Re: North Pole

["John S. Denker" <jsd@MONMOUTH.COM>]

Michael Edmiston wrote:
> Each student therefore gets a miniature earth suspended within a clear
> spherical shell, and the rod through the polar axes holds it all together.
> The clear shell obviously represents "the celestial
> sphere"

OK.

> and the rod is both the earth's axis

OK.

> and the celestial sphere's axis.

Not OK.

> The students use a fine-tip marker and draw some
> stars and constellations on  the sphere, as well as the
> ecliptic and a few dec/RA grid lines.

OK.

> Now... what did students do a few thousand years ago,
> and what will they do a few thousand years in the future?

A fair question.  Not the only question, but still OK.
My answer appears below.

> It is possible that
> they draw the objects on the sphere first.
...
> That would be in tune with the idea that the
> celestial sphere exists independent of the earth.

OK.

> However, that is not what is usually done.

Well, now, that rather depends on whether students are
learning astronomy from books, or whether they actually
go outside and look at the sky.

Did I ever tell you about the time I went stargazing in
a meadow near Aspen with a friend of mine who's a professor
at MIT?  He got out his charts and started getting his
telescope all set up and aligned so that he could use
the setting-circles to find the goodies we wanted to find.
He was about 1/4th of the way through the alignnment
process when he realized that I had just plunked my
telescope onto its tripod and manhandled it until
it was pointing in the right direction.  I had no idea
what was the Right Ascension or Declination of what I
wanted to look at, but I knew where it was on the sky.
My buddy was taken aback.  He was using what he thought
was the "scientific" approach, using a telescope that
cost about twice what mine did, and (because if its
smaller size) should have been easier to handle -- but I
was getting results faster, because I knew where stuff
was on the sky.  On what I call the celestial sphere, and
what my dictionaries call the celestial sphere.  I don't
need coordinates to know where stuff is.

A few thousand years ago, students would have been quite
happy to make charts of the stars without being able to
look up the RA and Declination in books full of numbers.
They would have gone outside and looked at the stars.
Since there weren't a lot of books full of numbers back
then, they wouldn't have had much choice.

As for people who learn "astronomy" from books and have
no idea what the night sky looks like, well, I suppose
they need coordinates.

The thing I call the celestial sphere existed for
billions of years before the earth even had a spin
axis, and will exist for billions of years after the
earth is gone.

============

A related question:  Ask your students what happens if
the geospin axis precesses.  Do they think the "celestial
sphere" will follow the earth's axis, taking the fixed
stars with it?  If they do think that, you may conclude
that the model is allowing (maybe even causing) some
serious misconceptions.

This posting is the position of the writer, not that of Blondlot,
Lysenko, or Schon.

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