There are two parts to the story of the world called Pluto in the 21st century. One part revolves around human decisions on Earth about what does, and does not, make a planet. The second part is focused on a tiny spacecraft, about the size of a bus, which endured nearly ten years racing through the void between planets. For all of that time, it was moving ever-closer to a small lump of rock and ice of which humanity spent all but the last 85 or so years in complete ignorance. The public furore over the International Astronomical Union’s move to demote Pluto to “minor planet” status in 2006 led to a lively, if sometimes ill-informed, debate in the wider media on “what makes a planet.” Coming as it did shortly after the January, 2006 launch of the New Horizons mission to Pluto and the Kuiper Belt, it also seemed to some observers like something of a slap in the face for mission scientists. And, because of Pluto’s extreme distance from Earth, the mission itself would not return its results for nearly a decade. Those who watched the launch in 2006 knew that they had a long wait in store, at least as long as we waited for the results of the Voyager visits to the outer planets back in the 1980s. This extended wait for results was despite the fact that New Horizons was the fastest craft ever launched from Earth: after its encounter with Jupiter, it would travel toward Pluto at 15 miles per second.
Space, as we just need to remind ourselves sometimes, is vast. And silent. And largely empty.
Neil de Grasse Tyson, at the time of writing The Pluto Files: The Rise and Fall of America’s Favorite Planet, was director of the Hayden Planetarium in New York City. It was his planetarium’s exhibit on the solar system, designed in 2000 after the International Astronomical Union’s 1999 preliminary debate on the status of Pluto, which first raised eyebrows. Tyson, following the IAU’s logic, decided to class Pluto as a Kuiper Belt Object. The Kuiper Belt, rather like the Asteroid Belt, is less a belt and more a sprinkling of ball bearings of various sizes that occupies a nebulous region at the edge of the Solar System. Pluto, which is slightly smaller than Earth’s Moon, is one of the larger objects in this region of space.
I’m not sure where the term “America’s favorite planet” originates; if it is just condescension by the author or comes from some pointless poll or other. It was the first planet discovered by an American, by which logic, Neptune must be France’s favorite planet and the English must pine for Uranus. When Kansan Clyde Tombaugh, who discovered the faint point of light in 1930, made his announcement, the discovery was seen as the conclusion to a decades-long search by luminaries right up to and including Percival Lowell, whose observations of Mars, though sadly illusory, had excited the world’s imagings decades before. From that point forward, the solar system was composed of nine planets. They were, right up until the 1990s, the only planets that we knew.
Tyson’s narrative about Pluto actually has very little to do with the planet itself partly because, as we now realize, we knew very little about it. Instead, The Pluto Files is a photo-heavy look at the history of human knowledge of Pluto, including the controversies around its relegation to “non-planet” status. Following the declassification of Pluto, Tyson was the focus of a mixture of consternation and incomprehension, and this is due in part to the fact that the decision by the IAU itself, which Tyson followed, was ill-considered. It wasn’t a case of “Pluto is no longer a planet because we’ve found that it’s made of cheese” or “Pluto is no longer a planet because it has exploded.” Instead, a series of abstruse technical reasons were given, poorly explained for an inadequately informed public (in part by a news-cycle driven media, just looking for another story to fill ninety seconds of airtime twenty-five times per day for two or three days). It was as though Pluto had suddenly been relegated to infamy by sullen deities skulking around Mount Olympus, looking for a cat to kick. Indeed, Pluto’s relegation seems a bit like the argument that a tomato is really a fruit, or that the raspberry is actually a droop, or that oak trees are really fish. They’re not. Yes, they are, technically, but colloquially, THEY JUST AREN’T. Science – and I say this as a fairly science-minded person – doesn’t do well trying to make terminology for vernacular use. And Science, as an abstract body, from the very best motives in the world, can make some monumental cock-ups.
All of this is part of why I find Tyson to be a frustrating figure. I’ve read several of his books, and he is an excellent communicator. He knows his field, and other fields besides, and he is able to articulate the nuances in such as way as to make most people understand concepts, at least on a basic level. But, with regular appearances in the media, particularly on programmes like The Daily Show and The Colbert Report, Tyson appears to have succumbed to the allure of stardom. When appearing on parody shows to communicate science, no matter how well intentioned, one is always in danger of becoming a parody oneself. His radio show on one or another of the anonymous satellite stations is usually forgettable. And of course, no one could ever have remade Carl Sagan’s Cosmos to my satisfaction. The 1980 series and companion book was – and is – a cornerstone of my science education and awareness. I tried to watch the reboot with Tyson as host, I found I could not – that could just be me (yes, I know it was made by the same people as the original). For me, The Pluto Files too falls into the same category; Tyson sides with the argument ex auctoritas, and tries to deploy it against school children who should frankly just be commended for being able to name the eight – or nine – planets in the correct order, and encouraged to learn more before the window of imagination and wonder is beaten out of them by the conformity mill of schools.
What is staggering about this story is that until mid-July 2015, no one really knew what Pluto was like. There were measurements taken from the Earth, of course, and blurry photographs that appeared to show a world in brown and yellow tones. Even the Hubble Space Telescope was out of its depth: Pluto was simply too distant and too small (Pluto’s diminutive size is one of the IAU’s arguments against its status as a planet). The largest of what we now know to be five moons and moonlets around Pluto, Charon, was only discovered in 1978, and the remaining four (Nix, Hydra, Styx, and Kerberos) weren’t even known until the early years of the 21st century.
What New Horizons found on its historic 14 July 2015 fly-by of Pluto was that it is a planet which defies all of our notions. It is apparently geologically active, with a faint atmosphere, with seas of methane ice, craters, mountains, and even what appear to be dunes. Unlike objects like Vesta and Ceres, both also members of the IAU’s minor planets club, and both recently visited and homes to mysteries of their own, Pluto looks like a rocky terrestrial planet, albeit a very cold one, or even a moon, like Titan or Europa (although very different from either of those worlds, obviously). Because of New Horizons’s ever-increasing distance from Earth, it will take at least a year to receive all of the probe’s observation from a single day’s flight through the Pluto system, and it will take years to make sense of that information. We have learned a great deal from visiting Pluto, and there is still much, much more to learn.
Science is an on-going endeavour. There is so much to learn, and it takes time in which to get all of the pieces together. With regard to just our own immediate stellar neighborhood, it will take centuries of sending probes to all of the planets, moons, and worldlets in our vicinity before we truly know them. And this is the point that Tyson’s book didn’t make. The humility of not knowing, rather than being so vastly assured of our understanding, is what should guide science. For a book about science to fail to make that point, to fail to say that we do not know yet what we do not know, that fails both the lay reading public and science.
Originally reviewed 22 October 2015.
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