Pluto Correctness

I recently finished reading two books that had Pluto in them (one had a little, one had a lot).

When is a Planet Not a Planet?: The Story of Pluto felt like an article that had been stretched into a small book by using lots of photos and illustrations. A pretty book, but it didn’t have anything new in it for me (to be fair to the book, I spent a big chunk of time in graduate school writing a paper about Pluto’s so-called demotion).

The Three Stigmata of Palmer Eldritch is supposed to be one of Philip K. Dick’s best books, so I was curious to read it. For Pluto, it’s just mentioned as a place where a ship crash lands. For the rest of the book, it was like the other things I’ve read by him—it had a lot of sci-fi elements but was really about people’s perceptions of their world. Weird and interesting.


To round out the Pluto references, my daughter started pre-school recently and I was fascinated to see that the teachers had crossed Pluto out of the solar system material they had (wanting to stay up to date, but not getting around to buying a new planet puzzle yet).

It’s a really interesting time right now—the change in status is new enough that a lot of old information is still out there, but it’s been long enough that younger kids have grown up only knowing that Pluto used to be a planet. It’s a paradigm shift in action with the new generation simply accepting the new status as normal while any disagreements among older generations start to fade away.

Up next: The Future of the Internet — And How to Stop It.

5 thoughts on “Pluto Correctness

  1. The teachers should NOT be crossing out Pluto or saying that Pluto is not a planet. They should not blindly accept the controversial demotion of Pluto by four percent of the IAU, most of whom are not planetary scientists. Their decision was immediately opposed by hundreds of professional astronomers led by Dr. Alan Stern, Principal Investigator of NASA’s New Horizons mission to Pluto. You should inform your daughter’s teachers that this controversy is ongoing and that the IAU view represents only one interpretation in a continuing debate. And you should teach your daughter the same thing.

    One reason the IAU definition makes no sense is it says dwarf planets are not planets at all! That is like saying a grizzly bear is not a bear, and it is inconsistent with the use of the term “dwarf” in astronomy, where dwarf stars are still stars, and dwarf galaxies are still galaxies. Also, the IAU definition classifies objects solely by where they are while ignoring what they are. If Earth were in Pluto’s orbit, according to the IAU definition, it would not be a planet either. A definition that takes the same object and makes it a planet in one location and not a planet in another is essentially useless. Pluto is a planet because it is spherical, meaning it is large enough to be pulled into a round shape by its own gravity–a state known as hydrostatic equilibrium and characteristic of planets, not of shapeless asteroids held together by chemical bonds. These reasons are why many astronomers, lay people, and educators are either ignoring the demotion entirely or working to get it overturned.

    I am writing a book about why Pluto’s demotion is wrong and have for three years been running a blog, “Laurel’s Pluto Blog,” advocating its being ignored or overturned. In the meantime, some good sources for the pro-Pluto position are “Is Pluto A Planet” by Dr. David Weintraub and “The Case for Pluto” by Alan Boyle, due out in October.

    1. I certainly agree that teaching people about the process around deciding what to call Pluto is much more interesting than just saying Pluto is or is not a planet. And this is exactly what is going on with that picture — the obvious first question someone is going to have is why is there a big X there?

      I also agree that the definition of a dwarf planet is confusing and could be improved upon — I just don’t think it matters what we call it. Pluto doesn’t get smaller, colder or shine any less bright if it is ‘demoted’ here on Earth.

      I also don’t think there’s a right or wrong answer here. We can decide to call something whatever we want. Is it wrong to switch the numbering of books in the Dewey Decimal system? That system is just something people put in place to help deal with a large set of information. Making a change to that would annoy lots of people, but there’s no inherent quality of language books that require they be labeled in the 400s instead of the 300s.

  2. No, Pluto doesn’t care how we classify it, but there’s a lot that’s wrong with this decision of the IAU’s, and they need to have the courage to come up with a better one. Especially now that they’ve lost credibility: the definition that was voted on in Prague three years ago remains controversial and is getting ignored by not just astronomers but the general public.

    Personally, I couldn’t agree more with Alan Stern’s statement that we need a simple definition for planet that you don’t have to be a professional astronomer to understand (he called it the “Captain Kirk definition”–Captain Kirk, sitting in his command chair on the starship Enterprise, looks at an object on the screen and declares that it’s a planet, not a moon, an asteroid, a star or whatever. And it’s obvious to the TV audience, most of whom are not astronomers, that he’s not babbling, that the people who gave the actor playing him the line, who are also laypeople, know what they’re talking about).

    1. I agree that the definition they came up with has room for improvement. There’s a difference though between wanting a definition that isn’t confusing and saying that any definition that ‘demotes’ Pluto is unacceptable.

      I’m not sure how simple a definition could get though. In the Captain Kirk example, if you’re looking at Ganymede on the screen you’re not going to have enough information to know what it is.

      Ganymede is big and round (bigger than Mercury) so just by looking at it you’d say it was a planet. It happens to be in orbit around Jupiter and therefore a moon, so context matters.

      Pluto is big and round too (although smaller than Ganymede) but context matters. There are a lot of facts about Pluto that make it definitely unlike the other 8 planets we recognize today and in some classification systems that’s going to rule it out of being called a planet.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s