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Is Pluto a Planet?

asked 2016-08-24 08:30:55 -0600

anonymous user


Why has Pluto been declassified as a planet? is this fair?

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answered 2016-08-27 22:38:08 -0600

DrPhiltill gravatar image

In my opinion the vote by the IAU that effectively made Pluto a non-planet was a mistake for three reasons.

  1. The vote was not simply defining terms; it was doing scientific classification. They defined "dwarf planet" and then they voted that "dwarf planet" is not a subcategory of "planet". That was an act of classification. It was intended by the voters at the meeting to be classification. Classification is an important task of science, and the doing of science is never done by votes. In fact, that is anathema. A scientist can never consider that any scientific question, including classification, could be settled by votes. It violates the very heart of how science works. Biologists know better than this. They have committees that assign names to species, but they are very strict and careful to let everybody know that they do not classify any species, they only name them to facilitate communication, because classification can only happen through publishing in scientific journals, and arguing, and building consensus over time, and that it can never be settled as a closed issue because new data can always lead to new debates about reclassifying species. They know that this is the very heart of how science works, and without open debate over classification then you have killed the scientific process. So shame on the IAU for voting on a matter of classification. It was shameful anti-science. It would have been fine if they defined the term "dwarf planet" to facilitate communication and then let scientists debate in the journals whether or not it makes sense to classify dwarf planets as a type of planet.

  2. The definition of "dwarf planet" is not based on a property of the body but rather on the environmental interactions of the body. They said a "dwarf planet" differs from a "planet" only in that the "dwarf planet" has not cleared its orbit. But that is a contingent, changeable thing. For example, Triton was probably a free Kuiper Belt object just like Pluto, but it got captured in orbit around Neptune as a moon. So when you study how these bodies originated, what made them obtain their geochemistry and size and other properties, you would want to put Triton and Pluto in the same category. However, the system of classification that the IAU voted upon would say that Triton is in a completely different category than Pluto. Note that is simply because of random events -- one happened to get captured by Neptune and the other happened to get flung into a resonant orbit with Neptune. So the randomness of history is the key element in the system developed by the IAU, rather than meaningful planetary geology. A system to define solar system bodies ought to consider the actual characteristics of the body and not even care about environmental interactions. I think planetary geoscientists -- the group that studies planets -- should be the ones to classify solar system objects. Unfortunately, the people that voted at the IAU meeting were overwhelmingly not ...

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Asked: 2016-08-24 08:30:55 -0600

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Last updated: Aug 27 '16