Planet Debate Holds Lessons

Opinion: Disputes over details shouldn't neglect users' concerns.

The recent brouhaha concerning whether Pluto is a planet included arguments that reminded me of errors often made by the techno-elite. Im talking about the kinds of errors that shift the definition of success, turning an IT departments focus away from meeting the real needs of real users.

For those whove been more troubled lately by exploding batteries than exploding stars, let me review the bidding. It seems that the new definition of "planet" will be based on whether something is big enough for its own gravity to pull it into a spherical shape. This definition also adds other objects, like the asteroid (or "minor planet," as some have long called it) Ceres, to membership in the club.

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A much more radical redefinition that I heard proposed was that only Mercury, Venus, Earth and Mars should be termed planets at all—the gaseous bodies Jupiter, Saturn, Uranus and Neptune would be termed "failed stars." If you cant stand on it, this reasoning goes, its not a planet. This is an interesting position but too extreme to have much chance of traction.

The final argument I heard, and the one that set me off, was that planets should be identified by their role in the evolution of the solar system—that the label should be bestowed only on the significant objects that have swept clear the space around the sun, accreting the debris left behind from the process of forming that star.

Ceres, being merely the major chunk of the debris called the asteroid belt, presumably would not qualify. Pluto, part of the other mess called the Kuiper Belt, presumably would not, either. This "space sweeper" definition also solves the problems of Earths moon (the largest satellite in proportion to its primary), Saturns moon Titan and Jupiters moon Ganymede (the latter two larger than Mercury, and the largest natural satellites overall). These objects would logically remain mere "moons."

The person I heard advocating this argument seemed overly self-satisfied with his logic, asserting that this definition was somehow more true to the "essential nature" of a planet, to which I felt a real need to say, "Get over yourself." Arguing with the TV screen doesnt get me anywhere, but I wanted to remind that speaker that the very word "planet" was coined by simple folk looking up at the night sky, not by exo-geologists (or whatever you call a person who studies dirt someplace other than here).

The word "planet" comes from the Greek "asteres planetai"—meaning "wandering stars"—because objects that orbit the sun will sometimes look to an earthbound observer as if theyre moving backward against the background of the far more distant stars.

Id argue, therefore, that the essential nature of a planet is anything bright enough to be visible to the unaided eye, small enough that it doesnt show a visible disk without magnification and orbiting the sun closely enough to exhibit whats technically termed "retrograde motion." (Theres a nice demonstration of this behavior at

By this definition, Pluto is not a planet and never should have been. The folks who built New Yorks Rose Center for Earth and Space planetarium, at the American Museum of Natural History, figured this out back in 2001: As far as the Rose Centers main exhibit is concerned, there are only eight planets—and Im just fine with that.

With all this as a rather long prologue, Ill get to my point: A technically sophisticated in-group can easily forget why something is actually interesting or useful to people who dont study it for a living. The coder and chip-head communities are wonderful examples.

Arguments about one programming language versus another tend to focus on power and elegance, when the only real advantage that matters is a greater or lesser likelihood of producing more correct code in less time. Arguments about Windows versus Macintosh devolve into accusations of who stole what from whom, instead of which system makes it easier for more people to do more of what they want to do at less cost and with less support.

Its not about what things are called; its about the reason that they were ever interesting enough to be given a name at all. Specialists, in anything, would do well to remember that.

Technology Editor Peter Coffee can be reached at

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