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…