Pluton or Planet?
Scientists at the annual meeting of the International Astronomical Union are apparently going to vote to let Pluto remain a planet and promote scores of similar bodies to that status. The proposed definition of a planet is:
"A planet is a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (b) is in orbit around a star, and is neither a star nor a satellite of a planet."
However, to make a distinction between the "classical" inner planets like the Earth, Jupiter and so forth, these smaller planets will also be called "plutons" with Pluto having the honor of being the first such celestial object discovered.
Does it make much of a difference calling one object a planet and another a pluton? As philosopher Ludwig Wittgenstein argued in his Philosophical Investigations: "Think of the tools in a tool-box: there is a hammer, pliers, a saw, a screw-driver, a ruler, a glue-pot, glue, nails and screw.—The functions of words are as diverse as the functions of these objects." The just as the word tool encompasses hammers, saws, and so forth, now the word planet encompasses plutons.
It's unlikely that schoolchildren will have to memorize the names of scores of new planets, uh plutons. After all how many of you can name all of the known moons of Saturn and Jupiter off the top of your head right now?