A Calendar for the Ages - the MS&T Stonehenge part 2

In the last post I discussed the historical background to the British Megalith Stonehenge, and briefly how it was decided to create a similar construction, albeit at half-scale, on the campus of what is now Missouri University of Science and Technology (MS&T). So we skip forward about 4,000 years from time of the last post and the new Chancellor of our campus wanders into the refreshment room at a Conference on Engineering Education in Oklahoma. There he saw one of his new faculty – and over a glass or two of the water of life (uisge beatha) mentioned that he had interest in a Stonehenge, while I mentioned that we had just developed a new method for cutting granite, and I had some idea of where to get the rock. Before I knew where we were, I was on a committee, and we were planning a monument.

The campus was already in process of building a new Mining Building, itself near the Computer Science building, and there was a nearby space beside the campus Observatory. And this became the site for the new megalith. (It consists of 55 stones). As with the early constructions, this was planned to be a working calendar, and Dr. Senne used computer models to predict the positions of the sun, and the North Star to ensure that the monument would be an accurate model for at least four millennia. But, because it was in a different location, and because of the limited space, we had to modify the Neolithic design. So this post will describe how the megalith acts as a calendar and then the next will describe how we made it. (It had to be half-scale because even at that size a single stone filled a rail car).

Figure 1. An ancient monument recreated (with modern power generation in the background)

The solar alignments were built around the center of the structure, and this can be found as a small metal disk, which has been surveyed into place by the National Geodetic Survey, and mounted in a cylinder of concrete.

Figure 2. The marker at the center, with the dot in the triangle being the focus.

The first and major alignments, as with the original, are those that mark the position of the sun at midsummer, and midwinter. The stones are aligned so that the sun can be seen as follows:

At midsummer the sun will rise over the Heel stone. This 35-ton block of granite at the far end of the approach walkway is not exactly aligned at present, since the church behind it conceals the very first seconds of the sunrise, but it is close. A tree that initially marred the alignment to the center of the stone has since died, and the alignment is now better than it was when built. The alignment should not change over the coming millennia. (Granite erodes at around one inch every thousand years, and the Heel Stone is set in a full truckload of cement, to guard against earthquake-induced movement).

Figure 3. View of the Heel Stone from the central marker (lower front right).

As the sun passes through the sky that day it will move relatively around the southern half, past the East and West markers, and at sunset will lie between the two legs of the North-West trilithon.

Figure 4. View of the North-West Trilithon, the midsummer sunset through these legs casts an orange beam that reaches to the central marker column, at its diameter. (lower front left).

For the midwinter sunrise, the current McNutt Hall, housing the Departments of Mining and Metallurgy, hides the first few minutes of the rising sun, yet the sun still first appears through the legs of the South-East trilithon. As time has passed the antenna on the building that, fortuitously, marked the point where the sun was first seen has been removed.

Figure 5. Looking through the South-East Trilithon to the point where the sun rises at midwinter.

During the course of that day the sun moves over its relatively shorter arc, and at sunset appears to go down between the legs of the South-West trilithon. As with other alignments the construction of the University residences has slightly displaced the true alignment to the sunset on the horizon. For the next few years I suspect that the tree that is now growing into that view will further block this alignment.

Figure 6. Looking through the South-West Trilithon, from the central marker, toward the midwinter sunset.

This gives us two days of the year, which really aren’t enough to define the seasons, but one can add two more, based on the two equinoxes in March and September. On those days the sun rises directly in the East, and sets directly in the West. Thus, by putting small notches on the East and West marker stones, the day the sun rises and sets in those places identifies two additional days.

Figure 7. The notches on the a) East and b) West marker Stones, with a notch on each to mark the sunrise and sunset at the two Equinoxes.

This still, however, only gives us four days, and the Chancellor was decidedly against adding the nineteen stones to give the ancient calendar. Dr. Senne suggested, and it was agreed, that the site should be “Americanized” and that the calendar should be based on the use of the sun position, as developed by the Anasazi Indians in Colorado.

However, instead of their complex curves, he suggested a simple analemma carved into two central stones that would mirror the position of the sun at midday as projected through a small hole set within the Southern Trilithon assembly.

Figure 8. Points showing the position of the sun at midday over the course of the year. (Stanford Solar Center)

The inverse of this curve (since it was projected through a small orifice) was therefore inscribed onto the two stones in the center. The faces carrying the inscription were the only two faces not cut with high-pressure water within the construction.

Figure 9. The central stones carrying the analemma markings.

For the winter half of the year, when the sun is lower in the sky, the sun’s image will fall on the vertical face, during the summer half the sun is higher and the image will fall on the horizontal face. At the equinoxes the sun image travels along the joint between the two stones.

Figure 10. A small brass plate is mounted just below the capstone of the Southern Trilithon. There is a small hole in this plate through which the sun’s image is projected onto the faces of the two central stones. (It takes about ten minutes or so, on either side of midday, for the image to cross to the line and then again to move off the stone.)

The analemma was scribed into the stone with a sand-blaster after Dr. Senne had laid a full-scale tracing on the rock, to show the required positions. To make it easier to identify the actual date the line has been marked at five-day intervals within each month, which are also identified.

Figure 11. The sun’s image centered on the line at midday on the ?th of ?. (You need to read the date from the analemma).

Unfortunately this marker is likely to erode away over the next 500 years, at which point, unless it is renewed, the calendar will cease to function. In his book Mike Parker Pearson noted that the lower surfaces at Stonehenge had been shaped, but it is hard to know, after this passage of time, whether there were superficial markings on the stones, such as we have created, that would give a different way of telling the days of the year.

There was one other thing that we added. Although the North direction is shown with its own marker stone, this might get displaced, or lost. Thus a window was created in the Northern Trilithon, so that a person of normal height, standing between the light wells beside the central marker, will see (on a clear night) the Pole Star within the window, for (Dr. Senne assured us) the next 4,000 years.

Figure 12. The Polaris Window on the Northern Trilithon.

I will complete this series with a short post on how we cut and installed it, next time.

A New view of an old Circle - Post one on Stonehenge

Back in 1983 I was asked to work on the construction of a Stonehenge monument to be built on the campus of what is now Missouri University of Science and Technology. The new Chancellor of the campus, Dr. Joseph Marchello, had helped establish the Center for ArcheoAstronomy at the University of Maryland. He had wanted to build a Stonehenge, and we had just developed a new way of cutting rock with high-pressure water, and had contacts with the Georgia Granite Association as a result. The monument, which ultimately consisted of 55 different stones, was designed by Dr. Joseph Senne, who was then Chair of the Civil Engineering Department on campus. But to understand why we built ours, one has to understand why the original was built, on Salisbury Plain in the UK, some 5,000 years ago. And this discussion has been helped by the new book “Stonehenge – A New Understanding” by Mike Parker Pearson, discussing the recent Stonehenge Riverside Project.

Figure 1. Location of the original Stonehenge (Google Earth)

Although there are legends that it was built by the Druids, they actually came after the circles had been built, and it should be remembered that, when the Romans came to the UK 2,000 years ago Stonehenge was already over 2,500 years old.

Figure 2. Romans versus Druids – the Roman version

In looking back on that period remember that the history was written by the Romans and that they had to justify their invasion. Thus the picture that they paint of British society at the time is colored by those needs, and their image of Druids as backward painted savages is unlikely to be close to reality.

But why was there a need for these circles? Well back some 50,000 years ago mankind had migrated out of Africa and slowly spread through Europe and Asia. But as they spread they originally retained their cultural structure as hunter-gatherers.

Figure 3. The migration of humanity from Africa into Europe and Asia (National Geographic DNA project)

They reached Spain and Portugal as Cro-Magnon man, but were still largely hunting and subsistence gathering at that time. Such groups are small, typically, as one sees with the Hatzabe in Africa today, they number around 20 individuals.

Figure 4. The Hatzabe a family group of about 20 individuals.

The group size is similar with the Sami in Scandinavia, families that still follow the herds of reindeer as they have done for millennia.

Figure 5. A Sami family group of reindeer herders from Northern Scandinavia

Such tribes (including the Bakhtiari of Iran that Bronowski documented in “The Ascent of Man”) are migrant, and do not have time for much other than staying alive. But, with time, the culture changed and people began to farm. This change began around 12,000 years ago, likely in the Middle East. It was not until 6,500 years ago (4,000 BC) that trees began to be cleared and farms established in Southern England.

One of the advantages of farming is that the tribe does not have to move continuously to sustain itself. Cronon, in Changes in the Land, notes that in non-agricultural Maine the population was sustained at around 41 persons per hundred square miles. With the beginning of agriculture further south in New England (pre-European arrival) the native peoples could sustain 287 people in a similar area. More intense development of crops and the domestication of animals followed, leading to larger and more closely knit communities.

But there is one problem with the switch to agriculture on an increasing scale, one needs to know when to plant the crops. And while initially this was likely imitative of nature, over time the tribes needed to develop a calendar.

Lying by the fire and staring up at the stars to work on the idea Neolithic Man was living in what we now call the end of the Stone Age. And they noticed that at different times of the year the moon lay at different points in the sky. And so they started to plot these positions, after a while they noticed that there were grooves on some of the local rocks, left from earlier glaciation, that aligned with the positions of the moon at mid-winter and mid-summer.

Figure 6. Grooves in the rock near Stonehenge (Dr. Parker Pearson ibid)

This led on to marking the positions of the moon (and possibly also some of the stars as was the practice in native tribes in America). These markings were made more permanent as they were more confident of their positioning, through the use of wooden poles. (Note that there is a similar though more primitive wooden circle at Cahokia in Illinois dating at around a thousand years ago).

Figure 7. Circle of wooden poles – the UK Woodhenge (Dr. Parker Pearson)

The village grew into the town of Durrington Walls, with wooden houses, which have been recently excavated to show the yellow-painted clay floors, and the location of beds, dressers and other wooden furniture.

Figure 8. Artist’s rendition of the town of Durrington Walls (Dr. Parker Pearson)

With confidence, and as the calendar became more reliably used, so the wooden poles were replaced with a more permanent set of bluestone columns that had been brought to the site up the river Avon.

Figure 9. An early stone circle – Bluestonehenge- on the banks of the Avon. (Dr. Parker Pearson)

There is a little controversy over what happened next, but it has been suggested that around this time a new set of folk, now known as the Beaker people, because they used clay pots with a spout (beaker) moved into the region. They had one critical difference to the earlier site inhabitants, in that they worshipped the sun, rather than the moon. Thus the old calendar would not work. But up where the grooves cut into the stone, they had set four stones (the Station Stones) into the ground in a rectangle to mark the position of mid-summer and midwinter moonrise. If you rotated around the stones ninety degrees, then these poles still marked the two days, but now they did it for the sun’s positions. This could not have been a co-incidence, and so the study of calendars proceeded, but at the new site, further up the hill at the current Stonehenge.

Figure 10. Alignment of the Station Stones (Dr. Parker Pearson)

And on a passing note, as I once mentioned in Nature, and Rodney Castelden noted in “The Making of Stonehenge” the rocks were likely hauled into place with oxen, which might be why the roads are so wide).

Figure 11. Oxen hauling the stones to the site (Rodney Castleden ibid)

The first major construction at the Stonehenge site was the surrounding ditch and mound of rock (which is a relatively soft chalk that can be excavated with antler picks) with a series of small pits (some of which have been found to contain human remains) set within the ring.

There has been discussion as to whether this was a ceremonial burial ground for high-ranking individuals. In much the same way as Bruce Bourque has noted in “The Swordfish Hunters” discussing the Red Paint People of Maine, the small number of burials, relative to the size of the local population and the length of time this existed, means that this could only be a special place and rite. So though it might be where high class folk were buried (as with Westminster Abbey) it had other uses, which was to develop the calendar.

Over the years a number of different circles, with a variety of pole positions, were tried. For a while the 28 and a half stones of the Sarsen Ring had favor, but the last stone circles they put in had nineteen stones (probably taken from the Bluestone ring at the bottom of the hill). Then they stopped. They had a calendar.

Figure 12. Part of the bluestone ring of smaller stones set within the Sarsen Ring at Stonehenge. The Heel Stone can be seen further back from the main circle. (Landscape Perception)

But why nineteen? Well nineteen times nineteen is 361. Add the four days when, in the Hyperborean calendar, “time stood still”, which have come down as the Celtic feast days Samhain, Imbolc, Beltane and Lughnasadh, and you have a remarkable resemblance to the 365 days of the year. The problem was solved for a couple of thousand years.

Until, of course, those pesky Romans showed up, and made us work with months of 28, and 30 and 31 days. Herumph!!

I’ll talk about the Building of the MS&T Stonehenge next time!.