Why Pluto Matters

The most interesting class I took in school was called Science, Knowledge and Technology and it covered different theories about how new ideas are created and diffused. I wrote a paper for that class looking at why Pluto’s status as a planet was being challenged and why so much attention was being focused on the subject. This was written last year right at the time that the International Astronomical Union ruled that there were only 8 planets and Pluto was not one of them.

I wanted to try to get the paper published somewhere, but never had the time to devote to it during school. Now that I’ve graduated and have some time, I think the subject might not be so relevant anymore. I would be interested in getting people’s thoughts and comments on what I’ve written though, so I’m posting it here if anyone is interested.

The first half of the paper covers how the number, and even the order, of the planets has changed numerous times before. The last part explains how this scientific issue doesn’t have a scientific solution. Basically, Pluto is whatever astronomers decide to call it and there is no scientific test that can be applied to resolve the dispute.

I started thinking of this paper again recently when I read an article about a new book on Pluto that argued the exact opposite position: the issue is a scientific question, not a matter of public opinion or a decision to be made by NASA or a panel of distinguished astronomers. I clearly don’t agree with this point of view, but what do you think?

5 thoughts on “Why Pluto Matters

  1. Which astronomers make the decision? What if the astronomy community is divided? What about the many planetary scientists who are not IAU members? Science should not be decided by dictate from on high. Maybe we need to wait until we get the data from New Horizons before jumping to conclusions.

    I strongly take issue with your claim in another entry that the younger generation is accepting the “new paradigm” of eight planets and that the debate will fade away with the older generation. I promise you, it won’t. Many young people are being taught both sides; even NASA gave an award to a lesson plan that asks kids to look at both sides of the debate and come up with their own conclusions. And the controversial IAU decision is most certainly not the final word on this.

    1. Even with more data about Pluto, the decision about how to classify it will still need to be made by people. New Horizons isn’t going to be able to send any data back that says definitely what Pluto is — it’s just going to see a ball of stuff.

      There’s a bunch of rocks, ice and gas circling the Sun in our solar system and we’ve made decisions about what to call those things — and over time we’ve made changes to that classification scheme.

      For instance, Ceres was called a planet when it was first found and it’s not considered a planet today. There was no doubt controversy around that change and I imagine school kids were annoyed that they had to relearn things too. Ceres hadn’t changed though, we had just found more stuff out there and rethought things (just like what’s going on with finding more Kuiper Belt objects).

      The process of this change is really interesting though and the most fascinating part is that it doesn’t really feel like science to most people. But this is exactly how science very often works. If you haven’t, read The Structure of Scientific Revolutions.

  2. What New Horizons will show is that Pluto has features far more like those of planets than like those of most rocks and ice in the solar system. Those rocks and ice are mostly rubble piles shaped only by chemical bonds. They have no geological processes or weather. In contrast, Pluto is in a state of hydrostatic equilibrium, meaning it is large enough to be pulled into a round shape by its own gravity, a characteristic of planets. It is almost certainly geologically differentiated, just like the terrestrial planets, and even has a thin atmosphere. In fact, Earth has more in common with Pluto than it does with Jupiter, a gas giant with its own “mini solar system” and a composition similar to that of the Sun.

    The Ceres example is often cited by those supporting the demotion of Pluto, but it turns out the demotion of Ceres was also in error. Ceres and other bodies in the asteroid belt were demoted because 19th century astronomers could not resolve them into disks even with their most powerful telescopes. However, with today’s telescopes, we can see that Ceres is in fact spherical and in a state of hydrostatic equilibrium. That means it is actually a small planet, and its status should be changed to reflect that. Classifying it as a “dwarf planet” would do that if we amend the IAU resolution to make dwarf planets a subclass of planets, describing objects orbiting the Sun that are large enough to be in hydrostatic equilibrium but not large enough to gravitationally dominate their orbits.

    Yes, classification systems are made by people. However, if it’s clear that the people who study these objects do not agree on how to classify them, then all the legitimate contending points of view should be taught equally rather than falsely portraying one view as the only acceptable interpretation and misleadingly claiming the debate is resolved.

    1. I agree that the debate around Pluto’s status is the important thing here and that all points of view should be represented. That conversation is far more interesting than whatever bucket Pluto ends up getting put in (planet, not a planet, subclass of planet…).

      I think there’s a disconnect here in saying that one side is falsely portraying one view as the only acceptable interpretation though.

      There are many arguments for classifying Pluto in different ways and the points could be endlessly debated. Or to put it another way, there’s no right answer here and more debate isn’t going to resolve anything so make a decision and move on.

      I imagine most astronomers in the IAU would rather get on to something they consider to be real science than to keep arguing over an arbitrary definition.

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