[[Image:Summer Solstice Sunrise over Stonehenge 2005.jpg|right|thumb|250px|The sun rising over [[Stonehenge]] at the 2005 Summer [[Solstice]].]]
[[Image:Newgrange ireland 750px.jpg|right|thumb|250px|The rising sun illuminates the inner chamber of [[Newgrange]], Ireland, only at the winter solstice.]]

'''Archaeoastronomy''' (also spelled '''archeoastronomy''') is the study of ancient or traditional [[astronomy|astronomies]] in their cultural context, utilising [[archaeology|archaeological]] and [[anthropology|anthropological]] evidence. The anthropological study of astronomical practices in contemporary societies is often called ethnoastronomy, although there is no consensus as to whether ethnoastronomy is a separate discipline or is a part of archaeoastronomy. 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 traditions.

==History of archaeoastronomy==
In 1927, decades before archaeoastronomy had grown up enough to even learn its modern name, ''Stonehenge as an Astronomical Instrument'' was among the articles printed in the premiere edition of the quarterly review of archaeology, ''Antiquity''.<ref>A.P. Trotter, [http://www.antiquity.ac.uk/ant/001/Ant0010042.htm Stonehenge as an Astronomical Instrument], ''[[Antiquity (journal)|Antiquity]]'' Vol 1:1, 1927, 42–53</ref>
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[[Image:Kheops-Pyramid.jpg|rightt|thumb|250px|[[The Great Pyramid]] of Giza (a.k.a. Kheops or Khufu) near Cairo, Egypt, constructed ~2570 BCE, world's tallest building until 1300 CE]]
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[[Image:Piazzismyth.jpg|right|thumb|250px|<center>[[Charles Piazzi Smyth]]</center><center>(1819-1900)</center>professor of astronomy, University of Edinburgh and Astronomer Royal of Scotland from 1845 to 1888]]
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[[Image:Cpsmyth.jpg|right|thumb|250px|illustration from Piazzi Smyth's book ''Our Inheritance in the Great Pyramid'' with claims of prophetic measurements therein]]
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[[Image:Richard_Anthony_Proctor.jpg|right|thumb|250px|<center>[[Richard Anthony Proctor]]</center><center>(1837-1888)</center>British astronomer, prolific author, international lecturer]]
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[[Image:Lockyer-Norman.jpg|right|thumb|250px|<center>[[Joseph Lockyer]]</center><center>(1836-1920)</center>British astronomer, founded science journal [[Nature %28journal%29|''Nature'']] in 1869]]
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[[Image:Auglish.jpg|right|thumb|250px|Early archaeoastronomy began by surveying alignments of Megalithic stones in the British Isles and sites like Auglish in [[County Londonderry]] in an attempt to find statistical patterns]]
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[[Image:Uxmal01-panorama.jpg|thumb|leftt|250px|It has been proposed that [[Maya civilization|Maya]] sites such as [[Uxmal]] were built in accordance with astronomical alignments]]
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Oddly enough, it was Great Britain's 19th century nationalistic debate on [[Metrology|metrology]], specifically pitting the French metric system against the British imperial system of measurements,<ref>Eric Michael Reisenauer, ''The battle of the standards: great pyramid metrology and British identity, 1859-1890'', The Historian, 2003, [http://www.encyclopedia.com/doc/1G1-135425064.html HighBeam Encyclopedia]</ref> that was the main catalyst in igniting interest in archaeoastronomy. In 1859 London literary mogul [[John Taylor %281781-1864%29|John Taylor]]'s ''The Great Pyramid: Why It Was Built? and Who Built It?'' adopted beliefs first advanced centuries earlier by Italian mathematician [[Gerolamo Cardano]] and later Oxford Professor of astronomy [[John Greaves]]. Having surveyed Egyptian pyramids in 1638, Greaves wrote ''The Origine and Antiquity of Our English Weights and Measures Discover'd''. Neither a scientist nor a visitor to Egypt, Taylor triumphed the British inch, virtually identical to the [[Pyramid inch|sacred inch]] of [[The Great Pyramid]], which he contended was the bank of measurements approved by God. A convert to Taylor's ideas, Astronomer Royal of Scotland [[Charles Piazzi Smyth]] wrote ''Our Inheritance in the Great Pyramid'' in 1864, the year Taylor died, then went to Egypt to do his own survey. As a champion for a cause that also viewed the monument as symbolic of biblical prophecy, Piazzi Smyth fell out of favor with scientists, and resigned his fellowship in the [[Royal Society of London]] in 1874. Among his leading critics was James Bonwick, Fellow of the [[Royal Geographic Society]], and author of ''Pyramid Facts and Fancies'' in 1877 and ''Egyptian Belief and Modern Thought'' in 1878. The tide was turning.

Far removed from the Anglican firestorm, Chicago M.D. Everett W. Fish wrote ''The Egyptian Pyramids: An Analysis of A Great Mystery'',<ref>Everett W. Fish, M.D., ''The Egyptian Pyramids: An Analysis of A Great Mystery'', C.H. Jones &amp; Company, 1880, (not copyrighted), [http://archaeoastronomy.com/egypt.html archaeoastronomy.com] digitized selected pages 112-146</ref> published in January 1880. Fish invoked the [[Baconian method]] of scientific inquiry in his study of astronomical features. He criticized Piazzi Smyth for over-reaching, but favored Piazzi Smyth's faith over Bonwick's agnosticism. Then, in 1883 British astronomer [[Richard Anthony Proctor]]'s ''The Great Pyramid: Observatory, Tomb and Temple''<ref>Richard Anthony Proctor, ''The Great Pyramid: Observatory, Tomb and Temple'', Chatto &amp; Windus, 1883, [http://books.google.com/books?hl=en&id=YQdFAAAAIAAJ Google] digitized book</ref> fully rejected Piazzi Smyth's mysticism and embraced pure science. On page 177 Proctor noted an ancient commentary on Plato's ''Timaeus'':
<blockquote>For we learn from Proclus that the pyramids of Egypt (which, according to Diodorus, had existed 3,600 years before his history was written, about 8 B.C.) terminated above in a platform, from which priests made their celestial observations.</blockquote>
The first author of a genuinely scientific book, at least penned in English, about what was later to be known as archaeoastronomy, is a narrow call between either Dr. Fish or [[Royal Astronomical Society]] fellow Proctor.

British astronomer [[Joseph Lockyer]] added more to this body of literature in 1894 with ''The Dawn of Astronomy: A Study of Temple-Worship and Mythology of the Ancient Egyptians'', followed a dozen years later with analysis of a subject closer to home, ''Stonehenge and Other British Stone Monuments Astronomically Considered''. Contemporaneously, archaeologist [[Francis Penrose]] wrote extensively about astronomical alignments of [[Greek temple]]s in the ''[[Philosophical Transactions of the Royal Society]]''. This particular topic seems to have been first introduced in Chapter 6 of archaeologist Heinrich Nissen's 1869 book ''Das Templum: Antiquarische Untersuchungen (The Temples: Antiquarian Investigations)'',<ref>Heinrich Nissen, ''Das Templum: Antiquarische Untersuchungen'', Weidmannsche Buchhandslung, 1869, [http://books.google.com/books?id=TokBAAAAQAAJ&pg=PA162 Google] digitized book, tabbed to Chapter 6, ''Die Orientirung des Templum (The Orientation of the Temples)''</ref> however any credit should be shared with fellow German, Bremen University professor Dr. B. Thiel, author of an appendix including remarks, ''Astronomical Auxiliary Tables'', page 233 via the preceding citation. This book remains untranslated into English even today. Nissen, an epigrapher as well, included many Latin and Greek citations within his book.

In the radicalized 1960s, a schism developed between two archaeoastromers performing independent research and an archaeological establishment uncomfortable with their bold implications. In quick succession these two professors from prestigious universities, one American, the other English, were theorizing megalithic stone circles, particularly the most famous, in the British Isles had been assembled with far more care and astronomical purpose than previously thought. Boston University astronomy professor [[Gerald Hawkins]] claimed, in the journal ''Nature'' in 1963, to have discovered, aided by computer analysis, 165 significant features including a dozen key solar and lunar alignments integrated into the circular Stonehenge complex. Two years later, Hawkins' findings were assembled in his book, ''Stonehenge Decoded''; and two years after that, Oxford professor of Engineering [[Alexander Thom]] came out with the first in a trilogy that deduced, from his having carefully surveyed many megalithic circles, a precise and profound ancient system that divided the year into eight, nearly equivalent intervals bracketed by solstices, equinoxes and their bisects, [[Cross-quarter day|cross-quarter]] dates. Stonehenge archaeologist [[Richard J. C. Atkinson]] denounced Hawkins,<ref>[[Richard J. C. Atkinson]], [http://antiquity.ac.uk/ant/040/Ant0400212.htm Moonshine on Stonehenge], ''[[Antiquity (journal)|Antiquity]]'' Vol 49:159, 1966, 212–6</ref> while Clive Ruggles challenged whether the evidence merited Thom's conclusions. His work ultimately was vindicated by investigative digs led by archaeologist Euan MacKie, who then proceeded to author new prehistories of Britain,<ref>E. MacKie, ''Science and Society in Prehistoric Britain'', Paul Elek, 1977, ISBN 0-236-40041-X</ref> citing Thom's research.

Meanwhile, the Atlantic Ocean was becoming a figurative gulf for a schism threatening to cripple the toddler that was archaeoastronomy. Healing of the rift began at the first International Conference on Archaeoastronomy<ref>C.L.N. Ruggles, ''Archaeoastronomy in the 1990s'', Group D Publications. 1993, ix, ISBN 1-874152-01-2</ref> in Oxford, England, sponsored by the [[International Astronomical Union|IAU]]. Field work in the UK, Egypt and Greece had used a purely statistical approach in collecting data for the interpretation of stone circles, pyramids and temples, while researchers in the West, analyzing petroglyphs, earthen mounds, runes, and a few megalithic sites along the northeastern US seaboard, had accessed some early colonial reports based on Amerindian [[ethnography|ethnographies]].<ref>M. Zeilik, The Ethnoastronomy of the Historic Pueblos, I: Calendrical Sun Watching, ''Archaeoastronomy'' No. 8 (Supplement to the ''Journal for the History of Astronomy''), 1985, pp. S1–S24; The Ethnoastronomy of the Historic Pueblos, II: Moon Watching, ''Archaeoastronomy'' No. 10 (Supplement to the ''Journal for the History of Astronomy''), 1986, pp. S1–S22.</ref> The 1981 conference report was published in two separate volumes because of the distinctive methodologies.<ref>A. F. Aveni (ed.), ''Archaeoastronomy in the New World: American Primitive Astronomy'', [[Cambridge University Press|CUP]], 1982, ISBN 0-521-24731-4; D. C. Heggie (ed.), ''Archaeoastronomy in the Old World'', [[Cambridge University Press|CUP]], 1982, ISBN 0-521-24734-9 </ref> In subsequent Oxford conferences held every four or five years in locations around the world, compromise, the sharing of techniques, as well as new advanced technology research tools have improved [[methodology|methodologies]] for both East and West.<ref>A.F. Aveni, ''World Archaeoastronomy'', [[Cambridge University Press|CUP]], 1989, xi–xiii, ISBN 0-521-34180-9</ref> Rather than merely establishing the existence of ancient astronomies, archaeoastronomers now seek to explain why people would have an interest in the night sky.

==Methodology==

Because of the wide variety of evidence, which can include artifacts 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.


===Artifactual analysis===
[[Image:NAMA Machine d'Anticythère 1.jpg|right|thumb|200px|The Antikythera mechanism (main fragment)]]In the case of artifacts such as the [[Nebra skydisk|Sky Disc of Nebra]], alleged to be a Bronze Age artifact depicting the cosmos, the analysis would be similar to typical [[Archaeology#Post-excavation analysis|post-excavation analysis]] as used in other sub-disciplines in archaeology. An artifact 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.

Another well-known artifact with an astronomical use is the [[Antikythera mechanism]]. In this case analysis of the artifact, 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.

===Symbolic analysis===
[[Image:Fajadadiagram.JPG|thumb|250px|left|Diagram showing the location of the sun daggers on the [[Fajada Butte]] petroglyph on various days]]
In some cases the use of an artefact may be known, but its meaning may not be fully understood. In such cases an examination of the symbolism on the artefact may be necessary.

A mundane example is the presence of [[astrological symbol]]s 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.<ref>C. van Driel-Murray, Regarding the Stars, ''TRAC 2001: Proceedings of the Eleventh Annual Theoretical Roman Archaeology Conference Glasgow 2001''. eds. M Carruthers, C. van Driel-Murray, A. Gardner, J. Lucas, L. Revell and E. Swift. Oxbow Books. 2002, 96–103, ISBN 1-84217-075-9</ref> 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.

More problematic are some [[petroglyph]]s. Symbols on rock are one such class of symbol which are occasionally argued to posses astronomical meanings. An example is the Sun Dagger of [[Fajada Butte]] which is a glint of sunlight passing over a spiral petroglyph. The location of the dagger on the petroglyph varies throughout the year. At the solstices a dagger can be seen either through the heart of the spiral or to either side of it. It is proposed that this petroglyph was created to mark these events. If no ethnographic nor historical data are found which can support this assertion then acceptance of the idea relies upon the reader’s own belief as to 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.

===Alignment analysis===<!-- This section is linked from [[History of astronomy]] -->
[[Image:Sun behind the Heel Stone.jpg|thumb|right|The Sun rising behind the Heel Stone at Stonehenge]]
One aspect of archaeoastronomy is alignment analysis, the study of the orientation of constructs and structures and calculation of the relation of the direction in which they faced with astronomical events. Stonehenge's Avenue is hypothesized to have an orientation to the summer solstice sunrise. In pyramids of Egypt are oriented in the cardinal directions.<ref>K. Spence, [http://hbar.phys.msu.su/gorm/dating/spence1.pdf Ancient Egyptian Chronoology and the astronomical orientation of the pyramids], ''[[Nature (journal)|Nature]]'', Vol 406, 16 November 2000, 320–324.</ref>

Alignment analysis may vary depending upon the researcher. As a coarse stereotype archaeoastronomers from an historical background tend to have an idea which is then tested by examining structures for alignments. Astronomically-minded archaeoastronomers may analyze large numbers of sites and attempt to find statistical patterns. This approach was employed in papers by pioneers in the field. [[Alexander Thom]] conducted extensive survey work of megalithic stone circles and concluded many sites were situated to observe the moon. In this instance the aim was to prove that there is an astronomical problem which requires an historical explanation. This latter approach continues to an extent in some modern research but it has comparatively little direct impact on mainstream archaeology.

One reason the statistically-led approach has proven unpopular with archaeologists and anthropologists was stated by the anthropologist Keith Kintigh:
{{blockquote|In light of the fact that archaeoastronomers bring considerable energy and expertise to their efforts, what accounts for archaeologists’ indifference?

<p>I think the principal reason is that archaeologists see archaeoastronomers as answering questions that, from a social scientific standpoint, no one is asking. 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.<ref>K. Kintigh, [http://www.wam.umd.edu/~tlaloc/archastro/ae5.html I wasn’t going to say anything, but since you asked: Archaeoastronomy and Archaeology], ''Archaeoastronomy & Ethnoastronomy News'' 5, 1992</ref>}}

Recent statistically led research has tended to be more discriminating, choosing archaeologically associated sites and where possible referring back to historical or ethnographic records to place the findings in a social context.

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.<ref>[http://www.brunton.com/manuals/current/Compasses/Transit.pdf ''Brunton Pocket Transit Instruction Manual'', p. 22]</ref>

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 [[calibration|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]].

==Recreating the ancient sky==
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===
{{main|Declination}}
[[Image:Circumpolar stars.jpg|thumb|300px|right|A time lapse photo showing the stars rotating around the celestial pole.]]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 if a specific body can be seen in that direction.
[[Image:Decdiag600.jpg|left|thumb|400px|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 mid-point. 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 need not wait until [[June 21]] to confirm the site does indeed face the summer solstice. For more information see [[History of solar observation]].

===Lunar positioning===
The Moon’s appearance is considerably more complex. Its motion, like the Sun, is between two limits — known as [[lunastice|''luna''stices]] rather than ''sol''stices. However, its travel between lunastices is considerably faster. It takes a [[Sidereal month#Sidereal month|sidereal month]] to complete its cycle rather than the year long trek of the Sun. This is further complicated as the lunastices marking the limits of the Moon’s movement move on [[Lunar standstill|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 ''[[Lunar phase|phase]]'' of the Moon. The cycle from one [[New Moon]] to the next runs on an entirely different cycle, the [[Sidereal month#Synodic month|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===
{{Main|Precession of the equinoxes}}
[[Image:Earth precession.jpg|thumb|right|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 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 25700 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 (constellation)|Draco]]. The effect can be substanstial over relatively short lengths of time, historically speaking. For instance a person born on December 25 in Roman times would have been born under the astrological sign of [[Capricorn (astrology)|Capricorn]]. In the modern period a person born on the same date is now a [[Sagittarius (astrology)|Sagittarian]]<ref>[http://www.montgomerycollege.edu/Departments/planet/M_AS101/Labs/WhatIsYourSignReally/What_is_your_sign_really.htm Astrological Things What is Your Sign, Really ?]</ref> due to the precession of the equinoxes.

===Transient phenomena===
[[Image:Tapestry of bayeux10.jpg|thumb|250px|left|Halley’s Comet depicted on the [[Bayeux tapestry]]]]Additionally there are often transient phenomena, events which do not happen on an annual cycle. Most predictable are events like [[eclipse]]s. In the case of [[solar eclipse]]s 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 [[Lydia]]ns, which following the eclipse failed to happen, to May 28, 585 BC.<ref>Herodotus, ''[http://www.perseus.tufts.edu/cgi-bin/ptext?lookup=Hdt.+1.74.1 The Histories]'', I.74</ref> Other easily calculated events are [[supernovae]] whose remains are visible to astronomers and therefore their positions and magnitude can be accurately calculated.

Some [[comet]]s are predictable, most famously [[Halley's Comet|Halley’s Comet]]. Yet as a class of object they remain unpredictable and can appear at any time. Some have extremely lengthy [[orbital period]]s 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 shower]]s should be predictable, but the [[meteor]]s are cometary debris and so require calculations of orbits which are currently impossible to complete. Other events noted by ancients include [[Aurora (astronomy)|aurorae]], [[sun dog]]s and [[rainbow]]s all of which are as impossible to predict as the ancient weather, but nevertheless may have been considered important phenomena.

Meteorite impacts and bolide explosions are also significant and do not occur at predictable times. On occasion, these impacts occur during meteor showers, while larger, more isolated cases occur and a relatively frequent basis. One such example is the alleged [[Umm al binni lake|Umm al Binni]] impact crater in Iraq, which may help explain the fall of Mesopotamian civilization as well as the 2200 BCE anomaly. Passages in the Epic of Gilgamesh as well as Biblical Revelations seem to describe meteorite impacts.

==Major topics of archaeoastronomical research==
===The use of calendars===
[[Image:AztecSunStoneReplica.jpg|thumb|250px|left|[[Aztec]] ''[[Aztec sun stone|Stone of the Sun]]'' replica in [[El Paso, Texas]], cast from the original to be found in Mexico's [[National Museum of Anthropology]]. A religious artefact showing how the [[Mexica]] people thought about time.]] A common justification for the need for astronomy is the need to develop an accurate [[calendar]] for [[agriculture|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 [[ecology|ecological]] signs, such as [[bird migration]]s 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.<ref>D. Turton and C.L.N. Ruggles, [http://www.jstor.org/view/00113204/dm991420/99p0147y/0 Agreeing to Disagree: The Measurement of Duration in a Southwestern Ethiopian Community], ''Current Anthropology'' Vol. 19.3, 1978, 585–600</ref> All the same, calendars appear to be an almost universal phenomenon in societies as they provide tools for the regulation of communal activities.

An example of a non-agricultural calendar is the ''[[Tzolk'in]]'' calendar of the [[Maya civilization]] of [[pre-Columbian]] [[Mesoamerica]], which is a cycle of 260 days. This count is based on an [[260-day Mesoamerican calendar|earlier calendar and is found throughout Mesoamerica]]. This formed part of a more comprehensive system of [[Maya calendar]]s which combined a series of astronomical observations and ritual cycles.<ref>A.F. Aveni, ''Empires of Time'', Basic Books, 1989, ISBN 0-465-01950-1</ref>

Other peculiar calendars include ancient [[Hellenic calendar|Greek calendars]]. These were nominally [[Lunar calendar|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]].<ref>S. McCluskey, The Inconstant Moon: Lunar Astronomies in Different Cultures, ''Archaeoastronomy: The Journal of Astronomy in Culture'' Vol 15. 2000, 14–31</ref> The lack of any universal calendar for ancient Greece suggests that coordination of panhellenic events such as [[Panhellenic Games|games]] or rituals could be difficult and that astronomical symbolism may have been used as a politically neutral form of timekeeping.<ref>A. Salt and E. Boutsikas, [http://antiquity.ac.uk/ant/079/ant0790564.htm Knowing when to consult the oracle at Delphi]. ''[[Antiquity (journal)|Antiquity]]'' Vol 79:305, 2005, 562–72</ref>

===Myth and cosmology===
[[Image:Argo-hevelius.jpg|thumb|250px|right|The constellation [[Argo Navis]] drawn by Johannes Hevelius in 1690.]]Another motive for studying the [[sky]] is to understand and explain the [[universe]]. In pre-scientific times [[mythology|myth]] was a tool for achieving this and the explanations, while not [[science|scientific]], are [[cosmology|cosmologies]].

The [[Inca]]s 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.<ref>B. Bauer and D. Dearborn, ''Astronomy and empire in the ancient Andes: the cultural origins of Inca sky watching'', University of Texas, 1995, ISBN 0-292-70837-8</ref> 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.<ref>G. Urton, ''At the crossroads of the earth and the sky: an Andean cosmology'', University of Texas. 1981, ISBN 0-292-70349-X</ref> 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 saw five, [[North]], [[South]], [[East]], [[West]] and [[Centre (geometry)|Centre]]. The Forbidden City occupied the centre of ancient Beijing.<ref>[[Ed Krupp|E.C. Krupp]], ''Skywatchers, Shamans and Kings'', John Wiley and Sons, 1997, 196–9, ISBN 0-471-32975-4</ref> One approaches the Emperor from the south, thus placing him in front of the [[Circumpolar constellation|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 [[constellation]]s. The Barasana of the [[Amazon Rainforest|Amazon]] plan part of their annual cycle based on observation of the stars. When their constellation of the Caterpillar-Jaguar falls they prepare to catch the pupating caterpillars of the forest as they fall from the trees.<ref>M. Hoskin, ''The Cambridge Concise History of Astronomy'', [[Cambridge University Press|CUP]], 1999, 15–6, ISBN 0-521-57600-8</ref> This provides planning for food procurement at a time when hunger could otherwise be a problem.

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 continuing and occasionally fractious debate.

===Displays of power===
[[Image:Intihuatana Solar Clock.jpg|thumbnail|250px|left|The Intihuatana (“tie the sun”) at [[Machu Picchu]] is believed to have been designed as an astronomic clock by the Incas, while some have speculated about the site’s possible [[astrological]] role]]The most common popular image of archaeoastronomy is the expression of hidden knowledge and power. By using stellar symbolism one can make claims of heavenly power.

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.<ref>R. Hannah, [http://scholar.lib.vt.edu/ejournals/ElAnt/V2N4/hannah.html The Constellations on Achilles’ Shield (Iliad 18. 485–489)]. ''Electronic Antiquity'' II.4, 1994, 15–6</ref> In North America shields depicted in [[Comanche]] [[petroglyphs]] appear to include Venus symbolism.<ref>[[Ed Krupp|E.C. Krupp]], ''Skywatchers, Shamans and Kings'', John Wiley and Sons, 1997, 252–3, ISBN 0-471-32975-4</ref>

[[Solstice|Solsticial]] alignments also can be seen as displays of power. 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.<ref>[[Ed Krupp|E.C. Krupp]], Light in the Temples, ''Records in Stone: Papers in Memory of Alexander Thom'', ed. C.L.N. Ruggles, 1988, 473–499, ISBN 0-521-33381-4</ref> 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 [[Sun|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.<ref>[[Rufinus]], [http://www29.homepage.villanova.edu/christopher.haas/destructioni%20of%20Serapeum.html The destruction of the Serapeum]</ref>

The use of astronomy at [[Stonehenge]] continues to be a matter of vigorous discussion.

==Archaeoastronomical organisations and publications==
There are currently two academic organisations for scholars of archaeoastronomy. [http://www.archaeoastronomy.org/ ISAAC&mdash;the International Society for Archaeoastronomy and Astronomy in Culture]&mdash;was founded in 1995 and now sponsors the Oxford conferences and ''Archaeoastronomy — the Journal of Astronomy in Culture''. [http://www.archeoastronomy.org/ SEAC&mdash;the Société Européenne pour l’Astronomie dans la Culture]&mdash;is slightly older; it was created in 1992. SEAC holds annual conferences in [[Europe]] and publishes refereed conference proceedings on an annual basis.

Additionally the ''Journal for the History of Astronomy'' publishes many archaeoastronomical papers. For twenty-seven volumes it also published an annual supplement ''Archaeoastronomy''.

==References==
{{reflist|2}}

==See also==
* [[Cultural astronomy]]
* [[List of archaeoastronomical sites sorted by country]] Sites where claims for the use of astronomy have been made.
* [[List of artefacts of archaeoastronomical significance]] Artefacts which have been interpreted as being used for some astronomical purpose.
* [[European Megalithic Culture]]
* [[Australian Aboriginal Astronomy]]
** [[Aboriginal stone arrangements]]
* [[Lunar standstill]]
* [[Medicine wheels]]
* [[Mound builder (people)|Mound builders]]
* [[Petroforms]]
* [[Megalithic geometry]]

==External links==
{{wiktionary}}
* [http://library.thinkquest.org/C0118421/main.html Archaeoastronomy] A Thinkquest website surveying archaeoastronomical sites across the world.
* [http://www.cliveruggles.net/ Clive Ruggles' webpages:] images, bibliography, software, and materials from his course at the [[University of Leicester]]
* [http://www.archaeoastronomy.org/ ISAAC], The International Society for Archaeoastronomy and Astronomy in Culture.
* [http://www.archeoastronomy.org/ SEAC] La Société Européenne pour l’Astronomie dans la Culture. Site in English.
* [http://www.arqueoastronomia.org/siac.htm SIAC] La Sociedad Interamericana de Astronomía en la Cultura.
* [http://www.spaceimaging.com/gallery/ancientobservatories/ Space Imaging’s Ancient Observatories gallery] — Satellite pictures of ancient observatories.
* [http://www.traditionsofthesun.org/ Traditions of the Sun] — NASA and others exploring the world’s ancient observatories.
* [http://video.google.com/videoplay?docid=-8410091707901559298 Tulum — Mayan Mystery] — Amateur archaeoastronomy from the archaeological site at Tulum.
* [http://www.atnf.csiro.au/research/AboriginalAstronomy/ Australian Aboriginal Astronomy]
* [http://www.sacred-texts.com/neu/eng/sac/index.htm Stonehenge and Other British Stone Monuments Astronomically Considered] - etext at sacred-texts.com
* [http://web.mac.com/aeionic/iWeb/Site%204/Astroarcheology%20Copan%20Ruinas.html Amateur Archeoastronomy of Mayan Copan Ruinas]
* [http://www.shastro.org.uk Society for the History of Astronomy]
* [http://www.panjika.co.cc High Precision Archaeoastronomy Eclipse Detector]

===Journals===
* [http://www.wam.umd.edu/~tlaloc/archastro/ae.html Archaeoastronomy and Ethnoastronomy News]
* [http://www.shpltd.co.uk/aa.html Archaeoastronomy: Supplement to the Journal for the History of Astronomy]
* [http://www.utexas.edu/utpress/journals/jarch.html Archaeoastronomy: The Journal of Astronomy in Culture]
* [http://www.cultureandcosmos.com/ Culture and Cosmos]
* [http://www.shpltd.co.uk/jha.html Journal for the History of Astronomy]

[[Category:Ancient astronomy]]
[[Category:Archaeoastronomy|*]]
[[Category:Archaeological sub-disciplines]]
[[Category:History of astronomy]]
[[Category:History of astrology]]
[[Category:Earth mysteries]]
[[Category:Ancient mysteries]]

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