The Zenithal Sun

A tropical Phenomenon

The Mayan civilization is a tropical one. As such, its season cycle is very different from that of temperate countries. Instead of four seasons (spring, summer, autumn and winter), the tropical regions only have two (the dry season and the rainy season).

Going from one season to the other is not linked to the equinoxes or solstices but rather to the zenithal sun episodes. Here below is a representation of the annual cycle of the seasons in Guatemala with the dry season, the rainy season and the two zenithal suns.

The propitious season for agriculture takes place between the two zenithal suns; it is the moment when the climate is both warm and humid, which allows the crop to grow fast and consequently get a rapid and abundant harvest.

The zenithal suns’ dates are just as stable as the equinoxes’ and solstices’ except for the fact that they vary with the latitude. For the Mayas, they happen between April 30th and August 13th in Izapa on the Pacific Coast of Guatemala and May 23rd and July 21st in Chichen Itza, Yucatan (Mexico) – (on the topic, refer to the online book entitled   Cycle of the Sun, Mysteries of the Moon and more particularly the chapter 4).

translation by Nelly Lewin

Xochicalco zenithal Pit (Image from the page

late april / mid may

early january

mid august / late july

early november

Establishing the zenithal suns’ dates and better still, forecasting them with anticipation is thus, for any tropical civilization in the world, a necessity so as to maximize the yield of these very fertile period which cover about hundred days between the two annual zenithal suns. This partly explains the importance of astronomy in these civilizations.

Through the constant observation of the sky, one can see that a particular star would always rise at a certain point a few days before such or such a zenithal sun, hence it would be possible to know beforehand the exact date of any given sun.

It would for example make possible to plough on time before the first rains as for the April/May sun and to anticipate the temperature falls for the sun of July/August.

What is a zenithal Sun?

A zenithal sun is defined by the fact that the sun is perfectly perpendicular to the earth plane at noon, which translates by the total vanishing of the  vertical elements shadows such as poles or pyramids. The shadow of a zenithal sun also stops at the precise doorstep of the houses.

When drilling a vertical hole at the top of a construction or in the ground to access a cavern, one can observe at the moment the sun is at its zenith a column of light descending right from the orifice. This is called zenithal tubes or wells (see the picture at the top of this page).

It is easy to imagine the impact this kind of event could have on the population and it is, as explained before, a phenomenon perfectly reproducible from year to another.

Izapa, a distinct place

Izapa is a place on the Pacific coast in the South of Mexico, close to the border with Guatemala. It was the seat of a civilization which flourished before the Mayas. It is thought to have been the link between the Olmecs and the first Mayas.

Izapa’s latitude is 14,8° north which means that the dates for its zenithal suns are April 30th and August 13th. The intervals between the two boil down to:

  1. -105 days for the fertile period,

  2. -260 days for the grand interval (end of rainy season and beginning of dry season.

Now, 260 days is precisely the periodicity of a TZOLK’IN rotation. If you add to it that the oldest representations of the calendar have been found in Izapa and that the long count starting date (August 13th -3114) corresponds to a zenithal sun under that latitude, the result is a theory according to which some of the Mayan calendars (TZOLK’IN, HAAB, Long Count) would have been created by the Izapan culture, even by the Olmec culture perhaps.

dry season

rainy season

Table 3 - Dates of Zenithal Sun Positions within Mesoamerica

The 2011 Zenithal Suns in Izapa

The two Izapa zenithal suns are reproduced here below thanks to Paul Neave Flash Planetarium. This tool precision doesn’t allow measurements under the degree, the chosen latitude is thus 15° north and 92°0 longitude west, the hours here indicated are the UTC ones, one should subtract 8 hours to get the local time.

The global and stellar environments of the suns are represented. As I am not an astrologist myself, I am not able to draw any conclusion, should any of you be in a position to do so, please let me know… I shall be glad to add relevant remarks to this page.

The only thing I can say is that the 13th of August Venus/Sun conjunction is not regarded by the Mayas as an auspicious one. The Ancient Mayas even used to stay home when Venus appeared in the sky with the Sun.