Egyptian Astronomy: An Introduction to Ancient Celestial Knowledge
Explore the fascinating blend of science and mysticism in ancient Egyptian astronomy, from their celestial deities to the solar calendar that influenced the Western world.
The study of astronomy in ancient Egypt shares similarities with other early civilizations, blending scientific observations with mystical beliefs.
In the Egyptian worldview, the sky was personified by Nut, a goddess depicted as a woman whose body enveloped the entire firmament. Geb, representing the Earth, served as her foundation, with the four cardinal points marking where Nut's body touched the ground. Through Nut, the sun god Amón-Ra journeyed across the celestial Nile in his boat.
Despite having a less advanced astronomical development compared to Babylon, it is notable that structures such as the Temple of Amón-Ra in Karnak, built around 3,700 BCE, were oriented to align with the sunrise on the summer solstice.
Similar alignments can be observed in the construction of the great pyramids, dating back to around 3,000 BCE.
The Egyptian calendar, like those of many ancient cultures, evolved over time. Initially, around 3,000 BCE, it was based on lunar cycles, but by 2,000 BCE, the solar cycle became predominant. The Egyptian year consisted of 365.25 days, divided into 12 months of 30 days each, plus an additional five days known as Epagómenos.
This calendar was segmented into three seasons: Inundation, Planting, and Harvest.
Egyptians developed three primary instruments for astronomical observation: the sundial, the water clock (Clepsydra), and the Merkhet, a type of astrolabe used to determine the positions of stars.
They meticulously tracked the passage of time by observing the stars. The Egyptians recognized 43 constellations and organized the sky into 36 decans, each lasting 40 minutes. This system enabled them to refine their timekeeping. The 18 nocturnal decans multiplied by the 40 minutes each equated to the 12 hours we recognize today.
By 2,700 BCE, they had adjusted their calendar to align with the heliacal rising of the star Sirius (Sotkis) from the constellation Canis Major.
This led the astronomer-priests to calculate a cycle in which the same stellar conditions and seasonal changes would recur, known as the Great Cycle of Sotkis or the Great Year, lasting 1,461 solar years.
Evidence from around 1,650 BCE, such as the Rhind Mathematical Papyrus, showcases the arithmetic and geometric advancements of the Egyptians.
The five observable planets, along with the Sun and Moon, constituted the seven celestial bodies that governed each day of the week.
Mystical beliefs and the significance of the Nile permeated all aspects of Egyptian life. Notably, the tombs and pyramids of pharaohs were constructed on the west bank of the Nile, while temples were built on the east bank.
Over thirty dynasties and more than 400 pharaohs ruled Egypt prior to Roman domination. One of their lasting contributions to astronomy is the solar calendar, which was transmitted to the West through Julius Caesar's conquests.
For the Egyptians, the sky was imbued with mythological and religious significance. The twelve stars used to divide the night into hours were associated with the twelve guardians of the sky, who accompanied deceased pharaohs on their nocturnal journey with Ra. Notably, constellations did not hold significant roles in their astronomical practices.
The oldest known representation of the starry sky was discovered on the lower tablet of a sarcophagus from Asiut, dating back to Egypt's First Intermediate Period.
