In article ,
SkySea wrote:

"Magnificent Universe" wrote:
A free fact sheet summarizing arguments both for and against Pluto's
planethood is now available for teachers and others interested in the Pluto
controversy. This is a PDF file that can be downloaded from
http://www.boydsmillspress.com/pluto.pdf . Please allow a couple minutes to
download.
Correct email: MagnificentUniverse "at" yahoo "dot" com.

I'd take issue with a couple the yes-no arguments.

Orbit: The "yes" argument doesn't address the fact that Pluto's orbit
is so eccentric that it crosses Neptune's orbit. Alone, a simliar
eccentricity in another planet's orbit is a different argument.

He could also have addressed the 17-degree inclination of Pluto's orbit, which
is more than twice the 7-degree inclination of Mercury's orbit.

KBO: You mention Eris as being larger than Pluto, then say that's
reason for Pluto being a planet. But not Eris?

Actually, he does suggest Eris being a planet too -- read his sheet more
carefully.

And there could be larger objects yet

Most likely there *are* larger objects there, not yet discovered.

- should they also be classified as planets?

He thinks they too should be called "planets".

And although Pluto is very large as KBOs go, that doesn't mean Pluto
should necessarily follow as being a planet. For example, Ceres is
very large (even spherical) for asteroids, but it is not called a
planet.

Ceres (along with Pallas, Juno, Vesta) were called "planets" during
the first half of the 1800's, i.e. during the time these four were the
only known asteroids. Then a large number of additional asteroids
were discovered, and Ceres, Pallas, Juno and Vesta lost their planetary
status.

Today, Pluto losing its planetary status is in a way just a repetition
of the process some 150 years ago, when Ceres, Pallas, Juno and Vesta
lost their planetary status. And it's basically for the same reason:
Ceres, Pallas, Juno and Vesta were not alone, there were many more
asteroids. And Pluto wasn't alone either, there were many more KBO's.
The number of known KBO's today even exceeds the number of known
asteroids in the 1950's, some 100 years after Ceres, Pallas, Juno, Vesta
lost their planetary status.


An additional argument could be made regarding classical planets vs.
modern, and the detection methods.

..... I *don't* think the detection method should influence the
classification of the detected object....

Pluto has been a planet for over 7 decades, and was the largest body
discovered by film photography and manual inspection of the photographs
by mechanical blink-comparator.

True

Basically, it was the last, largest, body discovered by a combination
of analog/mechanical/human collaboration.

False!

It wasn't last - many asteroids, plus several moons of planets, were
discovered later with similar techniques.

And it wasn't biggest - Uranus and Neptune were bigger. Yes, they too
were discovered by a "combination of analog/mechanical/human collaboration",
although these observations were visual rather than photographic. But
the methods were analog, and both mechanics and humans were involved.

Now it's done by computer, such as digital imaging.

Today computers are indeed an indispensible observational tool. But
the process isn't yet fully automated to the point that the computers
"rings a bell" (or automatically emails the IAU) to announce the
discovery of a new planet or other celestial object. The decision
whether any new object has been discovered or not is still being made
by humans. And analog techniques (e.g. the telescope optics) as well
as mechanics (e.g. the scope mounting) are both still involved.


Perhaps some time in the future we will have a super-CCD chip mounted
horizontally and above that an all-sky lens, all in a fixed mounting
pointing the optics straight upwards, and then have software which
determines observational parameters such as image scale, RA/Dec of
center of image, magnification, aperture, wavelength band, etc -- all
without any moving mechanical parts. This would be vaguely similar to
today's "software radio" (which uses generic hardware and then lets
software determine wavelength band, method of demodulation, etc - this
has been made possible by DSP's. digital signal processors). But
we're far from such a "software scope" yet - perhaps we must first wait
until the DSP's can operate at light frequencies?



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