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The Megalithic Portal and Megalith Map : Index >>
Stones Forum >> avebury/silbury
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avebury/silbury |
rbatham
Joined:
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from Western Australia
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|  Posted 19-05-2006 at 13:45
 I find plenty of information about solar/lunar alignments at stonehenge, but very little about Avebury and Silbury Hill. I see from the map that the hill lies due south of Avebury, so the midday sun casts a shadow in that direction. My trigonometry is a bit rusty and I'm trying to work out where the shadow would fall. At the summer solstice the sun is about 62degrees above the horizon. If the original hillwas a complete cone with slope angle 51 the shadow should fall outside of the base. At winter solstice the sun is about 15^ causing a longer shadow. Is there any indication of standing stones or other at the points of the solstices and equinox. ? Anybody know?
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PeteG
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from Avebury
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| Posted 19-05-2006 at 14:10
I have been looking for astronomical alignments at Avebury for 6 years now.
Silbury does not have anything noticable as a shadow caster.
There are lunar alignements with the Coves which I hope to confirm at the next lunar standstill in June.
PeteG
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archaeo
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from Portland, Oregon
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| Posted 20-05-2006 at 17:59
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....I see from the map that the hill lies due south of Avebury....
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I suggest a better map. Silbury Hill's centerpoint is 0.0038 degrees (nearly 1/4 km) difference in longitude from Avebury's center.
For better precision, try the topo maps at:
http://www.magic.gov.uk
where you can zoom in to a very fine scale and the cursor map tools will provide the coordinates.
Avebury is located at 1/7 of circumference in latitude. The geometry of the monument locations is more interesting than illumination variables. Here is a link to a page with tools. A trig calculator and the site coordinates are in the Neolithic_Calc program:
http://jqjacobs.net/astro/archaeoastronomy
Note the arc distances from Silbury Hill to Avebury and to the earlier Windmill Hill henge, the type site for "causewayed enclosures." And check out the arc distance from Windmill Hill to Knowth, contemporaneous sites on this landscape before Stonehenge, Avebury, and Silbury Hill. Now check the proportion of that arc with Knowth to Newgrange. More discussion:
http://jqjacobs.net/blog/neolithic.html
Now check the Stonehenge and Avebury relationship, esp. the proportions of arc and latitude difference. Recognize that astronomic number?
[ This message was edited by: archaeo on 2006-05-20 18:05 ]
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archaeo
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from Portland, Oregon
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| Posted 20-05-2006 at 18:02
Quote:
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There are lunar alignments with the Coves which I hope to confirm at the next lunar standstill in June.
PeteG
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How will you account for the change in illumination angles over so many centuries since construction?
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Anonymous
User not Registered | Posted 20-05-2006 at 18:05
Archaeo, i'm not too clever at doing all that. Would you mind summarising what you are getting at please?
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rbatham
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from Western Australia
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| Posted 21-05-2006 at 06:02
I'm a long way from these sites now.but i have visited them. My map is OS(Magic.gov.uk). I sai that Silbury was Due south not exactly. I was just interested in whether the hill was used as a sundial. I have been to jacobs and other sites. If the obliquity of the ecliptic has changed and sunrise was earlier in 5000Bc, so what. He talks as if the ancients used modern precission observatories and the differences are excessive. not so. I have checked my planetaruim against NASA and it is as accurate as theirs (Fred Aspenak NASA). Peter G is looking for alignments and he has plenty of stones tumuli etc in his area. It seems that the experts have allbut given up on Avebury due to damage to the original sight over the centuries. There may be alignments, maybe not. Because StonHen has them it may not be true of other circles.From cornwall to Orkneys there are circles with various numbers of stones ie Nine ladies in Derbyshire. Why 9? 9 planets? (joke?). We may be looking for what is not there but if we don't look then research stands still.
rbatham
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rbatham
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from Western Australia
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| Posted 21-05-2006 at 09:11
I
Avebury is located at 1/7 of circumference in latitude. The geometry of the monument locations is more interesting than illumination variables. Here is a link to a page with tools. A trig calculator and the site coordinates are in the Neolithic_Calc program:
http://jqjacobs.net/astro/archaeoastronomy
This 1/7 of Earth radius has come up before. Why build a monument at 1/7. Why not 1/6, 1/8, 1/9 etc. Well near the same meridian @ 1/6, 60N there is a standing stone in Shetlands as well as other sites. 1/8 45N Liburne, France, various ancient stones 1/9 40 N, Onda, Spain. cant find anything. rbatham
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cropredy
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from Oxon
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| Posted 21-05-2006 at 11:00
Rbatham, You say that if we don't look for the alignments , then research stops, true.
If you want to look and find the alignments , but not with all the modern gizzmos at your disposal, but in the manner that the people whom constructed the sites will have found them, then I will discuss my thoughts with you over on the sacred sites section.
If I let rip here, I cause upset.
Kevin
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Anonymous
User not Registered | Posted 21-05-2006 at 17:07
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On 2006-05-21 09:11, rbatham wrote:
..... Why build a monument at 1/7.
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Better question: Why, of all monuments in So. England, are three of the six largest Neolithic stone circles and the third largest henge cojoined at 1/7th of circumference? Why not none at all or just some small barrow?
Avebury is the outlier of outliers. Durrington Walls and Marden Henge may be 10% larger, but have no stone circles. Six stone circles are outliers over 100 m wide, larger than the others at 81 m or less, and three of the six were built at Avebury. Of these, the largest is an outlier in the outlier group, more than triple the size of the other five (332 m vs. 104 m +/-).
So the real question is, "Is it all a coincidence, or did the monument builders in South England know that the Avebury latitude equaled 1/7th of circumference?"
You won't find the answer in Spain, because that is not where the people who built Avebury lived. Faulty logic that. You might ask, "Why is the Heel Stone azimuth exactly 1/7th of circumference?" AND "Why are the mounds of Stonehenge's earthen henge at a 1/22nd of circumference azimuth?"
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archaeo
Joined:
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from Portland, Oregon
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| Posted 21-05-2006 at 17:21
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On 2006-05-21 09:11, rbatham wrote:
This 1/7 of Earth radius has come up before. ...
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Actually, it is latitude equals 1/7th of circumference.
And yes, I have discussed this before. I discovered the relationship in 2000. It is noted in "Possible Geodetic Properties and relationships of Neolithic Monuments of the Brithish Isles, A Preliminary Inquiry." I then wrote, "Latitude and colatitude are readily determined by measure, relative to local level, of the angular elevation of the axis of rotation's pole in the celestial sphere. This is not a very complicated determination and monument placement inferring this knowledge would imply only the most fundamental of geodetic understandings..."
Of course, doing so with the accuracy shown at Avebury (and Monks Mound, et.al.) requires some sophistication of understanding variables influencing such determinations.
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archaeo
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| Posted 21-05-2006 at 17:40
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On 2006-05-20 18:05, Anonymous wrote:
Archaeo, i'm not too clever at doing all that. Would you mind summarising what you are getting at please?
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Assuming reference to: "lunar alignments with the Coves which I hope to confirm at the next lunar standstill in June. PeteG"
And my reply, "How will you account for the change in illumination angles over so many centuries since construction?"
Over the past 5,000 years, at the latitude in question the rise/set azimuths for the sun and moon have changed by over 2 diameters. When you see summer solstice sunrise over Heel Stone today, bear in mind the sun was two diameters further north during solstice 5,000 years ago, so modern observations do not past determinations make!
What researchers are doing today is simulation in virtual environments. Of course, first you need accurate survey of the site. Then trustworthy assurance that the stones have not moved in 5,000 years. Good luck on that front, eh? This is why most of the Stonehenge presumed alignments are not accepted, that and the fact that the lines are so short they lack any modicum of accuracy in the first instance. Then, you need to recreate the horizon elevations. Even after all that, the environmental variables, like temperature and air pressure, modify the illumination angles. Now, add in the change in obliquity of the ecliptic, and you need to know the precise date of the alignment. In the final analysis, illumination alignments may be a fool's errand.
If there is any one circle large enough to study stone-to-stone alignments of a circle without the length of line issue, it is Avebury's outer circle. Unfortunately, not all the stones remain. I would inquire into the constants first, basic geometry then site-to-site relationships/bearings, and ignore variable illumination alltogether.
[ This message was edited by: archaeo on 2006-05-21 17:42 ]
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PeteG
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from Avebury
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| Posted 22-05-2006 at 01:21
Quote:
| bear in mind the sun was two diameters further north during solstice 5,000 years ago, so modern observations do not past determinations make! |
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As Gerald Hawkins pointed out in his 1964 film the heel stone has shifted and leant forward since it was first erected, by happenstance it still acts as an accurate marker for summer solstice sunrise.
At Avebury I photograph the events from the ground then create a panoramic that I use in Starry Night pro software to check how it would have looked in the neolithic.
I also use Memory Map which allows 3D viewing of the landscape with accurate OS maps.
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Anonymous
User not Registered | Posted 22-05-2006 at 08:10
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On 2006-05-21 17:40, archaeo wrote:
[quote] and ignore variable illumination alltogether.
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I take all your points about the difficulties in achieving precision and therefore certainty in individual cases. But a mass approach tells a story doesn't it? If most long barrows point SW or SE for instance....?
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JACKME
Joined:
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Messages: 17
from CUMBRIA
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| Posted 22-05-2006 at 09:06
Quote:
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On 2006-05-19 13:45, rbatham wrote:
I find plenty of information about solar/lunar alignments at stonehenge, but very little about Avebury and Silbury Hill. I see from the map that the hill lies due south of Avebury, so the midday sun casts a shadow in that direction. My trigonometry is a bit rusty and I'm trying to work out where the shadow would fall. At the summer solstice the sun is about 62degrees above the horizon. If the original hillwas a complete cone with slope angle 51 the shadow should fall outside of the base. At winter solstice the sun is about 15^ causing a longer shadow. Is there any indication of standing stones or other at the points of the solstices and equinox. ? Anybody know?
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Iam currently researching 3 sites with standing stones where the Sun is likely to shine down the back of the stone on the Summer Solstice. Jack
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JACKME
Joined:
19-09-2004
Messages: 17
from CUMBRIA
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| Posted 22-05-2006 at 09:08
Quote:
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On 2006-05-19 13:45, rbatham wrote:
I find plenty of information about solar/lunar alignments at stonehenge, but very little about Avebury and Silbury Hill. I see from the map that the hill lies due south of Avebury, so the midday sun casts a shadow in that direction. My trigonometry is a bit rusty and I'm trying to work out where the shadow would fall. At the summer solstice the sun is about 62degrees above the horizon. If the original hillwas a complete cone with slope angle 51 the shadow should fall outside of the base. At winter solstice the sun is about 15^ causing a longer shadow. Is there any indication of standing stones or other at the points of the solstices and equinox. ? Anybody know?
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Iam currently researching 3 sites with standing stones where the Sun is likely to shine down the back of the stone on the Summer Solstice. Jack
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rbatham
Joined:
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Messages: 679
from Western Australia
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| Posted 22-05-2006 at 11:51
[/quote]Iam currently researching 3 sites with standing stones where the Sun is likely to shine down the back of the stone on the Summer Solstice. Jack
[/quote] I keep gettjng replies about the 2 solar diameters difference in position, As I've said before this only amounts to Just over 1 degree change in azimuth. I've done some more thinking and pouring over maps. My original question was whether Silhill could have been sundial of sorts. Well, if the base angle is the same as the latitude then this suggests a gnomen. From the south the line of sight up the slope would point to the celestial north pole. If the hill was built before 2750 BC here would not have been a pole star when Thuban was approaching the position. (the pyramids have been dated using this star). From 5000Bc Vega, Arcturus and Vega were prominent circompolar stars. Was Silhill and Avebury built for navigation purposes? Could it be stellar alignments that were observed? The architects must have had Knowledge of a round Earth, and solar movements, a well developed mathematics. Avebury could have been a map showing the direction to towns and villages all over the country. I could say more, I'll continue to work on it. rbatham
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rbatham
Joined:
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Messages: 679
from Western Australia
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| Posted 22-05-2006 at 12:33
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On 2006-05-21 17:21, archaeo wrote:
[quote]
On 2006-05-21 09:11, rbatham wrote:
This 1/7 of Earth radius has come up before. ...
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Actually, it is latitude equals 1/7th of circumference.
[/quote] Sorry, meant circumference. Just a senior moment 
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Anonymous
User not Registered | Posted 22-05-2006 at 18:55
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Was Silhill and Avebury built for navigation purposes? Could it be stellar alignments that were observed? The architects must have had Knowledge of a round Earth, and solar movements, a well developed mathematics. .... rbatham
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From: http://www.jqjacobs.net/blog/neolithic.html
Preliminary Archaeogeodesy Study Results
for Three Major Neolithic Complexes
"....for Avebury, Silbury Hill and Windmill Hill, I determined their site-to-site relationships ... the Avebury to Silbury Hill arc equals 0.01307° (0.00100 R27), 1/1000th of lunar orbit per earth rotation. The Windmill Hill to Silbury Hill arc equals 0.02900° or 1/1000 of earth orbit per full moon period (0.00100 S29). These two arc distances and the placement of the three monuments presents precise fractions of astrogeodetic modules based on the three fundamental cosmic motions....."
Also:
"... Newgrange coordinate has been updated with a GPS reading for the center of Newgrange Mound ... Knowth Mound, Dowth Mound, and Dowth Henges GPS coordinates ... arc from Knowth Mound to Windmill Hill equals 3.60006° or CIR/99.9985, an excess of only 6.1 m. And the distance from Knowth to Newgrange equals 1/1000 of earth's diameter, therefore the distance from Newgrange to Windmill Hill is 314.19 times that from Newgrange to Knowth. From Avebury to Dowth Henge equals 3.59647 degrees...."
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Anonymous
User not Registered |  Posted 24-05-2006 at 02:52
I wonder what the ancients wrote on to work out all there sums?
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Anonymous
User not Registered | Posted 24-05-2006 at 04:10
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On 2006-05-24 02:52, Anonymous wrote:
I wonder what the ancients wrote on to work out all there sums?
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Good point. These monuments were built not in the Neolithic, but in the Paleolithic when the populace was supposedly hunter gatherers, dressed in skins and lived in caves. Long before the Celts entered Britain. To mark out a circle on the ground is easy, just put a stake at the centre and with a rope and scraper just mark around. But when the rope is 200m long or more this becomes unwieldy, so a system of surveying must have existed. Divide a circle into 12? easy. but other divisions require a knowledge of trig and geometry.
maybe Erich von Daniken wa right.rbatham
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