Read Online The Pluto Files: The Rise and Fall of America's Favorite Planet by Neil deGrasse Tyson - Free Book Online Page B
Authors: Neil deGrasse Tyson
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misconceived terminology, Luu had pointed out that Native Americans had been initially referred to as Indians “simply because Columbus screwed up” and thought he’d arrived in India, but that now we know Native Americans are not the native inhabitants of the Indian subcontinent. Using his own analogy, Stern referred to the alleged problem of Pluto’s small size by pointing out that nobody thinks a Chihuahua isn’t a dog just because it’s small—that there’s “something innate” about a Chihuahua, “something doggy” that automatically puts it in the class of dog for any observer. By analogy, Pluto’s roundness puts it in the class of planet.
In an effort to frame the ultimate definition of a planet—an effort that the IAU had been studiously avoiding—Stern presented the audience with a “rational sieve,” a physical test that anyone in the audience would be able to apply to any celestial object, whether already known or yet to be discovered. Its ease of application, he said, derived from its having an upper size limit and a lower size limit. At the upper end, any object big enough to fuse hydrogen in its interior is acting like a star and must be called a star. At the lower end, any object that doesn’t have enough mass to “become round of its own volition” by virtue of the physical process of hydrostatic equilibrium, which happens in objects with a minimum of about half the mass of Pluto, doesn’t deserve to be called a planet. Anything in between would be some sort of planet—although if it was orbiting another planet rather than a star, it could be called a planetary body.
Clear. Even persuasive. Yet, despite announcing his opposition to subjecting Pluto’s planethood to the democratic process, Stern appealed to a democratic invocation of sorts—the authority of public perception:
I guess the best sort of a test is the test that my favorite fifth grader, my daughter Sarah, suggested. It’s the “duh” test…. Like the Supreme Court justice on [the definition of] pornography, when it comes to a planet I’m not sure I can give you an exact definition, but I know it when I see it. By the same token, give a fifth grader a picture of Pluto and ask him if it’s a planet, and you get back: “Duh.”
Marsden, bearing encyclopedic knowledge of the cosmic catalog and willing to agree with everyone onstage, grouped Pluto with its neighbors in the trans-Neptunian Kuiper belt but was perfectly content to embrace dual status—major planet (one of the nine) and minor planet (asteroid)—in the same way as certain small bodies are classed as both asteroids and comets. Once upon a time his hope had been that Pluto would become officially known as number 10,000 in the list of minor planets, in which case, rather than being “a piddly little thing between Mars and Jupiter,” it could have been accorded the “nice, unargumentative name” Myriostos, which is Greek for 10,000. Having lost that fight, if a fight it was, he was now amenable to all points of view, provided that the large-enough-to-be-round asteroid Ceres would be treated the same way as Pluto.
Next came A’Hearn, who, like Marsden, was willing to be a dual classifier. He stated his case with utmost and characteristic precision:
Why do we care about classifying Pluto as a planet or as a minor planet, or as anything else for that matter? Why do we do classifications at all in astronomy, or in any other science for that matter? Why do we bother separating humans from chimpanzees?
The reasons we do the classifications is to try to find patterns that will help us to understand how things work or how they came to be. So the way we classify Pluto should be something which helps us to understand how it works or how it came to be, and if what you want to understand is how the interiors of solid bodies work, then you should probably be thinking of Pluto as a planet. If, on the other hand, you want to know how things got to where they are in
In an effort to frame the ultimate definition of a planet—an effort that the IAU had been studiously avoiding—Stern presented the audience with a “rational sieve,” a physical test that anyone in the audience would be able to apply to any celestial object, whether already known or yet to be discovered. Its ease of application, he said, derived from its having an upper size limit and a lower size limit. At the upper end, any object big enough to fuse hydrogen in its interior is acting like a star and must be called a star. At the lower end, any object that doesn’t have enough mass to “become round of its own volition” by virtue of the physical process of hydrostatic equilibrium, which happens in objects with a minimum of about half the mass of Pluto, doesn’t deserve to be called a planet. Anything in between would be some sort of planet—although if it was orbiting another planet rather than a star, it could be called a planetary body.
Clear. Even persuasive. Yet, despite announcing his opposition to subjecting Pluto’s planethood to the democratic process, Stern appealed to a democratic invocation of sorts—the authority of public perception:
I guess the best sort of a test is the test that my favorite fifth grader, my daughter Sarah, suggested. It’s the “duh” test…. Like the Supreme Court justice on [the definition of] pornography, when it comes to a planet I’m not sure I can give you an exact definition, but I know it when I see it. By the same token, give a fifth grader a picture of Pluto and ask him if it’s a planet, and you get back: “Duh.”
Marsden, bearing encyclopedic knowledge of the cosmic catalog and willing to agree with everyone onstage, grouped Pluto with its neighbors in the trans-Neptunian Kuiper belt but was perfectly content to embrace dual status—major planet (one of the nine) and minor planet (asteroid)—in the same way as certain small bodies are classed as both asteroids and comets. Once upon a time his hope had been that Pluto would become officially known as number 10,000 in the list of minor planets, in which case, rather than being “a piddly little thing between Mars and Jupiter,” it could have been accorded the “nice, unargumentative name” Myriostos, which is Greek for 10,000. Having lost that fight, if a fight it was, he was now amenable to all points of view, provided that the large-enough-to-be-round asteroid Ceres would be treated the same way as Pluto.
Next came A’Hearn, who, like Marsden, was willing to be a dual classifier. He stated his case with utmost and characteristic precision:
Why do we care about classifying Pluto as a planet or as a minor planet, or as anything else for that matter? Why do we do classifications at all in astronomy, or in any other science for that matter? Why do we bother separating humans from chimpanzees?
The reasons we do the classifications is to try to find patterns that will help us to understand how things work or how they came to be. So the way we classify Pluto should be something which helps us to understand how it works or how it came to be, and if what you want to understand is how the interiors of solid bodies work, then you should probably be thinking of Pluto as a planet. If, on the other hand, you want to know how things got to where they are in
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