What did they know?

Egyptian Astronomy
What did they know?
Helena Uthas, Columbia University (2013)
From Monday - How do the Stars Move?
Ancient Egypt
The 3 stages
1) Astronomical phenomena are viewed only as the actions,
moods, and warnings of the gods.
2) Astronomy is used for terrestrial purposes (agriculture or
navigation).
3) The final step is to study astronomy for the sake of gaining
knowledge.
Ancient Egypt had 31 dynasties!
The First Dynasty: 3100 – 2890 BC had 9 rulers.
The Thirty-first Dynasty: 343 - 332 BC.
In 332 BC Alexander the Great took Egypt without a fight.
King Ptolemy I, took over after Alexander's death.
Romans conquered the area 30 BC - Huge influences on Astronomy.
Nabta Playa - 5th Millennium BC
Calendar?
Was once a large basin in the Nubian Desert.
Nabta Playa - aligned with the stars?
Thomas G. Brophy: south line of three stones - Orion’s Belt, other three stones
inside the calendar circle - shoulders and head stars of Orion
Position of stones refers to 2 dates, 1st ~ 4800 BC and 2nd at precessional
opposition.
Showing motion of the sky over a precession cycle?
What is precession?
Nabta Playa - aligned with the stars?
Claim:
Representation of the Milky Way as it was in 17,500 BC
and maps of Orion at 16,500 BC!
Criticism of Thomas G. Brophy: “The Origin Map”
Egyptian Astronomy
Many Egyptian buildings were built with an astronomical
orientation. The temples and pyramids were constructed
in relation to the stars, zodiac, and constellations.
As early as 4000 BC, temples were built so that sunlight
entered a room at only one precise time of the year.
Egyptian Astronomers
Priests: recognized that the flooding (of the Nile) occurred
at the summer solstice - when Sirius rose before the Sun.
They could predict annual flooding - Powerful!
Egyptian Calendar
Ceremonial calendar
365 days, 12 months of 30 days + 5 ceremonial days (Epagomenal
days). 10-day week (3 weeks/month), 12 hr day, 12 hr night (the
hour varied in length according to the season, later the 24 hours
became equinoctial).
Lost one day every four years! - no correction.
Calendar based on Sirius
365 days + an extra quarter day
running concurrently... coincided every 1461 years.
- time of great celebration and the start of a new age!
Problem with ancient calendars
Difference in sidereal and solar time!
Later on, Alexandrian based philosopher
Ptolemy (AD 90 - AD 168), divided each of the
24 hours into 60 minutes.
Time- keeping - Sundials
~ 3500 BC
Time-keeping @ night:
plumb-lines "merkhets"
600 BC: aligned with Polaris creating a
north-south meridian.
What is the meridian?
Written language - hieroglyphics
Papyrus was first manufactured in Egypt and Southern
Sudan as far back as the 4th millennium BC.
Star Constellations
System of constellations, independent from the
Greeks and the Mesopotamians.
Osiris, the sun-god
of rebirth and afterlife
Sky goddess Nut - The Milky Way
The Sun gods
A rising morning Sun was Horus
Evening - Atum
(lifted kings from their tombs to the stars)
The noon Sun was Ra (strength)
Osiris, god of death and rebirth.
Red sunset: blood from the Sun God as he died.
Night was associated with death and day with life
or rebirth. - immortality.
Egyptian Cosmology/Mythology
Annual cycle of the flooding of the Nile.
The rising and setting of the sun god Ra every day.
The cycle of the birth and death of the pharaoh.
There were several creation myths, each with basically
the same cast of characters, but yet each subtly different
in its own way.
For the early cultures:
Cosmology were Mythology
(Readings)
Star Constellations - 36 Decans
First appeared in the 10th Dynasty (2100 BCE) on coffin lids
(were displayed on tombs and temples).
Could be used to tell the time (Sidereal clock).
Each decan rose above the dawn horizon for ten days every
year (36 X 10 = 360 days), + plus 5 added days to make up to
365 days.
Egyptian year being 6 hours too short - over 40 years the
calendar would be in error of 10 days.
Decans were connected with various diseases and with the
timing for the engraving of talismans for curing them.
The temple to Hathor at Denderah
From the 18th dynasty (ca 1500 BC). Decans in the
ceiling.
The temple to Hathor at Denderah
50 BC of the Egyptian Roman period - Zodiac.
Whilst Egyptian civilization declined, it
became absorbed by the Greek and Roman
cultures.
The city of Alexandria became one of the
most important centers of astronomy, the
birthplace of the great Ptolemy.
Egyptian contributions to astronomy:
the 24-hour division of the day!
The Great Pyramids of Giza
Thought to have been constructed to house the remains
of the deceased Pharaohs (4th dynasty - 2500 BC).
1st: Khufu (Cheops).
2nd: Khufu's son, Khafra (Chephren) - guarded by a huge sphinx.
3d: Menkaure (also known as Mycerinus).
The Great Pyramids of Giza
The Great Pyramid had taken 400,000 men 20 years to build,
working in three-month shifts 100,000 men at a time.
Alignment to true North
North-south axis is aligned to within three-sixtieths of a
degree of true north-south.
More accurate than the Meridian Building at the Greenwich
Observatory in London! (deviates from true north by ninesixtieths of a degree)
There is no evidence in ancient texts that Egyptians
used astronomical knowledge in building the pyramids.
How could they have done this?
Nature paper in 2000.
Mizar (in Ursa Majoris) and Kochab (in Ursa Minoris) revolved around the
pole on almost (but not exactly) opposite sides at the time of the
pyramids.
Giza–Orion correlation theory
•Like the pyramids, the three stars of Orion are not perfectly
aligned, the smallest of them is slightly offset to the East.
•All three are slanted in a Southwesterly direction.
•Their orientation to the Nile recreates Orion’s orientation to the
Milky Way.
Giza–Orion correlation theory
Mintaka, Alnilam, Alnitak
Robert Bauval:
Sphinx and the
three Pyramids at
Giza would align
with Orion’s Belt in
the year 12,500 BC.
from 1995
Wait...12,500 BC??
Along with Brophy's early date for Nabta Playa.
Made people go crazy!
"These extremely early dates as well as the proposition
that the nomads had contact with extra galactic aliens are
inconsistent with the archaeological record”
- University of Colorado archaeoastronomers and archaeologists.
Giza–Orion correlation theory
According to Bauval: Pyramids were largely built in
2500 BC, while the ground plan of the 3 pyramids was
physically established in 12,500 BC.
Criticized by other researchers
Giza–Orion correlation theory
If true:
Why would the Egyptians build the
pyramids according to the stars in Orion?
One argument:
Stars are gods (Orion being Osiris - sun-god
of rebirth and afterlife)
Kings would be brought to the Gods in the sky.
Correlation with golden mean and π
The surface area of the four sides would be a golden ratio
of the surface area of the base (1.618..).
Also the ratio of the Fibonacci series:
1,1,2,3,5,8,13,21,34,55,89...
The height of the semi-circle will be the radius of the
circle (which is 8/π/2).
•Perimeter is 365.24 - the amount of days in the year.
•The height x 10 to the power of 9 gives approximately the distance
from the earth to the sun.
•The perimeter divided by 2 x the height of the pyramid is equal to
pi - 3.1416.
•The weight of the pyramid x 10 to the power of 15 is equal to the
approximate weight of the earth.
•When the cross diagonals of the base are added together, the
answer is equal to the amount of time (in years) that it takes for the
earth's polar axis to go back to its original starting point ~26000
years (precession time).
•The measurements of the King's Chamber gives 2-5-3 and 3-4-5
which are basic Pythagorean triangles.
Did the Egyptians know math?
•Addition, subtraction, some division (only by 2) and
multiplication.
•Somewhat familiar with both roots and square roots
•Area of a triangle
•Right angled triangles
•No concept for zero
The Great Pyramid of Khufu from the
Fourth Dynasty was a mathematical
wonder!
Geometric precision - A near-perfect square base,
sides of 230 meters (error 20 cm), sloped upwards
at an angle of 51 deg, reached apex at 150 meters
above the desert floor.
Stonehenge - 3000 BC to 2000 BC
I. 2800 BC (Aubrey holes)
II. 2200 BC (Blustones)
III. 2100 BC (Sarsen stones)
Stonehenge - 3000 BC to 2000 BC
Stonehenge - 3000 BC to 2000 BC
Burial ground - cremated remains from 3000 BC.
50,000 cremated bones of 63 individuals buried at Stonehenge.
Construction phases spanning at least 1500 years.
It is thought that 4,000 people could have gathered at the site for the
mid-winter and mid-summer festivals (based on animal bones).
Stonehenge was produced by a culture that left no written records.
Stonehenge - 3000 BC to 2000 BC
Sir Norman Lockyer (1836 - 1920):
On summer solstice - sun rose at the
end of the main axis
(according to ~ 3000 BC).
Published in 1906.
Stonehenge - 3000 BC to 2000 BC
Gerald Hawkins (Nature 1963 and book
"Stonehenge Decoded" 1966):
He found astronomical alignments among 165
points of Stonehenge associated with the Sun
and the Moon.
Lunar eclipses could be predicted through a
system of moving stones around the circle.
Controversially, he went on to suggest that
Stonehenge was an ancient analog computer
- predicting solar and lunar eclipses.
Stonehenge - 3000 BC to 2000 BC
Fred Hoyle (famous Cambridge
cosmologist):
Solar System model with Earth at the
centre.
3 stones representing the Sun, Moon,
and one node of the Moon's orbit. The
3 stones were moved around at their
real rates relative to each other. When
the 3 markers lay close together or
almost opposite each other, eclipse
seasons took place.
Day of the eclipse was predicted!
The alignments are extremely precise, which
illustrates the high level of knowledge
possessed by the builders of Stonehenge.
What is declination and right ascension?
What would Sun’s declination be if Earth wasn’t
tilted?
Check out: http://pveducation.org/pvcdrom/properties-of-sunlight/declination-angle
Stonehenge Today
Neopagan and New Age beliefs, particularly the Neodruids (harmony and worship of nature).
My office is in Pupin 1334
Office hours: Thursdays 3-5 pm