Ancient Egyptian Astronomy – the Basis for the Pyramids

Ancient Egyptian Astronomy played a different part for that people than it does in many cultures. Their calendar was mostly defined by the yearly flooding of the Nile River. But Astronomy in ancient Egypt was still important. They recognized a number of constellations and other groups of stars. These groups of stars, called decans, were used for telling time at night.

Telling time by the stars

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Astronomy in ancient Egypt was the best way to tell the time during the night. Each group of stars rose forty minutes later each night. Observing the position of a group of stars in relation to the day of the year would tell a person what time it was. The ancient Egyptians kept astronomy tables to help them keep track of what decans to use to tell the time. The columns in these tables cover a year's worth of time in ten day intervals. They are placed in the order in which they rise. The ancient Egyptians liked everything, even their astronomy, to be very orderly.

Using Astronomy to track the year

Ancient Egyptian Astronomy was also used in the calendar, to determine when the thirteenth month should be added. The calendar had thirteen months because the twelve lunar months were not enough to make up a whole year. So, when the constellation of Sirius rose very late in the twelfth month, the thirteenth month began. This allowed the ancient Egyptians to use astronomy to accurately keep track of the years. Later on, they moved to a year of twelve thirty day months with five feast days at the end. Since this calendar was not made with reference to the stars, it soon became inaccurate and did not match the seasons.

Ancient Egyptian Astronomy and the pyramids

The stars also helped build the pyramids. Their eastern and western sides run almost due north, and their southern and norther sides run almost due west. This kind of positioning could not have been done without using astronomy to find due north and south. The ancient Egyptians were able to use an instrument called a merkhet, or indicator, to observe the rising and setting of certain stars. It was made of a narrow, horizontal piece of wood with a hole near one end. This let the astronomer look through and determine exactly where the star was.

Osiris and other gods

Astronomy played a part in ancient Egyptian religion, too. The constellation we call Orion was thought to represent Osiris, the god of death and rebirth. The Milky Way was the goddess Nut, who stretched all the way across the sky. She was the mother of Re, the sun god. Other stars represented Seshat, the goddess or writing, and the moon was Thoth, god of wisdom and learning. Most important in their mythology, though, was the horizon. It was over the horizon that the sun disappeared each day, and the sun was associated with Horus, who was thought to be incarnate in the Pharaoh. Religion was definitely very important in Ancient Egyptian Astronomy.

Ancient Egyptian accomplishments

While the ancient Egyptians didn't know all the things about astronomy that we do now, they had a good understanding of the sky. They were able to use it to help tell time, in building their monuments, and in their mythology. The stars have always been a source of wonder and interest to people, even as long ago as the ancient Egyptians.