The other Stonehenge Solstice connection

In a world around which the Universe rotates, the Sun moves its plane (circle) up and down along the polar axis. In summer, the plane is high over England, so the days are long. The sun’s circle rises from the north east and sets in the north west. In winter, the plane is low, so the sun’s circle rises from the south east and sets in the south west:

If you are not familiar with the idea of a solar plane, a post here explains it in more detail.  A lot more detail on the sun’s apparent movement can be found on this wikipedia page (which describes the ecliptic).

Stonehenge's alignment to Solstice

 
The alignment 
It's well known that Stonehenge is aligned to the Solstices. At Britain's latitude, the winter solstice sunset is only just over two degrees different from the opposing direction at summer solstice. At Stonehenge, the hills to the north east make the sun appear just that little bit later, which means that the two events are even closer than you would find on a flat plain. 

A posteriori evidence 

There is evidence from places such as Newgrange that the solstices may have been important to some Neolithic people. Sunrise at winter solstice produces a beam of light which shines down the Newgrange passage.

However, Newgrange is a long way from Stonehenge. It was constructed hundreds of years earlier. It also looks nothing like Stonehenge. Stonehenge does not appear to do anything special with the beams of sunlight, so the best we can say is that Newgrange (and similar monuments which are known to have a solstice function) might provide a fairly weak (a posteriori) link if the monuments are of the same type. 

Secrets of the Stonehenge Skeletons

Secrets of the Stonehenge Skeletons: Initial Critique

Interesting documentary last night shown on Channel 4: Secrets of the Stonehenge Skeletons.

1)  The Procession

In the graphics, the program described how up to 4000 people “formed a procession up the along the Avenue to pay their respects to the dead.... and observe the winter solstice sunset through the aligned stones”: This being one of the main conclusions of the documentary.

Extract from video feed of the programme

The problem with this idea is that the most recent English Heritage report has shown that it was unlikely to have been used for processions: The track-way would have been rutted at the elbow of the Avenue (see English Heritage report 31 entitled “The Avenue And Stonehenge Bottom”).

2)  The Solstice gathering

The program described how people walked up to Stonehenge to see the winter Solstice: At Winter Solstice, the sun can be seen setting at and through the bottom of the Great Trilithon stones when seen from the direction of the Avenue. 

The problem with this idea is that the Avenue is on a slope: You can not see the bottom of the stones from most of the Avenue (see photos in this post). 

Yet the monument has been shown to have been specifically designed to be seen from the Avenue (see English Heritage report 32 entitled “Stonehenge Laser Scan: Archaeological Analysis Report”). If the monument were built for the purpose described in the documentary, the builders appear to have chosen a particularly bad location. 

3) Metals

In the program, the reason for Stonehenge's decline was said to be due to the Beaker people, who apparently brought metals to England after Stonehenge was built: Stonehenge seemingly declined as a result. “Copper: A beautiful shiny new material: Metal. Nobody before had seen this in Britain” (quote from Documentary).

Extract from video feed of the programme

The problem with this is that his book (“Stonehenge: Exploring the Greatest Stone Age Mystery”) describes in a lot of detail how metals were likely to have been in use at Stonehenge when it was built: For example on page 125 he describes how copper used in ditch digging at Durrington Walls has been dated to 2480-2460Bc (and lists other evidence for copper use prior to 2500BC). The date given for the construction of Stonehenge is 2620-2480BC (see page 310). 

Both the program and the book appear to state that Durrington was built to construct Stonehenge. “This evidence showed that animals were being slaughtered [at Durrington] to mark the mid winter Solstice at Stonehenge.... and this was happening at exactly the same time as the second phase of the building of the monument.... so Durrington was effectively a builder's camp servicing Stonehenge's construction”

In other words, the sequence described appears to be wrong: If you are building a settlement to house workers, you build the settlement first, not the monument. If the settlement was built first, then Mike Parker Pearson's book suggests that metals were in use before Stonehenge was built. Yet at the same time, the documentary suggests that the discovery of metals was the reason that Stonehenge stopped being used.

4) Periglacial Stripes

The program described how two periglacial stripes were the reason that the location on Salisbury Plain was chosen for Stonehenge:

Extract from video feed of the programme

The problem with this is that periglacial stripes form as a result of slope weathering: There will be more than just two of them. The two that have been selected for the program make it appear as if they are special. 

Before the Avenue was built there would have been multiple stripes to choose from, probably radiating out from the hill summit in differing directions, and not just the two which are shown on the program (beneath the Avenue). The idea that these two stripes made the original location special appears hopeful rather then conclusive.

Overall 

In summary, some of the conclusions of the documentary appear to be discounted by the evidence of the team that contributed to it: This was a bit disappointing.

Additional note: (06-13)
The Periglacial Stripes: The criticism is more about the evidence presented rather than the possibility that this may have existed (as the reason to signify that the Stonehenge location was special). If better evidence exists, perhaps something not noted in either the program or the book by Mike Parker-Pearson, it would be great to see this and be able to strike it off the list.

Making Spherical Mirrors: Part 2

Making Spherical Mirrors; Part2. Using Modern Materials

This post is about how to construct a 9 piece frame for a segment of a spherical mirror. For the sample frame I used 30cm x 30cm square mirrors from IKEA.
 

Spherical mirrors sets are part of a ball. Imagine you have an orange and you cut a small square out of it's skin: This small 'spherical' square is what we are trying to create. When flat plane mirrors are placed into this arrangement, it will form a segment of a sphere: See part 1 for an explanation of the maths and what's being done.

At first, I tried using shaped plywood and a 16 mirror frame: 

Making Spherical Mirrors: Part 1

Introduction: Part 1

This post is about how to construct simple spherical mirror frames. For the sample frame (to be described in part 2) I used 30cm x 30cm square mirrors from IKEA. I'll show how it works here and then describe in part 2 how to make this even more cheaply.
 

Spherical mirrors sets are part of a ball. Imagine you have an orange and you cut a small square out of it's skin: This small 'spherical' square is what we are trying to create using mirrors. However, we are making it out of flat pieces of mirror. 

Imagine the square of orange peel has one square mirror placed at it's centre. When eight other mirrors are placed around the centre one, each edge (away from the centre) will be raised slightly: It will follow the curve of the ball.