Maya astronomy is the study of the Moon, planets, Milky Way, Sun, and other astronomical occurrences by the PrecolumbianMaya Civilization of Mesoamerica.
The Classic Maya in particular developed some of the most accurate pre-telescope astronomy in the world, aided by their fully developed writing system and their positional numeral system,
both of which are fully indigenous to Mesoamerica. The Classic Maya
understood many astronomical phenomena: for example, their estimate of
the length of the synodic month was more accurate than Ptolemy's, and their calculation of the length of the tropical solar year was more accurate than that of the Spanish when the latter first arrived.
European and Maya calendars
European calendar
In 46 BC Julius Caesar
decreed that the year would be made up of twelve months of
approximately 30 days each to make a year of 365 days and a leap year of
366 days. The civil year had 365.25 days. This is the Julian calendar. The solar year has 365.2422 days and by 1582 there was an appreciable discrepancy between the winter solstice and Christmas and the Vernal equinox and Easter. Pope Gregory XIII, with the help of Italian astronomer Aloysius Lilius
(Luigi Lilio), reformed this system by abolishing the days October 5
through October 14, 1582. This brought the civil and tropical years back
into line. He also missed three days every four centuries by decreeing
that centuries are only leap years if they are evenly divisible by 400.
So for example 1700, 1800, and 1900 are not leap years but 1600 and 2000
are. This is the Gregorian calendar. Astronomers use the Julian/Gregorian calendar. Dates before 46 BC are converted to the Julian calendar. This is the proleptic Julian calendar. Astronomical calculations return a year zero and years before that are negative numbers. This is astronomical dating.
There is no year zero in historical dating. In historical dating the
year 1 BC is followed by the year 1 so for example, the year -3113
(astronomical dating) is the same as 3114 BC (historical dating).
Many mayanists convert Maya calendar dates into the proleptic Gregorian calendar.
In this calendar, Julian calendar dates are revised as if the Gregorian
calendar had been in use before October 15, 1582. These dates must be
converted to astronomical dates before they can be used to study Maya
astronomy because astronomers use the Julian/Gregorian calendar.
Proleptic Gregorian dates vary substantially from astronomical dates.
For example, the mythical creation date in the Maya calendar is August
11, 3114 BC in the proleptic Gregorian calendar and September 6, -3113 astronomical.
Julian days
Astronomers describe time as a number of days and a fraction of a day since noon January 1, -4712 Greenwich Mean Time. The Julian day
starts at noon because they are interested in things that are visible
at night. The number of days and fraction of a day elapsed since this
time is a Julian day. The whole number of days elapsed since this time
is a Julian day number.
Maya calendars
There are three main Maya calendars:
The Long Count
is a count of days. There are examples of Long Counts with many places
but most of them give five places since the mythical creation date -
13.0.0.0.0.
The Tzolk'in is a 260-day calendar made up of a day from one to 13 and 20 day names.
The Haab' is a 365-day year made up of a day of zero to 19 and 18 months with five unlucky days at the end of the year.
When the Tzolk'in and Haab' are both given, the date is called a calendar round.
The same calendar round repeats every 18,980 days - approximately 52
years. The calendar round on the mythical starting date of this creation
was 4 Ahau 8 Kumk'u. When this date occurs again it is called a
calendar round completion.
A Year Bearer
is a Tzolk'in day name that occurs on the first day of the Haab'. A
number of different year bearer systems were in use in Mesoamerica.
Correlating the Maya and European calendar
The Maya and European calendars are correlated by using the Julian
day number of the starting date of the current creation — 13.0.0.0.0, 4
Ajaw, 8 Kumk'u. The Julian day number of noon on this day was 584,283.
This is the GMT correlation.
Sources of Astronomical Inscriptions
Maya Codices
At the time of the Spanish conquest the Maya had many books. These were painted on folding bark cloth.
The Spanish conquistadors and catholic priests destroyed them whenever
they found them. The most infamous example of this was the burning of a
large number of these in Maní, Yucatán by Bishop Diego de Landa in July, 1562. Only four of these codices exist today. These are the Dresden, Madrid, Paris and Grolier
codices. The Dresden Codex is an astronomical Almanac. The Madrid Codex
mainly consists of almanacs and horoscopes that were used to help Maya
priests in the performance of their ceremonies and divinatory rituals.
It also contains astronomical tables, although less than are found in
the other three surviving Maya codices. The Paris Codex contains
prophecies for tuns and katuns (see Mesoamerican Long Count calendar), and a Maya zodiac. The Grolier Codex is a Venus almanac.
Ernst Förstemann, a librarian at the Royal Public Library of Dresden, recognized that the Dresden Codex is an astronomical almanac and was able to decipher much of it in the early 20th century.
Maya Monuments
Mayan stelae
Stela E at Quiriguá, possibly the largest freestanding stone monument in the New World
The Maya erected a large number of stelae. These had a Long Count date. They also included a supplementary series.
The supplementary series included lunar data - the number of days
elapsed in the current lunation, the length of the lunation and the
number of the lunation in a series of six. Some of them included an 819-day count which may be a count of the days in a cycle associated with Jupiter. See Jupiter and Saturn below. Some other astronomical events were recorded, for example the eclipse warning on Quirigua Stela E - 9.17.0.0.0. A partial solar eclipse was visible in Mesoamerica two days later on 9.17.0.0.2 - Friday January 18, 771.
Calendric inscriptions
Many Mayan temples were inscribed with hieroglyphic texts. These contain both calendric and astronomical content.
Methods of astronomical observation
Figure from the Madrid Codex, interpreted as an astronomer
Maya astronomy was naked-eye astronomy based on the observations of the azimuths of the rising and setting of heavenly bodies. City planning and alignment was often arranged in line with astronomical paths and events.
Many wells located in Mayan ruins were also observatories of the zenithal passage of the sun.
One of the most studied sites for the topic of Mayan astronomy is the Caracol at Chichen Itza. The Caracol is an observatory aligned to follow the path of Venus through the year.
The grand staircase leading to the once cylindrical structure deviates
27.5 degrees from the alignment of the surrounding buildings to align
with the northern extreme of Venus; the northeast-southwest diagonal of
the site aligns with the sunrise of the summer solstice and the sunset
of the winter solstice.
Astronomical Observations
Solar
The Maya were aware of the solstices and equinoxes. This is demonstrated in building alignments. More important to them were zenithal passage days. In the Tropics the Sun passes directly overhead twice each year. Many known structures in Mayan temples were built to observe this. Munro S. Edmonson studied 60 mesoamerican calendars and found remarkable consistency in the calendars, except for a number of different year bearer systems. He thought that these different year bearers were based on the solar years in which they were initiated.
The Maya were aware of the fact that the 365 day Haab' differs
from the Tropical year by about .25 days per year. A number of different
intervals are given on Maya Monuments that can be used to approximate
the tropical year.
The most accurate of these is that the tropical year exceeds the length
of the 365 day Haab' by one day every 1,508 days. The occurrence of a
particular solstice on a given date in the Haab' will repeat after the
passage of 1,508 365-day Haab' years. The Haab' will lose one day every
1,508 days and it will take 1,508 Haab' years to lose one Haab' year. So
365 x 1,508 = 365.2422 x 1,507 or 1,508 Haab' years = 1,507 Tropical
years of 365.2422 days.
The Tropical Year in the Maya codices
The
solstices and equinoxes are described in many almanacs and tables in
the Maya codices. There are three seasonal tables and four related
almanacs in the Dresden Codex. There are five solar almanacs in the
Madrid Codex and possibly an almanac in the Paris codex. Many of these
can be dated to the second half of the ninth and first half of the tenth
centuries.
The Dresden Codex
The upper and lower seasonal tables (pages 61–69) unify the
Haab', the solstices and equinoxes, the eclipse cycle and the year
bearer (0 Pop). The table refers to the middle of the tenth century but
includes more than a dozen other base dates from the fourth to the
eleventh centuries.
The rainmaking almanac (pages 29b to 30b) refers to the Haab' and
the tropical year. During the year in question the summer solstice
preceded the Half Year by a few days. This confirms that the year was
either 857 of 899. It also describes a four-part rain-making ceremony
similar to Yucatecan ceremonies known from modern ethnography.
The Spliced Table (pages 31.a to 39.a) is the combination of two
separate tables. It includes rituals including those of the Uayab', the
Half Year, agricultural and meteorological matters. It contains a
reference to the Half Year, skybands, two of which contain Venus glyphs.
The table has four base dates; two in the fourth century, one in the
ninth and one in the tenth century. Three of these are also base dates
in the seasonal table.
The Burner Almanac (pages 33c to 39c) contains the stations of
the Burner cycle, a system for dividing the Tzolk'in that is known from
the colonial history of Yucatán. The almanac also refers to eclipse
seasons and stations of the tropical year. This almanac refers to a few
years before and just after 1520, when the codex may have already been
in the hands of the Spanish.
The Conjugal Almanac (pages 22c to 23c) is one of a series of
almanacs dealing with conjugal relationships between pairs of deities.
It may contain a reference to the vernal equinox.
In addition to the astronomical tables preserved in the Dresden
codex, there are illustrations of different deities and their relation
to the positions of the planets.
The Madrid Codex
Pages 10b,c - 11b, c of the Madrid Codex contain two almanacs
similar to the seasonal tables of the Dresden Codex. In the lower
almanac the Half Year of the Haab' occurred on the same day as the
summer solstice, dating this event to the year 925.
The long almanac (pages 12b to 18b) includes iconography of the
Haab, abundant rain and astronomy. The almanac contains several eclipse
glyphs, spaced at correct eclipse intervals. The eclipse and calendar
dates allow one to date the almanac to the year 924. The combination of
this almanac and the seasonal almanacs in this codex are the functional
equivalent of the two seasonal almanacs in the Dresden Codex.
Pages 58.c to 62.c are a tropical-year almanac. It is an 1820-day
almanac made up of 20 rows of 91 days each. One of the captions
associates an equinox with a glyph for Venus. This dates the almanac to a
date between 890 and 962.
The Bird Almanac (pages 26c to 27c) has an unusual structure (5 x
156 = 780 days). One of its pictures is probably a reference to the
vernal equinox. This almanac can't be dated.
The Paris Codex
The God C almanacs (pages 15a, b to 18a, b) are very incomplete
and partially effaced. It is impossible to ascertain their lengths or
dates. Two known Haab' rituals can be recognized. It's possible that the
God C almanacs are equivalent to the seasonal tables in the Dresden
Codex and the God C almanacs in the Paris Codex
The Books of Chilam Balam
The Book of Chilam Balam specifically refers to the Half Year, the solstices and equinoxes.
Building alignments
Anthony
Aveni and Horst Hartung published an extensive study of building
alignments in the Maya area. They found that most orientations occur in a
zone 8°-18° east of north with many at 14° and 25° east of north. He
believes that the 25° south of east orientations are oriented to the
position on the horizon of sunrise on the winter solstice and that the
25° north of west orientations are aligned with sunset on the summer
solstice.
Two diagonal alignments across the platform of the base Caracol
at Chichén Itzá, are aligned with the azimuth of the sunrise on the
summer solstice and an alignment perpendicular to the base of the lower
platform corresponds to the azimuth of the sunset on the summer
solstice. One of the windows in the round tower provides a narrow slit
for viewing the sunset on the equinoxes. The Caracol was also used to
observe the zenithal passage of the Sun. An alignment perpendicular to
the base of the upper platform and one from the center of a doorway
above the symbolate monument are aligned with the azimuth of the sunset
on zenith passage days.
Many
inscriptions include data on the number of days elapsed in the current
lunation, the number of days in the current lunation and the position of
the lunation in a cycle of six lunations.
Modern astronomers consider conjunction of Sun and Moon (when the Sun and Moon have the same ecliptic longitude)
to be the New Moon. The Maya counted the zero day of the lunar cycle as
either the first day when one could no longer see the waning crescent
Moon or the first day when one could see the thin crescent waxing Moon
(the Palenque system). Using this system, the zero date of the lunar count is about two days after astronomical new Moon. Aveni and Fuls
analysed a large number of these inscription and found strong evidence
for the Palenque system. However Fuls found "…at least two different
methods and formulas were used to calculate the moon's age and position
in the six-month cycle…"
Mercury
Pages 30c-33c of the Dresden codex are a Venus-Mercury almanac. The
2340-day length of the Venus-Mercury almanac is a close approximation of
the synodic periods of Venus (4 x 585) and Mercury (20 x 117). The
Almanac also refers to the summer solstice and the Haab' uayeb ceremonies for the tenth century AD.
Venus
Venus was extremely important to the people of Mesoamerica. Its cycles were carefully tracked by the Maya.
Because Venus is closer to the Sun than the Earth, it passes the
Earth during its orbit. When it passes behind the Sun at superior
conjunction and between the Earth and the Sun at inferior conjunction it
is invisible. Particularly dramatic is the disappearance as evening
star and its reappearance as the morning star approximately eight days
later, after inferior conjunction. The cycle of Venus is 583.92 days long but it varies between 576.6 and 588.1 days. Astronomers calculate heliacal phenomena (first and last visibility of rising or setting bodies) using the arcus visionis
- the difference in altitude between the body and the center of the Sun
at the time of geometric rising or setting of the body, not including
the 34 arc minutes of refraction that allows one to see a body before
its geometric rise or the 0.266,563,88... degree semidiameter of the
sun. Atmospheric phenomena like extinction are not considered. The
required arcus visionis varies with the brightness of the body. Because
Venus varies in size and has phases, a different arcus visionus is used
for the four different rising and settings.
Dresden Codex
The Dresden codex pages 24 and 46 to 50 are a Venus almanac. Bricker and Bricker write:
"The Venus table tracks the synodic cycle of Venus by listing the
formal or canonical dates of planet's first and last appearances as
'morning star' and 'evening star'. The emphasis, both iconographic and
textual, is on first appearance as morning star (heliacal rise), the
dates of which are given quite accurately, This first appearance was
regarded as a time of danger and the major purpose of the Venus table
was to provide warnings of such dangerous days. The table lists the
tzolkin days for the four appearance/disappearance events during each of
the 65 consecutive Venus cycles, a period of approximately 104 years.
The table was used at least four times with different starting dates,
from the tenth through the fourteenth centuries AD."
Because the Maya canonical period was 584 days and the synodic
period is 583.92 days, an error accumulated in the table over time.
Possible correction schemes from the codex are discussed by Aveni and Bricker and Bricker.
The Dresden Codex pages 8–59 is a planetary table that
commensurates the synodic cycles of Mars and Venus. There are four
possible base dates, two in the seventh and two in the eighth centuries.
Pages 30c-33c of the Dresden codex are a Venus-Mercury almanac.
The 2340-day length of the Venus-Mercury almanac is a close
approximation of the synodic periods of Venus (4 x 585) and Mercury (20 x
117). The Almanac also refers to the summer solstice and the Haab' uayeb ceremonies for the tenth century AD.
The Grolier Codex
The Grolier Codex lists Tzolk'in
dates for the appearance/disappearances of Venus for half of the Venus
cycles in the Dresden codex. These are the same dates listed in Dresden.
Building Alignments
The Caracol at Chichen Itza contains the remains of windows
through which the extreme elongations of the planet can be seen. Four of
the main orientations of the lower platform mark the points of the
maximum horizontal displacement of the planet during the year. Two
alignments of the surviving windows in the upper tower align with the
extreme positions of the planet at its greatest north and south
declinations.
Building 22 at Copan
is called the Venus temple because so many Venus symbols are inscribed
on it. It has a narrow window that can be used to observe the greatest
elongations of Venus.
The Governors Palace at Uxmal
differs 30° from the northeast alignment of the other buildings. The
door faces southeast. About six kilometers from the door is a pyramidal
hill. From the door one could observe the appearance of Venus just
before reaching an extreme elongation. The cornices of the building have
hundreds of masks of Chaac with Venus symbols under the eyelids.
Inscriptions
De Meis has a table of 14 Long Count inscriptions that record heliacal phenomena of Venus.
De Meis has a table of 11 Long Counts that record the greatest elongation of Venus.
The Bonampak
murals depict the victory of king Chaan Muan with his enemies lying
down, pleading for their lives on a date which was the heliacal rising
of Venus and a zenith passage of the Sun.
Mars
The Dresden Codex
The Dresden Codex contains three Mars tables and there is a partial Mars almanac in the Madrid codex.
Pages 43b to 45b of the Dresden codex are a table of the 780-day
synodic cycle of Mars. The retrograde period of its path, when it is
brightest and visible for the longest time, is emphasized. The table is
dated to the retrograde period of 818 AD. The text refers to an eclipse
season (when the moon is near its ascending or descending node) that
coincided with the retrograde motion of mars.
The upper and lower water tables on pages 69–74 share the same pages in the Dresden Codex but are different from each other.
The upper table has 13 groups of 54 days - 702 days. This is the
time needed for Mars to return to the same celestial longitude, if the
celestial period included a retrograde period. The table was revised for
reuse; it has seven base dates from the seventh to the eleventh
centuries.
The lower water table has 28 groups of 65 days - 1820 days. This
table has only one picture - a scene of torrential rain on page 74. This
has been erroneously interpreted as a depiction of the end of the
world.
The purpose of the table is to track several cultural and natural
cycles. These are planting and harvesting, drought, rain and hurricane
season, the eclipse season and the relationship of the Milky Way to the
horizon. The table was periodically revised by giving it five base dates
from the fourth to the twelfth centuries.
The Dresden Codex pages 8–59 is a planetary table that
commensurates the synodic cycles of Mars and Venus. There are four
possible base dates, two in the seventh and two in the eighth centuries.
The Madrid Codex
Page 2a of the Madrid codex is an almanac of the synodic cycle of
Mars. This heavily damaged page is probably a fragment of a longer
table. The 78-day periods and iconography are similar to the table in
the Dresden Codex.
Jupiter and Saturn
Saturn and particularly Jupiter,
are two of the brightest celestial objects. As the Earth passes
superior planets in its orbit closer to the Sun they appear to stop
moving in the direction of travel of their orbits and back up for a
period before resuming their path through the sky. This is apparent retrograde motion. When they start or end retrograde motion their daily motion is stationary before going in another direction.
Inscriptions
Lounsbury found that the dates of several inscriptions commemorating dynastic rituals at Palenque by K'inich Kan Bahlam II coincide with the departure of Jupiter from its secondary stationary point.
He also showed that close conjunctions of Jupiter, Saturn and/or Mars
were probably celebrated, particularly the "2 Cib 14 Mol" event on about
July 21, 690 (Proleptic Gregorian calendar date) - July 18 astronomical.
The Dumbarton Oaks Relief Panel 1 came from El Cayo, Chiapas - a site 12 kilometers up the Usumacinta river from Piedras Negras.
Fox and Juteson (1978) found that two of these dates are separated by
378 days - close to the mean synodic period of Saturn - 378.1 days. Each
date also falls a few days before Saturn reached its second stationary
point, before ending its retrograde motion. The Brickers identified two
additional dates that are part of the same series.
Susan Milbrath has extended Lounsbury's work concerning Jupiter
to other classic and post-classic sites. Central to her work is her
identification of God K (K'awil) as Jupiter. Another component of her
work is the tying together of the synodic cycles of Jupiter and Saturn
with the katun cycles of the Long Count. She finds a clear link between
God K images and dates coinciding with its stationary points in
retrograde. She believes that K'awil is the god of the retrograde cycles of Jupiter and Saturn. The Brickers question this interpretation.
Maya Codices
No clear Jupiter or Saturn almanac can be found in the codices.
Eclipses
The Dresden Codex
The Dresden codex
pages 51 and 58 are an eclipse table. The table contains a warning of
all solar and most lunar eclipses. It does not specify which ones will
be visible in the Maya area. The length of the table is 405 lunations
(about 33 years). It was meant to be recycled and has a periodic
correction scheme. The starting date is in the eighth century and has
corrections allowing it to be used up to the eighteenth century. The
table also relates eclipses and lunar phenomena to the cycles of Venus,
possibly Mercury and other celestial and seasonal phenomena.
An eclipse can occur when the Moon's orbit crosses the ecliptic.
This happens twice a year and is referred to as the ascending or
descending node. An eclipse can occur during a period 18 days before or
after an ascending or descending node. This is an Eclipse season. Three entry dates in the Dresden Codex eclipse table give the eclipse season for November - December 755.
The Madrid Codex
Pages 10a - 13a of the Madrid Codex are an eclipse almanac
similar to the one in the Dresden Codex. The table is concerned with
rain, drought, the agricultural cycle and how these correspond with
eclipses. These eclipses probably correspond to the eclipses in the
Dresden Codex (the eighth or ninth century).
The Paris Codex
The Katun Pages (pages 2-11) in the Paris Codex are concerned
with the rituals to be performed at Katun completions. They also contain
references to historical astronomical events during the fifth to the
eighth centuries. These include eclipses, references to Venus and the
relationship of Venus to named constellations.
Inscriptions
Lord Kan II of Caracol had altar 21 installed in the center of a ball court. It has
inscriptions that mark important dates of the accomplishments of his
ancestor Lord Water and himself. Lord Kan II used the dates of important
astronomical phenomena for these. For example:
9.5.19.1.2 9 Ik 5 Uo - April 14, 553, total lunar eclipse - Accession of Lord Water, grandfather of Kan II
9.6.8.4.2 7 Ik 0 Zip - April 27, 562, annular solar eclipse 8 days ago and penumbral lunar eclipse in 7 days - Star war to Tikal
9.7.19.10.0 1 Ahau 3 Pop - March 13, 593, partial solar eclipse five days ago - Ball game
The stars
The Maya identified 13 constellations along the ecliptic. These are the content of an almanac in the Paris Codex. Each of these was associated with an animal. These animal representations are pictured in two almanacs in the Madrid Codex where they are related to other astronomical phenomena - eclipses and Venus - and Haab rituals.
Paris Codex
Pages 21-24 of the Paris Codex are a zodiacal almanac. It is made
up of five rows of 364 days each. Each row is divided into 13
subdivisions of 28 days each. Its iconography consists of animals,
including a scorpion suspended from a skyband and eclipse glyphs. It
dates from the eighth century.
Madrid Codex
The longest almanac in the Madrid codex (pages 65-72,73b) is a
compendium of information about agriculture, ceremonies, rituals and
other matters. Astronomical information includes references to eclipses,
the synodic cycles of Venus and zodiacal constellations. The almanac
dates to the middle of the fifteenth century.
The Milky Way
The Milky Way
appears as a hazy band of faint stars. It is the disc of our own
galaxy, viewed edge-on from within it. It appears as a 10°-wide band of
diffuse light passing all the way around the sky.
It crosses the ecliptic at a high angle. Its most prominent feature is a
large dust cloud that forms a dark rift in its southern and western
part.
There is no almanac in the codices that refers specifically to
the Milky Way but there are references to it in almanacs concerned with
other phenomena.
Precession of the equinoxes
The equinoxes move westward along the ecliptic relative to the fixed stars, opposite to the yearly motion of the Sun along the ecliptic, returning to the same position approximately every 26,000 years.
The "Serpent Numbers" in the Dresden codex
pp. 61–69 is a table of dates written in the coils of undulating
serpents. Beyer was the first to notice that the Serpent Series is based
on an unusually long distance number of 1.18.1.8.0.16 (5,482,096 days -
more than 30,000 years). Grofe believes that this interval is quite close to a whole multiple of the sidereal year,
returning the sun to precisely the same position against the background
of stars. He proposes that this is an observation of the precession of the equinoxes
and that the serpent series shows how the Maya calculated this by
observing the sidereal position of total lunar eclipses at fixed points
within the tropical year. Bricker and Bricker think that he based this on misinterpretation of the epigraphy and give their reasons in Astronomy in the Maya Codices.
Archaeoastronomy (also spelled archeoastronomy) is the study of how people in the past "have understood the phenomena in the sky, how they used these phenomena and what role the sky played in their cultures". Clive Ruggles argues it is misleading to consider archaeoastronomy to be the study of ancient astronomy,
as modern astronomy is a scientific discipline, while archaeoastronomy
considers symbolically rich cultural interpretations of phenomena in the
sky by other cultures. It is often twinned with ethnoastronomy, the anthropological study of skywatching in contemporary societies. Archaeoastronomy is also closely associated with historical astronomy, the use of historical records of heavenly events to answer astronomical problems and the history of astronomy, which uses written records to evaluate past astronomical practice.
Archaeoastronomy uses a variety of methods to uncover evidence of
past practices including archaeology, anthropology, astronomy,
statistics and probability, and history. Because these methods are
diverse and use data from such different sources, integrating them into a
coherent argument has been a long-term difficulty for
archaeoastronomers. Archaeoastronomy fills complementary niches in landscape archaeology and cognitive archaeology. Material evidence and its connection to the sky can reveal how a wider landscape can be integrated into beliefs about the cycles of nature, such as Mayan astronomy and its relationship with agriculture.
Other examples which have brought together ideas of cognition and
landscape include studies of the cosmic order embedded in the roads of
settlements.
Archaeoastronomy can be applied to all cultures and all time
periods. The meanings of the sky vary from culture to culture;
nevertheless there are scientific methods which can be applied across
cultures when examining ancient beliefs.
It is perhaps the need to balance the social and scientific aspects of
archaeoastronomy which led Clive Ruggles to describe it as: "...[A] field with academic work of high quality at one end but uncontrolled speculation bordering on lunacy at the other".
History
In
his short history of 'Astro-archaeology' John Michell argued that the
status of research into ancient astronomy had improved over the past two
centuries, going 'from lunacy to heresy to interesting notion and
finally to the gates of orthodoxy.' Nearly two decades later, we can
still ask the question: Is archaeoastronomy still waiting at the gates
of orthodoxy or has it gotten inside the gates?
— Todd Bostwick quoting John Michell
Two hundred years before Michell wrote the above, there were no archaeoastronomers and there were no professional archaeologists, but there were astronomers and antiquarians.
Some of their works are considered precursors of archaeoastronomy;
antiquarians interpreted the astronomical orientation of the ruins that
dotted the English countryside as William Stukeley did of Stonehenge in 1740, while John Aubrey in 1678 and Henry Chauncy in 1700 sought similar astronomical principles underlying the orientation of churches. Late in the nineteenth century astronomers such as Richard Proctor and Charles Piazzi Smyth investigated the astronomical orientations of the pyramids.
The term archaeoastronomy was first used by Elizabeth Chesley Baity (at the suggestion of Euan MacKie) in 1973, but as a topic of study it may be much older, depending on how archaeoastronomy is defined. Clive Ruggles says that Heinrich Nissen, working in the mid-nineteenth century was arguably the first archaeoastronomer. Rolf Sinclair says that Norman Lockyer, working in the late 19th and early 20th centuries, could be called the 'father of archaeoastronomy'. Euan MacKie
would place the origin even later, stating: "...the genesis and modern
flowering of archaeoastronomy must surely lie in the work of Alexander Thom in Britain between the 1930s and the 1970s".
Early archaeoastronomers surveyed Megalithic constructs in the British Isles, at sites like Auglish in County Londonderry, in an attempt to find statistical patterns.
In the 1960s the work of the engineer Alexander Thom and that of the astronomer Gerald Hawkins, who proposed that Stonehenge was a Neolithic computer, inspired new interest in the astronomical features of ancient sites. The claims of Hawkins were largely dismissed, but this was not the case for Alexander Thom's work, whose survey results of megalithic sites hypothesized widespread practice of accurate astronomy in the British Isles.
Euan MacKie, recognizing that Thom's theories needed to be tested,
excavated at the Kintraw standing stone site in Argyllshire in 1970 and
1971 to check whether the latter's prediction of an observation platform
on the hill slope above the stone was correct. There was an artificial
platform there and this apparent verification of Thom's long alignment
hypothesis (Kintraw was diagnosed as an accurate winter solstice site) led him to check Thom's geometrical theories at the Cultoon stone circle
in Islay, also with a positive result. MacKie therefore broadly
accepted Thom's conclusions and published new prehistories of Britain.
In contrast a re-evaluation of Thom's fieldwork by Clive Ruggles argued
that Thom's claims of high accuracy astronomy were not fully supported
by the evidence. Nevertheless, Thom's legacy remains strong, Krupp
wrote in 1979, "Almost singlehandedly he has established the standards
for archaeo-astronomical fieldwork and interpretation, and his amazing
results have stirred controversy during the last three decades." His
influence endures and practice of statistical testing of data remains
one of the methods of archaeoastronomy.
It has been proposed that Maya sites such as Uxmal were built in accordance with astronomical alignments.
The approach in the New World, where anthropologists began to consider more fully the role of astronomy in Amerindian civilizations, was markedly different. They had access to sources that the prehistory of Europe lacks such as ethnographies and the historical records of the early colonizers. Following the pioneering example of Anthony Aveni,
this allowed New World archaeoastronomers to make claims for motives
which in the Old World would have been mere speculation. The
concentration on historical data led to some claims of high accuracy
that were comparatively weak when compared to the statistically led
investigations in Europe.
This came to a head at a meeting sponsored by the International Astronomical Union (IAU) in Oxford in 1981.
The methodologies and research questions of the participants were
considered so different that the conference proceedings were published
as two volumes.
Nevertheless, the conference was considered a success in bringing
researchers together and Oxford conferences have continued every four or
five years at locations around the world. The subsequent conferences
have resulted in a move to more interdisciplinary approaches with
researchers aiming to combine the contextuality of archaeological
research,
which broadly describes the state of archaeoastronomy today, rather
than merely establishing the existence of ancient astronomies,
archaeoastronomers seek to explain why people would have an interest in
the night sky.
Relations to other disciplines
...[O]ne
of the most endearing characteristics of archaeoastronomy is its
capacity to set academics in different disciplines at loggerheads with
each other.
— Clive Ruggles
Archaeoastronomy has long been seen as an interdisciplinary field
that uses written and unwritten evidence to study the astronomies of
other cultures. As such, it can be seen as connecting other
disciplinary approaches for investigating ancient astronomy:
astroarchaeology (an obsolete term for studies that draw astronomical
information from the alignments of ancient architecture and landscapes),
history of astronomy
(which deals primarily with the written textual evidence), and
ethnoastronomy (which draws on the ethnohistorical record and
contemporary ethnographic studies).
Reflecting Archaeoastronomy's development as an interdisciplinary
subject, research in the field is conducted by investigators trained in
a wide range of disciplines. Authors of recent doctoral dissertations
have described their work as concerned with the fields of archaeology
and cultural anthropology; with various fields of history including the
history of specific regions and periods, the history of science and the
history of religion; and with the relation of astronomy to art,
literature and religion. Only rarely did they describe their work as
astronomical, and then only as a secondary category.
Both practicing archaeoastronomers and observers of the
discipline approach it from different perspectives. George Gummerman and
Miranda Warburton view archaeoastronomy as part of an archaeology
informed by cultural anthropology and aimed at understanding a "group's conception of themselves in relation to the heavens', in a word, its cosmology. Todd Bostwick argued that "archaeoastronomy is anthropology – the study of human behavior in the past and present." Paul Bahn has described archaeoastronomy as an area of cognitive archaeology.
Other researchers relate archaeoastronomy to the history of science,
either as it relates to a culture's observations of nature and the
conceptual framework they devised to impose an order on those
observations
or as it relates to the political motives which drove particular
historical actors to deploy certain astronomical concepts or techniques.
Art historian Richard Poss took a more flexible approach, maintaining
that the astronomical rock art of the North American Southwest should be
read employing "the hermeneutic traditions of western art history and
art criticism" Astronomers, however, raise different questions, seeking to provide their students with identifiable precursors
of their discipline, and are especially concerned with the important
question of how to confirm that specific sites are, indeed,
intentionally astronomical.
The reactions of professional archaeologists to archaeoastronomy
have been decidedly mixed. Some expressed incomprehension or even
hostility, varying from a rejection by the archaeological mainstream of
what they saw as an archaeoastronomical fringe to an incomprehension
between the cultural focus of archaeologists and the quantitative focus
of early archaeoastronomers. Yet archaeologists have increasingly come to incorporate many of the insights from archaeoastronomy into archaeology textbooks and, as mentioned above, some students wrote archaeology dissertations on archaeoastronomical topics.
Since archaeoastronomers disagree so widely on the
characterization of the discipline, they even dispute its name. All
three major international scholarly associations relate archaeoastronomy
to the study of culture, using the term Astronomy in Culture or a
translation. Michael Hoskin sees an important part of the discipline as
fact-collecting, rather than theorizing, and proposed to label this
aspect of the discipline Archaeotopography. Ruggles and Saunders proposed Cultural Astronomy as a unifying term for the various methods of studying folk astronomies. Others have argued that astronomy is an inaccurate term, what are being studied are cosmologies and people who object to the use of logos have suggested adopting the Spanish cosmovisión.
When debates polarise between techniques, the methods are often
referred to by a colour code, based on the colours of the bindings of
the two volumes from the first Oxford Conference, where the approaches
were first distinguished. Green (Old World)
archaeoastronomers rely heavily on statistics and are sometimes accused
of missing the cultural context of what is a social practice. Brown (New World)
archaeoastronomers in contrast have abundant ethnographic and
historical evidence and have been described as 'cavalier' on matters of
measurement and statistical analysis. Finding a way to integrate various approaches has been a subject of much discussion since the early 1990s.
Methodology
For
a long time I have believed that such diversity requires the invention
of some all-embracing theory. I think I was very naïve in thinking that
such a thing was ever possible.
— Stanislaw Iwaniszewski
There is no one way to do Archaeoastronomy. The divisions between
archaeoastronomers tend not to be between the physical scientists and
the social scientists. Instead it tends to depend on the location of
kind of data available to the researcher. In the Old World, there is
little data but the sites themselves; in the New World, the sites were
supplemented by ethnographic and historic data. The effects of the
isolated development of archaeoastronomy in different places can still
often be seen in research today. Research methods can be classified as
falling into one of two approaches, though more recent projects often
use techniques from both categories.
Green archaeoastronomy
Green Archaeoastronomy is named after the cover of the book Archaeoastronomy in the Old World.
It is based primarily on statistics and is particularly apt for
prehistoric sites where the social evidence is relatively scant compared
to the historic period. The basic methods were developed by Alexander
Thom during his extensive surveys of British megalithic sites.
Thom wished to examine whether or not prehistoric peoples used
high-accuracy astronomy. He believed that by using horizon astronomy,
observers could make estimates of dates in the year to a specific day.
The observation required finding a place where on a specific date the
sun set into a notch on the horizon. A common theme is a mountain which
blocked the Sun, but on the right day would allow the tiniest fraction
to re-emerge on the other side for a 'double sunset'. The animation below shows two sunsets at a hypothetical site, one the day before the summer solstice and one at the summer solstice, which has a double sunset.
To test this idea he surveyed hundreds of stone rows and circles. Any
individual alignment could indicate a direction by chance, but he
planned to show that together the distribution of alignments was
non-random, showing that there was an astronomical intent to the
orientation of at least some of the alignments. His results indicated
the existence of eight, sixteen, or perhaps even thirty-two
approximately equal divisions of the year. The two solstices, the two equinoxes and four cross-quarter days, days half-way between a solstice and the equinox were associated with the medieval Celtic calendar. While not all these conclusions have been accepted, it has had an enduring influence on archaeoastronomy, especially in Europe.
Euan MacKie has supported Thom's analysis, to which he added an archaeological context by comparing Neolithic Britain to the Mayan civilization to argue for a stratified society in this period. To test his ideas he conducted a couple of excavations at proposed prehistoric observatories in Scotland. Kintraw
is a site notable for its four-meter high standing stone. Thom proposed
that this was a foresight to a point on the distant horizon between
Beinn Shianaidh and Beinn o'Chaolias on Jura.
This, Thom argued, was a notch on the horizon where a double sunset
would occur at midwinter. However, from ground level, this sunset would
be obscured by a ridge in the landscape, and the viewer would need to be
raised by two meters: another observation platform was needed. This was
identified across a gorge where a platform was formed from small
stones. The lack of artifacts caused concern for some archaeologists and
the petrofabric analysis was inconclusive, but further research at Maes Howe and on the Bush Barrow Lozenge
led MacKie to conclude that while the term 'science' may be
anachronistic, Thom was broadly correct upon the subject of
high-accuracy alignments.
In contrast Clive Ruggles has argued that there are problems with the selection of data in Thom's surveys. Others have noted that the accuracy of horizon astronomy is limited by variations in refraction near the horizon. A deeper criticism of Green archaeoastronomy is that while it can answer whether there was likely to be an interest in astronomy in past times, its lack of a social element means that it struggles to answer why
people would be interested, which makes it of limited use to people
asking questions about the society of the past. Keith Kintigh wrote: "To
put it bluntly, in many cases it doesn't matter much to the progress of
anthropology whether a particular archaeoastronomical claim is right or
wrong because the information doesn’t inform the current interpretive
questions." Nonetheless the study of alignments remains a staple of archaeoastronomical research, especially in Europe.
Brown archaeoastronomy
In
contrast to the largely alignment-oriented statistically led methods of
Green archaeoastronomy, Brown archaeoastronomy has been identified as
being closer to the history of astronomy or to cultural history,
insofar as it draws on historical and ethnographic records to enrich
its understanding of early astronomies and their relations to calendars
and ritual.
The many records of native customs and beliefs made by the Spanish
chroniclers means that Brown archaeoastronomy is most often associated
with studies of astronomy in the Americas.
One famous site where historical records have been used to interpret sites is Chichen Itza.
Rather than analysing the site and seeing which targets appear popular,
archaeoastronomers have instead examined the ethnographic records to
see what features of the sky were important to the Mayans
and then sought archaeological correlates. One example which could have
been overlooked without historical records is the Mayan interest in the
planet Venus. This interest is attested to by the Dresden codex which contains tables with information about the Venus's appearances in the sky. These cycles would have been of astrological and ritual significance as Venus was associated with Quetzalcoatl or Xolotl.[71]
Associations of architectural features with settings of Venus can be
found in Chichen Itza, Uxmal, and probably some other Mesoamerican
sites.
"El Caracol" a possible observatory temple at Chichen Itza.
The
Temple of the Warriors bears iconography depicting feathered serpents
associated with Quetzalcoatl or Kukulcan. This means that the building's
alignment towards the place on the horizon where Venus first appears in
the evening sky (when it coincides with the rainy season) may be
meaningful.
However, since both the date and the azimuth of this event change
continuously, a solar interpretation of this orientation is much more
likely.
Aveni claims that another building associated with the planet
Venus in the form of Kukulcan, and the rainy season at Chichen Itza is
the Caracol.
This is a building with circular tower and doors facing the cardinal
directions. The base faces the most northerly setting of Venus.
Additionally the pillars of a stylobate on the building's upper platform
were painted black and red. These are colours associated with Venus as
an evening and morning star.
However the windows in the tower seem to have been little more than
slots, making them poor at letting light in, but providing a suitable
place to view out.
Aveni states that one of the strengths of the Brown methodology
is that it can explore astronomies invisible to statistical analysis and
offers the astronomy of the Incas as another example. The empire of the Incas was conceptually divided using ceques radial routes emanating from the capital at Cusco. Thus there are alignments in all directions which would suggest there
is little of astronomical significance, However, ethnohistorical records
show that the various directions do have cosmological and astronomical
significance with various points in the landscape being significant at
different times of the year.
In eastern Asia archaeoastronomy has developed from the History of
Astronomy and much archaeoastronomy is searching for material correlates
of the historical record. This is due to the rich historical record of
astronomical phenomena which, in China, stretches back into the Han dynasty, in the second century BC.
A criticism of this method is that it can be statistically weak.
Schaefer in particular has questioned how robust the claimed alignments
in the Caracol are.
Because of the wide variety of evidence, which can include artefacts as
well as sites, there is no one way to practice archaeoastronomy.
Despite this it is accepted that archaeoastronomy is not a discipline
that sits in isolation. Because archaeoastronomy is an interdisciplinary
field, whatever is being investigated should make sense both
archaeologically and astronomically. Studies are more likely to be
considered sound if they use theoretical tools found in archaeology like
analogy and homology
and if they can demonstrate an understanding of accuracy and precision
found in astronomy. Both quantitative analyses and interpretations based
on ethnographic analogies and other contextual evidence have recently
been applied in systematic studies of architectural orientations in the
Maya area and in other parts of Mesoamerica.
Source materials
Because
archaeoastronomy is about the many and various ways people interacted
with the sky, there are a diverse range of sources giving information
about astronomical practices.
Alignments
A
common source of data for archaeoastronomy is the study of alignments.
This is based on the assumption that the axis of alignment of an
archaeological site is meaningfully oriented towards an astronomical
target. Brown archaeoastronomers may justify this assumption through
reading historical or ethnographic sources, while Green
archaeoastronomers tend to prove that alignments are unlikely to be
selected by chance, usually by demonstrating common patterns of
alignment at multiple sites.
An alignment is calculated by measuring the azimuth, the angle from north, of the structure and the altitude of the horizon it faces The azimuth is usually measured using a theodolite or a compass. A compass is easier to use, though the deviation of the Earth's magnetic field from true north, known as its magnetic declination
must be taken into account. Compasses are also unreliable in areas
prone to magnetic interference, such as sites being supported by
scaffolding. Additionally a compass can only measure the azimuth to a
precision of a half a degree.
A theodolite can be considerably more accurate if used correctly,
but it is also considerably more difficult to use correctly. There is
no inherent way to align a theodolite with North and so the scale has to
be calibrated using astronomical observation, usually the position of the Sun.
Because the position of celestial bodies changes with the time of day
due to the Earth's rotation, the time of these calibration observations
must be accurately known, or else there will be a systematic error in
the measurements. Horizon altitudes can be measured with a theodolite or
a clinometer.
Artifacts
The Antikythera mechanism (main fragment)
For artifacts such as the Sky Disc of Nebra, alleged to be a Bronze Age artefact depicting the cosmos, the analysis would be similar to typical post-excavation analysis
as used in other sub-disciplines in archaeology. An artefact is
examined and attempts are made to draw analogies with historical or
ethnographical records of other peoples. The more parallels that can be
found, the more likely an explanation is to be accepted by other
archaeologists.
A more mundane example is the presence of astrological symbols
found on some shoes and sandals from the Roman Empire. The use of shoes
and sandals is well known, but Carol van Driel-Murray has proposed that
astrological symbols etched onto sandals gave the footwear spiritual or
medicinal meanings.
This is supported through citation of other known uses of astrological
symbols and their connection to medical practice and with the historical
records of the time.
Another well-known artefact with an astronomical use is the Antikythera mechanism.
In this case analysis of the artefact, and reference to the description
of similar devices described by Cicero, would indicate a plausible use
for the device. The argument is bolstered by the presence of symbols on
the mechanism, allowing the disc to be read.
Art and inscriptions
Diagram showing the location of the sun daggers on the Fajada Butte petroglyph on various days
Art
and inscriptions may not be confined to artefacts, but also appear
painted or inscribed on an archaeological site. Sometimes inscriptions
are helpful enough to give instructions to a site's use. For example, a
Greek inscription on a stele (from Itanos)
has been translated as:"Patron set this up for Zeus Epopsios. Winter
solstice. Should anyone wish to know: off ‘the little pig’ and the stele
the sun turns." From Mesoamerica come Mayan and Aztec codices. These are folding books made from Amatl, processed tree bark on which are glyphs in Mayan or Aztec script. The Dresden codex contains information regarding the Venus cycle, confirming its importance to the Mayans.
More problematic are those cases where the movement of the Sun at
different times and seasons causes light and shadow interactions with petroglyphs. A widely known example is the Sun Dagger of Fajada Butte at which a glint of sunlight passes over a spiral petroglyph.
The location of a dagger of light on the petroglyph varies throughout
the year. At the summer solstice a dagger can be seen through the heart
of the spiral; at the winter solstice two daggers appear to either side
of it. It is proposed that this petroglyph was created to mark these
events. Recent studies have identified many similar sites in the US
Southwest and Northwestern Mexico.
It has been argued that the number of solstitial markers at these sites
provides statistical evidence that they were intended to mark the
solstices.
The Sun Dagger site on Fajada Butte in Chaco Canyon, New Mexico, stands
out for its explicit light markings that record all the key events of
both the solar and lunar cycles: summer solstice, winter solstice,
equinox, and the major and minor lunar standstills of the moon's 18.6 year cycle.
In addition at two other sites on Fajada Butte, there are five light
markings on petroglyphs recording the summer and winter solstices,
equinox and solar noon.
Numerous buildings and interbuilding alignments of the great houses of
Chaco Canyon and outlying areas are oriented to the same solar and lunar
directions that are marked at the Sun Dagger site.
If no ethnographic nor historical data are found which can
support this assertion then acceptance of the idea relies upon whether
or not there are enough petroglyph sites in North America that such a
correlation could occur by chance. It is helpful when petroglyphs are
associated with existing peoples. This allows ethnoastronomers to
question informants as to the meaning of such symbols.
Ethnographies
As
well as the materials left by peoples themselves, there are also the
reports of other who have encountered them. The historical records of
the Conquistadores are a rich source of information about the pre-Columbian Americans. Ethnographers also provide material about many other peoples.
Aveni uses the importance of zenith passages as an example of the
importance of ethnography. For peoples living between the tropics of
Cancer and Capricorn there are two days of the year when the noon Sun
passes directly overhead and casts no shadow. In parts of Mesoamerica
this was considered a significant day as it would herald the arrival of
rains, and so play a part in the cycle of agriculture. This knowledge is
still considered important amongst Mayan Indians living in Central
America today. The ethnographic records suggested to archaeoastronomers
that this day may have been important to the ancient Mayans. There are
also shafts known as 'zenith tubes' which illuminate subterranean rooms
when the sun passes overhead found at places like Monte Albán and Xochicalco. It is only through the ethnography that we can speculate that the
timing of the illumination was considered important in Mayan society.
Alignments to the sunrise and sunset on the day of the zenith passage
have been claimed to exist at several sites. However, it has been shown
that, since there are very few orientations that can be related to these
phenomena, they likely have different explanations.
Ethnographies also caution against over-interpretation of sites. At a site in Chaco Canyon can be found a pictograph with a star, crescent and hand. It has been argued by some astronomers that this is a record of the 1054 Supernova. However recent reexaminations of related 'supernova petroglyphs' raises questions about such sites in general and anthropological evidence suggests other inrepretations. The Zuni people,
who claim a strong ancestral affiliation with Chaco, marked their
sun-watching station with a crescent, star, hand and sundisc, similar to
those found at the Chaco site.
Ethnoastronomy is also an important field outside of the
Americas. For example, anthropological work with Aboriginal Australians
is producing much information about their Indigenous astronomies and about their interaction with the modern world.
Recreating the ancient sky
...[A]lthough
different ways to do science and different scientific results do arise
in different cultures, this provides little support for those who would
use such differences to question the sciences' ability to provide
reliable statements about the world in which we live.
— Stephen McCluskey
Once the researcher has data to test, it is often necessary to
attempt to recreate ancient sky conditions to place the data in its
historical environment.
Declination
To calculate what astronomical features a structure faced a
coordinate system is needed. The stars provide such a system. If you
were to go outside on a clear night you would observe the stars spinning
around the celestial pole. This point is +90° if you are watching the
North Celestial Pole or −90° if you are observing the Southern Celestial
Pole. The concentric circles the stars trace out are lines of celestial latitude, known as declination.
The arc connecting the points on the horizon due East and due West (if
the horizon is flat) and all points midway between the Celestial Poles
is the Celestial Equator which has a declination of 0°. The visible
declinations vary depending where you are on the globe. Only an observer
on the North Pole of Earth would be unable to see any stars from the
Southern Celestial Hemisphere at night (see diagram below). Once a
declination has been found for the point on the horizon that a building
faces it is then possible to say whether a specific body can be seen in
that direction.
Diagram of the visible portions of sky at varying latitudes.
Solar positioning
While
the stars are fixed to their declinations the Sun is not. The rising
point of the Sun varies throughout the year. It swings between two
limits marked by the solstices a bit like a pendulum,
slowing as it reaches the extremes, but passing rapidly through the
midpoint. If an archaeoastronomer can calculate from the azimuth and
horizon height that a site was built to view a declination of +23.5°
then he or she need not wait until 21 June to confirm the site does
indeed face the summer solstice.
Lunar positioning
The Moon's appearance is considerably more complex. Its motion, like the Sun, is between two limits — known as lunistices rather than solstices. However, its travel between lunistices is considerably faster. It takes a sidereal month
to complete its cycle rather than the year-long trek of the Sun. This
is further complicated as the lunistices marking the limits of the
Moon's movement move on an 18.6 year cycle.
For slightly over nine years the extreme limits of the moon are outside
the range of sunrise. For the remaining half of the cycle the Moon
never exceeds the limits of the range of sunrise. However, much lunar
observation was concerned with the phase of the Moon. The cycle from one New Moon to the next runs on an entirely different cycle, the Synodic month. Thus when examining sites for lunar significance the data can appear sparse due the extremely variable nature of the moon. See Moon for more details.
Stellar positioning
Precessional movement.
Finally
there is often a need to correct for the apparent movement of the
stars. On the timescale of human civilisation the stars have largely
maintained the same position relative to each other. Each night they
appear to rotate around the celestial poles due to the Earth's rotation
about its axis. However, the Earth spins rather like a spinning top. Not only does the Earth rotate, it wobbles. The Earth's axis takes around 25,800 years to complete one full wobble.
The effect to the archaeoastronomer is that stars did not rise over the
horizon in the past in the same places as they do today. Nor did the
stars rotate around Polaris as they do now. In the case of the Egyptian pyramids, it has been shown they were aligned towards Thuban, a faint star in the constellation of Draco.
The effect can be substantial over relatively short lengths of time,
historically speaking. For instance a person born on 25 December in
Roman times would have been born with the sun in the constellation Capricorn. In the modern period a person born on the same date would have the sun in Sagittarius due to the precession of the equinoxes.
Additionally
there are often transient phenomena, events which do not happen on an
annual cycle. Most predictable are events like eclipses. In the case of solar eclipses these can be used to date events in the past. A solar eclipse mentioned by Herodotus enables us to date a battle between the Medes and the Lydians, which following the eclipse failed to happen, to 28 May, 585 BC. Other easily calculated events are supernovae whose remains are visible to astronomers and therefore their positions and magnitude can be accurately calculated.
Some comets are predictable, most famously Halley's Comet. Yet as a class of object they remain unpredictable and can appear at any time. Some have extremely lengthy orbital periods which means their past appearances and returns cannot be predicted. Others may have only ever passed through the Solar System once and so are inherently unpredictable.
Meteor showers should be predictable, but some meteors are cometary debris and so require calculations of orbits which are currently impossible to complete. Other events noted by ancients include aurorae, sun dogs and rainbows
all of which are as impossible to predict as the ancient weather, but
nevertheless may have been considered important phenomena.
Major topics of archaeoastronomical research
What has astronomy brought into the lives of cultural groups throughout history? The answers are many and varied...
— Von Del Chamberlain and M. Jane Young
The use of calendars
A common justification for the need for astronomy is the need to develop an accurate calendar for agricultural reasons. Ancient texts like Hesiod's
Works and Days, an ancient farming manual, would appear to contradict
this. Instead astronomical observations are used in combination with ecological signs, such as bird migrations to determine the seasons. Ethnoastronomical work with the Mursi of Ethiopia shows that haphazard astronomy continued until recent times in some parts of the world.
All the same, calendars appear to be an almost universal phenomenon in
societies as they provide tools for the regulation of communal
activities.
Other peculiar calendars include ancient Greek calendars. These were nominally lunar, starting with the New Moon. In reality the calendar could pause or skip days with confused citizens inscribing dates by both the civic calendar and ton theoi, by the moon. The lack of any universal calendar for ancient Greece suggests that coordination of panhellenic events such as games or rituals could be difficult and that astronomical symbolism may have been used as a politically neutral form of timekeeping.
Orientation measurements in Greek temples and Byzantine churches have
been associated to deity's name day, festivities, and special events.
Myth and cosmology
The constellation Argo Navis drawn by Johannes Hevelius in 1690.
Another motive for studying the sky is to understand and explain the universe. In these cultures myth was a tool for achieving this and the explanations, while not reflecting the standards of modern science, are cosmologies.
The Incas arranged their empire to demonstrate their cosmology. The capital, Cusco,
was at the centre of the empire and connected to it by means of ceques,
conceptually straight lines radiating out from the centre. These ceques connected the centre of the empire to the four suyus, which were regions defined by their direction from Cusco. The notion of a quartered cosmos is common across the Andes.
Gary Urton, who has conducted fieldwork in the Andean villagers of
Misminay, has connected this quartering with the appearance of the Milky Way in the night sky. In one season it will bisect the sky and in another bisect it in a perpendicular fashion.
The importance of observing cosmological factors is also seen on the other side of the world. The Forbidden City in Beijing
is laid out to follow cosmic order though rather than observing four
directions. The Chinese system was composed of five directions: North, South, East, West and Centre. The Forbidden City occupied the centre of ancient Beijing. One approaches the Emperor from the south, thus placing him in front of the circumpolar stars.
This creates the situation of the heavens revolving around the person
of the Emperor. The Chinese cosmology is now better known through its
export as feng shui.
There is also much information about how the universe was thought to work stored in the mythology of the constellations. The Barasana of the Amazon
plan part of their annual cycle based on observation of the stars. When
their constellation of the Caterpillar-Jaguar (roughly equivalent to
the modern Scorpius) falls they prepare to catch the pupating
caterpillars of the forest as they fall from the trees. The caterpillars provide food at a season when other foods are scarce.
A more well-known source of constellation myth are the texts of
the Greeks and Romans. The origin of their constellations remains a
matter of vigorous and occasionally fractious debate.
The loss of one of the sisters, Merope, in some Greek myths may
reflect an astronomical event wherein one of the stars in the Pleiades
disappeared from view by the naked eye.
Giorgio de Santillana, professor of the History of Science in the School of Humanities at the Massachusetts Institute of Technology,
along with Hertha von Dechend believed that the old mythological
stories handed down from antiquity were not random fictitious tales but
were accurate depictions of celestial cosmology
clothed in tales to aid their oral transmission. The chaos, monsters
and violence in ancient myths are representative of the forces that
shape each age. They believed that ancient myths are the remains of
preliterate astronomy that became lost with the rise of the Greco-Roman civilization. Santillana and von Dechend in their book Hamlet's Mill, An Essay on Myth and the Frame of Time
(1969) clearly state that ancient myths have no historical or factual
basis other than a cosmological one encoding astronomical phenomena,
especially the precession of the equinoxes. Santillana and von Dechend's approach is not widely accepted.
By including celestial motifs in clothing it becomes possible for the
wearer to make claims the power on Earth is drawn from above. It has
been said that the Shield of Achilles described by Homer is also a catalogue of constellations. In North America shields depicted in Comanchepetroglyphs appear to include Venus symbolism.
Solsticial alignments also can be seen as displays of power. When viewed from a ceremonial plaza on the Island of the Sun (the mythical origin place of the Sun) in Lake Titicaca,
the Sun was seen to rise at the June solstice between two towers on a
nearby ridge. The sacred part of the island was separated from the
remainder of it by a stone wall and ethnographic records indicate that
access to the sacred space was restricted to members of the Inca ruling elite. Ordinary pilgrims stood on a platform outside the ceremonial area to see the solstice Sun rise between the towers.
In Egypt the temple of Amun-Re at Karnak has been the subject of much study. Evaluation of the site, taking into account the change over time of the obliquity of the ecliptic show that the Great Temple was aligned on the rising of the midwinter sun. The length of the corridor down which sunlight would travel would have limited illumination at other times of the year.
In a later period the Serapeum in Alexandria was also said to have contained a solar alignment so that, on a specific sunrise, a shaft of light would pass across the lips of the statue of Serapis thus symbolising the Sun saluting the god.
Major sites of archaeoastronomical interest
Clive Ruggles and Michel Cotte
recently edited a book on heritage sites of astronomy and
archaeoastronomy that provides a list of the main sites around the
world.
At Stonehenge in England and at
Carnac in France, in Egypt and Yucatán, across the whole face of the
earth, are found mysterious ruins of ancient monuments, monuments with
astronomical significance... They mark the same kind of commitment that
transported us to the moon and our spacecraft to the surface of Mars.
— Edwin Krupp
Newgrange
The sunlight enters the tomb at Newgrange via the roofbox built above the door.
Newgrange is a passage tomb in the Republic of Ireland dating from around 3,300 to 2,900 BC
For a few days around the Winter Solstice light shines along the
central passageway into the heart of the tomb. What makes this notable
is not that light shines in the passageway, but that it does not do so
through the main entrance. Instead it enters via a hollow box above the
main doorway discovered by Michael O'Kelly. It is this roofbox which strongly indicates that the tomb was built with an astronomical aspect in mind. Clive Ruggles notes:
...[F]ew
people - archaeologists or astronomers- have doubted that a powerful
astronomical symbolism was deliberately incorporated into the monument,
demonstrating that a connection between astronomy and funerary ritual,
at the very least, merits further investigation.
Since the first modern measurements of the precise cardinal orientations of the pyramids by Flinders Petrie, various astronomical methods have been proposed for the original establishment of these orientations. It was recently proposed that this was done by observing the positions of two stars in the Plough / Big Dipper which was known to Egyptians as the thigh. It is thought that a vertical alignment between these two stars checked with a plumb bob
was used to ascertain where north lay. The deviations from true north
using this model reflect the accepted dates of construction.
Constellations on the astronomical ceiling of Senemut Tomb
Some have argued that the pyramids were laid out as a map of the three stars in the belt of Orion, although this theory has been criticized by reputable astronomers.
The site was instead probably governed by a spectacular hierophany
which occurs at the summer solstice, when the sun, viewed from the
Sphinx terrace, forms - together with the two giant pyramids - the
symbol Akhet, which was also the name of the Great Pyramid. Further, the
south east corners of all the 3 pyramids align towards the temple of
Heliopolis, as first discovered by the Egyptologist Mark Lehner.
The astronomical ceiling of the tomb of Senenmut (c. 1470BC)
contains the Celestial Diagram depicting circumpolar constellations in
the form of discs. Each disc is divided into 24 sections suggesting a
24-hour time period. Constellations are portrayed as sacred deities of
Egypt. The observation of lunar cycles is also evident.
El Castillo
El Castillo, also known as Kukulcán's Pyramid, is a Mesoamerican step-pyramid built in the centre of Mayan center of Chichen Itza
in Mexico. Several architectural features have suggested astronomical
elements. Each of the stairways built into the sides of the pyramid has
91 steps. Along with the extra one for the platform at the top, this
totals 365 steps, which is possibly one for each day of the year
(365.25) or the number of lunar orbits in 10,000 rotations (365.01).
Plumed Serpent
A visually striking effect is seen every March and September as an
unusual shadow occurs around the equinoxes. A shadow appears to descend
the west balustrade of the northern stairway. The visual effect is of a
serpent descending the stairway, with its head at the base in light.
Additionally the western face points to sunset around 25 May,
traditionally the date of transition from the dry to the rainy season.
The intended alignment was, however, likely incorporated in the
northern (main) facade of the temple, as it corresponds to sunsets on
May 20 and July 24, recorded also by the central axis of Castillo at
Tulum.
The two dates are separated by 65 and 300 days, and it has been shown
that the solar orientations in Mesoamerica regularly correspond to dates
separated by calendrically significant intervals (multiples of 13 and
20 days).
Many astronomical alignments have been claimed for Stonehenge, a complex of megaliths and earthworks in the Salisbury Plain
of England. The most famous of these is the midsummer alignment, where
the Sun rises over the Heel Stone. However, this interpretation has been
challenged by some archaeologists who argue that the midwinter
alignment, where the viewer is outside Stonehenge and sees the sun
setting in the henge, is the more significant alignment, and the
midsummer alignment may be a coincidence due to local topography.
As well as solar alignments, there are proposed lunar alignments.
The four station stones mark out a rectangle. The short sides point
towards the midsummer sunrise and midwinter sunset. The long sides if
viewed towards the south-east, face the most southerly rising of the
moon. Aveni notes that these lunar alignments have never gained the
acceptance that the solar alignments have received.
The Heel Stone azimuth is one-seventh of circumference, matching the
latitude of Avebury, while summer solstice sunrise azimuth is no longer
equal to the construction era direction.
This is an architecturally outstanding Neolithic chambered tomb on the Mainland of Orkney, Scotland
– probably dating to the early 3rd millennium BC, and where the setting
sun at midwinter shines down the entrance passage into the central
chamber (see Newgrange). In the 1990s further investigations were
carried out to discover whether this was an accurate or an approximate
solar alignment. Several new aspects of the site were discovered. In the
first place the entrance passage faces the hills of the island Hoy,
about 10 miles away. Secondly, it consists of two straight lengths,
angled at a few degrees to each other. Thirdly, the outer part is
aligned towards the midwinter sunset position on a level horizon just to
the left of Ward Hill on Hoy. Fourthly the inner part points directly
at the Barnhouse standing stone about 400m away and then to the right
end of the summit of Ward Hill, just before it dips down to the notch
between it at Cuilags to the right. This indicated line points to
sunset on the first Sixteenths of the solar year (according to A. Thom)
before and after the winter solstice and the notch at the base of the
right slope of the Hill is at the same declination. Fourthly a similar
'double sunset' phenomenon is seen at the right end of Cuilags, also on
Hoy; here the date is the first Eighth of the year before and after the
winter solstice, at the beginning of November and February respectively –
the Old Celtic festivals of Samhain and Imbolc.
This alignment is not indicated by an artificial structure but gains
plausibility from the other two indicated lines. Maeshowe is thus an
extremely sophisticated calendar site which must have been positioned
carefully in order to use the horizon foresights in the ways described.
Uxmal
The Palace of the Governor at Uxmal.
Uxmal is a Mayan city in the Puuc Hills of Yucatán Peninsula,
Mexico. The Governor's Palace at Uxmal is often used as an exemplar of
why it is important to combine ethnographic and alignment data. The
palace is aligned with an azimuth
of 118° on the pyramid of Cehtzuc. This alignment corresponds
approximately to the southernmost rising and, with a much greater
precision, to the northernmost setting of Venus; both phenomena occur
once every eight years. By itself this would not be sufficient to argue
for a meaningful connection between the two events. The palace has to be
aligned in one direction or another and why should the rising of Venus
be any more important than the rising of the Sun, Moon, other planets,
Sirius et cetera? The answer given is that not only does the palace point towards significant points of Venus, it is also covered in glyphs which stand for Venus and Mayan zodiacal constellations.
Moreover, the great northerly extremes of Venus always occur in late
April or early May, coinciding with the onset of the rainy season. The
Venus glyphs placed in the cheeks of the Maya rain god Chac, most likely
referring to the concomitance of these phenomena, support the
west-working orientation scheme.
Chaco Canyon
The Great Kiva at Chaco Canyon.
In Chaco Canyon, the center of the ancient Pueblo culture in the
American Southwest, numerous solar and lunar light markings and
architectural and road alignments have been documented. These findings
date to the 1977 discovery of the Sun Dagger site by Anna Sofaer.
Three large stone slabs leaning against a cliff channel light and
shadow markings onto two spiral petroglyphs on the cliff wall, marking
the solstices, equinoxes and the lunar standstills of the 18.6 year
cycle of the moon.
Subsequent research by the Solstice Project and others demonstrated
that numerous building and interbuilding alignments of the great houses
of Chaco Canyon are oriented to solar, lunar and cardinal directions.
In addition, research shows that the Great North Road, a thirty-five
mile engineered “road”, was constructed not for utilitarian purposes
but rather to connect the ceremonial center of Chaco Canyon with the
direction north.
Lascaux Cave
According
to Rappenglueck, the eyes of the bull, the bird, and the bird-man may
represent the three stars Vega, Altair, and Deneb commonly known as the Summer Triangle.
In recent years, new research has suggested that the Lascaux cave paintings in France may incorporate prehistoric star charts. Michael Rappenglueck of the University of Munich
argues that some of the non-figurative dot clusters and dots within
some of the figurative images correlate with the constellations of Taurus, the Pleiades and the grouping known as the "Summer Triangle". Based on her own study of the astronomical significance of Bronze Age petroglyphs in the Vallée des Merveilles
and her extensive survey of other prehistoric cave painting sites in
the region—most of which appear to have been selected because the
interiors are illuminated by the setting sun on the day of the winter solstice—French
researcher Chantal Jègues-Wolkiewiez has further proposed that the
gallery of figurative images in the Great Hall represents an extensive
star map and that key points on major figures in the group correspond to
stars in the main constellations as they appeared in the Paleolithic. (Note that these interpretations rose skepticism among the scientific community). Appliying phylogenetics to myths of the Cosmic Hunt, Julien d'Huy
suggested that the palaeolithic version of this story could be the
following: there is an animal that is a horned herbivore, especially an
elk. One human pursues this ungulate. The hunt locates or gets to the
sky. The animal is alive when it is transformed into a constellation. It
forms the Big Dipper. This story may be represented in the famous
Lascaux shaft ‘scene’
Fringe archaeoastronomy
At least now we have all the
archaeological facts to go along with the astronomers, the Druids, the
Flat Earthers and all the rest.
— Sir Jocelyn Stephens
Archaeoastronomy owes something of this poor reputation among scholars to its occasional misuse to advance a range of pseudo-historical accounts. During the 1930s, Otto S. Reuter compiled a study entitled Germanische Himmelskunde,
or "Teutonic Skylore". The astronomical orientations of ancient
monuments claimed by Reuter and his followers would place the ancient
Germanic peoples ahead of the Ancient Near East in the field of astronomy, demonstrating the intellectual superiority of the "Aryans" (Indo-Europeans) over the Semites.
Since the 19th century, numerous scholars have sought to use archaeoastronomical calculations
to demonstrate the antiquity of Ancient Indian Vedic culture, computing
the dates of astronomical observations ambiguously described in ancient
poetry to as early as 4000 BCE. David Pingree,
a historian of Indian astronomy, condemned "the scholars who perpetrate
wild theories of prehistoric science and call themselves
archaeoastronomers."
More recently Gallagher, Pyle, and Fell interpreted inscriptions in West Virginia as a description in Celtic Ogham
alphabet of the supposed winter solstitial marker at the site. The
controversial translation was supposedly validated by a problematic
archaeoastronomical indication in which the winter solstice sun shone on
an inscription of the sun at the site. Subsequent analyses criticized
its cultural inappropriateness, as well as its linguistic and
archeaoastronomical claims, to describe it as an example of "cult archaeology".
Archaeoastronomy is sometimes related to the fringe discipline of Archaeocryptography,
when its followers attempt to find underlying mathematical orders
beneath the proportions, size, and placement of archaeoastronomical
sites such as Stonehenge and the Pyramid of Kukulcán at Chichen Itza.
Archaeoastronomical organisations and publications
Additionally the Journal for the History of Astronomy publishes many archaeoastronomical papers. For twenty-seven volumes (from 1979 to 2002) it published an annual supplement Archaeoastronomy. The Journal of Astronomical History and Heritage (National Astronomical Research Institute of Thailand), Culture & Cosmos (University of Wales, UK) and Mediterranean Archaeology and Archaeometry (University of Aegean, Greece) also publish papers on archaeoastronomy.
Various national archaeoastronomical projects have been
undertaken. Among them is the program at the Tata Institute of
Fundamental Research named "Archaeo Astronomy in Indian Context" that has made interesting findings in this field.
