Remember when Pluto got reclassified as a dwarf planet? A lot of you do, and a lot of you are very upset about it. It’s been years and you’re still pissed.
Quick summary for the five people in existence who don’t know what the Pluto Situation is: for most of our lives, Pluto was the ninth planet in our Solar System. But we didn’t know much about it because it’s really far away. It has an eccentric orbit which occasionally brings it inside the orbit of Neptune, the eighth planet. It’s tiny by planetary standards, one-sixth the mass of our Moon with a little more than half the Moon’s radius. Tiny, cold, distant, wonky. But still, one of us. A planet.
Things started to get hinky for Pluto in the 1970s, when similar bodies in the region of the Solar System called the Kuiper Belt were discovered. Things got hinkier still with the discovery of Eris in 2005, a Kuiper Belt object 27% more massive than Pluto. At that time, the astronomical community entered a debate about what constitutes a planet versus other kinds of bodies in our solar system. In 2006, the International Astronomical Union voted to define major planets in a way which didn’t include Pluto. Pluto, along with Eris and other similar bodies were designated “dwarf planets,” a distinction intended to acknowledge a key way in which these bodies were not like the major planets.
And then the whole world seriously lost its shit.
I don’t need to go into depth about what happened, since most of you were involved and are still losing your shit about it. By all accounts, NASA (it wasn’t actually NASA) personally came into your homes and kicked your puppies and ate all the chocolate and left an unspeakable mess in the bathroom. NASA (it wasn’t actually NASA) should be ashamed of itself. NASA (it wasn’t actually NASA, people) can eat a dick. Etc.
I was one of the outliers. When Pluto was demoted (actually, it was re-classified) my response was this:
Science is sooooo cool.
Think about it. Over the course of the last 80 years, we went from knowing Pluto only as a pinprick of light more than 30 times farther from the Sun than us to knowing its size, mass, approximate make-up, that it has its own satellites, and that it’s not the only one of its kind. By studying Pluto we came to better understand that region of space and the make-up and history of our Solar System. Our body of knowledge grew in amazing ways.
And we’ve come to learn that while Pluto shares some characteristics in common with the other major planets, it’s also different. Those differences are significant enough that a new classification was deemed necessary by a majority of experts in the appropriate field of study.
This is how science works. It’s a process of discovery, testing, exploration, revision, and new discovery. We are constantly learning things which require us to revise our understanding of the universe. We throw out ideas which don’t work, we try out new ones. We’re wrong far more often than we’re right. This is a good thing.
And Pluto being re-classified is an exciting part of that. Our knowledge of the outer Solar System grew enough that we had to change the way we think and talk about it. And so Pluto’s a dwarf planet now, along with Eris and—
But wait. There was a talk wherein a Harvard astronomer said they think Pluto should be a planet again. And you all rose in unison and screamed, “IN YOUR FACE, NASA!” (It wasn’t freaking NASA!)
Listen. I get it. You grew up (unless you more 85 years old) with Pluto as the ninth planet. There were all those cool posters on the walls at school, and there was the cartoon dog owned and operated by the Disney Megalocorp, and you’ve got all these warm fuzzy feelings about little ol’ Pluto, the Littlest Planet That Could, etc.
You have affection for Pluto.
You have nostalgia for Pluto.
And NASA (it wasn’t—never mind) ruined it for you. They put the word “dwarf” in front of “planet” and now they can just die in a fire.
But fortunately Harvard somebody said a thing and the media misreported it and — oh, bloody hell.
I wasn’t even going to write about this topic. I made a few weary tweets about it the other day when the entire internet was all “Pluto is a planet again!” But that was all the energy I’d planned to put into it, because it’s like fighting the wind with a butter knife.
Sorry, Sean. You’re very smart and talented and funny and possibly an excellent (terrifying) dancer, but when it comes to this matter, you’re wrong. And, honestly, you’re wrong in a way which I have to take seriously because I sincerely believe it’s a dangerous kind of wrong.
Whoa, you may be thinking. This got dark.
First things first. I highly recommend listening to the Beautiful Failures podcast by oddball brothers Matt and Sean Ferrell. It’s funny and informative and engaging. The Pluto matter isn’t the first thing I’ve disagreed with, but even when I disagree with Sean and Matt, my brain is delightfully challenged. Every episode has been dense with insight. So listen.
In the most recent episode, on the movie Alien 3, Sean included some commentary at the beginning about The Pluto Situation. He’s firmly in the Pluto is a planet camp, and he made some good points about the arbitrary nature of definitions and the fact that scientists can sometimes (often?) act as though their provisional hypotheses are Universal Truth. Without a doubt, science is a messy endeavor and is not immune to the ideologies and personal biases of its practitioners. But the scientific method is a self-correcting process in which knowledge and understanding are generally refined and strengthened over time.
Sean went on to note that the IAU defined a planet as having three characteristics. A planet:
- is in orbit around the Sun,
- has sufficient mass to assume hydrostatic equilibrium (a nearly round shape), and
- has “cleared the neighbourhood” around its orbit
A dwarf planet is a body which meets the first two criteria, but which has failed to clear its orbit. Thus, Pluto (along with Eris and other similar bodies) is a dwarf planet. Except Sean supports the idea that Pluto is actually a planet planet, arguing the definition can be what we choose, since we’re the ones creating it. Why can’t the definition, he asserts, be a body that’s in orbit around the Sun, has enough mass to be round, has cleared its orbit … or is Pluto?
At which point I nearly crashed into a telephone pole, because I was listening to the podcast as I was driving. Also I am a terrible driver.
Like I said, I get it. You’re all in love with Pluto and you’ll never stop being mad at NASA. Pluto will always be your planet. And, well, whatever. I invite you to consider the following which appeared in my Tumblr feed the other day:
The real problem with people fussing over Pluto all the time is it represents the priorities of the public – preserving traditions rather than accepting facts. The pursuit of science is about building a sustainable catalog of truths, and there is no advantage in altering truths to appease nostalgia. (Source)
For science to work, it needs to be free from appeals to tradition and a host of other logical fallacies. At a micro level, it’s not, because science is done by people and people are a mess. But at a macro level, the method needs to stand firm against these fallacies. “…or is Pluto” is exactly the wrong way to do science, because the only reason to append that to an otherwise careful, rigorous, and defensible definition of “planet” is to appease what is basically an 8-year long tantrum. And it’s dangerous because it’s exactly this kind of thinking that has given us anti-vaxxers and global warming denialists. It’s people thinking their feelings and opinions trump facts.
Now, of course, the definition of planet noted above isn’t a fact in the strictest sense of the word. It’s open to debate and discussion and refinement. That Harvard somebody was actually engaging in the process when he suggested Pluto be re-classified as a planet again. I applaud that process. Make your case, scientists! I’m listening!
As time passes and our knowledge of space advances, I wouldn’t be the least surprised if the definition is modified further. If the IAU got together tomorrow and said, “Upon consideration and review of the evidence, we deem the pertinent parts of the definition to be only 1 and 2, and thus Pluto is a planet,” my first question would be what were the determining factors in removing the “clearing the orbit” criteria? If the answer to that question is based on observation, sound astronomical research, etc., then I’d think,
Science is sooooo cool.
And then I’d think, “Oh, look. Eris, Haumea, Makemake and a few others are also planets too!” Because if Pluto is a planet, they are planets too. Remember: “… or is Pluto,” isn’t a scientific criteria.
But if the answer to my question is, “NASA and Neil deGrasse Tyson got tired of all the angry emails and asked us to do change it back so everyone would just shut up already,” I’d be disappointed. I’d be disappointed in the scientists who gave in to public pressure (science isn’t a popularity contest), but I’d be even more disappointed in us as a society for being so fixated on what we call Pluto because of our feelings that we fail to see what makes Pluto so distinctive and fascinating.
In the end, no matter what it’s called, Pluto and its related Kuiper Belt objects aren’t quite the same as Mercury, Venus, Earth and Mars, or the four gas giants Jupiter, Saturn, Uranus and Neptune, or the asteroids, or the members of the Oort Cloud. What makes them similar is interesting, but what makes them different is truly important.
 Not all members of the astronomical community agree with this decision. Which is cool, because challenge and disagreement are part of what makes science such an effective tool.
 Pluto was further designated as the prototype for the plutoid category of trans-Neptunian objects, so it’s still special.
 Something really, really cool for which NASA is actually responsible is the New Horizons Mission, which is a probe on its way to Pluto. NASA, target of so much misdirected ire about the Pluto/dwarf planet thing, finds Pluto important enough to send a probe to visit it. In less than a year, the probe will do a close fly-by, and then we’re going to learn even more cool things about Pluto and its satellites. Perhaps, based on this knowledge, we’ll need to come up with a better definition of what Pluto is. Or perhaps it will be even clearer that the dwarf planet distinction is appropriate. Either way, our knowledge of the Solar System is going to expand in amazing ways.