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On 12/11/10 2:01 PM, Apache Runner wrote:...

Thank you for your answers.

I fear, despite my setup, my question became, "...how the heck did they
figure out the ecliptic so long ago?"

Given hindsight and the wealth of information available at my
fingertips, I can wrap my head around discovering and mapping the ecliptic.

What still puzzles me, given the zodiac is placed along the ecliptic
(ignoring precession), how were they able to marry the ecliptic (using
the path of the the sun through the stars as a definition of ecliptic)
and star background almost 3000 years ago--800 to 1100 years prior to
Ptolemy or Hipparchus? Obviously they could not view the Sun and stars
simultaneously.

For example:  It is noon on any given day, the sun directly south at XX
degrees above the horizon.  If it were not for the sun, what star
pattern would I see?

Bill B.


> Bill -
>
> A few more items - here's a build-it-yourself Stonehenge website:
>
> http://www.christiaan.com/stonehenge/index.php?pg=stonehenge-build-your-own-stonehenge
>
> The history of the precession of the equinoxes in the west is a bit
> murky.   It's often attributed to Hipparchus, but he left no writings.
> It was pushed by Ptolemy.    Supposedly, the longitude of bright stars
> were measured over some time period and shown to shift relative to the
> equinox, with comparisons of data over about 150 years - long enough to
> make significant observations - that is to say, the shift is enough to
> be detectable.   Another method is timing the difference between a
> tropical and sidereal year which is interesting because you (well, I in
> any case) have to think through how this was done.
>
>
>   Neugebauer proposed that the Babylonians knew about the precession.
>
> Somewhat tangentially, but perhaps related - some of my students built a
> clepsydra out of spare parts and tested it out as a mapping device (e.g.
> comparing longitudes of distant cities).    It was an interesting
> project, and I wish they'd been a bit more ingenious about it, but I
> think with some effort, one can build one that's reasonably accurate.
>
> On Sat, Dec 11, 2010 at 9:23 AM, Apache Runner  > wrote:
>
>     The easiest way to do it is to chart the sunrise/sunset location
>     against markers lying on the horizon.    Historically, you can find
>     things like the Hopi sun calendar, or orientation of grave barrows
>     in northern Europe.  The discussion of  astronomical alignments of
>     places like Stonehenge seem to still be in flux, but there are
>     pointers to the path of the ecliptic.    With decent markers on the
>     horizon, you can see when the Sun appears to "stand still" against
>     the markers at the solstices.  (Sostice = "sun stop")
>
>     A more interesting issue is the knowledge of cycles of the Moon -
>     the Saros cycle for example.    People would have to wait 18+ years
>     to accumulate information from one eclipse to the next (18 years,
>     11.3 days between lunar eclipses).   Half a year is nothing compared
>     to figuring out eclipses.
>
>
>
>     On Sat, Dec 11, 2010 at 1:10 AM, Bill      > wrote:
>
>         I am guessing when I get an answer to my question, I'll slap
>         myself on the forehead and utter, "Of course." But here goes.
>
>         I look at star charts and planispheres with the current
>         ecliptic--the path of the sun through the stars--neatly added. I
>         take it for granted that if I could see the stars and the Sun
>         simultaneously that is the relationship I would see. Easy to
>         confirm with an almanac and spherical trig.
>
>         The zodiac signs--a form of right ascension or SHA--lie along
>         the ecliptic as opposed to the celestial equator. The zodiac
>         etc. have been around for about 3000 years, spanning the
>         Sumerian's lunar calendar, the Babylonians, and the sexagesimal
>         system. The shift of the First Point of Aries to its present
>         location on the celestial equator also appears to indicate a
>         long history of ecliptic knowledge.
>
>         My question, how the heck did they figure out the ecliptic so
>         long ago?  No pi, no trig.  A viewer would have to wait half a
>         year to see the star pattern that would have that day's Sun
>         superimposed on it. Yes?  A lunar calendar with 12 cycles a year
>         and a leap month every three years would not be a big help.
>
>         Bill B.

   

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