dedicated to the quetzal-feathered serpent god Kukulcan (or Gukumatz) who, according to Mayan myth, gave mankind the arts of civilization, including law, agriculture, fishing and medicine.

With their astronomical and mathematical skills, the ancient Maya were able to conceive complex methods for reckoning the passage of time, including a sacred calendar of 260 days, as well as a secular calendar of 365 days, based on the solar cycle.

Notes and related links:

  1. Sticks, Stones, & Shadows: Building The Egyptian Pyramids by Martin Isler
  2. The Pyramid Builder: Cheops, The Man Behind the Great Pyramid by Christine El Mahdy
  3. Astronomy Set In Standing Stone
  4. Portal to the Heritage of Astronomy
  5. The 2,000 Year-Old Computer: Decoding The Antikythera Mechanism [BBC]
  6. The Venus Table: Ancient Mayan Astronomy