PARIS, FRANCE—Since the International Astronomical Union (IAU) demoted Pluto to "dwarf planet" status in 2006, the peoples of the world have lived in fear of another planet being stripped of its rank in the solar system. The IAU shocked everyone, including its own members, yesterday with the announcement that Earth does not, in fact, fit the description of "planet."
Dr. Steven Foster of MIT spoke with The Colon to offer his explanation of the union's decision. "We definitely jumped the gun in claiming Earth was a planet," began the professor of over 30 years. "We should have known better, since astronomy is mostly guesswork and connecting dots in the sky. Even so, there are specific criteria a body must meet to be considered a true planet."
First, the object in question must orbit the sun. "The scientific community is still pretty sure about this one. Our assumptions about Earth's orbit haven't led us astray yet," offered the grandfather and space nerd. "Of course, we can't be 100% sure since they tell us not to look directly at the sun, but pretty much everyone in the IAU accepts that Earth meets this requirement."
Second, a planet must be massive enough to be roughly spheroidal. "This is where things get really hazy," Foster, 57, continued. "Nobody can see the earth from every angle all at once, so we have no way of knowing its true shape. Sure, we have some images of a pretty round-looking Earth, but who's to say that hasn't changed? For all we know, the camera lens shape is the reason the world looks like that." There is also debate among astronomers about the word "roughly" in the definition and just how spheroidal something must be to fit the bill. Due to all this uncertainty, the IAU has determined that Earth does not meet the second criterion.
Third, a planet must have "cleared the neighborhood" around its orbit. "This is where we lost Pluto," Foster explained. "It shared its orbit with some other bodies and had to be downgraded to 'dwarf planet' status." But what about Earth? "It gets tricky again since we can't see all of Earth's theoretical orbit at once. We tend to assume that our 'planet' has cleared its neighborhood since it maintains a moon, but for all we know, some sort of giant space yam could be just behind the sun, occupying our supposed orbit. Maybe it's constantly across the sun from Earth so we can never know if it's there." Unable to prove beyond a reasonable doubt that Earth is alone in its orbit, the union has retracted its planetary status based on the second and third criteria.
It is unclear what this change in title will mean for Earth or its inhabitants. Foster explained that the "dwarf planet" label doesn't quite suit Earth, so astronomers have taken to calling it a "space rock." "Again, that's assuming Earth is even made of rock," he quickly added, "I mean, I'm no geologist."