Ancient Egyptian Astronomy. Some Historical Background.

Ancient Egyptian

Astronomy

Some Historical Background

What Constituted Ancient Egypt

Timeline• 7500 BC: Earliest permanent settlements.• 3100 BC: Early Dynastic, Egypt unified• 2700-2150 BC: Old Kingdom• 200-1750 BC: Middle Kingdom• 1550-1050 BC: New Kingdom• 1050-332 BC: 3rd Intermediate/Late Period• 332-30 BC: Ptolemaic Period• 30 BC: Roman Conquest

Early Dynastic Period

• Egypt grew out of a loose collection of farming villages, each with various traditions.

• Villages formed alliances, creating kingdoms.• Egypt was finally unified around 3100 B.C.• The Early Dynastic Period was a time of internal

consolidation. Other than for trading, there were no international aspirations.

• Even in this early period, the features of pharonic were established.

• The first stone buildings were constructed.

Old Kingdom• The pyramid age. • Pharaohs considered divine. • Centralization of power in the pharaoh.• Concrete evidence of Egyptian presence beyond the

Nile Valley in Lebanon and Sinai. • Huge advances in the fields of building, technology,

writing, and art.• First funerary texts, which mention the stars.• Ended with a gradual decentralization of power that

led to complete anarchy.

Middle Kingdom• Emerged with the recentralization of power in the

pharaoh, originally a local ruler from Thebes.• Never reached the heights of the Old Kingdom.• Pyramids were still built, although now with mud brick

faced with stone.• With internal stability, Egypt expands South into Nubia

(Sudan) for trading goods, especially gold. However, Nubia is not annexed and remains more of a colony.

• Eventually, Northern Egypt is invaded by the Hyksos, who established themselves in the delta region at Avaris. Egyptians retained the South and were based in Thebes.

New Kingdom• A reunified Egypt builds an true empire and annexes

many conquered peoples.• No more pyramids, building now concentrates on temples

and tombs in the Valley of the Kings.• Most of these gains are lost under the religious

reformer/heretic pharaoh Akhenaten. • Successors to Akhenaten regain what was lost. Egypt

peaks in influence under Ramesses the Great.• After Ramesses’ death, Egypt goes into a slow decline,

with high priests eventually rivaling the pharaoh in power. Egypt splits internally, greatly weakening the country.

Later Egypt• Egypt is no longer the dominant power in the region. • Characterized by brief resurgences and periods of foreign

domination.• Last native pharaoh, Nectanebo II flees into exile in 343

BC after losing a major battle to the Persians.• Alexander the Great conquers Egypt in 332 BC.

Descendants of his general, Ptolemy, establish a line of Greek pharaohs, who increasingly come under the influence of Rome.

• With the Roman conquest in 30 BC, Egypt ceases to be a sovereign nation.

Astronomy’s Practical Beginnings

Nilometers• Egyptians were farmers.• To anticipate the Nile,

which flooded annually, Egyptians needed a calendar.

• Measuring flood depth was helpful for anticipating the growing season.

• With just the right amount of water, the flood would deposit a thick layer of nutrient- rich Nile mud.

Telling Time of Day• 24 hour days. Sundials during daylight• For night, divided the path along the ecliptic into 36

groups of stars called decans, which rise about 40 minutes apart.

• Called decans because first helical risings of each decan are about 10 days apart.

• The Egyptian hours were lengthened/shortened so that day/night would always be 12 hours.

• This was done for religious reasons so that rituals could be done by the hour.

The Egyptian Calendar• 365 day year.• New year started with the first helical rising of Sirius,

more importance of Sirius later. • 10 day weeks, 36 weeks in a year. • 12 lunar months of 30 days. • 5 extra days to make lunar and solar calendars align.• 3 seasons: Inundation: Jul.-Oct. (Nile flooded),

Sowing : Nov.-Feb (planting crops), Dry: Mar.-Jun. (harvesting).

• It is believed that the monuments were built during inundation, when the fields were flooded.

Calendar Problems• The approximate ¼ day left over was discounted. • No leap years.• After every four years, the calendar would be about a

day off.• In 100 years, the calendar would be about 25 days

off. A complete cycle was 1460 years.• This 1460 year cycle was called a “Sothic Cycle,”

after Sirius, “Sothis” in Greek. • In time, the calendar alone was useless for predicting

the Nile’s movements.

Not to Fear…• Sirius, visually the brightest star, could also be used

to predict the Nile. • Shortly after the helical rising of Sirius, just ahead of

the Sun, the Nile flooded. Because of precession, this is no longer accurate.

• As a result, Sirius became important, eventually becoming associated with the goddess Isis, goddess of among other things, rebirth. This becomes important later.

• The Nile flood leads to rebirth of the land.

The Dog Days of Summer• We have the Egyptians to thank for this

phrase.• Every summer, Sirius becomes invisible

when it moves into the glare of the Sun.• Thinking the bright Dog Star lent it’s heat

to the sun, the Egyptians coined the term “Dog Days of Summer” to describe the hottest period of the year.

Astronomy in Architecture

Pyramids• Tombs started off simple

and became increasingly complex, culminating in the pyramids.

• The earliest pyramids were stepped, creating a staircase to heaven.

• The Step Pyramid is 200 feet tall and almost 5000 years old. It also has 3 ½ miles of tunnels underneath.

Giza, Last Wonder of the Ancient World

The Giza Pyramids• Oldest and only surviving member of the 7

Wonders of the Ancient World.

• The Great Pyramid is almost 500 feet tall, has a base of 13 acres, contains about 2.3 million blocks weighing an average of 2.5 tons each.

• More interesting are the architectural features, which may have astronomical significance.

• The other pyramids are “only” 450 and 215 feet tall.

Inside the Great Pyramid

More Mythology• The Southern facing “air shafts” point to

Sirius, associated with Isis and to Orion, associated with the god of death/rebirth, Osiris.

• The Northern shafts point to circumpolar stars Alpha Draco and Kochab, more on this later.

• The circumpolar stars were called “The Immortals” because they never set.

• Sirius and Orion equate to rebirth.

Orion’s Belt On Earth?

Not Exactly

More Pyramid Astronomy• All pyramids are orientated to the four cardinal

directions.• The Great Pyramid is closest, being less than 1/20th of

a degree (3 arc minutes) off of true North. • Perhaps done by looking at the Immortals.• There was no North Star, the Celestial Pole was a

point directly between Mizar and Kochab. • When these stars were vertical of each other, true

North was indicated.

Were the Pyramids Modeled on the Zodiacal Light?

Later Pyramids• Stars remained important to

a lesser degree.• Ancient texts still mention

the king’s spirit stellar journey.

• However, architects would not take the trouble to construct shafts pointing at the stars after the Great Pyramid.

• Quality of construction declined.

The pyramid on the right is actually about 1000 years newer.

The Valley of the Kings• By this time, the sun

was the central symbol of rebirth.

• Although less important than before, stars were still depicted in tombs.

• Astronomical ceilings often depicted constellations and the hours of the day as seen by Egyptians.

Astronomical Ceiling

Obelisks, Stone Sun Pillars?

• Tall pillars carved from a single stone, often capped with Gold and dedicated to the sun god, Ra.

• Coincidently, as Ra rose in importance, stellar associations lessened.

• This transition started taking place shortly after completion of the Great Pyramid

Just For Scale

Temple of Abu Simbel

Celestial Alignment• Built by Ramesses II, known as “The Great,”

this temple not only has statues 70 feet tall in the front, but extends almost 200 feet into the mountain.

• Despite its vast size, the temple is aligned so that on the 20th of October and February, the sun shines into the inner sanctuary.

• According to legend, one of these dates is Ramesses’ birth or coronation day.

An Astronomical Achievement

• At a cost of $80 million at the time, the two temples at Abu Simbel were dismantled from 1964-8, moved up 200 and back 600 feet to escape the rising Nile, caused by construction of the Aswan High Dam.

And the Alignment Survives!

At A Glance• Like many other ancient societies, the

Egyptians first became interested in astronomy for practical purposes.

• As civilization progressed, people began to attach deeper meanings to objects in the night sky.

• More than anything else, architecture embodies the astronomical knowledge of Ancient Egypt.

Warning:When reading about Ancient Egypt, especially works of a speculative nature, be on the

lookout for…

…Bologna…

…Cheesy Theories Filled With Holes…

…and Loony Toons

Getting Serious• There is a lot of outlandish, recklessly speculative

material on Ancient Egypt.

• Often, authors take a quite reasonable theory or genuine unknown and transform it into something completely unrecognizable.

• These books make a good read, but shouldn’t be taken too seriously.

• Speculative authors often completely ignore any evidence that contradicts their theories.

Pyramids have been…• Encoded ancient mathematics.• Repositories for lost, ancient knowledge. • The Biblical grain storehouses of Joseph.• Prophecies in stone. • Built by survivors from Atlantis. • Built by aliens.• Power plants.• Weapons of mass destruction (not kidding!)

Yeah Right…