Alta Vista, Stone Calendar In Zacatecas
A unique event happens on June 21 at the archaeological ruin site of Alta Vista. We rarely consider this phenomenon although we all feel the tug of seasonal change as the sun moves over the Tropic of Cancer at Alta Vista on zenith day.
While Alta Vista archaeological ruin site is so out of the tourist track that few people visit except during the annual Zenith Day, the designers of Alta Vista considered the seasonal movement of the sun over the earth so important that they built standing stones, groups of columns, walls with sight lines, and sundial stones to record the sun's movement.
Squat and peer through slits in the walls to see sun alignments on the distant mountains and you will peer into the world of zenith days, seasonal change, daylight savings times, the changing of the leaves, the running of the salmon, the midnight sun of the arctic and the winter doldrums of the northern latitudes. Shadows on the many columns and rows of stone north and south will quickly demonstrate the elegant simplicity of a standing stone's ability to record the apparent movement of the sun.
Northerners rarely connect the movement of the sun over the earth with the resultant four seasons. The phenomenon may only come to consciousness at ruins sites such as Monte Alban in Oaxaca City where the ancients built a zenith observation stone to record the May and August zenith days, at Chichen Itza where a snake shadow moves down a staircase on the equinox, or at the Izapa ruin site where stone columns are set in the cardinal points, and perhaps at that circle of stones on the Salisbury Plain, Stonehenge.
Mexico's first century observers could record the movement of the sun by measuring shadows on the ground but likely didn't know that it is not the sun that moves over the earth but the tilted angle of the earth's axis that causes the apparent movement of the sun, north and then back to south each year as the earth revolves around the sun. They could see the shadows change but perhaps could never have imagined the four seasons and the midnight suns in the far northern and southern hemispheres.
Then again, since their ancestors had crossed the polar regions during the ice age, they might just have had legends full of the disappearing sun and its long winter absences.
Sun positions over the Zenith stone
at Monte Alban archaeological site
European geographers such as first century Rome's Pliny living at latitude 41 knew that the climate went through drastic seasonal changes throughout the year. And the Greeks, three hundred years before Pliney, determined the circumference of the earth by measuring the suns shadow.
For those living well south of the Tropic of Capricorn the Summer occurs during the winter months when it is cold in the northern hemisphere. In South America and Africa the longest periods of daylight and hottest weather occurs during December and January. The sun is at its zenith on the Tropic of Capricorn on December 21 and appears to be directly overhead in the mid-day at 24° 30′ 0″ S, 69° 15′ 0″ W, over the driest place on earth, the Atacama Desert of Chile.
After December 22 the sun appears to move north over the earth each day towards its zenith day over the Tropic of Cancer at Chalchihuites, latitude 23° 28′ 58″ N, 103° 52′ 39″ W, on the Summer Solstice. The northern hemisphere warms in June because the tilt of the axis of the earth has positioned the northern hemisphere beneath the direct rays of the sun. Zenith day at the Tropic of Cancer is the longest period of daylight in the northern hemisphere. If you traveled north from Chalchihuites, the duration of daylight would increase until at the north pole the sun would not set at all on the 22nd of June. At Prudhoe Bay for example the sun does not set from mid May to mid July.
The walls are designed with sightlines to distant
Sightlines to clefts in the distant mountains can track the
movement of the sun during the year
Concomitantly, in the southern hemisphere, June 21 is the shortest day of the year. At the South Pole on June 21 the sun does not rise at all. Between these apparent extreme movements of the sun over the earth are the Fall Equinox, which occurs on September 22, and the Spring Equinox, which occurs on March 22. These two dates are zenith days of the sun over the Equator at Belem in Brazil, near latitude zero, half way between the Tropic of Cancer and Tropic of Capricorn. On these dates the period of daylight and darkness are equal in the northern and southern hemisphere at the Tropics of Cancer and Capricorn.
Walls are constructed to allow sight lines to distant mountains to track the
movement of the sun during the year
With the stone observatory of Alta Vista and other solar-related structures like it the people of ancient Mexico appear to have worshipped the sun. They were deeply concerned with the readily observable change each day in the suns shadow as they tracked the sun's movement north and south. Perhaps they feared that someday it would not return, so much so that they built the marvelous stone calendar at Alta Vista
Stones laid out east and west can track the
movement of the sun both during the day
and during the year
Bus to Alta Vista Ruin Site from Zacatecas.
Three-hour Omnibus de Mexico bus with trips each hour the 100 miles to Sombrerete for 160 pesos. From Sombrerete another 35 miles to Chalchihuites via a local bus. Taxi to Alta Vista archaeological site, arrange for return
Related Link Alta Vista Columns
Chichen Itza Equinox Event
Archaeoastronomer Anthony F. Aveni of Colgate University, famed for his work with sun and star alignments on other Mexican sites, collaborated with Charles Kelly in 1977 Aveni, Anthony F., Horst Hartung, and J. Charles Kelley. 1982. "Alta Vista (Chalchihuites): Astronomical Implications of a Mesoamerican Ceremonial Outpost at the Tropic of Cancer." American Antiquity, vol. 47, pp. 316-335.