10 years ago today the International Astronomical Union dealt a death blow to Pluto’s eighty-six year claim to planethood. The decision was, shall we say, not received well by many Americans, and several state legislatures passed resolutions rejecting it. The California State Assembly went so far as to call IAU action a “scientific heresy.” (Me thinks, Assembly members may have a wee bit too much time on their hands).
The ignominious treatment of Pluto was hard to swallow for the the thousands of adults who had been taught, in no uncertain terms, since the 1st grade, that there were 9 planets. Punto. We were taught that educated folks should know the 9 in order from their distance to the sun. Clever mnemonics sprung up like weeds: “My Very Educated Mother Just Served Us Nine Pizzas” was a personal favorite. And “My Very Educated Mother Just Served Us Nine” doesn’t work.
To be fair, the IAU didn’t actually remove Pluto’s planetary status. It just gave him a downgrade to “Dwarf Planet,” a newly-created category to deal with celestial bodies that orbit the sun and are rounded by their own gravity, but don’t have enough mass to share the stage with the Big Eight “real” planets. I doubt the God of the Underworld appreciates that subtle distinction, but then, he is probably also used to such demeaning treatment.
Behind the Pluto brouhaha rests a fascinating reality of the human psyche. We regularly create categories to make better sense of our world. The categories become real to us, so real that we take them to be woven into the created fabric of the universe. Challenge those categories and people become unsettled. They pass resolutions to curb the heresy. But whether Pluto is a planet or a dwarf planet doesn’t have much (any?) affect on our lives. Whether a tomato is a fruit or a vegetable doesn’t change its taste or whether it shows up during the main course or dessert (or on the breakfast plate if in England). Does it makes sense to call a platypus a mammal even though it is the egg-laying outlier to the entire class of Mammalia? They will keep on laying eggs either way. Yet people become quite animated in their defense of the “real” category to which these things belong even when there are no real stakes involved in the outcome. Curious.
Still, it bothers me that Pluto isn’t a planet anymore.