Imagination is a wonderful thing and the overheard remark can be the beginning of a long conversation: point in case -- our evolving discussion of the planet/not planet Pluto.
Discovered in 1930, Pluto was once listed as the Solar Systems ninth Planet -- famously remembered in the mneumonic phrase 'My very eager mother just served us nine pizzas'. In 2006, Pluto was removed from the list of major planets and reclassified as a 'dwarf' planet. This was not an undisputed move... and there are those, including my sons, who still argue for Pluto's inclusion in the Major Arcana.
There are some anomalies about this little piece of ice, however. It's orbit is distinctly odd. Unlike the other astral bodies which orbit the sun in a flat plane, Pluto cuts through the plane at an angle. This brings it, on occasion, closer to the sun than does Neptune's orbit. Pluto is, it turns out, a part of a collection of icy astral bodies. This collection is called the 'Kuiper Belt', named after the astronomer who hypothosized its existence almost 40 years before it was discovered.
All of this we discovered listening to an interesting book on tape 'When is a Planet Not a Planet?: The Story of Pluto' The boys were fascinated. Actually, to be honest, so was I. It was disconcerting, to say the least, to have the skies as I knew them changed at the whim of the scientific community. Having some sense of why they change them -- and having a chance to argue the point, if only in my own home, gave me back a sense of control. And so the discussion began.
The first idea that was put forth came from my science fiction eldest -- at 8, Jason is a passionate fan of the science fiction genre. What if, he wondered, Pluto is really a space observation station, placed on the outer reaches of our solar system to monitor the happenings within? He was quite excited by this idea and so, when we arrived home, we set him up on the computer so that he could begin writing. I promised him that, if he finished writing the story, we would get the book published using the Blurb it site -- and perhaps even submit it to the 'Written and Illustrated by' contest. The younger brother was not to be outdone, however. This morning, early -- and I do mean, early -- 5:30 am to be precise -- he announced that his theory was simply this: Pluto had once been part of a much larger planet. There had been a massive explosion and Pluto, a small piece, had been BLASTED away. It was, therefore, truly a 'wanderer' as the Greek word 'Planete' implied. Moreover, the reason for its odd orbit was that it was new to the whole process and was so just 'learning' to orbit. No wonder it wobbles a bit!