Why This Planetary Scientist Won't Sign the Petition to Declare Pluto a Planet

Graphic from the Declare Pluto a Planet petition

Last week, I was invited to sign a petition on Change.org asking the International Astronomical Union (IAU) to reclassify Pluto as a planet. As a planetary scientist, my opinion is that Pluto is a planet. I've previously written that I consider the IAU classification criteria for planets to be deeply flawed, as does every single planetary scientist I've ever spoken to about this issue. But I will not sign this petition.

Science is not a democracy. The opinion of the majority does not change the principles of the Universe. Pluto doesn't care whether we call it a planet or not, nor did its nature change when the IAU declared it not to be a planet. The Universe is entirely indifferent to what we think of it. The Universe is formed on objective truths that don't change with human language or opinion.

Our understanding of science changes all the time. It is both evidence-based and theory-based. We can gather evidence to form theories based on the evidence, or we form theories and gather evidence to prove or disprove them. Scientist make conclusions based on the evidence or the soundness of a theory. Scientists can disagree on conclusions because of differing interpretations or seemingly contradictory evidence. Scientists do not form conclusions based on popular public opinion.

I remember a story I was told during my first NASA internship when I was an undergraduate student studying astrophysics. I was studying gamma-ray bursts (GRBs) from scientists who had been studying this phenomena for years. At an early conference on the subject, the question was posed as to whether GRBs were galactic (originating close to us, within our galaxy) or cosmological (originating far from us, in the cosmos). The majority decided that because GRBs were so very energetic, they must be close to us, they must be galactic. Only a couple of years later, new data from a new space observatory added proof to the theory that GRBs were cosmic, not galactic. The Universe didn't care that the majority of scientists had decided incorrectly. The truth is what it is regardless.

It doesn't matter that the IAU in 2006 voted that Pluto is not a planet. It doesn't matter if they change their minds in 2015, five years from now, fifty years from now, or never. Pluto doesn't care. The Universe remains unchanged.

My biggest issue with the petition is that science is not determined by majority vote. Voting and public opinion is not part of the scientific method. If tomorrow, a study is published stating that the majority of people have voted that the Sun is a planet, their vote will not make it so. Petitions and meeting polls are fun and interesting, but not scientific.

If the Change.org petition had asked the IAU to reconsider the classification of Pluto or reconsider its definition of a planet, I would sign it. Such a request should ideally come from the IAU membership and not from the general public, however. The IAU membership is the deciding body at IAU meetings and a request to reopen the discussion should come from them.

As the petition is worded, “Declare Pluto a Planet,” I cannot get behind. Making a scientific declaration via an Internet petition of the general public is not thoughtful, accurate, or sound. I can appreciate the enthusiasm of the petition creator and backers. I can agree that Pluto should be classified as a planet. But I feel that I would be bending my scientific integrity to lend my name to such an initiative. I very much hope that if IAU leaders and membership come across the petition, they will take it in the spirit of a request for further discussion on the issue.