Philip Metzger: “Planet Pluto!”

Artist’s concept of NASA’s New Horizons spacecraft as it passes Pluto and Pluto’s largest moon, Charon, in July 2015. Image Credit: NASA/JHU APL/SwRI/Steve Gribben

The truth is, we felt the need for a small number of dominant planets because it’s what humans always knew a solar system to be, ever since we looked up to see lights moving in the nighttime sky. We now know better than this, but we haven’t examined ourselves well enough to see this is the origin of our “intuition” about planets. We still think the intuition is somehow natural and therefore right. This response to our intuition is different than what scientists did at the time of Galileo. Back then, we gave up our intuition and radically embraced the new view. It took time and lots of fighting, but that was the outcome. We redefined the central word of planetary science in a way that communicated a scientific revolution. This time, we redefined our central word in a way that communicates business as usual. Faced with the specter of hundreds of new planets cluttering up the crystalline celestial spheres, hundreds of worlds too scattered and under the influence of their larger neighbors, we opted to purge the pantheon instead.

This is disappointing. We rejected the ancient world’s geocentrism. Couldn’t we reject its belief in orderly, reigning planets as well? In my opinion, this is why the public is not more engaged in the central questions of planetary science. We have hidden it from them. We created a vocabulary that focuses attention on the old familiar planets that seem least changeable. We pushed Pluto and the other paradigm-shattering worlds into a lower tier of importance. As a result, we made our branch of science more “intuitive” and a lot less revolutionary.

Philip Metzger

One of the best arguments I’ve seen for keeping Pluto as a planet – and adding the dozens, potentially hundreds, of planetary bodies in the Kuiper Belt to the list. All the major breakthroughs in science came from people abandoning ‘the old ways’, changing the traditional view of the world with new data and thinking. This recent definition of ‘planets’ puts up artificial barriers instead of enabling us to look at the solar system as a whole that evolved together.