Pluto is not a planet, and that matters

Why is it harmful to insist that Pluto is still a planet?

In 2006, the International Astronomical Union (IAU) changed the definition of a planet in such a way that it downgraded Pluto to the status of “dwarf planet”. The definition of a planet was previously that a body must firstly be in orbit around the sun, and, secondly, have enough mass that its gravity had forced the object into a spherical shape. In other words, in order to be called a planet, an object had to be spherical and orbiting the sun. In 2006, an additional criterion was added: the object must have cleared its orbit of all other objects of similar size. Due to the size of Pluto’s moon Charon, Pluto was deemed a “dwarf planet”. Pluto exists at the closer edge of what’s called the Kuiper Belt, a region of space that contains many rocky, icy objects like Pluto. It even includes some other dwarf planets – all of them except Ceres, which is in the Asteroid Belt – and those dwarf planets are called “plutoids” after the most famous and first discovered of their number.

The decision to downgrade Pluto was faced with widespread criticism from everyone who had grown up learning that our solar system has nine planets in it. This idea has never quite faded from the public consciousness, and had renewed force when NASA’s New Horizons probe did a flyby of Pluto in 2015. It can easily be argued that our eagerness to make Pluto a planet is a good thing. People personify Pluto because we are human, and it has a heart on its surface, and isn’t that cute? This encourages people to care about space, and isn’t that what this is all about? If people care about space, then we can do more exploring! This whole “Let Pluto Be a Planet” thing has a net positive effect, right?

“The idea that science is hard facts, with no wiggle room, is a fundamental misunderstanding of science and the scientific process.”

However, the effect may not actually be net positive. An argument that is often made in discussions about Pluto’s planetary status is: “I learned that Pluto was a planet when I was a kid! You can’t just change science!” But that is fundamentally wrong. You can, and, in fact, must change science. Aristotle thought that light came from our eyes. Einstein thought the universe was static. Many people thought that light moved through a material called “aether”. Then other scientists came along and studied, learned, and established more accurate views of the universe. The idea that science is hard facts, with no wiggle room, is a fundamental misunderstanding of science and the scientific process. At its core, science is about curiosity and discovery. It is always changing, growing, being tweaked to give as accurate a description of our universe as possible. Some things, like evolution and gravity, have been tested over and over to the point where they are, for all intents and purposes, facts, but even within these well-accepted scientific consensuses, we are constantly learning and adjusting our understanding of the details.

But what does Pluto have to do with this? Pluto undeniably exists, unlike the aether or spontaneous generation. As recently as 2006, it was a planet, we all learned that in school. So why can’t we just call it a planet? The answer is because that idea is symptomatic of a wider anti-science attitude. Ignoring scientific consensus on something as simple as the definition of a planet is a slippery slope to ignoring other things, things that are more important to our immediate lives. Evolution is just a “theory”, right? Why should we believe in that? I didn’t have vaccines, and I’m fine, so my kids don’t need them either. It’s snowing outside, who are these scientists to say Earth is warming? It sounds a bit ridiculous when phrased like that, but they all have the same basis.

“Ignoring scientific consensus on something as simple as the definition of a planet is a slippery slope to ignoring other things.”

Before I go on, I want to point out that I have no problem with Pluto. But it is not a planet. I have no inherent problem with making Pluto a planet, either, but if you make Pluto a planet, you have to make all the other dwarf planets into planets as well, in which case, you’d better come up with a rhyme for Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, Pluto, Haumea, Makemake, Eris, and possibly more, as more dwarf planets are discovered. Making a singular exception to a definition because “that’s how it was when I was a kid” may not in and of itself be the worst thing in the world, but it is symptomatic of a wider distrust of science and scientists, and therein lies the problem.

Widespread confidence in experts is decreasing at a remarkable rate, particularly when it comes to scientists. Symptoms of this include the anti-vaccination movement, climate change denial, and so-called alternative medicine, like essential oils and crystal healing. These are all more obviously destructive than fighting to call Pluto a planet. They lead to countless deaths around the world. Calling Pluto a planet, while not as directly destructive, is a symptom of the same underlying problem. It would be unreasonable to say that everyone who thinks Pluto should be a planet is also an anti-vax climate change denier. Yet, there is a slippery slope present in society when it comes to ignoring scientific consensus.

Nothing happens in a vacuum. If the “Pluto Should Be A Planet” movement was happening, but we as a society had faith in science and scientists, it would not be nearly as insidious. The trouble comes when it is surrounded by other, more destructive denials of scientific consensus. Scientists are not infallible, they are far from it. Yet, we must be aware of why we are arguing to change science, and whether our arguments actually go against the scientific process itself.