[meteorite-list] 8000BC Big Dipper Petroglyph: Evolution of star positions

From: lebofsky at lpl.arizona.edu <lebofsky_at_meteoritecentral.com>
Date: Mon, 12 Sep 2011 07:53:34 -0700
Message-ID: <45e83cdaba09030ff03974b702f2e745.squirrel_at_webmail.lpl.arizona.edu>

Hi Chris:

I rarely disagree with you, but I do this time (sort of).

There IS an option in "Starry Night" to look at the constellations over
time (using proper motion). The Big Dipper (an asterism, not a
constellation), looks very similar in 8,000 BCE to what it looks like
today. Chris: it is called constellations over time.

And "using a different method" (or whatever the statement was) to say what
the Big Dipper looked like then makes no sense. I doubt that the
petroglyph could have been used to depict what the Big Dipper looked like
100,000 years ago.

Larry

> That's because precise calculation of the positions of the planets-
> including Earth- is only possible for a few thousand years. Beyond that,
> the chaotic nature of orbital dynamics in a multiple body system becomes
> dominant. No software, professional or amateur, can provide an accurate
> topocentric sky map for more than a few thousand years either way from
> the present.
>
> That is quite different from estimating the shapes of asterisms over
> time. In most cases, the proper motion of the brighter stars is well
> known, and makes it possible to know what constellations will look like
> over periods of millions of years. But since the purpose of sky charting
> software is primarily to produce accurate topocentric star maps, they
> generally limit themselves to a much shorter period. They won't let you
> look at the Big Dipper 100,000 years ago, not because they can't
> accurately render it, but because they can't accurately position the
> entire asterism in the sky.
>
> Chris
>
> *******************************
> Chris L Peterson
> Cloudbait Observatory
> http://www.cloudbait.com
>
> On 9/12/2011 5:20 AM, karmaka wrote:
>> Hello Robert,
>>
>> thank you for the interesting images.
>>
>> The depiction of the 'Big Dipper' 100.000 years ago matches other
>> simulations and depictions I've seen so far.
>>
>> Precise calculations with astronomical software for amateurs are usually
>> only possible
>> until a few thousand years back in time. There must be a reason why.
>>
>> 'Redshift 7 Premium' for example allows only calculations which do not
>> go back further than 4713 BC.
>>
>> Best regards
>>
>> Martin
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Received on Mon 12 Sep 2011 10:53:34 AM PDT