Transcript Maya .(English)

ARCHAEOASTRONOMY
Thursday meeting – January 25 2007
Roberta Zanin
1
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
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the heaven. (Fabian, 2001)
1
Outline
• Astroarchaeonomy
two examples of building alignments:
1. Stonehenge
2. 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
3
2
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 horseshoeshaped arrangement of Trilithons
and four great stones as stations.
4
3
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 horseshoeshaped arrangement of Trilithons
and four great stones as stations.
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3
Stonehenge alignments
Heel Stone
6
4
The Caracol: Maya observatory
(Chichén Itzá, Yucatan-Mexico)
viewing
shaft
A.Aveni, Tropical Astronomy, Science 1981
These windows align with some
astronomical sightlines:
Venus rising at its northernmost
southernmost positions,
as well as the equinox sunset
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5
The Caracol: Maya observatory
(Chichén Itzá, Yucatan-Mexico)
These windows align with some
astronomical sightlines:
viewing
shaft
Venus rising at its northernmost
southernmost positions,
as well as the equinox sunset
Since Venus’s 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.
A.Aveni, Tropical Astronomy, Science 1981
8
5
The Caracol: Maya observatory
(Chichén Itzá, Yucatan-Mexico)
N. Strobel, Astronomy without a telescope
These windows align with some
astronomical sightlines:
Venus rising at its northernmost
southernmost positions,
as well as the equinox sunset
Since Venus’s 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.
9
5
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
10
5
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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6
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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6
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
13
6
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
3. the west plane faces
the zenith passage with a
precision within 1º 14
6
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.
Modern
(day)
Maya
(day)
Lunar
period
29.53059
29.53086
Solar
period
365.2420
365.2466
Mars
period
779.94
780
Venus
period
583.93
583.9203
Venus had been recognized as
morning and evening star!
Greek astronomers had recorded
Venus as two different stars. 15
9
Venus: morning and evening star
Superior
conjunction
Venus is an inferior planet:
it has phases as the Moon
Dresden
Codex
(day)
Modern
(day)
Morning star
(after heliacal rise)
236
263
Invisible
(superior conjunction)
90
50
Evening star
250
263
Invisible
(inferior conjunction)
8
8
Total
584
584
Skywatchers
Inferior
conjunction
Heliacal rise=Sun 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.
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8
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.
Modern
(day)
Maya
(day)
Lunar
period
29.53059
29.53086
Solar
period
365.2420
365.2466
Mars
period
779.94
780
Venus
period
583.93
583.9203
It seems incredible!
But
we have forgotten what can be
achieve by careful naked
eye observation using simple
instruments.
17
7
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.
no thickness gnomon
At the beginning, gnomons were used as sundials
(by dividing the plate into equal intervals),
as well as to establish cardinal directions
(south=the 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)
Maya used the zenith passage which are characterized
by shadowless moments as reference day.
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11
The zenith-horizon system
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.
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.
Tropics are the maximum latitudes at which the Sun can be
observed at zenith: ZENITH PASSAGES.
N. Strobel, Astronomy without a telescope
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10
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 Sun’s 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)
20
12
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
Moon’s orbit precesses
intersection of the Moon’s
orbit with the ecliptic
twice a year
at different dates
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13
Stonehenge: an eclipse predictor
only when, not where
+
Full moon
4
markers
G. Hawkins, The Stonehenge Decoded, Nature 1963
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14
Stonehenge: an eclipse predictor
only when, not where
56 a perfect number!
+
Full moon
56/2=28
Moon’s orbit is 27.322days
Moon marker – twice a day
and skip one each cycle
4
markers
G. Hawkins, The Stonehenge Decoded, Nature 1963
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14
Stonehenge: an eclipse predictor
only when, not where
56 a perfect number!
+
56/2=28
Full moon
Moon’s orbit is 27.322days
Moon marker – twice a day
and skip one each cycle
4
markers
56*6.5=364
Earth’s 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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14
Stonehenge: an eclipse predictor
only when, not where
56 a perfect number!
+
56/2=28
Full moon
Moon’s orbit is 27.322days
Moon marker – twice a day
and skip one each cycle
4
markers
56*6.5=364
Earth’s orbit is 365.25 days
Sun marker – every 6.5 days
and during solstices half more
56/3=18.66
Orbit of Nodes is 18.61 y
Node markers – every four months
G. Hawkins, The Stonehenge Decoded, Nature 1963
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14
Stonehenge: an eclipse predictor
only when, not where
+
Full moon
4
markers
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
G. Hawkins, The Stonehenge Decoded, Nature 1963
26
14
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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