Re: Ironic SAA

On Aug 27, 5:50 am, Margo Schulter <mschul...@xxxxxxxxxxxxxxx> wrote:
alliso...@xxxxxxxxxxx wrote:

We all know that the earth does not revolve around the Sun once every
365 days, and every 366 days every fourth year. The calendar in
standard use assumes thusly because it is convenient and simple to do
so for civil purposes.

Hi, there, and that's pretty much my reaction also: I have no complaint
to direct to Julius Caesar, nor to Pope Gregory XIII, who in response
to the known fact mentioned for example by Dante around 1300 that the
Julian calendar was off by about "a hundredth of a day," followed his
astronomical advisers in introducing the rule that only years divisible
by 100 which were also divisible by 400 would be leap years (like 1600
and 2000).

What strikes me is that from either an observational or theoretical
point of view, the precise conventions we use for timekeeping -- or
RA and Dec or whatever -- are pretty provincial matters compared to
the scale of the universe, or even of our own Milky.

I'd see RA and Dec and the mapping of the night sky into constellations
as simply useful conventions for naming and finding things, much like
speaking of "sunrise/sunset" or "moonrise/moonset" -- which don't
necessarily imply a Ptolemaic or more generally geocentric model of
our Solar System!

Here and elsewhere, professional and amateur astronomers who follow
these conventions are indeed practicing astronomy, whether it's
attempting to observe some star cluster or galaxy and discern some
of its structure, or refining the Cepheid period-luminosity
relationship, or studying supernova dynamics, or getting new
information from millimeter wave surveys.

The excitement of this group is that we have both the excitement
of first-hand visual observation, and the opportunity to learn more
about the theoretical background and context, even if we don't
have the equipment to do all of the relevant studies at different
wavelengths ourselves.

Most appreciatively,

Margo Schulter
mschul...@xxxxxxxxxx
Lat. 38.566 Long. -121.430

This highly technical matter has its roots in the difference between
the correct working principles of structural and timekeeping
astronomers before Flamsteed and the astrologically based convenience
which emerged in the late 17th century -

http://en.wikipedia.org/wiki/Right_ascension

No astronomer,not a single one in the pre-empiricist era would ever
have thought of using a clock and external references to justify the
Earth's axial and orbital motion no matter how convenient it was to
track celestial phenomena via the calendar system.










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