INTRODUCTION: This is AudioExplorations, a podcast series from AccessScience, the McGraw-Hill Encyclopedia of Science & Technology Online at www.accessscience.com. I'm Jessa Forte Netting. Today Dorian Devins speaks with astrophysicist Neil de Grasse Tyson, director of the Hayden Planetarium at the American Museum of Natural History in New York, for this AudioExploration: Pluto. This segment: "Ninth Planet Nostalgia: Tyson says 'Get over it!'"

DORIAN DEVINS: I know you talked a lot recently about Pluto and you've been on that for much longer than, and way before it came into the public sphere, but it's probably a good example of how science works in a way. I mean I don't want to make you go over the whole thing with Pluto, because you've going through it for so long.

DR. NEIL deGRASSE TYSON: Get over it.

MS. DEVINS: But how we classify things as planets, for example as planets, and how science does continuously change in how it sees things and how, as new information comes in that…

DR. TYSON: Yeah, one of my concerns was that over that period people might think that something was changing about Pluto. Pluto is still Pluto, it's not… Pluto is just being Pluto, and what did change was the depth and breadth of our understanding of what matters in the solar system. And in fact here at the American Museum of Natural History we take what I judge to be the high road, as the scientific and pedagogical high road. What we did was we said, "The enumeration of planets in modern times is no longer an interesting exercise either scientifically or pedagogically." The enumeration of planets was a fun thing to do when all you could do was look up in the night sky and say, "Ooh, there are these things to count." How many of them are there? What names do they have? What's their order from the sun? But in the era of the telescope and of space missions and of space probes there's so much else to think about, to talk about. You know, what are the soils of Mars made of? Tell us about the rings of the Jovian planet. Tell us about the many moons. The moons are where the action is, and if there are ice volcanoes on one and methane rivers and one has a liquid ocean that's probably been liquid for billions of years, kept warm by the gravitational stresses of Jupiter and surrounding moons. That's the moon Europa by the way. And there's so much else to think about, to talk about, to celebrate, that to say "What I want to know is the names … how many planets there are in the solar system". It's like, "Give me a break". So step back, take a breath, step back and ask, "What are the coolest things to know about the solar system?" And if you rank the coolest things to know, the number of planets will be very low on that list. And that's how it should be. So this whole debate about how you define a planet, I wasn't all that much interested in it. Because what we do here is we group the objects in the solar system by like properties and that’s how we present the solar system. There are other objects that are more like Pluto than either Pluto or those objects are like other things in the solar system. That's the catch, that's how you create a classification. Pluto is icy and it orbits the sun among other icy objects, so we present it that way. That upsets some people but there's no tablet written in the sky that says, "The universe will not upset you". I mean, the universe is what it is. It could care less what you think about it. So I hope that the next generation of teachers, textbook writers and students get exposed to the solar system in the sequence of ideas and phenomena that matter. And later on you can say, "Oh by the way, they used to count planets and here's how they used to define it".

MS. DEVINS: It does seem to be almost an object lesson in the problem with how science is taught though, because you see people react so strongly and sometimes it seems like it's only because they don't want to have to re-memorize another sequence or…

DR. TYSON: Because we're all intellectually lazy. Because we don't — oh, I have to memorize another list? And well, when the real answer is you shouldn’t be memorizing lists at all. That's really the answer here. And just yesterday I was at a cocktail party and someone there recognized me as the Pluto killer, and said, "Do you realize that to take Pluto away from the solar system that's — Pluto was there in our hearts and minds, that was as firm as the floor you step on when you get out of bed in the morning". And I said, "Whoa, whoa". He felt strongly about this one, I didn't have a rebuttal to that, I said I don't blame him, I blame the teachers who … not the teachers, I blame the textbook writers who believe that memorizing planets in order was a worthwhile scientific exercise.

MS. DEVINS: Wow, you shook his whole universe.

DR. TYSON: That's right, destabilized his physical foundations.

MS. DEVINS: But it does also bring up a point of sentimentality, which I think exists a little bit with people and their knowledge that they learned from the textbooks when they're kids and how hard they kind of hold fast to that.

DR. TYSON: It could be a little deeper than that because people in Europe didn't care as much about Pluto. The public didn't care that much. And I'm convinced that Mickey's dog is behind it all, right? When you think about it, Pluto as a dog was first sketched the same year that Pluto the object was discovered. And Pluto the object was discovered by an American, Disney is an American company and so they both have the same tenure in our consciousness as Americans in this country. And so I will not under-recognize the potential for that on people's sentiment when they hear that Pluto the object has been declassified. And I think there could be more to it than just pure sentiment for a cosmic object.

MS. DEVINS: But it's also a good, I guess a good opportunity to have the public see what a bit of a debate is like in science.

DR. TYSON: Yeah, except that it was not a scientific debate, it was a debate over lexicon. It really wasn't a scientific debate. No one was arguing about what Pluto was made of or where its orbit was, or no one had any argument about that at all. The problem was the word 'planet' had never been defined, hadn't been defined since ancient Greece. And when you don't have a definition people are jockeying for what that definition ought to be. That's where the fights broke out. And so the international astronomical union tried to settle that debate and they came out with a plan that grouped Pluto with its brethren in the outer solar system, but still made it a point so that means there are eight planets, so they still made the planet issue an issue. But, so fine, given their definition Pluto is not a planet. Even if they define it to be a planet we still wouldn't change the exhibits here because they're not based on planethood, they're based on properties that the objects exhibit.

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