<HTML>Dave Moore wrote:
>
> Martin Stower wrote:
> >
> > Dave Moore wrote:
> >
> > > Okay, folks, here's a view looking south from Giza in 10430
> > > BC, the low point of Zeta Orionis (Alnitak) in the
> > > precessional cycle.
> >
> > How precisely can the date of this low point be determined?
> >
> > Bauval also talks about meridian transit of Orion's Belt
> > (from the diagrams, Alnitak) on the vernal equinox in 10500
> > BC <i>at sunrise</i>. Presumably this would compromise
> > visibility . . . but (also) how good is the coincidence?
>
> Let's deal with the dates first:
>
> At 10430 BC, Alnitak was 9.53 degrees above the southern
> horizon at its highest. At 10500 BC, Alnitak was 9.57 degrees
> above the southern horizon at its highest.
>
> In other words, there's precious little difference (certainly
> too small to be seen with the naked eye). 10500 BC is an
> acceptable figure, even though it is 70 years out.
OK, there's a small window around the correct date in which the fit is good enough.
What I had in mind was more: is there any uncertainty about the correct date?
I've seen differing figures quoted for the length of the precessional cycle. I don't know if this represents genuine uncertainty or merely didactic simplification - but if there is such uncertainty, it would follow that the date above is uncertain also.
Is there such uncertainty?</HTML>
