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----- Original Message -----
From: "Stephen Shaw" <srshaw@Dal.Ca>
To: <naturens@chebucto.ns.ca>
Sent: Monday, August 18, 2014 2:25 AM
Subject: RE: [NatureNS] Neolithic stone rings etd.
> Hi Dave: You need an astronomer with an interest in history for this, so
> stand by, hopefully, for input.
>
> I've forgotten most Euclid, but how do you subdivide a circle easily ('a
> snap') into 12 subunits? I can see how you draw the first line and find
> its centre (will become the centre of the circle) with a rawhide
> compass-divider, and how you can draw the second diameter at right angles
> to this with the same gear, and then complete the circle. You are then
> left with a circle with 4 equal quadrants, each of which has to be
> subdivided finally into 3 segments to make a total of 12, like the hours
> on a clock. Isn't this the difficult problem of trisecting the angle
> (bisecting is a snap with a simple compass, but I thought trisection was
> not)? Please advise.
> Once you've somehow accomplished the trisection of 4 segments into 12
> sub-segments with 30° central angles, then 24, 48, 96... segments are easy
> (bisection), as you imply. But subunits of 60 segments are not part of
> this series, so that remains rawhide-unexplained too.
> Steve (Hfx)
> ________________________________________
> From: naturens-owner@chebucto.ns.ca [naturens-owner@chebucto.ns.ca] on
> behalf of David & Alison Webster [dwebster@glinx.com]
> Sent: Sunday, August 17, 2014 7:34 PM
> To: NatureNS@chebucto.ns.ca
> Subject: [NatureNS] Neolithic stone rings etd.
>
> Dear All, Aug 17, 2014
> The August issue of National Geographic has an article that features
> the
> stone rings and other old (~5000 yrs.) structures of the Orkney Islands.
>>From this article & Wikipedia; the circular Ring of Brodgar; spaced for 60
> stones of which 27 remain and the slightly nearly circular but elliptic
> (so
> they say) ring of the Stones of Stenness; spaced for 12 megaliths with
> perhaps 1 or 2 never erected.
>
> Is it now so widely recognized that such structures served as
> observatories (an analog calendar and crude sundial) that it is too
> obvious
> to mention ? Alignment to the winter solstice at sunset (which would also
> fit the summer solstice at sunrise I think) is mentioned but surely these
> could have been used to keep track of time throughout the year.
>
> Even short stones would cast a long shadow at sunrise and sunset and
> the
> changes in direction with time would be consistent from year to year. A
> circular structure with 12 stones is a snap to lay out if you have enough
> rawhide and this natural and practicable number likely accounts for our 12
> signs of the zodiac, 12 months of the year and 24 hours in the day. But a
> ring with 60 markers is slightly more tricky to lay out, using Neolithic
> hardware, then say a ring of 48 or 96. The number 60 has the advantage of
> being divisible by 2,3,4,5&6 so the designer of this ring was just a step
> away from a 360o circle; dividing a circle into 60 or 360 parts is
> essentially the same problem and both have similar advantages if fractions
> are difficult to deal with.
>
> Yt, Dave Wwbster, Kentville
>
>
>
>
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