Guayabo Sky Map Stone

I had a passive interest in archaeology and archaeoastronomy, but a strange stone at the Guayabo National Monument in Costa Rica sparked my interest. --Michael O'Reilly F.

 

During the late 1970's my family and I lived in a second floor apartment in Moravia Costa Rica. Moravia is a small and quiet town northeast of San Jose. A nice thing about this apartment was the small balcony that we shared with my neighbor on the second floor. From this balcony we had a spectacular view of the southern sky adorned with a high rim of mountains that mark the southern boundary of the central valley. Eventually I was able to buy a used reflector telescope and amateur astronomy quickly became my hobby. Over the years I came to know the southern sky, partly because the northern sky was blocked from view on the balcony and partly because the area near the celestial south pole is full of interesting objects to observe. Not even the glare from the city lights could obscure the star clouds and with the help of a telescope, they were splendid. The position of these objects became burned into my memory after many years of observing this particular area of the sky.

Early in 1975, my family and I decided to pack a picnic lunch and drive up to the Guayabo National Monument. The park is well known for its natural beauty and is the largest remnant of the indian civilization in Costa Rica. The indians who lived here were called Huetares. They lived in this area until the Spaniards came. The park is deep in the forest about half way up the southern slope of Turrialba volcano. The ancient indian city is just now beginning to be uncovered. In 1975 it was estimated that only 3% of the complex had been uncovered.

The dominant feature of Guayabo National Monument is the central mound which is a mound buttressed with a round stone wall. In all directions there are smaller mounds, stone walkways, streets and holding ponds for water. In all areas of the park you can see stone carvings. These stone carvings are random lines that wander all over the surface of the rocks. There is one stone however that is quite different from the rest. In 1975, this 1 1/2 foot diameter stone was located at the south or southeast side of the central mound imbedded in the stone walkway that surrounds the central mound. On a trip to Guababo in 1994, I discovered that this area was now closed to the public and the stone had been removed. A park ranger showed me the stone that was stored in a trailer on the park grounds. He told me that a mould was to be made of is so that a copy could be place in the walkway where the original once rested.
 

(Fig.1) Conception of the southern sky as it might have looked to residents of the country's largest pre-Columbian city 500 years ago. The central mound is on the right.
 

During this trip, the first time I saw the stone I aimed my camera at it, focused and decided not to take a picture because it really was not very impressive and it would be a waste of film. After wandering around the park I later returned and looked down at the stone again. After a moment it all came clear and I could not believe what I was seeing. The image of the southern sky and this stone merged into one image in my head. Naturally I took a picture, many pictures and that same day worked in my makeshift darkroom so that I could compare the images with my star maps.

 

 

 

 

(Fig. 2) Photograph of the stone when it was used as a paving stone in the walkway that surrounds the central mound.

Before I reveal what I feel is the startling meaning of this stone, I will first talk about other things that will make the meaning clearer.

Our galaxy in which we live is a flat disc shaped cloud of stars, we live on the outer limits of this disc but within the central plain of the galactic disc. When we look parallel or into this disc in the night sky we see a multitude of stars, stars so distant but dense that they appear to be a luminous cloud arching across the sky, this is the milky way. Now if we were to look away from the plain of the galaxy, the night sky will appear less populated with stars and darker.

We will now concern ourselves with a small portion of the sky, -90° (the south pole) to -60° latitude (the southern cross falls along this -60° latitude). Within this -60° latitude we find many interesting non stellar objects. From the vantage point of Costa Rica approximately +10° north of the equator looking due south in December, with a clear horizon we can see the Large Magellanic cloud. In the October night sky a little further down on the horizon we can see the Small Magellanic Cloud. They were both reported and used for navigation by Magellan in 1519. These two objects are of particular interest because they are the nearest external aggregation of stars nearest to the Milky Way galaxy. Although the clouds are considerably smaller than our galaxy and do not exhibit spiral structure, they are however separate galaxies. Now if we look south in April we will find the sky quite different because we are looking into the disc of the galaxy and we see the luminous cloud called the Milky Way but within this luminous cloud of stars is a dark spot called the Coal Sack. This dark object lies within the constellation Crux along with the Southern Cross. This dark spot in the Milky Way is due to a large cloud of obscuring matter that hides the myriad of stars lying beyond.

If we look at the southern sky in March along the -60° latitude we find two other interesting objects, a star cloud in the constellation Centaurs and NCG 3372 or the Keyhole Nebula in Carina.

I have divided a circular map of the southern region of sky below the -60° latitude into 24 parts with number 1 starting between June and July and numbering counter clockwise until we reach number 24. On this map I have placed the location of the objects referred to above. With this calendar-map combination we can detect what non stellar objects will be in the sky in any given month of the year, or if we see the objects in the sky first, we can tell exactly what season or month it is.
 

(Fig. 3) Modern day map of the region of sky below the -60° latitude.

Now we will examine the stone, which looks like a spider web with some imperfections. If we count the radiating lines at their ends we find that there are 24 of them, but one of these lines is not connected to the main network of lines. This is line number 1 on fig. 3. If we count counter clockwise like on our modern map, (fig. 3), line 8 intersects with an oval shaped line. On our modern map the line 8 intersects with the Small Magellanic Cloud. If we count on, we find that line 12 points to another oval shaped area, on our modern map line 12 intersects with the Large Magellanic Cloud. Between lines 19 and 20 of the stone (fig. 4) we find a small raised area, this corresponds to the Coal Sack located on fig. 3. Between lines 19 and 18 is another faint carving raised area, this corresponds to the star cloud between lines 18 and 19 on fig. 3.
 

(Fig. 4) Ancient map of the region of sky below the -60° latitude.
 

 

 

I believe that line 1 that is not connected to the other line system indicates the longest day of the year (summer solstice), because it coincides perfectly with the locations of the Magellanic Clouds. The circle in the center indicates the unknown part of the sky below the horizon to those who view the southern sky form +10° north of the equator. The closed areas between line 21 of the stone and ending on the line 9 could indicate cloud cover see fig. 4.
 

 

 

 

(Fig. 5) The green area in the center indicates the part of sky not visible to the observer +10° north of the equator. Go to (Fig. 1) and notice that the area of sky is only visible down to -80° latitude.

The earth's axis does not remain exactly fixed in space but describes a cone with an apex angel of 47 degrees. Instead of being an annual cycle, however, it takes 25,800 years to complete. If we take this procession into account we find that the stone loses accuracy and gets progressively worse as we go back in time. It still works today but as time goes on it will cease to be accurate. I feel that the stone was created roughly 500 years ago.

The following diagram is average rainfall in Costa Rica during the period 1979-61. Information taken from: Atlas Estadístico de Costa Rica Nº 2 - 1981. Notice that rainfall is greatest between November and May.

 

(Fig. 6) Rainfall 1979-61

Pay attention now! this is interesting. Below is the stone with a crescent shaped area indicating what if feel is an indian circular bar chart.
 

 

(Fig. 7) Green area indicates cloud cover over the mountains.

I used a filter on a graphic arts program to convert the above image (fig. 7) from the polar to rectangular coordinate system.

 

 

(Fig. 8) The stone displayed with the rectangular coordinate system showing cloud cover over the southern mountains during May to October.

Compare figure 8 and figure 6 and you will begin to see similarities between the two. Rainfall and cloud buildup go hand-in-hand. The clouds build up during the rainy season obscuring the sky behind them. I think whoever made the stone was showing the observer the months and area of sky that were likely to be obscured.

 

(Fig. 9) How cloud cover builds up during the rainy season obscuring the sky behind them.
 

 

 

 

 

Conclusions:

1. The stone is an ingenuously combined celestial map of the southern sky between -90° and -60° latitude and calendar .
   
    

2. The person who made the calendar-map understood the movement of the celestial sphere to the degree that he indicated the unknown part of the sky that is always below the southern horizon to an observer at +10° north latitude.
   
    

3. From what I can see the calendar-map has little to do with star locations or lunar movements, but is concerned with faint non stellar objects as points of interest, and the longest day of the year (summer solstice). It is possible the the stone was a teaching aid.

I do not claim to be a scientist or archaeologist and I am sure that my methods do no follow the proper guidelines of these disciplines. I feel that someone with the training, time, experience and interest in this matter should take the ball and prove or disprove this theory. After all, if I am wrong and nothing is done, nothing is lost, but if I am right and nothing is done... this priceless gift from the past could end up as land fill.
 

Bibliography

Una interesante hipótesis astronómica. La Nación, San Jose, March 25, 1979:7. (Supplement Ancora)

Mystery Stone Challenges Experts. The Tico Times, San Jose, May 11, 1979:1,12-13.

Parques Nacionales de Costa Rica. p. 67.
 

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