Calendars and Ceremonies: Native American Astronomy prepared by Ruth Howes Marquette University with support from the Wisconsin Space Grant Consortium

Aerial View of Pueblo Bonito at Chaco Canyon An Anasazi Ruin Photograph 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 year as earth’s speed around the Sun varies.

Sidereal and Solar Noon Day 1 Sun Sidereal Noon Day 2 Orbital motion Earth viewed from north pole so rotates counterclockwise The Solar Day is 4 minutes longer than the sidereal day because the earth must rotate a bit more to compensate for its rotational motion. 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 amount of sunlight and the angle of the sunlight on different spots 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 on Earth in each of the four seasons Image credit Tom Ruen using Full Sky Observatory Software and Downloaded from Wikipedia

Special Points on the Ecliptic (Northern Hemisphere) Summer solstice: North pole tipped directly towards the sun Most hours of daylight Sun as far north as it goes Winter solstice: South pole tipped directly towards the sun Least hours of daylight Sun as far south as it goes Equinox: Sun’s light falls directly on the equator Day and night equal in length

How the tilt of the earth’s axis causes seasons Four positions shown are the solstices and equinoxes Drawing by Smack for Wikipedia

North South Equinox Summer Solstice Winter Solstice Motion of the position of sunrise along the eastern horizon Position changes rapidly at equinox; slowly at solstice

A notch viewed at sunrise across a diagonal in the Great House of Wijiji. It clearly marks the winter solstice and provides warning to allow priest to prepare for a ceremony. National Park Service image downloaded from

Panoramic View of Cusco Photo courtesy of Tony Biker downloaded from Wikipediawww.bikertony.com

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

Galileo image downloaded from Months are defined on the basis of the moon’s revolution around the earth

Time PeriodLength Year 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 are limited 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 include ruins and such writing as remains.

Casa Rinconada: the largest Kiva at Chaco Canyon. At the summer solstice, the rising sun enters a window on the eastern wall and highlights a niche on the western wall. National Park Service image downloaded from

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

Palenque temple: photograph by Koyaanis Qatsi downloaded from Wikipedia

Mayan numerals Downloaded from Wikipedia

Back of a Mayan stele showing dates. Downloaded from Wikipedia

The Mayan Calendar Two types of year: The Vague Year: 365 days; 18 months of 20 days each plus 5 extra days. Used for agriculture and many ceremonies. They seem to have adjusted it 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 period is 584 days. 5 Venus years equal 8 solar years.

North American Tribes used wood for construction. They left no written records, and sages often died before they passed on knowledge. Ethnologist, James Murnie, who was half Pawnee described the Pawnee cosmology which was certainly included the solar year and may have included the motion of the planet Mars. The Navajo used a calendar based on the rising of particular constellations.

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

Two Versions of the Sun Dance Indians at Roanoke by John White, 1585 Downloaded from Wikipedia Sioux Sun Dance From etching by George Catlin Downloaded from Wikipedia

The Gregorian Calendar Year is 365 days divided into 12 months roughly 30 days long. Every 4 th 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 will not be one. Adopted in England (and the colonies) in The calendar had to be adjusted by 11 days. People were understandably 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 astronomical phenomena. Constellations: particularly the Pleiades Meteor Showers Possibly the supernova of It appeared near the crescent moon as drawn by the Anasazi. New discoveries currently. circle of standing stones in Brazil year old observatory at foot of Andes.

Pictograph from Chaco Canyon showing what may be a supernova. National Park Service image downloaded from