August 17, 2006

Gay marriage and counting the planets

When I first wrote on Language Log about the issue of same-sex marriage, I thought, and still think, that there was some dirty work afoot in talking about the issue as if it was a linguistic one. It is not about defining what the word "marriage" will stand for, I argued; there are already dictionary entries allowing a sense in which there can be a same-sex marriage, so it's not a contradiction to talk about such a union (the way it would be a contradiction to talk about a kind of triangle that had four corners). It's not about word meaning at all; it's about whether certain people will get certain rights. The laws of my home state currently deny my friends Susannah and Kirstin the right to file joint tax returns or be considered each other's default inheritor of property, and so on. Writing a law that ensures they will be denied those rights cannot honestly be downplayed as harmless democracy in a matter of mere lexicography (recall President Bush's remark that "Marriage ought to be defined by the people, not by the courts"). It's interesting to compare this with the current issue of how many planets there are. That truly is just a matter of lexicography.

Next week astronomers will vote on a newly proposed definition (not redefinition — we've never really had a definition before). There are various positions out there, including a restrictive one that says Pluto is an eccentrically-orbited snowball from the Kuiper belt that should never have been included, so there are 8 planets, and a very inclusive one that allows at least 53 spherical sun-orbiting bodies to count as planets (an idea some astronomers refer to contemptuously as "No Snowball Left Behind"). The official proposal is to say that a planet is a body that meets the following four conditions.

  1. it has sufficient mass to assume near-spherical shape because of its own gravity, and
  2. it is in orbit around a star, and
  3. it is not itself a star, and
  4. it is not a satellite of a planet in the sense of having an orbit that goes around a center of gravity that is located inside a body that is independently a planet.

Under this definition, the number of planets will go up from 9 to at least 12, and unless a committee keeps a lid on things, the number could go way up from there to 53 or more.

The last of the four clauses quoted looks a little bit gerrymandered, doesn't it? It turns out to allow Charon to be a planet: Charon looks a lot like the largest moon of Pluto, but in fact it does not orbit around a center of gravity inside Pluto; it revolves around a center of gravity determined by both bodies and located in the space between them, so you can see the two of them as a pair of small planets orbiting the sun but at the same time slowly twirling around each other like a couple waltzing around the outer edge of a ballroom. (Our own moon's orbit is around a center of gravity located deep within the earth, so the moon definitely can't count as a planet.)

Given clause 4, the peculiar anomaly of Charon's almost-independence of Pluto scrapes in as an extra planet. Pluto retains planet status too. (One astronomer who thinks it shouldn't is Neil deGrasse Tyson. He said recently, in a remark that is a clear example of linguifying, that fans of Pluto get lucky with the proposed official definition: "It is one of the few that allow you to utter Pluto and Jupiter in the same breath.")

The other two objects that get into the hall of planetary fame are Ceres (which was first counted as a planet and then demoted in modern times to being considered a very large and unusually spherical object of the asteroid belt between the earth and Mars), and 2003 UB313, unofficially known as Xena (yes, it's been jokingly named after the warrior princess on TV).

But in all of this, no planet loses any rights. Orbits stay the same, like masses, distances, year lengths, and so on. No census issue is raised: the very same objects are, uncontestedly, out there, governed by the same laws of physics. If the new definition gets the votes at the International Astronomical Union on August 25, all that will happen is that we will start using the word "planet" somewhat differently (if we decide to go along with astronomers' usage: we don't have to).

That's what it's like when a truly terminological issue comes up. When the International Astronomical Union makes its decision, I predict there will be no lawsuits. Only the definition of a word is at issue. It's not that way with the issue of whether you count as married to the dying domestic partner whose doctor you want to consult with; the marriage issue has real consequences for people's lives and is not just a matter of how we define a word.

Oh, and one other piece of lexicography is on the table: astronomers are thinking of introducing the word pluton, meaning something like "planet that is really nothing more than a God-forsaken frozen slushball way out beyond Neptune drifting around in the Kuiper belt and damn lucky to be called a planet at all". I paraphrase, but you get the general drift. Pluto and Charon and Xena may get to be called planets, but they are not quite to be compared with the gas giants (Jupiter, Saturn, Uranus, Neptune) or the inner planets that are warm enough that there has been speculation about the existence of life on them (Mercury, Venus, Earth, Mars). (One of the latter group, Earth, is actually known to have developed blogs, pepperoni pizza, cell phones, and intimate massage, all of which are considered prime indicators of the probability of some kind of life.)

Posted by Geoffrey K. Pullum at August 17, 2006 08:32 PM