Wednesday, July 15, 2009

"Unscientific America" and the case of Pluto

There has been a lot of web discussion about Chris Mooney and Sheril Kirshenbaum's new book, “Unscientific America” (particularly over PZ Myers review, see their response to PZ Myers here). I’d like to focus on one part from the beginning of the book, the one that got PZ exercised, that I think illustrates an important problem with the book. You can read the excerpt from the book that deals with the issue of the demotion of Pluto here.

[numerous t-shirt slogans omitted]So read a small sampling of the defiant T-shirt and bumper sticker slogans that emerged in late 2006 after the International Astronomical Union (IAU), meeting in Prague, opted to poke the public with a sharp stick. The union's general assembly voted to excommunicate the ninth planet from the solar system, thus abruptly stripping Pluto of a status as much cultural, historic, and even mythological as scientific.
Here the IAU, as representative scientists, is shown as being antagonistic to the public. But why? Why is the Pluto decision “poking the public with a sharp stick? The IAU was making a ruling based on our scientific understanding to resolve a long standing problem. This ruling did not come out of nowhere and the lead-up was well publicised.

In the astronomers' defense, it had become increasingly difficult to justify calling Pluto a planet without doing the same for several other more recently discovered heavenly objects--one of which, the distant freezing rock now known as Eris (formerly "Xena"), turns out to be larger. But that didn't mean the experts had to fire Pluto from its previous place in the firmament. In defining the word "planet," they were arguably not so much engaged in science as a semantic exercise …....
Keeping Pluto a planet was a lot more than semantics. Up until the notorious 2006 decision, there was no accepted definition of a planet. Also, by the 1990’s it was increasingly evident that Pluto was not like the other planets. It’s orbit was unusual, very much tilted to the plane of the other planets, and much more elliptical, even coming inside the orbit of Neptune at its closest approach to the Sun. Pluto was also very small, while it was originally thought to be 90% the size of Earth, subsequent study showed it was 2/3rds the size of Earth’s Moon. In the meantime, the Kuiper Belt objects had been discovered. Small icy objects with orbits similar to Pluto’s in inclination and distance. As time went on, larger and larger Kuiper Belt objects were discovered, approaching that of Pluto in size (eg Sedna). The Kuiper Belt object composition was also similar to that of Pluto.

It was increasingly obvious that Pluto was just a large Kuiper belt object and that sooner or later other icy worlds, the same size as Pluto or bigger, would turn up. As well, while the classical planets were thought to be formed from accretion of smaller objects, the Kuiper belt objects (including Pluto) were thought to be leftovers from the formation of the solar system. So Pluto had a different history to the classical planets. Spurred by this knowledge, from 1998 there were various attempts to create a definition of a planet that would deal with Pluto and the new Kuiper Belt bodies. Attempts to find a definition that would have a sensible physical definition and keep Pluto as a planet all failed.

The issue was finally forced by the discovery of UB313 (Eris). It was (just) larger than Pluto, was it a planet? The IAU finally had to come up with a definition of a planet. After a number of attempts, a panel of notable scientists and writer Dava Sobel (Longitude, The Planets) provided a definition that was based on physical properties, and tried to avoid any arbitrariness. They proposed that a planet was anything that was large enough that gravity pulled it into a sphere. They then divided the Planets into Classical Planets (Mercury to Neptune) and Dwarf Planets (things like Pluto, Ceres and Eris) based on whether the planet was gravitationally dominant (ie was it big enough to sweep away all the floating junk in the planets local area, dwarf planets didn't).

Again, as you will note, the issue wasn’t one of semantics, but finding a set of physical properties of the objects that could separate planets from non-planets without an arbitrary dividing line. If Pluto was to be called a planet, then what definition would exclude the dozens of icy lumps in similar orbits that were a tad smaller? If you didn’t exclude them, then up to 20-40 planets would have been created. The public may have been ready for a 10th planet, but over 20? More than semantics were at stake here.

In the end, after a fair bit of argy-bargy, the definition of “Planet” adopted was one where an object was big enough to be spherical and have enough gravitational grunt to sweep up all the debris near it. Things that were merely spherical became dwarf planets. Pluto got demoted.

Why suddenly kick Pluto out of the planet fraternity after letting it stay in for nearly a century, ever since its 1930 discovery? "No do-overs," wrote one cartoonist..... how could this planetary crackup happen in the first place? Didn't the scientists involved foresee such an outcry from the public? Did they simply not care? Was the Pluto decision really scientifically necessary?

There was nothing sudden about it. Back in 1995 astronomer Dave Jewitt received death treats for suggesting that Pluto was just a Kuiper belt object. In 1998 the first serious attempts to define a planet went rumbling through the professional and amateur astronomical worlds, and listservs buzzed with debate. In 2001 Neil deGrasse Tyson cheekily put up an exhibit at the Hayden planetarium suggesting that Pluto should not be a planet. This was widely reported in tradition and electronic media. The issue arose again in 2004 with the discovery of Sedna, and yet again when Eris, larger than Pluto was discovered.

Previous attempts to define a planet that kept Pluto as a planet had failed, but now a ruling was absolutely required, otherwise Eris (and any other large transneptunian object subsequently discovered) would be in limbo. From the discovery of Eris to the fateful meeting in 2006 there was a well publicised debate.

It's not like this was not without precedent, for 40 years from around 1806 the solar system had 11 planets, Mercury to Uranus and Ceres, Pallas, Vesta and Juno (by 1845 there were 17). They were listed in professional and popular works on the planets and astronomy. More and more of the lumps of rocky rubble turned up, until there were nearly 100 of them. Then in 1846, in a parallel to the recent events, Neptune was discovered; Ceres, Pllas, Vesta and Juno were demoted to "minor planets" and everyone moved on.

The furor over Pluto is just one particularly colorful example of the rift that exists today between the world of science and the rest of our society.
How? What is this meant to show? That scientists are mean? That seems to be one theme ("The International Astronomical Union (IAU)... opted to poke the public with a sharp stick", "Didn't the scientists involved foresee such an outcry from the public? Did they simply not care?"). Astronomers did forsee an outcry from the public, and they did care (especially as several of their own number had a strong attachment to Pluto s a planet). But they needed to make a decision, they had an object larger than Pluto, and they needed a definition of a planet to decide on its status, or Eris would have remained in scientific limbo. The Pluto decision was scientifically necessary.

Does it show that scientists are poor communicators? From 2001 on the debate over Pluto's status was accompanied by high visibility events such as Neil deGrasse Tyson's planetarium exhibit, which was well covered in the media. Listen to his story of receiving hate mail from 3rd graders here. The discovery of Sedna and then Eris were high profile events in which the question of Pluto's planet hood was raised with discussion of why a planetary determination was necessary. The lead up to the IAU meeting was covered in the traditional and electronic media. For example, Mike Brown the leader of the team that discovered Eris kept a rapidly updated web page and wrote popular articles for outlets such as the New York Times. The IAU issued press releases, had a large media presence and had a special presentation by Joycelyn Bell Burnell (the discover of Pulsars) to explain the significance and reasoning behind the decision that was made. What more could they do?

Is the point that the American public are woefully ignorant of science? We should be happy that they knew what Pluto was. From 1995 to 2009 nearly 50% of Americans did not know that Earth took a year to orbit the Sun, one in 5 Americans did not know that Earth orbits the Sun (don't get cocky non-Americans, the figures are similar for Europe and Australia and Yes, I know I got the curve for that wrong in the diagram, I'll fix that later fixed).

So what, exactly, is Moony and Kirshenbaum's point? That scientists shouldn't have chosen a definition that excluded Pluto? They needed a rational, non-arbitrary demarcation, we had a choice between 8 planets and a bunch of smaller stuff, or something like 20+ planets based on rational definitions. I'm not sure that the public would be pleased with having to learn Mercury, Venus, Earth, Mars, Ceres, Vesta, Pallas, Jupiter, Saturn, Uranus, Neptune, Pluto, Charon, Orcus, Ixus, Quoarar, Sendna, Eris .... and so on as the solar systems planetary lineup. Either way, a non-arbitrary decision had to be made.

Was their point that scientists didn't try hard enough to get their points across? It's hard to see what more they could have done, they pursued all available avenues of public communication and this was riding on the coat-tails of very exciting discoveries that the public were interested in and had significant exposure in traditional media. How more high profile could they get?

To put this in perspective, NASA has an enormous outreach program, high profile impact because of the stunning nature of the subjects it covers (and people really like space exploration), flashy websites, stunning images, education sites and helpful animations. And STILL one in five Americans don't realise that Earth rotates around the Sun and around 50% don't realise that Earth takes a year to rotate around the Sun. If those simple facts can't be gotten across with a huge expenditure of money, how are ordinary astronomers with modest budgets going to get their ideas about Pluto across.

The most disturbing thing is that Mooney and Kirshenbaum should have known the history of the Pluto debate, the details are easily available and there are two substantial books about this. Mooney and Kirshenbaum's statements about the issues are almost completely wrong. If they can't something as simple as this right, what about the other issues in this book?

UPDATE: You can read the IAU's own document on communicating science at the 2006 "Pluto" meeting here (Warning 25 Mb document). The IAU put a lot of thought and resources (press releases, arranging journalist interviews, web links, web-based video and interviews etc.) into communicating science and the Pluto issue at this meeting. Not everything worked, but we can safely say that the public reaction occurred despite a large amount of outreach and communication on the part of the IAU and other astronomers.

Like all my Pluto Posts, this one should be read listening to Jimmy and the Keys "They Demoted Pluto".

And really, really listen to Neil deGrasse Tyson's talk on Pluto's demotion (It's really quite informative and amusing, according to him, Europeans did not have the same visceral reaction).

Read Govert Schilling's “The Hunt for Planet X” (ISBN: 978-0-387-77804-4) and Neil deGrasse Tyson's book The Pluto Files, The Demotion of a Planet (ISBN-13: 9780393065206).

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