Pluto not a planet, dang it! Yes it is! No it isn't! Yes IT IS! NO IT ISN'T!! ....

I thought this story could be used in teaching concepts like the arbitrariness of language (the idea of arbitrarily applicable relational responding-AARR the core of RFT) or language as function. In other words, words work the way they do because we agree, as a social system, to have certain words function in certain ways. This article shows how definitions are just things we make up, and as such, can be made up to mean different things, depending upon what is most useful. As we search for the most useful definitions in ACT (such as what is defusion? what is experiential avoidance?) its important to keep in mind that we get to make this up and that words aren't real things, but ways of speaking that can be more or less useful.

I love how there's this arbitrary argument about whether pluto will be called a "planet" anymore. It's so humorous and so human...

Pluto Demoted: No Longer a Planet in Highly Controversial Definition
http://www.space.com/scienceastronomy/060824_planet_definition.html

Capping years of intense debate, astronomers resolved today to demote Pluto in a wholesale redefinition of planethood that is being billed as a victory of scientific reasoning over historic and cultural influences. But already the decision is being hotly debated.

Officially, Pluto is no longer a planet.

"Pluto is dead," said Caltech researcher Mike Brown, who spoke with reporters via a teleconference while monitoring the vote. The decision also means a Pluto-sized object that Brown discovered will not be called a planet.

"Pluto is not a planet," Brown said. "There are finally, officially, eight planets in the solar system."

The vote involved just 424 astronomers who remained for the last day of a meeting of the International Astronomical Union (IAU) in Prague.

"I'm embarassed for astronomy," said Alan Stern, leader of NASA's New Horizon's mission to Pluto and a scientist at the Southwest Research Institute. "Less than 5 percent of the world's astronomers voted."

"This definition stinks, for technical reasons," Stern told SPACE.com. He expects the astronomy community to overturn the decision. Other astronomers criticized the definition as ambiguous.

The resolution

The decision establishes three main categories of objects in our solar system.

* Planets: The eight worlds from Mercury to Neptune.
* Dwarf Planets: Pluto and any other round object that "has not cleared the neighborhood around its orbit, and is not a satellite."
* Small Solar System Bodies: All other objects orbiting the Sun.

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Pluto’s Demotion is Well Deserved and Long Overdue

Dwarf planets are not planets under the definition, however.

"There will be hundreds of dwarf planets," Brown predicted. He has already found dozens that fit the category.

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Stern called it "absurd" that only 424 astronomers were allowed to vote, out of some 10,000 professional astronomers around the globe.

"It won't stand," he said. "It's a farce."

Stern said astronomers are already circulating a petition that would try to overturn the IAU decision.

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.

Gingerich also did not like the term "dwarf" planet.

"I thought that it made a curious linguistic contradiction," Gingerich said in a telephone interview from Boston (where he could not vote). "A dwarf planet is not a planet. I thought that was very awkward."

Gingerich added: "In the future one would hope the IAU could do electronic balloting."

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Textbooks will of course have to be rewritten.

"For astronomers this doesn't matter one bit. We'll go out and do exactly what we did," Brown said. "For teaching this is a very interesting moment. I think you can describe science much better now" by explaining why Pluto was once thought to be a planet and why it isn't now. "I'm actually very excited."