Pluto's Planethood: What Now?
Two leading scientific experts debate whether eight is enough.
- By airspacemag.com
- Air & Space magazine, September 2006
(Page 5 of 5)
Brown: This is why this whole debate is not about science. There is no correct definition of the word "planet." If you think the physics of the body is important, you have hundreds. If you think the dynamics are important, you have eight. And it’s unlikely that there will be any compromise. It’s a religious schism.
A&S: So what’s the next step forward? Unfortunately—and this may have been the fault of the press—the public was told astronomers were going to decide once and for all on a single definition. And that didn’t work.
Brown: Given the circus-like nature of what happened, my recommendation is that we drop the word "planet." Why don’t we use new scientific words to describe these concepts instead of forcing the word "planet" to mean things it was never intended to mean. The public is dying to know how many planets there are. Is Pluto a planet? Is Eris a planet? I think the best answer from the IAU in Prague would have been to say the word planet is just not a scientific word, and we have these other words to describe the solar system. But we are not going to mess with this one. It’s a cultural word, like the word "continent." And culture can figure out what it wants to do. If culture wants Pluto to stay a planet, great. If it wants Pluto not to be a planet, fantastic. Deciding which of several equally rational classification systems gets to own the word "planet" has absolutely nothing to do with science and everything to do with culture.
Stern: I disagree that it’s just about culture, I think it’s actually about science. And I think it’s naive that we will get rid of the term "planet." It’s a useful construct in space exploration and astronomy. We’re all reductionists. There are certain broad classes of objects in the universe, and I think planet is a perfectly legitimate class that has a lot of diversity in it. We just to have learn to adapt to the fact that there are many classes of planets that we didn’t recognize before because we didn’t have the data to see it.
A&S: Do you think we’ll see a repeat of this at the next IAU meeting in 2009?
Brown: Who knows? Maybe we’ll do it forever.
Stern: I’m perfectly happy with an outcome where it takes years or decades to shake things out between these two major philosophical approaches. But what I’m adamantly opposed to is the perception in the public that because the IAU has spoken, and produced what even Mike says is a flawed definition, that it’s over and we’re all just going to accept that as dogma, and all the textbooks will change. I’m much happier with saying, "We haven’t decided. It requires more observation, and science has to progress for another X years."
Brown: But if, as I believe, the debate is not about science, then no amount of observation is going to change people’s minds. The current scientific culture has voted in favor of a dynamical definition for the word "planet." No advances in science will ever change the results of a vote like this, just a change in scientific culture.