(urth) Crotali

[Jeff Wilson]

On 6/20/2010 12:20 AM, Mr Thalassocrat wrote:
>
>
> On Sun, Jun 20, 2010 at 12:47 PM, Jeff Wilson <jwilson at io.com
> <mailto:jwilson at io.com>> wrote:
>
>
>     Most constallations' component stars have no physical association
>     among them and only appear to lie closely together as seen from
>     Earth. This lack of unity means proper motion will make them
>     unrecognizable and/or disperse them entirely.
>
>     Precession of the equinoxes however takes place on a shorter scale,
>     currently a bit under about 26,000 years per full ciruit of pole
>     stars. This implies that Apu Punchau is about 13,000 years before
>     Severian, or 39,000, or 65,000 or 91,000...
>
> You're right, of course.


That's not to say that proper motion has no part to play in the Book. 
it puts a fuzzy upper limit on how many 26,000 year cycles can pass. 
Starting about 03:30, this episode of Cosmos shows a few changing over 
+/- a million years.

http://www.youtube.com/watch?v=TYobCdq9BEA&feature=fvsr

They are unrecognizeable IMO after a million years, so that's about 40 
precession cycles. Also, the displacement seems to be only 1/4 of the 
retrograde precession, spring planting under winter stars, so the split 
could be as little as 6500 years before adding multiples.

Hmp - reading Urth's appendix in this light seems to confirm not just 
the Ship's intervention in the eclipse, but the truly continental size 
of the mirror-sails: not just the 1/2 degree width of the moon is 
covered, as if by a Yesodi peephole, but several constellations worth of 
arc of mirror would be required to allow Severian to see his familiar 
constellations out of their season.

-- 
Jeff Wilson - jwilson at io.com
IEEE Student Chapter Blog at
< http://ieeetamut.org >