ARCHAEOASTRONOMY

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ARCHAEOASTRONOMY
Thursday meeting January 25 2007 Roberta Zanin
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Archaeoastronomy the study of the practice of
astronomy using both the written and unwritten
records. It began as a meeting ground for three
established disciplines (A.Aveni-Journal of
Archaeological Research,Vol.11, No.2, 2003)

• Astroarchaeology a methodology for retrieving
• astronomical information from the study of
  alignments
• associated with ancient architecture. (Hawkins,
  1966)
• History of Astronomy it is concerned with
• acquisition of precise knowledge by ancient
  cultures.
• (Crowe and Down, 1999)
• Ethnoastronomy a branch of cultural anthropology
• that develops an understanding of cultural
  behavior
• as gleaned from indigenous perceptions of events
  in
• the heaven. (Fabian, 2001)

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Outline

• Astroarchaeonomy
• two examples of building alignments
• Stonehenge
• Chichén Iztá (Mexico), the Caracol and El
  Castillo
• as proof of the perfect astronomical knowledge of
  
• these two ancient cultures.
• History of astronomy
• how this knowledge could be obtained without any
• modern instruments
• 1. how to predict an eclipse
• 2. how to measure the cycle of celestial bodies
• Conclusions Ethnoastronomy

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Stonehenge

• Phase I (2950-2900 BC)
• a circular bank with a ditch, inside the
• bank a circle of the 56 Aubrey holes.
• An earthwork, called Avenue, along
• which the Heel Stone was located.
• Phase II (2900-2400 BC)
• Aubrey holes partially filled, wooden
• settings in the center and at the
• eastern entrance.
• Phase III (2550-1600 BC)
• a circle of Sarsens within a horseshoe-
• shaped arrangement of Trilithons
• and four great stones as stations.

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Stonehenge

• Phase I (2950-2900 BC)
• a circular bank with a ditch, inside the
• bank a circle of the 56 Aubrey holes.
• An earthwork, called Avenue, along
• which the Heel Stone was located.
• Phase II (2900-2400 BC)
• Aubrey holes partially filled, wooden
• settings in the center and at the
• eastern entrance.
• Phase III (2550-1600 BC)
• a circle of Sarsens within a horseshoe-
• shaped arrangement of Trilithons
• and four great stones as stations.

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Stonehenge alignments
Heel Stone
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The Caracol Maya observatory (Chichén Itzá,
Yucatan-Mexico)
These windows align with some astronomical
sightlines Venus rising at its northernmost
southernmost positions, as well as the equinox
sunset
viewing shaft
A.Aveni, Tropical Astronomy, Science 1981
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The Caracol Maya observatory (Chichén Itzá,
Yucatan-Mexico)
These windows align with some astronomical
sightlines Venus rising at its northernmost
southernmost positions, as well as the equinox
sunset
viewing shaft
Since Venuss orbit is tilted 4º with respect to
the ecliptic, its position shifts against the
horizon, the northernmost and the southernmost
positions correspond to the farthest northern
and southern points above the celestial equator.
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A.Aveni, Tropical Astronomy, Science 1981
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The Caracol Maya observatory (Chichén Itzá,
Yucatan-Mexico)
These windows align with some astronomical
sightlines Venus rising at its northernmost
southernmost positions, as well as the equinox
sunset
Since Venuss orbit is tilted 4º with respect to
the ecliptic, its position shifts against the
horizon, the northernmost and the southernmost
positions correspond to the farthest northern
and southern points above the celestial equator.
N. Strobel, Astronomy without a telescope
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The Caracol Maya observatory (Chichén Itzá,
Yucatan-Mexico)
Staircase almost perfect match with Venus
setting at its northernmost position
The building diagonal is aligned with winter and
summer solstices
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El Castillo Pyramid of Kukulkán (Chichén Itzá,
Yucatan-Mexico)
1. At the equinox sunsets, a play of light and
shadow creates the appearance of a snake that
gradually undulates down the stairway of the
pyramid.
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El Castillo Pyramid of Kukulkán (Chichén Itzá,
Yucatan-Mexico)
1. At the equinox sunsets, a play of light and
shadow creates the appearance of a snake that
gradually undulates down the stairway of the
pyramid.
this sinuous shadow joins with one of the
snake-head sculpture carved into the base of the
monument
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El Castillo Pyramid of Kukulkán (Chichén Itzá,
Yucatan-Mexico)
1. At the equinox sunsets, a play of light and
shadow creates the appearance of a snake that
gradually undulates down the stairway of the
pyramid.
this sinuous shadow joins with one of the
snake-head sculpture carved into the base of the
monument
2. It was used as calendar each of the 4
stairways has 91 steps 1 step on the top
365 steps
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El Castillo Pyramid of Kukulkán (Chichén Itzá,
Yucatan-Mexico)
1. At the equinox sunsets, a play of light and
shadow creates the appearance of a snake that
gradually undulates down the stairway of the
pyramid.
this sinuous shadow joins with one of the
snake-head sculpture carved into the base of the
monument
3. the west plane faces the zenith passage with
a precision within 1º
2. It was used as calendar each of the 4
stairways has 91 steps 1 step on the top
365 steps
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Maya astronomy

Maya were skilled observers of the sky they
calculated the complex motions of the Sun, the
stars and planets and recorded this information
in their codices (Dresden Codex).
From this information, they developed calendars
to Keep track of celestial movements their
solar calendar was more precise than the present
Gregorian calendar.
Venus had been recognized as morning and evening
star! Greek astronomers had recorded Venus as
two different stars.
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Venus morning and evening star
Superior conjunction
Venus is an inferior planet it has phases as the
Moon
Inferior conjunction
Heliacal riseSun and Venus rise together. After
heliacal rise, Venus rises before the sunrise
morning star. After superior conjunction, Venus
rises after the sunrise, so set after the
sunset evening star.
Skywatchers
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Maya astronomy

Maya were skilled observers of the sky they
calculated the complex motions of the Sun, the
stars and planets and recorded this information
in their codices (Dresden Codex).
From this information, they developed calendars
to keep track of celestial movements their solar
calendar was more precise than the present
Gregorian calendar.
It seems incredible! But we have forgotten what
can be achieve by careful naked eye observation
using simple instruments.
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Marking time without instruments

To determine the solstice day is rather easy only
by studying shadows at summer solstice the Sun
is at its highest point and the shadows it casts
are the shortest vice versa at winter solstice.
Gnomons, simple long sticks located on a plate,
were already used by Greek astronomers.
At the beginning, gnomons were used as
sundials (by dividing the plate into equal
intervals), as well as to establish cardinal
directions (souththe position of the shortest
shadow of a day) and as calendar (by dividing the
period between two solstices into intervals, each
of one characterized by a particular shadow
length)
no thickness gnomon
Maya used the zenith passage which are
characterized by shadowless moments as reference
day.
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The zenith-horizon system

At temperate zones, the observer views
circulatory motion. In this case it is simpler
using the celestial pole and the celestial
equator as reference lines.
The horizon functions as fundamental reference
line, together with the zenith. Here star motion
is vertical. The sun can be observed at
zenith at the equinoxes.
Tropics are the maximum latitudes at which the
Sun can be observed at zenith ZENITH PASSAGES.
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N. Strobel, Astronomy without a telescope
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Zenith Tubes
There is no evidence that gnomons were used by
Maya, but they used zenith tubes to identify
the shadowless moment. These tubes admit the
Suns image to pass vertically into a darkness
chamber

At the ruins of Xochicalco, Mexico, a 8 m long
perfect straight tube, which opens into a
roundish chamber (10 m diameter), was found. The
cross section of this tube is hexagonal with a
2.5º of FOV.
A.Aveni, Tropical Astronomy, Science (1981)
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When an eclipse occurs?
Sun-Moon angle 0º (new phase) SOLAR
ECLIPSE Sun-Moon angle 180º (full phase) LUNAR
ECLIPSE
AND Moon at the line of nodes
intersection of the Moons orbit with the
ecliptic
Moons orbit precesses
twice a year at different dates
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Stonehenge an eclipse predictoronly when, not
where

Full moon
4 markers
G. Hawkins, The Stonehenge Decoded, Nature 1963
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Stonehenge an eclipse predictoronly when, not
where
56 a perfect number! 56/228 Moons orbit is
27.322days Moon marker twice a day and skip one
each cycle

Full moon
4 markers
G. Hawkins, The Stonehenge Decoded, Nature 1963
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Stonehenge an eclipse predictoronly when, not
where
56 a perfect number! 56/228 Moons orbit is
27.322days Moon marker twice a day and skip one
each cycle

Full moon
4 markers
566.5364 Earths orbit is 365.25 days Sun
marker every 6.5 days and during solstices half
more
G. Hawkins, The Stonehenge Decoded, Nature 1963
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Stonehenge an eclipse predictoronly when, not
where
56 a perfect number! 56/228 Moons orbit is
27.322days Moon marker twice a day and skip one
each cycle

Full moon
4 markers
566.5364 Earths orbit is 365.25 days Sun
marker every 6.5 days and during solstices half
more
56/318.66 Orbit of Nodes is 18.61 y Node markers
every four months
G. Hawkins, The Stonehenge Decoded, Nature 1963
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Stonehenge an eclipse predictoronly when, not
where

Solar eclipse Moon, Sun and a node in the same
position Lunar eclipse the Sun and a node
opposite to the Moon and the other node
Full moon
4 markers
G. Hawkins, The Stonehenge Decoded, Nature 1963
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Conclusions

• Ancient astronomers were surely skilled sky
  observers
• They knew the precise cycle of many celestial
  objects, they were
• able to predict important astronomical events
  such as eclipses.
• This whole knowledge had been obtained without
  any modern
• instruments. If this appear us incredible is only
  because we are no
• more accustomed to take simple measurements.
• It is not
  necessary to invoke the help of gods
• coming from the tenth planet of
  the solar system!
• (A. Alford, Gods of the new millennium)
• Astronomical knowledge in ancient cultures was
  used for religious
• (to time rituals, to decide where to build a
  temple) and civil purposes
• (when to sow and harvest) Ethnological
  implications.
• They were not interested in accuracy!
• We should remember this difference with
• the modern science.

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THE END
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Backup Slides
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When the gnomon has a finite thickness, there
will be two dial centers and double noon lines.
The double noon lines are spaced a distance
equal to the thickness of the gnomon and this
space is known as the noon gap.
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Precession of Moon
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