Megalithic Calendar

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Megalithic Calendar

Postby Boreades » 10:45 am

Or, Megalithic time-keeping
Or, Equinox and Solstice, the red-herrings
Or, the TME Christmas Bonus.

Something topical for this time of the year.

Question: What do we mean by a Solstice?
Answer (from someone with an MBO* degree) : It's the day of the year when the sun is visible for the longest or shortest time.

Time. There it is, the word's been said.

What time?
How would megalithic folk, with no clocks or watches, have any idea what the time was?
Or how to tell the time?
Or measure the passage of time?

Question: In the absence of a clock, what would megalithic folk have been observing or measuring?
Answer: It was the observed motion and positions of the sun, moon, planets and stars.

All these observed positions are, of course, relative to the Earth, and especially where you are on the Earth. Last Sunday, 21 December 2014, apparently, the northern hemisphere experienced the shortest day of its year at 23:03 GMT - the moment the North Pole is tilted furthest from the sun as the Earth continues on its orbit.

According to a recent BBC article:
The solstice doesn't always occur on 21 December. Sometimes it nudges into the early hours of 22 December, which will happen again next year. The hour of day also varies. Last year's arrived at 17:11. Next year's will at 04:38.

Especially for those of us who get up in the dark to travel to work, the more astute of these early risers might have perceived a curious development, which may have passed by the more bleary-eyed unnoticed. It would seem logical that after the shortest day has elapsed the mornings would start getting lighter earlier, but this isn't what happens - the mornings continue darkening until early in the new year!

e.g. Sunrise and sunset in London in 2014/5
Day / Sunrise / Sunset / Day length (h:mm:ss)
11 December 2014 - 07:56 / 15:51 / 7:55:37
21 December 2014 - 08:04 / 15:53 / 7:49:45
31 December 2014 - 08:06 / 16:01 / 7:54:39
31 January 2015 - 07:41 / 16:48 / 9:06:42

So what is behind this peculiarity, which appears to fly in the face of received wisdom about the solstice - surely the shortest day should experience the latest sunrise and earliest sunset? It's because there's not 24 hours in a day! There are two reasons why the length of the solar day varies, the first being the fact that the axis of the Earth's rotation is tilted - 23.5 degrees from vertical - and second, the Earth's speed varies because it moves in an elliptical orbit around the sun, accelerating when it is closer to the star's gravitational pull and decelerating when it is further away.

Image
* MBO = Master of the Bleeding Obvious
Boreades
 
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Re: Megalithic Calendar

Postby Boreades » 10:55 am

At the height of summer in the Northern hemisphere the distance from the sun is different to the height of summer in the Southern hemisphere - 147 / 152 million km

if you could record the position of the sun in the sky at the same time every day, let’s say sometime around noon and subtracting one hour if you are observing daylight saving time, you would notice that the sun takes a rather strange path.

Image

Why does the sun take this strange path? There are two reasons and they are completely independent from each other.

1. The Earth is tilted on its axis 23.5° in relation to the plane of its orbit around the sun.
2. The Earth does not orbit the sun in a circle, but in an ellipse.

Perihelion (when the Earth is closest to the sun) will occur around January 2nd.

But what's all this got to do with the Megalithics?

In the absence of any handy timepieces, the Watchers were watching the changes in the observed position of sun rise and sun set, at that latitude. The extremes of which don't exactly coincide with the solstices.
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Re: Megalithic Calendar

Postby spiral » 10:47 am

Yes it was a bit of bugger for the ancients.

Still the Incas came up with a neat solution - they tethered the position of the Sun.

They simply built giant hitching posts called Intihuatana and then retied the sun to it on the dates of the equinox (equal day and night).

The beauty of this is that if the sun wanders off, and doesn't come back, you are condemned to perpetual darkness and vice versa..

It pays to keep things in balance, but your archaeos aint interested in balance, they want longest or shortest, tallest or smallest etc.
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Re: Megalithic Calendar

Postby Boreades » 1:34 pm

No surprise that the astronomical community has a "proper name" for these figure-of-eights : Anelemma. But the shape of these anelemma varies depending on your latitude. Here's what it looks like for Greenwich (51.48 degrees north)

Image

Notice the slight but significant differences between (a) the grid azimuth angle, from the current geographic north-south and (b) the observed northern & southern extremes.

For northern latitudes, the earliest sunset occurs a week or two before the December solstice, and the latest sunrise occurs a week or two after the solstice. Thus, the darkest evening occurs in early to mid-December, but the mornings keep getting darker until about the New Year.

Ref: http://en.wikipedia.org/wiki/Analemma
Last edited by Boreades on 1:57 pm, edited 2 times in total.
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Re: Megalithic Calendar

Postby Mick Harper » 1:52 pm

So when and where are the two halves 'in balance'?
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Re: Megalithic Calendar

Postby Boreades » 2:14 pm

When "in balance"?

A tricky question. That must surely have vexed our Megalithics as well. Stonehenge and Avebury are (surely?) evidence of a profound belief in the symmetry and harmony of the universe around us. Or is that an anthromorphic projection on my part?

I hypothesis that the first measurements that didn't, err, measure up (sic) must have caused a lot of megalithic head-scratching by the Captains of The Watchers.

Captain to crew: "You must have measured it wrong, go back and start again, come back with new data in a few (hundred?) years"
Later, crew to Captain: "I canna change the laws of physics, Cap'n!"
(or something like that)

After starting this threat, and scouring t'interweb for more on "analemma sunrise and sunset", I found mathbabe.org
http://mathbabe.org/2012/06/30/analemma/
which nicely reinforces the point(s) I'm stumbling towards.

What is time, anyway? How do we know what time it is? What with time zones, and daylight savings time, we’ve definitely corrupted the idea of it being noon when the sun is at its highest in the sky or anything as definitive as that.

So let’s imagine there are no time zones, that you are just in some specific place on the earth. You never move from that spot, because you’re afraid of switching time zones or what have you, and you’re wondering what time it is. If someone comes by and tells you it’s daylight savings time and to reset your clock, you tell them to go to hell because you’re thinking.

From this vantage point it’s definitely hard to know when it’s midnight, but you can for sure detect three things: sunrise, high noon, and sunset. I say “high noon” to mean as high as it gets, because obviously if you’re way north or way south of the equator the sun will never be totally overhead, as I noticed from living in the northeast my whole life.


If we use the highest high-noon to define "North", and the lowest high-noon to define "South", then the Megalithics Meridian is not exactly the same as our "modern" meridian.
(It's north, Jim, but not as we know it.)

This matters for Megalithic Mapping and Meridian Meanderings. More on that later.
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Re: Megalithic Calendar

Postby spiral » 3:56 pm

To my lazy way of thinking, your ancients would just count moons and recalibrate each year using the sun/moon to get a calendar. Counting moons is easier, than gaining a degree in pure maths.

Still.... if I had a degree in pure maths, I would want to prove that the ancients were far cleverer than previously thought as this sort of thing sells, and is politically correct, and also shows that I didn't get booted out of college.

Along similar lines.. does it really matter that computer or watch time does not always match sundial or landmark time? I mean we are talking about the odd 15 minutes. I am not convinced this mattered to your ancients as many were err... using the same landmarks, dials etc

No, your ancients happily judged, counted and re calibrated. Realising that things were roughly in balance, and sensing that humans are incredibly good at informed punting, and incredibly crap at exact, long calculation.

THat is until some maniac came along and decided as there was one true god, there was one true method of keeping time, and it was Histime to fit Hisstory. Imposing a chronology that was based on year 1= birth of solar deity, or some such type of thinking.
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Re: Megalithic Calendar

Postby Boreades » 4:41 pm

Agreed, a lunar calendar is the easiest to get started with. The moon is visible even on cloudy days, and wouldn't(?) need as much precision as a solar calendar (I stand to be corrected).

The esteemed phys.org even suggests that Scottish Engineers led the world in this field as well.

World's Oldest Calendar in Scotland?

The Mesolithic monument was originally excavated in Aberdeenshire, Scotland, by the National Trust for Scotland in 2004. Now analysis by a team led by the University of Birmingham, published today (July 15, 2013) in the journal Internet Archaeology, sheds remarkable new light on the luni-solar device, which pre-dates the first formal time-measuring devices known to Man, found in the Near East, by nearly 5,000 years. ... Until now the first formal calendars appear to have been created in Mesopotamia c, 5000 years ago. But during this project, the researchers discovered that a monument created by hunter gatherers in Aberdeenshire nearly 10,000 years ago appears to mimic the phases of the Moon in order to track lunar months over the course of a year.

Refs:
http://phys.org/news/2013-07-world-olde ... .html#nRlv
and
http://www.bbc.co.uk/news/uk-scotland-n ... d-23286928



I canna change the laws of Physics, Cap'n!
But I can knock up a nice line of lunar calendar posts fer ye.

But as our friend Jon has so admirably demonstrated, Stonehenge works as a solar observatory, not lunar. How about Avebury though? I'm open to suggestions.
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Re: Megalithic Calendar

Postby spiral » 6:31 pm

Stonehenge might be a solar observatory but that does not mean ordinary folks were operating a solar calendar.

To to my mind different groups of ancient brits were most probably using localised combinations of lunar/tidal/solar practical calendars, tied to the tasks they undertook -- think localised task time zones rather than geographic time zones.

I can't see shed-loads of Brits suddenly switching to congregating round one big in your face, giant solar calendar.

Stonehenge certainly isnt precision engineered.
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Re: Megalithic Calendar

Postby Boreades » 11:07 pm

Good point!
If other places are to be believed, it was only the advance of the railways that did away with local time zones and the like.

But?
<< Stonehenge certainly isnt precision engineered. >>
Except it was the cutting edge precision engineering of its time?
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