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Possible alignments at Mycenae, Greece

The are nine tholoi around Mycenae/Mikines (in Peloponnese, Greece), but two are from the last (same) building period (1300 - 1200 BCE): Treasury of Atreus (also called Treasure of Atreus, Tomb of Agamemnon or T3) and Tholos of Clytemnestra (T6). These two may have possible alignments (see a reference to my work by Schaefer [2000], page 131).

Region around Treasury of Atreus (made with GPS Visualizer)

The following stomion (passage) directions were measured (using compass and compensation in March 2004):

Name of tholos	Code (Spathari [2001])	Stomion direction [°]
Atreus, main dromos	T3	102.5
Atreus, side chamber	T3	188.0
Clytemnestra	T6	167.8
Aegisthus	T9	198.9
Lion	T10	325.8
Epano Phournos	T11	185.5
Cyclopean	T12	277.2
Genii	T13	302.0
Kato Phournos	T14	272.9
Panagia	T15	254.4

Beside possible alignments also sound measurements (reverberation time: RT₆₀) were done at the Treasury of Atreus (T3), T6, T11, T13, T14 and T15.

The below ideas are the result of the folowing visits: April 1998, June 1998, March 1999, March 2004, April 2007, April 2008, and Sept. 2009.

Possible equinox alignment at Treasury of Atreus

The location

The longitude and latitude of the Treasury of Atreus is: 22° 45' east and 37° 44' north both +/- 1'. It is build around 1250 BCE.

The horizon around the Treasury of Atreus

The horizon, formed by Mount Zara, seen from just in the covered passage (stomion) can be seen below:

A panorama picture made at the beginning of the dromos of this tholos, can be viewed as a normal picture.
You can see the following below:

location of sunrise at summer solstice

approximate location of sunrise at spring equinox

^st

Sun inside Treasury of Atreus.

The reason why the sun will be on the inside chamber wall, is explained with the following picture:

The picture let you see a compilation of three things:

the wall + triangular structure (in literature called relieving triangle, but I doubt the correctness of this term) is a picture made at eye height from near the back wall towards the outside

View of triangular structure from outside

Remember that the top layers of the triangular structure have moved somewhat (see above picture), so that the highest part of the top is obstructed.

Close-up view of triangular structure from inside

the two column wise inset is a picture made from the horizon just from mid way the doorway passage
the blue line is the horizon (due to the hill opposite Treasury of Atreus).

As you see, the sky can be seen just at the back wall at eye height (there is bright sky light to be seen). The altitude from eye height near the back wall along the base of the triangular structure towards the outside its top, is around 22°.8 +/- 1° (measured using clinometer):

Sun's path inside Atreus
Treusury of Atreus (Wace [1949], plate 5)

The maximum altitude that the sun light is still to be seen on the wall is presently at 23° 45' +/- 5'.

The direction of the dromos is:

some 100° 45' +/- 1°

some 105° 6'
from Wace [1921], plate 56. I assume this is excluding correction for magnetic north, so if I include this (3° 24'), the direction becomes 101° 42'
around 102° 5' +/- 15'

including the correction for magnetic north

101° 13' +/- 5'

So with all this information, it can be deducted (using e.g. SkyMap) that the sun will shine two periods inside the chamber:

sunrises around spring equinox (March 21^st)

sunrises around autumn equinox (Sept. 23^rd)
Precise dates and times not yet known, but it will be in the range between 05:30 and 06:30 UTC (remember local time is UTC+2 or UTC+3 [incase of daylight-saving/summer time])!

Furthermore the sun light looks to be in the chamber (at present times) for something like a month.

Modeling of the Treasury of Atreus

A 3D world around Treasury of Atreus has been made (the actual top of the hill opposite Treasury of Atreus is not yet visible in the world, I am working on this though).

An animation of the sun path on the back wall can be seen below:

Sunrise on June 20^th, 1998

With the help of Vassilis Merekoulias and Panagiotis Christias we proofed that the sun could not enter into the chamber on the longest day. The archeological office in Nafplion gratefully provided the permission to observe this from 06:30 local time. This experience let to the idea that the sun would get into the building around the equinoxes.

Sunrise on March 31^st, 1999

On March 31^st, 1999 video was made of the sunlight on the chamber wall.

A composite picture of the chamber wall has been made on two moments (08:58 and 09:18 local time [UTC+3]) when the sun was not behind the clouds:

A video of the last moments (around 09:23 local time [UTC+3]) the sun light shines on the chamber wall.

not

Sunrise on Sept. 20^_th, 2002

On this day George Chronis, security office of Mycenae made pictures of the sun on the back wall, which is indeed within the predicted timeframe.

Sunrises in March, 2004

To find out the first date the sun shines on the wall in March 2004, a journey was planned from March 10 until 17th 2004 to be sure the first light inside the chamber was in the middle of the trip. The following results where found:

On March 11th, 2004 the sun was not obstructed by clouds, but was not within the chamber
On March 12th, 2004 no sun due to clouds
On March 13th, 2004 no sun due to clouds
On March 14th, 2004 the sun was not obstructed by clouds and it looked like the sun wanted to peep in (around 8:33 [UTC+2]), but there was only very faint light. But a shadow was casted during a few minutes. I think this was the sun's glare that gave this glare.
On March 15th, 2004 the sun was inside the chamber for 3 whole minutes (8:32 to 8:35 local time [UTC+2]). A video has been made.

Sun on backwall at 8:33 [UTC+2]
On March 16th, 2004 the sun was inside the chamber for some 5 minutes (8:30 to 8:35 local time [UTC+2]). A video has been made (click picture to see animation).

Sun on backwall at 8:33 [UTC+2]

Observations in September 2006 and March/April 2007

Shophia Terovola did observations of the sunlight in the chamber. I am very grateful for her effort and she provided permission to put these dates on this web page. Here are the dates:

first event seen on Sept. 2nd, 2006
last event seen on Sept. 20th, 2006
first even seen around March 27th, 2007 (not fully sure about date)
last event seen around April 7th, 2007 (plus or minus one day)

That the sunlight was not seen before or after these dates could be due to clouded weather, no observation done or no possibility to have sun inside the chamber.
The declinations of these dates are fitting with the declinations found for the first day (March 15th, 2004) and the calculated end date (April 12th, 2007).

Sunrises in April, 2007

To find out the last date the sun shines on the wall in April 2007, a journey was planned from April 14 until 20th 2007 to try to catch the last light inside the chamber. The following results where found:

April 15th, 2007; the sun was not obstructed by clouds and was not within the chamber:-( No sun glare was seen, so at least I was 2 or more days too late.
On the right bottom side of the inside of the triangular structure a small part is blocked off by a small stone (this small stone is not original, but was part of restorations done in 1950's (Pers. comm. Gregory Chronis [2007]).
April 16th, 2007; the sun most of the time (90%) obscured by clouds. Some video have been taken from the outside towards the small stone that blocks the sun light.

The sun peeped through the clouds and thus some sun light has been seen on this small stone. If that small stone would not have been (like in former times) there is a large chance that the sunlight would have been projected on the chamber wall.
April 17th, 2007; 100% clouded
April 18th, 2007; 0% clouds. Made some pictures from a hanging camera in front of the triangular structure.
April 19th, 2007; 0% clouds. Made sure that even the top of the triangular structure can let the sun shine through.
April 20th, 2007: high up clouds, so a milky sun. Got the sun light through the doorway into the chamber and reiterated the sun through the triangular structure, and indeed the sun light goes really through the very top of the triangular structure.

The present opening of the triangular structure is at its base some 17% smaller then originally (due to this small stone on the right):

This reduces the number of days the sun shines at present times inside the chamber from the calculated(/original?) 34 days to 28 days (so untill around April 12th). Remember beside this modern obstruction, the outside of the triangle has also changed (caved in/pushed up somewhat) and this would also considerably change the sky window of the triangular structure.

Sunrises in April, 2008

To really find out the last date the sun shines in present days on the wall, again a journey was planned now from April 8th until 14th 2008 to try to catch the last light inside the chamber. The following results where found:

April 8th, 2008.
No clouds. The Sun touched the outside of the top of triangular structure at 05:26 [UTC]. Was not inside the chamber, because the site is closed until 05:30 [UTC]:-( Started video taping at 05:31 [UTC] until 06:12 [UTC].
April 9th, 2008
Lots of clouds, at least 99%. The Sun casted a sunspot at 05:28 [UTC] in the chamber. Could have been somewhat earlier, because there were clouds and the tholos was still closed off... Same for the moment of final sunlight, it is not precisely known, weak sunlight was present on the wall around 06:08 [UTC], but definitely not anymore at 06:10 [UTC].
April 10th, 2008
Sun was visible all the time, but it was in a haze (very high up clouds). The Sun touched the top of the triangular structure on the outside wall before 05:27 [UTC]. The sun got into the chamber around 05:33 [UTC]. The Sun left the chamber for a few minutes around 05:42 [UTC], because the light path was obstructed by the modern repair. After coming back, it left the chamber at 06:06 [UTC].
Not only the sunlight passes through the triangular structure, this owl takes a nap in one of the other tholos tombs:

April 11th, 2008
The Sun was visible all the time, but it was in a heavy haze. The sun was not seen earlier then around 05:49 [UTC] in the chamber (so this 'is' the light as of yesterday 5:42 [UTC]; it might thus be that the sun now comes in much later due to another internal obstruction). The Sun light left the chamber at 06:03 [UTC]; did not see explicit sun light, but an object (like hand) casted no shadow anymore at that time.
April 12th, 2008
The Sun was visible all the time, but it was in a heavy haze. The sun was not seen earlier then around 05:52 [UTC] in the chamber. The Sun light left the chamber at 06:00 [UTC].
April 13th, 2008
Clouded and a very heavy haze. No direct sunlight in the chamber at the moments when there was some Sun. It is save to say that today no Sun would have entered.
April 14th, 2008
100% clouded.

Sunrises in Sept, 2009

The aim of trip was to search for possible buildings on mount Zara (Google Earth might have revealed something; but it could be wishful thinking;-). But due to possible issues with snakes this has been postponed (winter time would be better). So only sun spot observations:

Sept. 17th, 2009
Hazy weather (24 C). Sun came inside the chamber around 05:54 [UTC]. It left the chamber around 06:18 [UTC]. See for a video here.
Sept 18th, 2009
Less hazy weather (cleared somewhat up due to the thunderstorm last night, with several power outages). Sun inside the chamber around 05: 58 [UTC]. It left the chamber around 6:19 [UTC]. See for a video here.
Sept 19th, 2009
Less hazy weather (some high clouds and at the first few minutes also some low clouds). Sun inside the chamber around 06: 01 [UTC]. It left the chamber around 6:21 [UTC].
Sept 20th, 2009
Still hazy weather (many high clouds and low clouds). Sun inside the chamber for around 4 minutes due to clouds (~20% of time).
Sept 21st, 2009
Cloudy. When clouds were gone, Sun was in chamber (at somewhat earlier than 06:04 [UTC). So this was not the fist possible light in the chamber (it was too strong). The sun was last seen around 06:20 [UTC]. It was already the camera obsura effect and close to full blocking. (around 85% of Sun).
Sept 22nd, 2009
High clouds, Sun came in chamber at 06:05 [UTC). The sun left around 06:20 [UTC].
Sept 23rd, 2009
At the start a few light clouds, Sun came in chamber at 06:07 [UTC). The sun left around 06:18 [UTC].

Reconstruction of the sky window of the triangular structure

!!!Paragraph still under construction!!!

The above observations of the sun spot on the back wall can be summarized in the below graph, where the start (light blue) and end (dark blue) azimuth and apparent altitude of the Sun have been plotted. The yellow curve is the apparent altitude of the horizon (due to mountain Zara).

observed altitude as function of azimuth

A computer model for the triangular structure and the tholos has been made and the resulting sky window is the space within the pink-ish line-form and the yellow horizon curve. You might wonder why the computer model is so close to the observations? This is because the input parameters of the computer model (height, width and length of the triangular structure) have been changed in such a way that it best maps the observations.

It is not that easy to measure in real live the in/outside of the triangular structure (unintended protruding rocks, shifted stones due to small cave-in/push-up over time, difficult to reach, precision needed, tourist/archaeological monument, etc.). This will need permission from the owners of the monument (Hellenic Minsitry of Culture) as a good precise size analysis will be needed. This permission will be seeked in the coming time (say for a winter time project?).

Two aspects have changed the sky window of the triangular structure over time:

the slight cave in/push-up of several of the top stone layers (see the slightly moved stones at the top of the triangle).
the modern obstruction in the right lower corner (since the 1950s).

If we assume that the above changes can be compensated for, then the sky window of former times will be larger. See below picture:

Skywonow of the former and present triangular structure

Skywonow of the former and present triangular structure

So some (not all!) explanation to the above picture:

the red-ish line-form is the sky window of the triangular structure when it was build (using data from Wace [1921-1923]). So nice and smooth on the sides, and also no unintended protruding stones inside. The last might not be reality... Still trying to make this more precise (might also need on site investigations, as stated above).
the pink-ish line-form is the sky window of the triangular structure as witnessed today (deducted from the observed sun spots).
both of the above sky windows are limited by the horizon's apparent altitude (yellow curve).
the thick blue line is a declination of 0 [deg]; using so present equinox definition and independent of the epoch.
the thin blue lines, right beside the thick blue line, are declinations of 0.25 and -0.25 degree. A declination difference of ~0.25 degree happens between center of the Sun and the left (or right) rim of the Sun or a appr. a day earlier or later.
there are some more light blue-ish lines for different declinations (steps of 5 degrees; see legend).

With the present data (still investigating this though), we need an extra three days after(/earlier) equinox to see an increased lowest location of the sun spot.

As stated by Heilbron [1999]: equinox alignments need to be build in sturdy and well settled buildings; so if the Treasury of Atreus was meant to be aligned with equinox, the relieving triangle did not survive the test of time fully;-).
The triangular structure of the tholos of Clytemnestra has stand much better the test of time (so they had the techynology).

If planning your own observations

It is important to write down if an observation was done and if the sun did not reach the wall due to clouds. A form and procedures is available.

Since when is the light in the chamber experienced?

There are a few accounts that it is known for quite some time:

A different light in Treasury of Atreus; the sun light through the top hole. Drawing by E Dodwell, 1834 hanging in Mycenae Museum. Note also a cave-in/push-up at the triangular structure.
Another light into the tholos, by English Photo Co. in 1907 (picture hanging at Hotel La Belle Helene de Menelas; House of Schliemann, Mycenae/Mikines: + 30 275 106225, e-mail: bellhel@+otenet.gr [remove plus sign!]). This light might have been produced as follows: It was when the Sun was shining in the direction of the dromos (no shadow on both dromos walls), but it looks not to be through the triangular structure. It looks that part of the triangular structure was still caved in/pushed up, as seen in the 1834 drawing.
around 1950's the cave-in/push-up (which changed the triangular structure slightly) has been repaired (by Wace/Mylonas?). This would be the earliest date that light through the tringular structure could be witnessed in its full glory.
around 1960's someone (still living in 2004 in Mycenae) working at the site, knew about the sun getting inside the building.
around 1980's a party tried with mirrors and artificial light to mimic the light path inside the chamber, to see what corners it could reach
end April 1998 the first investigation of the light was published on the web by the author (Victor Reijs). A computer (VRML) model had been made and first it was thought that the chamber would receive Sun light around summer solstice (using a crude map of the region), but an actual visit near summer solstice (June 1998) made it possible to deduct that the sun would get in around the equinoxes.
first video taken of the sun light in the chamber in March 1999 by the author (Victor Reijs).
in Dec. 1999 an article was published in National Geographic with a picture of the light beam (Alexander [1999], page 71), it is assumed to be taken in Sept. 1998.
Informed John Lavery in August 2001 about my work and received back a postcard in 2001, where he acknowledged he received my copies of my web page. He made (date unknown) a personal note about light inside Treasury of Atreus (Atreus illuminated; pers. comm, Gregory Chronis [2007]; Gregory had a copy but was not able to retrieve it), but I never saw the note (also due to John's untimely death [200?]). If you have a copy of this note, please let me know.
the book Mycenae; A guide to its Ruins and its History (Mylonas [2002]) has a picture of the sun light patch. Don't know yet when the picture was taken (it was not in the earlier versions, like 1972, of his book).

It does not look like that it is known (widely) that this phenomena is around equinox.

Some conclusions

The sun light can at present be seen on the wall of the chamber around the equinoxes (spring and autumn)!
This is true if the triangular structure was open! But it seems though that it could have been decoratively closed some time(s) by a plaque. Furthermore triangular structures and light boxes (like Newgrange, Crantit and Carrowkeel) are always prone to be filled, so it is difficult to say more about this.
I don't think the triangular structure is only for relieving the load. The lintel above the passage is able to bear the load. It is some 120 cm thick and made of granite.

failure strain

H = SQRT(6 * M / failure strain/young's modulus) = SQRT (6 * 100 / 43800) = 0.12 [m]

This can also be calculate with a structural beam design and stress analysis program (Beam 2D). This program calculates an H of around 0.2 [m] (due to the high stress/moment at the end points).
The following can now be deducted:

H (0.2 [m]) is considerably smaller then the thickness of the lintel (1.2 [m]) at Treasury of Atreus. So, even if the triangular structure was not present (and thus all weight was on the lintel), the lintel would not break with the present construction setup.
Due to the presence of the triangular structure, the thickness of the lintel could be zero. Except for keeping the former entrance doors into place, it needs some thickness.

thick

but

me know

While visiting all the 9 tholos thombs around Mycenae in 2004, the number of broken lintel stones is around 5-6 of a total of around 25 stones. Most of the lintel where fallen due to instable support, so I think it is not possible to state that lintels were broken due to pressure, but more due to breaking when falling down.
It is very well possible that all tholos thombs had triangular structures. Even the olds ones, because in 1997 this was at least found in one (the tomb of Aegisthus) of the three oldest tholos thombs (Spathari [2001], page 65).
The story goes that the closed triangular structure was there to keep the spirits close to the body (as long as it was not yet fully decomposed). After decomposition it looks like Mycenean culture did not regard bones as respectful (they were shoveled aside or thrown out of the chamber) (Mylonas [1949], page 77).
The National Archaeological Museum in Athena (Mycenaean room, items: 1322, 1433, 1470 and 1479), Munich Museum, Mycenae Museum (in former times this piece [alike A55] was in the museum in Nafplion/Nauplia/Nauplion (Pers. comm. G. Chronis [2004])) and The British Museum (ground floor of the museum, just outside Room 11, items: A53, A54, A55 and possibly A56 and A57 [Pryce]) have fragments available.

A 53

A 55

A 54

The apex of the triangle (in Athens, #1470) has on the right (but perhaps also on the left side) a clear ridge.

A sketchy picture of the apex

Such a ridge is not seen on other fragments seen in London (such as A.53, but it has a uneven surface in the middle band on the right side) or Athens (such as #1479).
If all these fragments are part of Treasury of Atreus, I don't know.

A reconstrution of the facade can be seen below (other reconstructions are made, but it seems the below one is the most recent (compiled by Mylonas [1975] page 63, and incorpoartes ideas of Chipiez, Perrot, Marinatos and Wace):

The facade of Treasury of Atreus (after Mylonas [2002])

The above reconstruction has the apex spirals wrong (using #1470 as the template): The three (or more?) rows of spirals in the apex have: on the very top row; clock wise single spirals (with in the middle a clear depression, for an ornament?); on the middle row anti clock wise double spirals; and the third row is unknown.
So my reconstruction can be seen below (partially using Chipiez, Donaldson, Marinatos, Mylonas, Perrot and Wace):

The facade of Treasury of Atreus (after Reijs [2004])

A building at the same location as Treasury of Atreus was destroyed when building the Treasury (Wace [1949], page 130). Was this a building that already utilized the possible equinoxial alignment?
I got a very interesting quote through Peter Hastings from Robert Graves book 'The Greek Myths Complete Edition' (Chapter 111 Point 2) concerning the myth of Thyestes and Atreus:

"Thyestes pointed out that the sun always rose in the Ram at the Spring festival - hence the story about the golden lamb - but the soothsayer Atreus did better: he proved that the sun and the earth travel in different directions, and that what appear to be sunsets are, in fact, settings of the earth. Whereupon the Argives made him king (Lucian: On Astrology 12; Polybius, quoted by Strabo: i.2.15) Hyginus and Servius both agree that Atreus was an astronomer, but make the first to predict an eclipse of the sun mathematically, and say that when the calculation proved correct, his jealous brother Thyestes left the city in disgust (Hyginus: Fabula 258; Servius on Virgil's Aeneid i.572). Socrates took the myth more literally: regarding it as evidence of his theory that the universe winds and unwinds itself in alternate cycles being accomplished by great destruction of animal life (Plato: The Statesman 12-14)."

A quote from Hesiod (Works and Days, considered to be written around 700 BCE) clearly refers back to the importance of equinox:

"Keep all the warnings I give you, as the year is completed and the days become equal with the nights again, when once more the earth, mother of us, bears yield in all variety."

2001

"This is one of the most telling passages in the poem for it directly suggests that time was being kept by watching the movement of the Sun along the horizon from day to day."

Some people say that the triangular structure was closed up and that the whole dromos (and thus the whole monument) would have been fill in with sand (as custom: although on the sign of Treasury of Atreus it says explictly that the dromos was not filled in). This is then used as an argument that there is no significance on for instance a possible alignment.
Perhaps true, but having everything filled in by sand will not deny that they build the whole structure and thus in my humble opinion, every aspect might hold something about the culture that made it (even if we now think every thing was filled-up by sand). I am sure it was open for many years to make sure that this magnificent building was seen to impress. See also the article of D. Mason [2007]. It is the only tholos that can be seen from the palace.
There could very well be a link with the Minoan culture at the time the Treasury of Atreus was build (1250 BCE). In that case it is interesting to see that the Minoan graves are directed to eastern and western directions, so also here is a possible equinox relation. There are some 500-600 graves also around Mycenae; a study of their directions could be very worthwhile!

Possible geographical alignment at Tholos of Clytemnestra

In the Tholos of Clytemnestra (some 500 m more to the north of the Treasury of Atreus and build around 1225 BCE) the triangular structure is on the inside fully closed up with big nicely cut and fitting stones, but in this case the dromos points to the south (around 167.8°), and it looks to be aligned with the mythological interesting mound at Nafplion: Palamidi. If weather permitting also the lower hill of Acronauplia is visible.
The mythology is: Palamides was the son of Clymene (which in turn was the daughter of Atreus or Catreus) and he died a tragic death, set up by his father (Nauplius)

triangular structure at Tholos of Clytemnestra

Vaguely the hill Palimidi is seen from just above the triangular structure,
in the direction of the dromos

Acknowledgments

I would like to thank Panagiotis Christias, George Chronis, Gregory Chronis, Agamemnon Dassis, George Dassis, Lesley Fitton, Peter Hastings, Dave Karr, David Mason, Natalia Merekoulias, Vassilis Merekoulias, Doug Schwartz and Shophia Terovola for helping me in getting all this information into daylight.