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Astro arqueolog­a

Jan 16, 2015

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Astro arqueología

  • 1. ARCHAEOASTRONOMY Roberta Zanin

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

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

1 3. Outline

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

2 4. Stonehenge

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

3 5. Stonehenge

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

3 6. Stonehenge alignments Heel Stone 4 7. A.Aveni, Tropical Astronomy, Science 1981 The Caracol: Maya observatory (Chichn Itz, Yucatan-Mexico) viewingshaft These windows align with some astronomical sightlines: Venus rising at its northernmostsouthernmost positions,as well as the equinox sunset 5 8. A.Aveni, Tropical Astronomy, Science 1981 The Caracol: Maya observatory (Chichn Itz, Yucatan-Mexico) viewingshaft These windows align with some astronomical sightlines: Venus rising at itsnorthernmostsouthernmost positions,as well as the equinox sunset Since Venuss orbit is tilted 4with respect to the ecliptic,its position shifts against thehorizon, the northernmost and the southernmost positions correspondto the farthest northern and southern points above the celestial equator. 5 9. N. Strobel, Astronomy without a telescope The Caracol: Maya observatory (Chichn Itz, Yucatan-Mexico) These windows align with some astronomical sightlines: Venus rising at itsnorthernmostsouthernmost positions,as well as the equinox sunset Since Venuss orbit is tilted 4with respect to the ecliptic,its position shifts against thehorizon, the northernmost and the southernmost positions correspondto the farthest northern and southern points above the celestial equator. 5 10. Staircasealmost perfectmatch with Venus setting at its northernmost position The building diagonal is alignedwith winter and summer solstices The Caracol: Maya observatory (Chichn Itz, Yucatan-Mexico) 5 11. El Castillo: Pyramid of Kukulkn(Chichn Itz, Yucatan-Mexico) 1. At the equinox sunsets, a play of light and shadowcreates the appearance of a snake that gradually undulates down thestairway of the pyramid. 6 12. El Castillo: Pyramid of Kukulkn(Chichn Itz, Yucatan-Mexico) 1. At the equinox sunsets, a play of light and shadowcreates the appearance of a snake that gradually undulates down thestairway of the pyramid. this sinuous shadow joinswith one of the snake-head sculpture carved into the base of the monument 6 13. El Castillo: Pyramid of Kukulkn(Chichn Itz, Yucatan-Mexico) 1. At the equinox sunsets, a play of light and shadowcreates the appearance of a snake that gradually undulates down thestairway of the pyramid. this sinuous shadow joinswith one of the snake-head sculpture carved into the base of the monument 2. It was used as calendar: each of the 4 stairwayshas 91 steps + 1 step onthe top = 365 steps6 14. El Castillo: Pyramid of Kukulkn(Chichn Itz, Yucatan-Mexico) 1. At the equinox sunsets, a play of light and shadowcreates the appearance of a snake that gradually undulates down thestairway of the pyramid. this sinuous shadow joinswith one of the snake-head sculpture carved into the base of the monument 2. It was used as calendar: each of the 4 stairwayshas 91 steps + 1 step onthe top = 365 steps3. the west plane facesthe zenith passage with a precision within 1 6 15. Maya astronomy From this information, they developed calendars toKeep track of celestial movements: their solarcalendar was more precise than the presentGregorian calendar. Maya were skilled observers of the sky: they calculated the complexmotions of the Sun, the stars and planets and recorded this informationin their codices (Dresden Codex). 9 Venus had been recognized as morning and evening star! Greek astronomers had recorded Venus as two different stars. Modern (day)Maya (day) Lunar period 29.53059 29.53086 Solar period 365.2420 365.2466 Mars period 779.94 780 Venus period 583.93 583.9203 16. Skywatchers Venus: morning and evening starVenus is an inferior planet: it has phases as the MoonInferiorconjunction Superior conjunction 8 Heliacal rise=Sun and Venus rise together. After heliacal rise, Venus rises before the sunrise: morning star. After superior conjunction, Venus rises after the sunrise, so set after thesunset: evening star. Dresden Codex (day) Modern (day) Morning star (after heliacalrise) 236 263 Invisible (superior conjunction) 90 50 Evening star 250 263 Invisible (inferior conjunction) 8 8 Total 584 584 17. Maya astronomy From this information, they developed calendars to keep track of celestial movements: their solar calendarwas more precise than the present Gregorian calendar. Maya were skilled observers of the sky: they calculated the complexmotions of the Sun, the stars and planets and recorded this informationin their codices (Dresden Codex). 7 It seems incredible!But we have forgotten what can be achieve by careful nakedeye observation using simple instruments. Modern (day)Maya (day) Lunar period 29.53059 29.53086 Solar period 365.2420 365.2466 Mars period 779.94 780 Venus period 583.93 583.9203 18. Marking time withoutinstruments Gnomons, simple long sticks located on a plate,were already used by Greek astronomers . To determine the solstice day is rather easy only by studyingshadows: at summer solstice the Sun is at its highest point andthe shadows it casts are the shortest; vice versa at winter solstice.At the beginning, gnomons were used as sundials (by dividing the plate into equal intervals), as well as to establish cardinal directions(south=the position of the shortest shadow of a day) and as calendar (by dividing the period between two solstices into intervals, each of onecharacterized by a particular shadow length) Maya used the zenith passage which are characterizedby shadowless moments as reference day. 11 no thickness gnomon 19. The zenith-horizon systemAt temperate zones, the observer views circulatory motion. In this case it is simpler using the celestial pole and the celestial equator as reference lines.The horizon functions as fundamentalreference line, together with the zenith. Here star motion is vertical.The sun can be observed at zenith at the equinoxes. Tropics are the maximum latitudes at which the Sun can beobserved at zenith: ZENITH PASSAGES.10 N. Strobel, Astronomy without a telescope 20. Zenith Tubes There is no evidence that gnomons wereused by Maya, but they used zenith tubes to identify the shadowless moment. These tubes admit the Suns image to pass verticallyinto a darkness chamber A.Aveni, Tropical Astronomy, Science (1981) At the ruins of Xochicalco, Mexico,a 8 m long perfect straight tube, which opens intoa roundish chamber (10 m diameter), was found. The cross section of this tube is hexagonal with a2.5 of FOV. 12 21. Sun-Moon angle 0 (new phase) SOLAR ECLIPSE Sun-Moon angle 180 (full phase) LUNAR ECLIPSE When an eclipse occurs? AND Moon at the line of nodesintersection of the Moonsorbit with the ecliptic twice a yearat different dates Moons orbit precesses 13 22. Stonehenge: an eclipse predictor only when, not where G. Hawkins, The Stonehenge Decoded, Nature 1963 Full moon 14 + 4 markers 23. Stonehenge: an eclipse predictor only when, not where G. Hawkins, The Stonehenge Decoded, Nature 1963 Full moon 14 + 4 markers 56 a perfect number! 56/2=28Moons orbit is 27.322days Moon marker twice a day and skip one each cycle 24. Stonehenge: an eclipse pre