The Pluto Files: The Rise and Fall of America's Favorite Planet.

• Author: Ferzan, Kimberly Kessler
• Position: Book review

THE PLUTO FILES: THE RISE AND FALL OF AMERICA'S FAVORITE PLANET. By Neil deGrasse Tyson. New York & London: W.W. Norton & Co. 2009. Pp. 194. $23.95.

INTRODUCTION

In case you haven't heard, Pluto isn't a planet anymore (and maybe it never was). In grade school, we all memorized the planets, giving little thought to what made something a planet besides revolving around the Sun and being part of some familiar mnemonic. However, scientific discoveries about Pluto and other parts of space led scientists to question Pluto's planetary status and ultimately, to strip Pluto of its standing among the planets. This leads to the inevitable question--what is a planet?--which turns out to be a more difficult and fascinating question than one might think.

The Pluto Files grapples with the question of what it is to be a planet. The book is as much a cultural study as an astrophysical one. "Gathered here in one place is a record of Pluto's rise and fall from planethood, given by way of media accounts, public forums, cartoons, and letters I received from disgruntled schoolchildren, their teachers, strongly opinionated adults, and colleagues" (p. xi). The Pluto Files thus presents the question of the meaning of planet not through rigorous argumentation but through the crosswinds of culture and science.

But why should lawyers care about Pluto? Because it is a prism through which we can understand how man interacts with the world by creating conceptual categories. Like scientific constructs, legal constructs may turn on the way the world "really is" A donor must be dead for an organ donation to be legal. (1) Like science, law must construct its own categories of meaning-for instance, criminal law's efforts to distinguish defenses as justifications and excuses. In addition, law must draw difficult lines. In our effort to treat like cases alike, we must categorize the world, lumping some items together while splitting others. (2) The Pluto Files is a fascinating prism through which to view all of these endeavors.

It is not often that one encounters a book that meets so many different descriptions. It is the sort of fun, easy read that one can take on vacation. It makes you laugh out loud. You can use it to look smart at cocktail parties. Your children will be interested in what you are reading. And it gives you a new prism through which you can gain insights into your own profession and place in the world.

In this Review, I begin with The Pluto Files' detailing of Pluto's discovery through its downfall. The book is an extraordinary interweaving of the empirical, the conceptual, and the social. Not only does Tyson present the scientific case for demoting Pluto, but he also places it within the larger cultural text--including copies of the hate mail he received from school children, song lyrics, newspaper cartoons, and excerpts from The Colbert Report. The declassification of Pluto was an empirical and social phenomenon. In Part II, I systematize the debate, discussing how we might understand the Pluto problem as an instance of a purely stipulated "nominal" kind, a natural kind, or simply an inevitable line-drawing issue. In this Part, I push against an implicit theme in the book--that science, and not popular sentiment, could and should determine Pluto's status. In Part III, I turn to the lessons that law can draw from Pluto's demise, ranging from law's use of natural kinds, to law's need to understand its categories, to the consequences of legal classifications. The Pluto Files is not a tale of a giant ice ball in space; it is an accessible account of how man finds meaning in the world.

1. THE PLUTO FILES: THE BOOK ITSELF

   The Pluto Files documents Pluto's discovery to its demotion. It is written by Neil deGrasse Tyson, an astrophysicist and director of the Hayden Planetarium at the American Museum of Natural History ("AMNH"). (3) As Tyson characterizes it, "Pluto's demotion became a window on who and what we are as a culture, blending themes drawn from party politics, social protest, celebrity worship, economic indicators, academic dogma, education policy, social bigotry, and jingoism" (p. 135).

   Although Tyson has a knack for writing accessible astrophysics for a popular audience, this book is also downright funny. This isn't your elementary school science book. For instance, Tyson hypothesizes that America's attachment to Pluto, the planet, comes from its attachment to Pluto, Mickey Mouse's pet. Tyson, sensitive to the treatment of species as a result of his work at the AMNH, then asks, "[H]ow [did] it c[o]me to be that Pluto is Mickey's dog, but Mickey is not Pluto's mouse[?]" (p. 15). He answers:

   I would later learn that if you are a Disney character who wears clothes, no matter what your species, you can then own pets, who themselves wear no clothes at all, except perhaps for a collar. Pluto runs around naked except for a collar that says "Pluto." Mickey runs around with yellow shoes, pants, white gloves, and the occasional bow tie; The haberdasheral hierarchy is clear. (p. 15) The chapters proceed chronologically, detailing Pluto's story from discovery through its demotion. Pluto was discovered by Clyde Tombaugh on February 18, 1930, in Arizona (p. 3). It was found because scientists postulated a Planet X that explained perturbations in Neptune's orbit (pp. 3, 24-25). Pluto was named by Venetia Burney, an eleven-year-old girl in Oxford, England, whose grandfather was a retired librarian from Oxford University and was friends with many astronomers (p. 9). Prior to the planet's discovery, the only "Pluto" readily accessible to Americans was Pluto Water, a mineral water laxative (p. 7). In May 1931, Disney released "The Mouse Hunt" with Mickey's new pet, Pluto (p. 13), and Americans fell in love with both Plutos (p. 14).

   As science marched on, empirical discoveries challenged Pluto's planetary status. Assumed at discovery to be about the same size as Neptune, eighteen times Earth's size (p. 25), Pluto's estimated size plummeted to less than one percent the mass of Earth by 1978 when Pluto's moon, Charon, was discovered (p. 27). As Pluto slowly disappeared, astronomers realized that it could not fulfill the role of Planet X, but by that time, scientific discoveries allowed the recalculation of orbits, ultimately leading to the conclusion that there was no Planet X in the first place (p. 28).

   We've named and lost other planets. We started with seven "wanderers" (planet means "wanderer" in Greek): Mercury, Venus, Mars, Jupiter, Saturn, Sun, and Moon (p. 31). After Copernicus, our solar system dropped to six (losing the Sun and Moon, adding Earth) (p. 31). Ceres and Pallas, later deemed asteroids, were once planets until they simply became "too small" to count (pp. 28-30). At the time when asteroids were counted as planets, we had twenty-three planets in our solar system (p. 30 fig.2.4).

   Pluto is different from the (other) planets in many respects. Its volume is mostly ice (p. 33). It is tiny, and its orbit is eccentric as it tilts more than seventeen degrees from the plane of the solar system (p. 34). Pluto's moon, Charon, is so large relative to Pluto that unlike (other) planets where the moon orbits the planet, Charon and Pluto orbit a fixed spot in free space (p. 34). Pluto's path is messy (p. 37). Some of these properties make Pluto more closely resemble comets and asteroids (p. 52).

   Pluto's planetary status was questioned far before its demotion. In 1956, astronomer Gerard Kuiper proposed that an object cannot be a planet if it takes too long to rotate on its own axis--Pluto takes more than six days. (4) However, what science did not know was that Venus takes 243 days to spin once on its own axis (p. 61). In contrast, "Plutophiles," as Tyson dubs them, clung to Pluto's moon as indicia of Pluto's status (p. 51). This, too, was a problematic criterion. In 1994, astronomers discovered that the asteroid Ida has an orbiting moon (p. 51). And more such discoveries have been made (p. 51).

   As it turned out, Pluto is not unique. In 1992, astrophysicists discovered small objects, all with tipped orbits, in the "Kuiper belt" (pp. 53-55). With these discoveries, Clyde Tombaugh (still alive in the early 1990s) saw the writing on the wall and fought to keep Pluto as a planet (pp. 56-57). Pluto was in trouble.

   Pluto's fall was hastened by the February 2000 opening of the Rose Center for Earth and Space, part of the AMNH. Tyson was appointed director of the Hayden Planetarium in 1996 and his appointment included serving as project scientist for the creation of the Rose Center (p. 61). Unwilling to spend funds on an unstable classification scheme, Tyson organized a panel debate on Pluto in 1999 (pp. 68-69). The panel--"[t]he right people at the right time and at the right place" (p. 70)--was comprised of Michael A'Hearn, a comet and asteroid specialist; David Levy, amateur astronomer and discoverer of dozens of comets and asteroids; Jane Luu, professor and codiscoverer of the first Kuiper belt object; Brian Marsden, comet and asteroid specialist and director of the International Astronomical Union's ("IAU's") Minor Planet Center; and Alan Stern, a specialist in small objects in the solar system (p. 69).

   The panelists took various sides. Luu claimed Pluto was not a planet (pp. 70-71). It belonged with the "swarm" of similar tiny objects in the Kuiper beit (pp. 70-71). If the other Kuiper beit objects had been discovered simultaneously with Pluto (as the asteroids were), then none of them (Pluto included) would have been planets today (p. 71). Luu further maintained:

   If Pluto continues to be referred to as the ninth planet, it would only be due to tradition and sentimental reasons. People are fond of planets, because the idea of a planet conjures up notions of home, life, happy things, and astronomers are always looking to find more planets, not to lose them. So in the end, the question goes back to this: Should science be a...