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Re: North Pole



John Clement wrote:

For what it is worth, a few definitions from the American Heritage
dictionary:

celestial sphere: An imaginary sphere of infinite extent with the earth at
its center on which the stars, planets, and other heavenly bodies appear to
be located.

No problem.

Note that planets and nearby stars are observed to move
w.r.t the celestial sphere.

celestial pole: either of two diametrically opposite points at which the
extensions of the earth's axis intersect the celestial sphere.

No problem.

Clearly not synonymous with "celestial sphere".

ecliptic: 1. The apparent path of the sun among the stars; The
intersection plane of the earth's solar orbit with the celestial sphere.

No problem.

2. A great circle on a terrestrial globe inclined at an approximate angle of 23
degrees 27 minutes to the equator.

Not a good definition.
It is an approximate temporary consequence of definition (1)
but hardly a good long-term definition.

I suspect that the discussion is more over implication than explicit
definition. It looks to me as if there may be 2 variations on the
definition of celestial sphere.

Really? There's no hint of a second definition in any
dictionary I've seen.

One of these meanings may be commonly used
by a particular group such as astronomers or amateur astronomers. The only
way to settle it may be by a poll at an astronomy meeting.

I don't see a question. It seems totally clear that the
celestial pole could (and in fact does) move w.r.t the
celestial sphere, just as nearby stars do. Similarly the
ecliptic could (but in fact does not to any great degree)
move w.r.t the celestial sphere.

Note that the geographic "spin defined" coordinates
(declination / right ascension) are by no means the only
coordinates used by astronomers. I get 16,000 hits from
http://www.google.com/search?q=galactic-coordinates

This posting is the position of the writer, not that of Fritz Lang,
Aldous Huxley, or George Orwell, although they might be amused that it
would be necessary to say so.

This posting is the position of the writer, not that of SUNY-BSC, NAU or the AAPT.