Calendars and Ceremonies:Native American Astronomy

prepared by Ruth HowesMarquette University

with support from theWisconsin Space Grant Consortium

Aerial View of Pueblo Bonito at Chaco Canyon

An Anasazi RuinPhotograph from National Park Service taken by Fritz Swanson

Basic Units of the Calendar

Day: time between two appearances of the Sun at a fixed position

Zenith: sun directly overhead

Nadir: sun directly opposite the zenith

Sunrise and sunset vary over the year so sophisticated cultures used the zenith

The Day

Solar day: measured relative to a position on earth (zenith)

Sidereal day: measured relative to the fixed stars.

Solar day is about 4 minutes longer than the sidereal day because the earth must turn a bit more to catch up

with the moving sun.

Length of the solar day varies several minutes over a yearas earth’s speed around the Sun varies.

Sidereal andSolar NoonDay 1

Sun

Sidereal NoonDay 2

Orbitalmotion

Earth viewed from north pole so rotates counterclockwise

The Solar Day is 4 minutes longerthan the sidereal day becausethe earth must rotate a bit more to compensate for its rotationalmotion.

Observer faces the fixed star.

The Year

Ecliptic: 1) earth’s orbit around the sun 2) sun’s apparent motion through the fixed stars

Year: The time it takes the sun to move around the ecliptic and back to it’s initial position.

Earth’s axis is tipped at an angle of 23½o relative to a perpendicular to the plane of the ecliptic.

Seasons are caused by this tip which changes the amountof sunlight and the angle of the sunlight on differentspots on Earth.

Summer: Pole tipped towards the sun.

Winter: Pole tipped away from the sun.

n.b. Earth’s orbit is very nearly circular so the slight variation in its distance from the sun does not cause seasons.

Sunlight onEarth in eachof the four seasons Image creditTom RuenusingFull Sky ObservatorySoftware andDownloaded fromWikipedia

Special Points on the Ecliptic (Northern Hemisphere)

Summer solstice: North pole tipped directly towards the sunMost hours of daylightSun as far north as it goes

Winter solstice: South pole tipped directly towards the sunLeast hours of daylightSun as far south as it goes

Equinox: Sun’s light falls directly on the equatorDay and night equal in length

How the tilt of the earth’s axis causes seasonsFour positions shown are the solstices and equinoxesDrawing by Smack for Wikipedia

North South

Equinox

SummerSolstice

Winter Solstice

Motion of the position of sunrise along the eastern horizonPosition changes rapidly at equinox; slowly at solstice

A notch viewedat sunriseacross a diagonal in the Great House ofWijiji. It clearly marksthe winter solsticeand provides warningto allow priest to prepare for aceremony.

National Park Service image downloaded from http://www.nps.gov/chcu/culture.htm

Panoramic View of CuscoPhoto courtesy of Tony Biker www.bikertony.com downloaded from Wikipedia

Incan City of Machu-Picchu showing horizon with many featuresImage from Chmouel downloaded from Wikipedia

Galileo image downloaded fromhttp://grin.hq.nasa.gov/IMAGES/SMALL/GPN-2000-000473.jpg

Months are defined on thebasis of the moon’s revolution around the earth

Time Period Length

Year 365.2425 days

Sidereal Month 27 days, 7 hours, 43 minutes

Synodic Month 29 days, 12 hours, 44 minutes

Synodic Month: One lunar revolution from full moon to full moon. Defined relative to the positions of the earth and the moon.

Sidereal Month: One lunar revolution measured with respect to the fixed stars.

Months and Years are not composed of even numbers of days.

The development of calendars occurred many times in many cultures.

Native American cultures are very diverse so examples arelimited in scope.

European diseases and conquerors destroyed many of the materials that explained Native American astronomy and calendars.

Archaeoastronomy: the cross disciplinary study of astronomy in archaic cultures. Sources includeruins and such writing as remains.

Casa Rinconada: the largest Kiva at Chaco Canyon. At the summer solstice, the rising sun enters a windowon the eastern wall and highlights a niche on the western wall.

National Park Service image downloaded fromhttp://www.nps.gov/chcu/culture.htm

Another method for determining the winter solstice: If the rising sun follows the edge of the stone when observed from the Navajo sun symbol,it is the solstice. This avoids problems with clouds. Chaco Canyon.National Park Service image downloaded from http://www.nps.gov/chcu/culture.htm

Palenque temple: photograph by Koyaanis Qatsi downloaded from Wikipedia

Mayan numerals

Downloaded fromWikipedia

Back of a Mayanstele showing dates.

Downloaded from Wikipedia

The Mayan Calendar

Two types of year:

The Vague Year: 365 days; 18 months of 20 days eachplus 5 extra days. Used for agriculture andmany ceremonies. They seem to have adjustedit to keep it in synch with the sun.

The Ceremonial Year: 260 days; 13 months of 20 days each

Every 52 years, the two calendars were synchronized.

In addition, the Maya tracked Venus whose synodic periodis 584 days. 5 Venus years equal 8 solar years.

North American Tribes used wood for construction.They left no written records, and sages oftendied before they passed on knowledge.

Ethnologist, James Murnie, who was half Pawneedescribed the Pawnee cosmology whichwas certainly included the solar yearand may have included the motion of theplanet Mars.

The Navajo used a calendar based on the risingof particular constellations.

Pawnee LodgePhotographed by William H. Jackson, 1873. American Indian Select List number 84. From US National Archives; download from Wikipedia

Two Versions of the Sun Dance

Indians at Roanoke byJohn White, 1585

Downloaded from Wikipedia

Sioux Sun DanceFrom etching byGeorge Catlin

Downloaded fromWikipedia

The Gregorian Calendar

Year is 365 days divided into 12 months roughly 30 days long.

Every 4th year adds a day (leap year) to stay with sun.

This is slightly too long so every year divisible by 100 is not a leap year unless it is divisible by 4. For example,2000 was a leap year. 2100 will not be one.

Adopted in England (and the colonies) in 1752. The calendarhad to be adjusted by 11 days. People wereunderstandably upset.

Painting by William Hogarth (1755) showing election propaganda A poster reading “Give us our Eleven days!” on floor at right. Digitized by the York Project and downloaded from Wikipedia

The Native Americans also observed other astronomicalphenomena.

Constellations: particularly the Pleiades

Meteor Showers

Possibly the supernova of 1054. It appearednear the crescent moon as drawn bythe Anasazi.

New discoveries currently.circle of standing stones in Brazil.4200 year old observatory at foot of Andes.

Pictograph from Chaco Canyon showing what may be a supernova.National Park Service image downloaded from http://www.nps.gov/chcu/culture.htm