Martin Hendry, a senior lecturer in astronomy at Glasgow University and member of the IAU, said: “Unless the science underlying this is rigorous, how can we expect to agree on a definition that will be not only understood by ourselves, but other forms of life if and when we encounter them?” ~Scotland on Sunday

I know I wake up in the middle of the night wondering, “Will the alien visitors understand our system of defining planets?”  Don’t you?  My guess is that if we ever come across other intelligent forms of life somewhere in the galaxy, they would immediately have nothing to do with us if they knew how ridiculous we were capable of being over defining the number of planets in our own solar system.  For the sake of future interstellar goodwill, the IAU needs to stop meddling with a perfectly decent, arbitrary number of planets.   

When the IAU started fiddling with the definitions of what it meant to be a planet, I suspected nothing good could come from it.  Then, after the brief “pluton” compromise–which all other scientists hated because it infringed on their own plutonian terms–we found that Pluto had been cast down to “dwarf planet” status.  Now others are (sort of) going after Neptune:

Harold Weaver, from the John Hopkins University Applied Physics Laboratory and a New Horizons project scientist, said: “Since many ‘Plutinos’, including Pluto, cross Neptune’s orbit, I’d say Neptune’s neighbourhood still needs some clearing.”  

This is, of course, completely logical given the guidelines used to demote Pluto to “dwarf planet.”  But what would we call Neptune?  Would it fall under the category of “gas giant-with-cluttered-orbit”?  Bit of a mouthful.  But it is time that somebody draw a line somewhere to stop this madness by making an appeal to the beautiful arbitrariness of tradition.  Pluto was declared a planet 90 years ago, and in those ninety years we have since discovered that it has a moon (or, for the anti-Plutonians out there, a sizeable neighbour).  Pitiful little Mercury doesn’t even have a moon, nor does Venus, so why pick on Pluto because it’s so small?  It sounds like interplanetary bullying to me.  Ninety years may not be much in the world of astronomy, or even in human history, but it’s long enough to establish a fine tradition.  If this means that we have to make makeshift categories to accommodate Ceres, Charon and the abominably nicknamed Xena, we should do so, but what is unnecessary to change is unnecessary to change.