Dear List (still with Ron Hartman on my mind ... I think he would what
I'm posting here).
The maximum it will "deform" from our insignificant vantage point...the
bowl by 5% and the entire asterism they might move up to 2%. So, yes -
it will look basically the same unless you are an astronomer.
If you wonder how I came up with that:
Star motions are basically measured in milliarcseconds per year (mas).
There are 3,600,000 mas in one degree. The Moon and Sun are both about
a half degree, and they are pretty small (About 720 of them in a
necklace would be required to circle the heavenly sphere).
If you make believe you are looking at the inside face of a shell we
are in, astronomers use two coordinates to locate any point (R.A. and
declination). The is nothing much different in the motion of this
stars in the range of motions in either, so let’s just for fun look at
the most separation that could happen in 8000 years without trusting
any canned software (nothing against them - they are great, but take
the fun of learning out and replace it with a black box and results
delivered on a silver platter).
Here are the speeds of the motions of RA for each of the stars in the
big dipper (the plough; el arado, el carro, the pan, etc.):
Dubhe: 136 mas/yr
Merak: 81 mas/yr
Phecda: 108 mas/yr
Megrez: 104 mas/yr
Alioth: 112 mas/yr
Mizar: 121 mas/yr
Alkaid: 121 mas/yr
If you assume the absolute worst case, of two stars running away from
each other in opposite directions, that would be Dubhe (-136) and
Alkaid (+121), you get a separation speed of 257 mas/yr. In 8000 years
that gives you 2,000,000 mas. That is just a wee bit more than the
angular diameter of the Sun or Moon - and that is worst case;
declination actually looks less acute, but it is fine to estimate.
In conclusion, each star at most has moved relative to each of its
companions one half degree in the extreme. This compares to the size
of the big dipper: the four stars in the "bowl" portion span about 10
degrees. From the end of the handle to the opposite tip of the bowl is
about 25 degrees.
So that's the maximum it will "deform" from our insignificant vantage
point...the bowl by 5% and the entire asterism they might move up to
2%. So, yes - it will look basically the same unless you are an
astronomer.
A similar question came up with the 6000 (or whatever) year old Orion's
belt stars when comparing them for the hypothesis that the three main
pyramids in Giza were in the belt stars' configuration. I believe it
was Rob who mentioned this controversial claim. I don't buy it, but it
has been looked at ad naseum and the conclusion is that they are still
close enough so it is a viable conjecture.
Kindest wishes
Doug.
-----Original Message-----
From: lebofsky <[email protected]>
To: bartraj <[email protected]>
Cc: epgrondine <[email protected]>; meteorite-list
<[email protected]>
Sent: Mon, Sep 12, 2011 12:30 am
Subject: Re: [meteorite-list] 8000BC Big Dipper Petroglyph
Hi Robert:
I took "Starry Night," a planetarium program "back" about 8,000 years
(6,000 BC) and, as I would have predicted, the 7 stars in the Big Dipper
are not far off from what we see today. You would have to go back many
10s
of thousands of years in order to see a big diffence. I remember seeing
predictions of the dipper being more of a pan cake flipper in 100,000
and
that 100,000 years ago, the bowl was much deeper and I think the handle
flatter. I have not gone that far with the program (there might be a
preset demo of it in the program, but it is late and have not looked for
it).
Larry
Hello Ed, Martin, Cris, List,
There has been some discussion on meteorite-list about Chinese
researcher
Wu Jiacai, who recently announced the finding of groups of
petroglyphs in
Inner Mongolia. In his interpretation, the petroglyphs show that an
intellectually advanced ethnic group, the Chifeng people of the
Hongshan
Culture, were forced to leave their homeland because of a singular
destructive event, perhaps comet- or meteorite-related.
http://www.globaltimes.cn/NEWS/tabid/99/ID/673451/Falling-meteor-depicted-in-5000-year-old-rock-carving-in-north-China.aspx
While looking into this event, I came across reports of an earlier
find by
Wu Jiacai, an early Neolithic depiction of the Big Dipper. See for
example
http://www.megalithic.co.uk/article.php?sid=2146412586
It made the news in Chinese papers. Here is a summary of a 2010
interview
with Wu Jiacai in a Mongolian home town newspaper.
http://www.swcf.cn/wh/2010-01/12/content_900.htm The newspaper
article
features a superimposed diagram of the shape of the Big Dipper in
8000BC.
Maybe some of the astronomers here can assess whether this shape is
plausible.
-------------
Summary
After more than a year of on-site research at Baimiaozi Mt., Wu had
identified ten distinct groups of rock art, mostly depicting animals
and
people. Among them was a 310 cm-long yam-shaped stone on which 19
clearly
visible stars had been chiseled and ground into the stone's
upward-facing
side, with the markings depicting the seven stars of the Big Dipper
on the
northern part of the face.
[A better view of the stone, from Wu Jiacai's personal blog, is here
https://www.dropbox.com/gallery/18663629/1/Hongshan%20Culture?h=bdfa66
]
The total length of the Big Dipper is 119cm. The indentations marking
the
stars are 6cm in diameter, with a maximum depth of 5 cm. The shape of
each
star resembles an upside-down mantou (steamed bread), wide on the
outside
and smaller within. The star-shapes are smooth, with rounded surface
[indentations] that also contain a natural-colored residue of dust and
body oil [from touching].
Following astronomers' reconstructions of star positions from 100,000
years ago to today, Wu Jiacai found complete matches between the
configuration of the Big Dipper's seven stars 10,000 years ago and the
configuration of stars in the rock art.
Gai Shanlin [a Manchu from Hebei], who is the regional archaeological
expert on rock art, inspected the inscribing-polishing methods. He
recognized the drawing of the seven stars of the Big Dipper as an
early
Neolithic artifact by ancestral people.
End Summary
------------
Regards
Robert A. Juhl, Tokyo
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