Dr. Free-Ride: You heard what happened with Pluto, right?
Younger offspring: It’s not there any more.
Dr. Free-Ride: Uh, it’s still there, just as big as it was and pretty much where it was before.
Elder offspring: But it’s not a real planet any more. Pluto got kicked out and they made Xena a planet instead.
Dr. Free-Ride: Umm, that’s not right either.
Younger offspring: Why’d they kick Pluto out?
Elder offspring: It’s too little to be a real planet.
Dr. Free-Ride: The real issue is that they decided a planet has to clear the area around its orbit. Remember how Pluto’s orbit overlaps Neptune’s?
Younger offspring: Hmmph.
Dr. Free-Ride: But you know, Pluto — and Xena, too — aren’t completely out of it. They’re in a new group called “dwarf planets”. And there are at least two other dwarf planets.
Younger offspring: So Pluto is still a planet.
Dr. Free-Ride: Yeah, it’s just not a “classical planet”.
Elder offspring: And Xena is really a kind of planet, too.
Dr. Free-Ride: Do you think they’ll still be able to use the nine planets song at your old school?
Younger offspring: No, ’cause they’re on their summer vacation now.
Dr. Free-Ride: I meant when they get back from vacation.
Elder offspring: They can use it, but they should replace Pluto with Xena in the song.
Younger offspring: No, Pluto and Xena are the same kind of dwarf planet!
Dr. Free-Ride: They could shorten the song and make it “eight planets”.
Elder offspring: “Great planets”.
Dr. Free-Ride: That would work. But then they might need a new song about the dwarf planets and how they’re different from the classical planets.
Elder offspring: “Ape planets, grape planets”!
Dr. Free-Ride: Child, you’ll learn about the ape planets in good time.