The Aztec “Sun Stone”

It  was the beginning of the end…the year 1521 AD…Cortes and his band of Spanish Conquestadores were passing judgement on their captives the Mexicas (Aztecs) on the very soil where these indigenous peoples had once walked in harmony with nature. The natives of this glorious land were to become no more than a passing flicker in time and memory.

Over two hundred and fifty years had passed since this unfortunate historical event. Then, without warning, the torch of ancient Aztec history rekindled the long forgotten pride once bestowed within the hearts and souls of these courageous Mexican warriors.

Perhaps by fate or design, whatever the cause, it was during the renovation of Mexico City’s central plaza in 1790 that the most exciting addition to this country’s historical past was uncovered…the Aztec “Sun Stone”.

Neither photographs nor drawings can do justice to the marvel in craftsmanship required to produce this single piece of carved basalt stone. Measuring 3.6 meters (12 feet) in diameter, this single stone weighs an estimated 24 tonnes (Ill.1).


Illustration 1. The Aztec “Sun Stone” was discovered in 1790,  measuring 3.6 meters in diameter and weighing an estimated 24 tonnes.


An additional two hundred years have passed and various theories for the unique design are abundant. They are put forward in an attempt to uncover the reasons for the mysterious intertwining geometric markings dispersed throughout the stone.

The most evident symbol is the face within the centre circle; it representing the Sun (Tonatiuh), but it is the balance of these markings that have stumped the finest of archaeologists.

Supported by other written ancient documents, the inner circle of twenty small glyphs have been successfully decoded and represent the twenty days to the month, having thirteen months to a complete cycle; this was their “almanac year” of 260 days. The second counting system was the “solar year”, totalling 365 days and consisting of eighteen (18) months each having four weeks of five days (20 days) per month…this totalled 360 days. By adding five extra days, known as the nemontemi (empty days), it brought the total count to 365 days…this is what we are taught !!!

Although it may appear irrelevant to the Giza pyramid complex, the “Sun Stone” will be one of several astronomical measuring systems chosen to guide us toward a similar design used by the ancient Egyptian pyramid builders.

The first step is to create a basic geometric duplication of the stone from the photograph above (Ill. 2). 


Illustration 2. The basic geometric design of the “Sun Stone”.


Note the Sun’s face drawn in the centre, having two inner rings “earrings” representing circular objects on opposite sides of the Sun’s face. Four oddly positioned rectangles are also attached to the side of the face; two above and two below the “earrings”. When combining these object we can notice the similarity between them and the Aztec glyph Xihuitl representing the solar year (Ill. 3). The similarity in formation could be a construed as the inner portion of the stone’s design representing the solar calendar of 365 days…as expressed by archaeologists.


Illustration 3. The glyph Xihuitl representing the solar year, most similar to the centre design of the “Sun Stone”


Given the centre face as the first indication to a solar reference, coupled with the eight lines required to produce the glyph Xihuitl, and the eight triangular points surrounding the outer ring of the stone, should be most obvious to astronomers. These points indicate the ancient’s full knowledge of planet motion around the Sun when using Earth’s annual measure of time!

Venus and Earth share an intriguing orbital feature…Venus travels (1 + 5/8) of its orbit for every orbit of Earth and this sets the stage for an astronomical and geometrical feature between both planets…These two planets will realign with each other every eight Earth years…IN THE SAME ORBITAL LOCATION WHERE THEY STARTED FROM ! Venus and Earth are the only two planets in our solar system having a realignment ratio equally divisible into a 360 degree circle, and the ancient Aztecs were fully aware of this astronomical fact. To prove it, we simply compare the basic geometric design from illustration 2 to the orbital alignment locations for Venus and Earth as illustrated below (Ill. 4).  


Illustration 4. Travelling in a counter clockwise direction, the eight locations for Venus are shown for each complete and successive orbit of Earth around the Sun.


Starting the cycle with Earth and Venus aligning with the Sun at position #1 (12 o’clock); Earth orbits the Sun once while Venus completes its first orbit and continues to position #2. The second full orbit of Earth will place Venus in position #3…continuing the count for eight Earth years. The end of the eight year cycle brings both planets back to the original start position. From the orbital diagram, we can now realize why the Sun Stone has two triangles pointing toward the twelve o’clock position; one represents the location of Earth and the other for Venus at their start location.

There are two simple but important mathematical relationships between both planets that should be remembered.

1) Venus travels thirteen “parts” of its orbit for every eight “parts” of orbit that Earth completes (13/8, or 1.625:1 ratio).

2) Earth and Venus aligned in the same orbital location every 8 Earth years.

There is one other significant feature that the designer(s) wanted to express and it is demonstrated by the two “earrings” and the four rectangular forms surrounding the face.

In four complete orbits of Earth, Venus will travel six complete orbits around the Sun then continue to a point exactly 180 degrees in orbit from the start position. The four rectangles surrounding the face represent four Earth years, and the two “earrings” represent the two locations for Venus set 180 degrees from each other.

The “solar year” count within the Mayan calendar system totals 365 days, and this confirms that the designer(s) knew the orbital ratios for Venus and Earth.

We may have actually assumed in the wrong direction…

Eight counts of 365 Earth days is equal to thirteen complete orbits of Venus, and Venus orbits the sun in 224.7 Earth days. Working in the reverse direction…if the calendar was set by comparing the orbital period of Venus to that of Earth then this measure would calculates to 224.62 Earth days for one complete orbit of Venus, a 0.08 day error per orbit of Venus.


The ancients knew the number of days to the Earth year most accurately, but elected to use the full day count to register the location of the planet Venus. However, there was one additional planet to be considered…our outer neighbour Mars !!

Recalling the second counting system…the “almanac year”; it is based on a 260 Earth day cycle and it is this count that ties both Earth and Mars together in their respective orbits.

Mars orbits the sun in 686.98 Earth days, compared to 365.256 days for Earth. The time required between two consecutive alignments of two planets is termed the synodic period. To calculate this value requires simple mathematics, and for Earth and Mars the total time is 780 Earth days. It is at this point where we stop and investigate another simple mathematical situation….3x260 days = 780 days.

…780 Earth days equals three complete “almanac years” !!


To illustrate, we set Earth and Mars at the 12 o’clock location (Ill. 5, position #1). Rotating counter clockwise for 260 Earth days, Earth and Mars will travel to a location in orbit where they are 120 degrees apart from each other (Ill. 5, position #2). The second count of 260 Earth days (Ill. 5, position #3) shows Earth having completed one orbit and leading Mars by an additional 120 degrees, totalling 240 degrees in orbit. After the third count of 260 Earth days, both planets realigning at a point 48.71 degrees from the start position (Ill. 5, position #4).


Illustration 5. The orbital locations for Earth and Mars at the end of each “almanac year” of 260 days. Three “almanac years” equals one synodic period for Earth and Mars.


The three counts of 260 days indicates to us that the ancients understood the orbital alignment of Earth and Mars. To confirm, they designed another geometrical feature within the stone.

From illustration 5, we can continue to plot the sequential orbital locations where Earth and Mars will align until the 360 degree circle is complete (Ill. 6.)


Illustration 6.  The alignment locations for the planets Mars and Earth, starting from the 12 o’clock position.


Compared to the Venus/Earth pattern, it is noticed how the last alignment location (position #8) falls short of the complete 360 degree circle. However, there is the common element of eight locations within the 360 degree circle and it is this pattern that the designer(s) emphasized. By rotating the start point to geometrically “balance” the pattern we have a different view of the alignment locations (Ill. 7).


Illustration 7. The eight locations where Mars and Earth align are “balanced” geometrically.


From  illustration 3, the glyph Xihuitl  is reintroduced and compared to the “balanced” pattern of the eight locations where Earth and Mars align (Ill. 8).


Illustration 8. The glyph Xihuitl, assumed to symbolize the solar year, is superimposed over the eight alignment locations for Earth and Mars


Xihuitl is the symbol for the solar year and drawn geometrically identical to the eight alignment locations for Earth and Mars. Were archaeologists lead astray with the concept of this glyph representing a solar year? Is it possible that it represents a synodic year of 780 days, this being equivalent to three almanac years, or the interval between each realignment of Earth and Mars in the heavens?


The Sun Stone contains two simplified Earth calendar systems, each relating directly to the planets Venus and Mars. Included within the design are the orbital characteristics of these same three planets. What must be acknowledged is the simple fact that the ancient Aztecs were most knowledgeable of planet motion. It is unknown how or when the Aztecs may have gained such knowledge, however it is most obvious they understood and comprehended the central solar disc (Sun) and visualize the basic mathematical relationship between the orbital paths for our two neighbouring planets: Venus and Mars when compared to Earth.

The Aztec “Sun Stone” is….astronomy carved in stone !!      

To contact the author, e-mail Clive Ross: