Calling Them Planets Is True to Word’s Root

Re “Plutonic Love Fades,” editorial, Oct. 12: In order to decide whether Pluto and the recently discovered Quaoar should be called planets, it is helpful, amusingly enough, to follow the approach of the father in the movie “My Big Fat Greek Wedding” who was always coming up with Greek etymologies for words. The term “planet” comes from the Greek word meaning wanderer, which was used in order to distinguish the then-known planets, which looked like stars, from the stars themselves, which seemed to be fixed in the heavens. Because the planets were observed to be constantly changing their position against the background of the so-called fixed stars -- indeed, their paths even performed loops due to their apparent retrograde motion (which we now recognize as due to the relative motion of Earth and planet) -- the term “wanderer” seemed appropriate.

With regard to Pluto and Quaoar, there is nothing in the term “wanderer” that pertains to size. There can be little wanderers as well as big wanderers, as any parent with little children will tell you. Thus, from an etymological standpoint, Pluto and Quaoar, as well as the asteroids, and the so-called Kuiper Belt objects, are all planets, all wanderers, but just of smaller size than the more prominent wanderers that we customarily call the planets.

Frank R. Tangherlini

Associate Prof., Physics (Ret.)

San Diego