"Once every 248 Earth years, Pluto swings inside the orbit of Neptune. It stays there for twenty years. During those twenty years, Pluto is closer to the Sun than Neptune. During this period of time, like the other eight planets, Pluto's atmosphere undergoes a fundamental change in character, briefly developing an atmosphere. As methane and nitrogen frozen at the poles thaw. As it moves toward its farthest point from the Sun, Pluto's atmosphere freezes and falls back to the ground" (Dejoie & Truelove 2008). These eccentricities further suggested that Pluto was really much more "like a new group of objects found in the outer solar system," called dwarf planets and not worthy of the status of the other eight (Inman, 2008, p.2). Still, many astronomers argued in favor of a more inclusive definition that would still retain Pluto's status as a planet. In fact, one radical proposal: "would have made full-fledged planets of 50 or more additional objects" (Inman 2008, p.2). One scientist said the language of the resolution is flawed because while it requires that a planet cleared the neighborhood around its orbit." "Earth, Mars, Jupiter and Neptune all have asteroids as neighbors...It's patently clear that Earth's zone is not cleared," he said. "Jupiter has 50,000 Trojan asteroids," which orbit in lockstep with the planet (Britt 2006).

Thus, even today the definition of what is a planet is not absolute. "Owen Gingerich, historian and astronomer emeritus at Harvard who led the committee that proposed the initial definition, called the new definition 'confusing and unfortunate' and said he was 'not at all pleased' with the language about clearing the neighborhood," and called the term dwarf planet "a curious linguistic contradiction," saying "A dwarf planet is not a planet. I thought that was very awkward" (Britt 2006). The dissatisfaction over the reconfiguration of the term had political overtones as well. The IAU was criticized for being undemocratic in the way that it conducted the balloting, given that 424 astronomers were allowed to vote, out of about 10,000 professional astronomers around the globe (Inman, 2006, p.2).

The debate...

Many ordinary individuals protested the demotion of Pluto, not because they new or cared very much about astronomy, but because they had always learned that there were nine planets, and it seemed strange and unfamiliar to exclude one from that number. Astronomers not permitted to vote were outraged that they did not have a part in the decision-making process. And given that definitions of what constitute planets and other astral bodies will likely to continue to shift, as the knowledge that continually accumulates from space exploration changes dearly-held conceptions of the universe, it may be best for schoolchildren to pause before coming up with another mnemonic to remember the order of the solar system.
Works Cited

Britt, Robert Roy. "What is a planet>" Space.com. 2 Nov 2000. August 2, 2008. http://www.space.com/scienceastronomy/solarsystem/planet_confusion_001101-2.html

Britt, Robert Roy. "Scientists decide Pluto's no longer a planet." MSNBC.com. August 24, 2006.

August 2, 2008. http://www.msnbc.msn.com/id/14489259/

Cain, Fraser. "Why is Pluto not a planet>" Universe Today. April 10, 2008. August 1, 2008. http://www.universetoday.com/2008/04/10/why-pluto-is-no-longer-a-planet/

Cain, Fraser. "Why do some scientists think that Pluto is not a planet?" Universe Today.

April 19, 2008. August 2, 2008. http://www.universetoday.com/2008/04/19/why-do-some-scientists-consider-pluto-to-not-be-a-planet/

Dejoie, Joyce & Elizabeth "Libby" Truelove. "The Dwarf Planet Pluto." High Energy

Astrophysics Science Archive Research Center (HEASARC). August 1, 2008. http://starchild.gsfc.nasa.gov/docs/StarChild/solar_system_level1/pluto.html

Greene, Nick. "Planets Mnemonic." About.com. August 30, 2008. August 1, 2008. http://space.about.com/b/2006/08/30/planets-mnemonic.htm

Inman, Mason. "Pluto not a planet." National Geographic News. August 26, 2007. http://news.nationalgeographic.com/news/2006/08/060824-pluto-planet.html