Dwarf planets, dwarf continents, and the year of the potato
Sunday, August 27th, 2006So Pluto isn’t a planet anymore, at least in the opinion of the majority of voters at this year’s meeting of the International Astronomical Union (IAU).
I assume that astronomers need to categorize celestial bodies for some important reasons (perhaps teaching), and I gather that the new definitions of planets and dwarf planets are useful to them and their students.
But nevertheless, I don’t think the IAU–or anybody else–should authoritatively decide which celestial bodies may be called a planet and which may not.
The cateogry of planets is not one that (mainly) concerns experts: Planets are not asteroids, organic molecules, marsupials, or negligence. I expect that the majority of the population of the better-educated countries can cite their Roman/Greek names, and many people (but not me!) believe that their constellations directly affect their lives. In addition, the known planets have been hte object of poems, symphonies, and science-fiction literature. Pluto’s inclusion in the canon of planets might also help explain that NASA got $ 700 M of funding for the New Horizons mission to Pluto. It’s hardly imaginable that the same amount would have been allocated to explore a dwarf planet, and not surprisingly, NASA laments:
“Poor New Horizons. When it launched in January 2006 it was with all the prestige of the first spacecraft to study Pluto, the last unvisited planet in the solar system. That changed seven months later, when astronomers decided that Pluto was not a planet. For the time being, New Horizons is at least the first mission to a dwarf planet — the new class of objects into which scientists dumped Pluto.”
The cultural importance of the category of planets should forbid a professional organization to arrogate to itself the authority to define it. Nobody has done that for continents, either, and so there is a number of classification models that co-exist peacefully. Can you imagine that a Geographers’ Society would authoritatively decide that Australia is too small to be a continent and should be categorized as a dwarf continent, together with Greenland? Even if the U.N. tried to do that, most people would rightly think that diplomats have gone mad, just after solemnly declaring 2008 the year of the potato …
Now, things would look different if the IAU’s definition was only for “internal” use among members of the scientific community. But if that were the case, the IAU should and could have made that clear.
It will be interesting for sociologists to see whether people will stick with the old canon of planets or if they submit to the new definition. The latter would mean a significant increase of societal power on the part of the IAU, namely the authority to define certain important cultural categories.
P.S. if you feel the need to signal definitorial awareness, you will find some related t-shirts and bumper stickers here: http://www.cafepress.com/buy/pluto

