Revisiting the Planets, Redux

25 August 2006

The International Astronomical Union (IAU) voted Thursday on a definition of the word planet. The proposed definition we reported on last week was rejected and the IAU defined a planet as a celestial body that

• is in orbit around the Sun,

• has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and

• has cleared the neighborhood around its orbit.

According to the IAU, this leaves our solar system with eight planets, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. By this definition, Pluto is not a planet because it has not cleared its neighborhood.

The IAU also rejected use of the proposed term pluton, for the class of objects similar to Pluto. That term is also commonly used by geologists for an igneous mass that forms when molten rock cools underground and it was thought that there could be confusion between the geological and astronomical senses–although that doesn’t seem very likely. Context would rule out any chance of confusion in most cases. After all, there isn’t any confusion of the geological and anatomical uses of vein.

More problematic for pluton is that in French and Italian this is the name for the former-planet Pluto. This could cause much confusion between the class and the specific body in those languages.

Instead of pluton, the IAU decided on another linguistically problematic term, dwarf planet, which is defined as a celestial body that:

• is in orbit around the Sun,

• has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape,

• has not cleared the neighborhood around its orbit, and

• is not a satellite.

Benjamin Zimmer over at Language Log has a good discussion as to why this is a questionable form in English. In English compound nouns, the more general term is usually the second noun. Catfish are fish, not felines and mountain lions are cats, not masses of rock. Although there are exceptions, like sea lion. Although a dwarf star, arguably the most similar term to dwarf planet, is most definitely a star.

But perhaps the most cogent commentary on the subject is by Ruben Bolling who penned this cartoon. The third example is the best.

Planets & Plutons: An Update

18 August 2006

Back in November of last year, I wrote about the International Astronomical Union (IAU) and how planets were named. The IAU is currently meeting and has proposed a definition of planet. (It has not had a formal definition of the term to date.) The organization will vote on the proposal on Thursday. In addition to getting into the lexicographical game by coming up with a definition, the IAU is also proposing a new term, pluton, for Pluto-like objects that orbit the sun beyond Neptune.

The new definition was prompted by the continuing debate over whether or not Pluto should be considered a planet and by the discovery of 2003 UB313, unofficially nicknamed Xena after the warrior princess of television fame, an object much further and much larger than Pluto. But the IAU had some surprises when it announced its proposed definition this week.

Under the proposed definition, a planet is an object that

• has sufficient mass to assume near-circular shape because of its own gravity, and

• is in orbit around a star, and

• is not itself a star, and

• 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.

If the proposal passes, there will (for the moment) be twelve planets, instead of the current nine. And there are several surprises in the new planetary nominees. One item that is not surprising, but was by no means certain, is that Pluto will retain its planetary status. And given this, Xena will also be a planet–no surprise given that it is larger than Pluto. But the other two new planets are the shockers.

One is Ceres, the largest of the asteroids. Ceres, discovered in 1802, was once considered a planet, but had long since been demoted to asteroid status. It is only 930 km in diameter (Pluto is 2,274 km in diameter; Earth is 12,756 km, and the Earth’s Moon is 3,476 km.) The new IAU definition of planet includes Ceres because it is a circumsolar object (it orbits the sun directly and not another object) and because it has enough mass to form a sphere.

The second surprise is Charon, Pluto’s moon. Even though it orbits Pluto, and not the sun directly, Charon makes the planetary cut because of the fourth criterion. The barycenter (center of gravity) of the Pluto-Charon system is outside Pluto. (By comparison, the barycenter of the Earth-Moon system is 1,700 km beneath the Earth’s surface.) Pluto-Charon is essentially a dual planet.

The number of planets is not fixed at twelve and as more trans-Neptunian objects like Pluto and Xena are discovered many will also be so designated. There are several other known objects that might make the grade at a future IAU meeting, including Sedna and Quaoar, which are both larger than Ceres and Charon. Another is 2003 EL61, which is also larger than Charon and Ceres, but which has an elliptical shape rather than round.

The IAU is proposing a name for these icy trans-Neptunian objects, calling them plutons. This is a useful term, although it is also a geological term for an igneous rock formed below the Earth’s surface–there will probably be little or no confusion between the two. Pluton is superior to trans-Neptunian object as it can also be applied to such objects in other star systems, when and if they are discovered.

But what is of interest to us word mavens is not so much which objects receive planetary designations by the IAU, but the IAU’s attempt to define the word planet. First, they are not using the methodology that lexicographers do. They are not surveying usage and deriving a definition from how people use the term. Instead, as is usually the case for technical definitions, they are establishing a rigid definition intended to categorize objects by criteria that are scientifically useful. While this method is perfectly fine for technical definitions, their results are highly questionable.

The first problem with the definition is that of the barycenter codicil that admits Charon to planetary status. The barycenters of planet-moon systems are not fixed, changing over time. The Earth’s moon, for example, is moving away from the Earth by about 4 cm a year. In 40 million years (which may seem long to us but is only a moment in planetary time) the Moon will become a planet when the barycenter of the Earth-Moon system moves above the Earth’s surface. If objects can move in and out of planetary status in relatively short periods, does the categorization tell us anything meaningful?

Another is the question of how round is round? No planet is perfectly spherical. The Earth is somewhat pear-shaped, a bit fatter in the southern hemisphere than in the north. Saturn is noticeably squashed at the poles. What an object is made of and how fast it rotates are as important as mass in whether or not gravitational forces shape it into a sphere. As I have noted, 2003 EL61 is considerably larger than Ceres, but it is egg-shaped due to its rotation and the fact that it is probably made largely of ice instead of rock. This inserts an subjective and arbitrary judgment into what should be objective and meaningful criteria. The key isn’t roundness, it’s mass; in which case the definition should cut out the middle-man and specify a minimum mass.

But the larger question is whether or not any definition of "planet" serves a useful astronomical purpose. When objects are as different as rocks like the Earth, gas giants like Jupiter, and ice balls like Pluto, is there any sense in trying to lump them into a single category? Astronomy might be better served to classify the objects that orbit the sun into terrestrial bodies (big rocks like Mercury, Venus, Earth, Mars, as well as many moons), asteroids (rocks that are too small to be considered in the first category), gas giants (Jupiter, Saturn, Uranus, and Neptune), and plutons (Pluto, Xena, and comets).

Astronomers should take their cues from another discipline. At one time, biologists considered race an important category in studying humans. But over time, it became clear, that although the characteristics associated with race were biologically determined, the characteristics could not be used to form any scientifically useful categories. Skin color, for example, tells you nothing about the person except their skin color. Today, no reputable biologist attempts to classify people by race. This is not to say that race is not culturally relevant, but it is meaningless as far as the science of biology is concerned. Biologists have gotten out of the race business, leaving the definition of racial categories to social scientists and lexicographers.
Similarly, astronomers should do the same thing with the word planet. They should declare that astronomically, the category is useless. Leave it to the lexicographers to find a definition based on how people (astronomers, schoolchildren, and the general public) use the term. Planets would still exist, but whether an object is defined as a planet should not concern an astronomer. In such a descriptive definition, the planets would consist of the eight classical planets and, depending on who you asked, Pluto and some of the other trans-Neptunian objects.

Little is served by a scientific body giving its imprimatur to a definition that has little or no scientific utility.

See the website Bad Astronomy for an excellent, if opinionated, review of the astronomical issues associated with the IAU’s definition of planet.

Prescriptivist’s Corner: Plural None

30 June 2006

Several of you have written about the following sentence that appeared in last week’s A Way With Words contending that it is grammatically incorrect:

None of these are accurate, although all of them have elements of truth.

The contention is that none derives from no one and therefore should take the singular, as in:

None of these is accurate�

This contention is not correct. None can take either the singular or the plural verb form. The reasons for this are as follows.

First, it is not quite accurate to say that none comes from no one. As far back as you care to go in English, it has been a single word. The earliest Old English form is nan, cognate with the Old Frisian form. It is true that it ultimately is a compounding of the Germanic ne- and the word for one, but this happened long before there was an English language.

The second, and more important, reason is that grammar is determined by usage, not by etymology. It does not matter where none came from. What matters is how people, especially those writers we respect, use it. Grammar is not logical and cannot be determined via deduction; it is arbitrary and capricious, subject to the desires of those who speak the language.

Third, those who insist that it must always take the singular ignore the grammatical concept of notional agreement or notional concord, where the subject-verb agreement follows the logic of sense, not the arbitrariness of grammatical markers.

But you don’t have to take my word for it. Fowler (1926) wrote about none:

It is a mistake to suppose that the pronoun is sing. only & must at all costs be followed by sing. verbs.

Barzun (1966) says:

Lexicographers, who know as well as journalists that none = no one, point out that it is rather more commonly treated in modern usage as a plural, as if it mean no ones; and the same is true of colloquial habit, as anyone’s ears will tell him. Literature shows both usages without a clear preponderance.

The OED2 (1989) says:

Many commentators state that none should take singular concord, but this has generally been less common than plural concord, especially between the 17th and 19th centuries.

Merriam-Webster’s Dictionary of English Usage (1989) goes into excruciating detail on the subject, coming up with:

Evidence in the Merriam-Webster files, all gathered in the 20th century, shows no trends. The possible effect of editorial opinion can occasionally be found: we have a pretty long run of Time citations that are mostly singular, and about as long a run from the New Yorker that are mostly plural. It appears that writers generally make it singular or plural according to whatever their idea is when they write. This matching of verb (or referring pronoun) to a pronoun by sense, rather than formal grammatical number, is known as national agreement.

Garner (1998) concludes:

none = (1) not one; or (2) not any. Hence it may correctly take either a singular or a plural verb.

Peters (2004) states:

None is variable, and may take either singular or plural.

So there you have it. My best advice when such questions arise is to discard what your eighth-grade English teacher taught you and consult a good dictionary of usage.

Department of Animal Speech

9 June 2006

News reports from a few weeks ago told of researchers at St. Andrew’s University in Scotland who have discovered that bottlenose dolphins use signature whistles, to identify themselves to others in their pod. In typical fashion, the news reports played this up, saying that dolphins had "names" for one another and some even going so far as stating that this is proof of animal use of language.

First, the news that dolphins use signature calls is not new; we’ve known that since the 1960s. And it is hardly unique in the animal world; it is common among birds, for example. Nor is it truly a name–there’s no evidence of one dolphin calling another by its signature; instead the calls are used for self-identification. What is new is that Dr. Vincent Janik of St. Andrews has determined that the key to the signature is the pattern of frequency variation over time. Janik was able to make dolphins respond by artificially playing the frequency pattern belonging to another in their pod, with other aspects of the sound, like harmonics or "tone" and the clicks that dolphins also make, removed. So, we’ve learned something new about the structure of dolphin signature whistles. It’s interesting, but hardly earth-shattering. We’re not going to be rewriting the linguistic textbooks because of this discovery. (For a linguist’s opinion on the matter, see Mark Liberman’s post on languagelog.com.)

We’ve been through this before, perhaps most famously with apes who have allegedly been taught sign language. The most famous of these is probably the chimp Washoe, who starting in 1967 was taught American Sign Language (ASL) by Allen and Beatrice Gardner of the University of Nevada. Washoe and the other apes who have been "taught" ASL did learn a large number of signs and could apparently communicate simple concepts to their trainers. Their degree of mastery of ASL is disputed– independent observers have difficulty interpreting the signs and have noted that many of the responses given by the apes are actually prompted by the trainers. None of the apes ever learned the grammar or syntax of ASL. And claims that the apes have created new words, have attempted to sign to other apes as opposed to their human trainers, and have taught other apes to sign are undocumented. Finally, the apes have never been seen using ASL to solicit information from their trainers. Their use of signs is entirely reactive.

Part of the issue with the press confusing animal communications with language is a failure to grasp the essentials of how language is distinguished from other forms of communication. Many animals communicate, but only humans have language.

Linguist Charles Hockett devised a system of thirteen criteria for comparing different forms of communication. Human speech has all thirteen and by looking what criteria various forms of animal communication have, we can determine how close that communication is to speech.

The thirteen criteria are:

• Arbitrariness. The elements of the signal are not analogous to the real-world situation. Phonemes and words are arbitrary–the sound / kæt / has no real-world analog for a feline. The orientation and speed of the dance of a honey bee, on the other hand, is analogous to the direction and distance of the food source and is not arbitrary.

• Auditory-vocal channel. Sound is the medium for the message. This is true of all human languages, with the exception of sign languages for the deaf. Many animal communications, however, are visual, tactile, or auditory but not vocal (e.g., a beaver slapping the water with its tail as a warning).

• Broadcast transmission & directional reception. Any receiver within earshot can hear the signal and determine where the source is. Many animal communication methods share this criterion with language.

• Discreteness. The set of elements that compose the potential elements are limited in number and contrast with one another. Animal grunts and growls fail this criterion, but there are some animal communication systems that possess it.

• Displacement. It is possible to communicate about events remote in time and space. With a few exceptions, such as the dance of the honey bee, most animal communications do not possess this characteristic, although it is difficult to determine this for sure.

• Duality of patterning. The elements have no intrinsic meaning but can be combined into larger structures (e.g., words) that do have meaning. Generally, animal communications also lack this. Although some, like bird song, might possess it.

• Interchangeability. The message is the same regardless of who delivers it. Many animal communication systems, such as courtship signals, depend on who delivers the message–a female cannot meaningfully deliver the male courtship signal, for example. Some primate systems, like the calls of gibbons, are interchangeable.

• Productivity. There is a virtually infinite capacity to combine elements into new meanings. This varies. Some animal communications systems are productive, bee dancing for example. Others, such as warning or courtship signals, are not.

• Rapid fading. The signal is transitory. This is true of many animal communications systems, but not all such as that of marking territory with scent. Note the human writing and modern human recording media do not possess this either.

• Semanticity. The elements of the signal have stable meanings associated with them. Some animal signals have stable semantic content, such as the elements bee’s dance, others do not, such as a dog’s bark which has different meanings depending on the context.

• Specialization. The medium (sound waves in the case of language) has no purpose other than carrying the message. Again, this varies with some animal systems possessing it and others not.

• Total feedback. The sender can also hear the message and make corrections. Another mixed bag here.

• Traditional communication. The method of communication is taught to succeeding generations rather than being instinctual. Generally animal communications lack this, although some may be taught.

Where does dolphin "naming" fit into this?

• Arbitrary: Yes. The "names" have no real-world analogs.

• Auditory-vocal: Yes.

• Broadcast: Yes,

• Discrete: No. Janik’s demonstration that it is frequency modulation that is the key makes this system non-discrete.

• Displacement: No.

• Duality of patterning: Yes.

• Interchangeability: Yes and no. Dolphins use only their own names, not those of others.

• Productivity: Limited. There are an infinite number of possible dolphin names, but these are just names and other messages cannot be communicated. (It may be that dolphin "names" are only part of a larger system of communications that we don’t yet understand. In which case productivity may be generally characteristic of dolphin communications.)

• Rapid fading: Yes.

• Semanticity: Yes.

• Specialization: Yes.

• Total feedback: Yes.

• Traditional communication: Apparently no. Young dolphins appear to instinctually "name" themselves.

So, while dolphin naming shares many characteristics with human languages, it differs from language in several key aspects.

(Source: The Cambridge Encyclopedia of Language, 2nd Edition, David Crystal, ed., Cambridge University Press, 1997)

Department of Foot In Mouth

19 May 2006

Tony Snow, the new White House press secretary, got off to an inauspicious start at his first press briefing on Tuesday by using the term tarbaby when asked about the government collecting phone records on millions of Americans:

I don’t want to hug the tarbaby of trying to comment on the program, the alleged program, the existence of which I can neither confirm nor deny.

The term has a history of use as a derogatory term for African-Americans. Snow was using the term in its sense meaning an intractable problem that brings discredit to those who attempt to solve it and undoubtedly did not intend any offense, but he did display significant insensitivity in using it.

The term comes from 1881 Joel Chandler Harris story of Uncle Remus, where Brer Fox smears a doll with tar in hopes of using it to ensnare Brer Rabbit:

Brer Fox...got ‘im some tar, en mix it wid some turkentime, en fix up a contrapshun what he call a Tar-Baby.

From this original use, the term was extended to its metaphorical sense of a difficult problem. But by the 1940s, the term was being used as a racial epithet. From Sinclair Lewis’s Kingsblood Royal of 1948:

"I didn’t know she was a tar-baby."�"Don’t be so dumb. Can’t you see it by her jaw?"

Sometimes people take offense at words and phrases like nitpicking, picnic, or call a spade a spade, falsely believing there to be a history of racist usage in them. In such cases, people should not be afraid to use the term in question–if someone takes offense, one can simply point out their error. But in this case, the term does have a long history of racist usage. Snow would have been better served choosing a more neutral metaphor like playing in traffic or touch the third rail.