Like almost anyone who has read about Stonehenge I am familiar with the idea that Stonehenge was aligned to the summer solstice sunrise. Like a smaller group I am aware that the actual orientation of the monument is toward the winter solstice sunset and that the evidence from surrounding sites points towards its use at the mid-winter festival.

Unlike modern man, the people in the neolithic did not know when these events should occur unless they had solar instruments to measure when they should occur. So, unlike the modern pagans who leave their City of London banking jobs to don their white coats on the day the modern high priests in the BBC tell them is "mid-summer solstice", the neolithic farmers had to work it out for themselves.

Typical Sunrise/set at Stonehenge. Cloud blankets horizon
and the only blue sky is a patch and well above horizon.
Thus the sun is obscured by clouds and the edge of solar
disc not at all visible

And whether mid-summer of mid-winter, there is are two huge problems with these in terms of a "calendar":

  1. The "Solstice" or as we might call it in English the "Sun [setting position] stays the same [for about a week]", is just that. The sun sets in almost the same position for about a week. it would be necessary to carry out very precise measurements, at the limit of human observation, to determine the exact day of the solstice
  2. It is very rare to see the sun at the point it rises or sets on the horizon. This is because whilst we often see the sun, we usually see it through a gap in the clouds during the day. However, as the sun gets lower, the larger these gaps need to be until when it is at the horizon, the breadth of the cloud layer we are looking through is around 100miles across.

These two make it impossible to use the solstice in determining the calendar. To illustrate this, the following table shows how the sun's position (angle from East-West line) moves in the two weeks around mid summer:



15 16 17 18 19 20 21 22 23 24 25 26 27 28
Angle 23.29° 23.33° 23.36° 23.39° 23.41° 23.42° 23.43° 23.43° 23.42° 23.41° 23.39° 23.36° 23.32° 23.28°
of sun's
1/4 1/5 1/7 1/13 1/25 1/50 0 0 1/50 1/25 1/13 1/7 1/5 1/3

For a whole fortnight, the sun is within 0.15° of the summer solstice position. This means that if we could by chance photograph the sun on mid-summer's day and then at the same time a week later, 2/3 of the sun's diameter would over overlap. This is why there are photos of Mid-Summer solstice sunrise!! It is not that anyone actually gets a photo of the sun rising on the precise day of mid-summer, it is that it is that the sun "stands still" and so there are a couple of weeks when that illusive photo can be taken.

17 18 19 20 21 22 23 24 25 26 27 28 29 30
Angle 2.36° 1.98° 1.59° 1.20° 0.81° 0.44° 0.04° -0.35° -0.74° -1.13° -1.52° -1.91° -2.30° -2.69°
of sun's
4.7 4.0 3.2 2.4 1.6 0.9 0.08 -0.7 -1.5 -2.3 -3.0 -3.8 -4.6 -5.4

In contrast the sun moves roughly 3/4 of its diameter daily at the equinoxes. So, for example, in the fortnight around solstice the sun moves 0.15° whereas in the fortnight around the equinox (equal day and night) the sun moves 10.1°. That is 67x faster. But it gets worse! In the four days around Solstice, the sun moves just 0.01° but at equinox it moves 1.16° making it 116x further. And on the actual two days of equinox, it doesn't move at all (at least to the accuracy of the figures available).

So, even today, the position of the sun cannot be used to tell the day of the equinox from the position at mid-summer!

Conclusion: Stonehenge is not calendar set using the summer or winter solstice.

In other words, we can say very confidently, that if there were ceremonies at Stonehenge at the winter (or summer) solstice, then they would already know the date using a more accurate means based on an alignment toward the Autumn or Spring equinox.

The search for Stonehenge Calendar

The theoretical Calendar machine

Idealised solar calendar

Once I realised that the solstice was entirely unsuited for the purpose of determining the days of the calendar such as the Solstice, I started to work out what was needed. The key things appeared to be these:

  • Because the sun is unlikely to be viewed on any particular date, particularly close the horizon, a solar calendar needs to able to calculate the date from perhaps one or two sunrises in a month (my estimate of the likelihood of a suitable sunrise at Stonehenge).
  • To further increase this chance, one should create a "false horizon" above the height of the real horizon, because by raising the observing height just a few degrees, the size of the "window" through the cloud needed to view the sun reduces dramatically making it much more likely that the enough of the sun to discern its position will be viewed at least on some days around the required point.

The False horizon

Believing that a "false horizon" was a necessary part of a stellar observatory, it seemed obvious to me that the "Henge" stones (the "hanging" stones from which it gets its name) were intended to create this false horizon.

"Henge" lintels showing possible "False Horizon"

Likewise, it seemed possible that the embankments around many stone circles, notably Avebury, were also "false horizons", creating an horizontal line above the dense layer of cloud that tends to obscure our view of the sky and stellar objects close to the horizon.

However, as I show above in the "idealised solar calendar", not only is a false horizon needed, but also so way to identify the position. But no such markers are present at any embankment around a henge nor at Stonehenge, which if any site were to retain them, then it would be Stonehenge where this apparent "false horizon" is made of stone and not earth.

More importantly, as the sun rises and set on an east-west alignment at the equinox, the whole theory of it being an accurate calendar seemed to be improbable because as the following plans show, there is absolutely no obvious alignment anywhere close to the east west at Stonehenge.

Plan of Stonehenge. No large-scale features
suggest an obvious east-west alignment.
(shown North to Top)
Plan of centre portion of Stonehenge. No inner
features suggest an obvious east-west alignment.
(shown North to Top)

A New Dawn

Theoretical "solar calendar"

Then last night after I watched yet another program on Stonehenge I took another look at the site on google earth. After another fruitless look at the stones I started looking further afield. At first I was excited by what appeared to be a stone lying down due east of the site. Strangely this did not appear on any plans of the site, but another quick look on google earth revealed it to be some form of "box" (lighting?).

View of Stonehenge from around position of unnamed cairn
to the east of Stonehenge shown on map to right.
Note there is almost no line of sight through the monument
and no obvious incremental markings.

As shown on the map to the left, there is a very obvious barrow to the east of the Stonehenge complex. If stonehenge were the markers and the barrow was the observation point, could the barrow and stonehenge be used as a solar calendar? Looking at the view from the barrow, the answer is clearly no. The site may have looked differently before the giant Sarsens which now dominate the site, but now, this viewpoint would be completely useless as a solar calendar.

However, as Stonehenge was not directly west of this cairn, I began to wonder whether there might have been some kind of site directly east of the cairn toward the horizon. And as I searched for the horizon toward the west, I happened to look east:

Overview of Stonehenge showing that the site is located along an east-west line between two high points.

There on a high point to the east were a series of mounds called the "kings Barrows". Could these be the "comb" features?

Kings barrows

According to New King barrow cemetery consists of 6 aligned Bronze Age barrows - 4 bowl barrows and 2 bell barrows. Of these 5 are close to 50m in diameter (the last to the north at 4m is much smaller):

Amesbury 28 bell barrow - a large bell barrow of 49 m diameter, partly disturbed at the east. .

Amesbury 29 bowl barrow - a Bronze Age bowl barrow of 51 m diameter, partly disturbed at the east.

Amesbury 30 bowl barrow - a 3,2 m high bowl barrow of 41 m diameter. .

Amesbury 31 bowl barrow - a well-preserved bowl barrow with partly preserved quarry ditch. .

Amesbury 32 bowl barrow - the most northernly located barrow has 44 m in diameter and 2,6 m of height.

And it continues that these barrows sited along the top of a hillock are: "perfectly visible from the distance, especially from Stonehenge."

So, could these be the "comb" features?

[N.B. according to this site there were more stones at this site:

In 1720, Stukeley wrote: "On Salisbury Plain near Stonehenge in the sheep-penning there several barrows called the Kings Graves. The stones which once stood there are lately carried away."

Plate I of Inigo Jones's Stonehenge^ is a very careful drawing by J. Hassell; when one
stands on his viewpoint and compares the Stonehenge stones with the drawing, one sees
how exact it is. He shows two large stones, like undressed sarsens, on the side of the hill
above the penning and just over Stone 91. There can be little doubt that these are the stones
mentioned by Stukeley.
Wessex Archaeology, P93 ]

A solar Month?

Using Google I was able to work out that the angle as viewed from Stonehenge of the middle of the top to the middle of the bottom cairn was approximately 10.8 degrees. At an average of 0.388 degrees/day it would take the sun approximately 27.8 days to change position from the first to the last. In other words precisely one lunar month, and there being four division, each division represents 7 days, or has we known it a "week"!

I don't believe that can have been missed by others, so I won't even suggest I've discovered anything new with this "solar month", however it does show the barrows appear to be part of some kind of calendar. But the cairns are too far apart because a week is too long to easily estimate the fine division of each day. And it is impractical to put markers in between because the sun will rise at an angle and so we need a flat horizon and so there is no easy way to fit a series of marker stones between undulating cairns to mark the passage of the days.

However, if one were to view the cairn form say, between each upright at Stonehenge, could this provide the necessary fine division to distinguish the day?

The east side of the Stonehenge uprights are 1180m from the cairns. The sarsens in the ring are about  3.2m apart.

That means the time it takes so that the sunset viewed over a cairn to move from one sarsen to the next is:

(3.2/1180) / tan(.388) = 0.40 days

Or to turn that around, and observer moving along the stones to view the sun setting directly over one of the cairns, would need to move 2.5 sarsens. This means that the gaps between sarsens are more than fine enough to determine the day of the equinox albeit the scale is hardly linear. But is Stonehenge wide enough so that there is no gap?

The ring is approximate 30m across. So the time it takes to move across the circle is:

(30/1180) / tan(.388) = 3.75 days.

Thus the circle is only wide enough for half the week and not a full week. However, 3.75 is very close to half of 7 days, so what if the gaps between the cairns were as important as the cairns. Checking the heights, they are only 2.7m high. More importantly the centre of the Stone circle is precisely west of the point between the 2nd and 3rd cairn. So, it seems that approximately every 3-4 days, (if the sun were visible) an observer would need to move across the stone circle from south to north and then change from aligning the sunrise with either a dip or a peak between the cairns.

Why so Convoluted?

In fact, the whole mechanism is so convoluted it is hard to believe that someone could not have worked out a simpler scheme. If it were not that the distance between the five main mounds is almost precisely one month, the intervals between the mounds one week and the distance across Stonehenge is nearly half a week, it would all seem far too convoluted to be anything but chance. Why for example, didn't they just have a line of Stones spaced at perhaps half a day between them at Stonehenge? It is almost as if it is intentionally deceiving!

Why e.g. is there not a hint of this important east-west alignment at Stonehenge? Why is the whole focus of the monument toward the least useful part of the year at the solstice and not at the far more important (in terms of a calendar) equinoxes?

The answer I believe is that Stonehenge was intended to deceive. Like the magician, the intention is to focus the visitor on the solstices so that should anyone try to replicate the true function, they will replicate the most useless feature of the site - the apparent important alignment with the solstice - ignoring the only really important alignment of equinox. Likewise, the stellar and lunar alignments also focus attention away from what is really important.

In other words, Stonehenge was built in order to accurately align a calendar with the sun, but it was built in such a way, that any trying to replicate the function would fail, thus protecting those who owned the monument.

And to ensure that deception was complete, I'm sure that each solstice, the "priests" would parade up to the monument on days approaching the solstice explaining that they had careful observations to perform. And they would wait, each day telling the crowds "not yet today", until on the day they knew from their observation of the equinox some 3months before, they would proclaim "it is the turning of the year".

And no onlooker would have a clue how they managed to divine the exact day of solstice from the monument.


For next article in this series see:  Pyramid

Addendum - since writing the article I've been told the barrows are categorised as bronze age. I'm not sure what evidence was used for this dating, but there is no reason why mounds which were contemporary with Stonehenge might not have been reused in the Bronze age.