Monday, September 8, 2008

"Pluto Is Not A Planet... Get over it." --Neil deGrasse Tyson

As Randall Munroe reminds us in his often witty and memorable comic xkcd, there are many different emotions still involved in the discussion of the planethood of Pluto and other objects in our Solar System and it's been over 2 years since the demotion. In the past, I've found myself to take a somewhat middle of the road position. Pluto used to be a planet, but is no longer. Plain and simple. I've even used the moniker PlutoWasAPlanet for XboxLive and other internet services and it always attracts laughter when I mention the name to people.

And that's how I feel we should approach something like this - with laughter. One of the most popular groups on Facebook is the When I was your age, Pluto was a planet group - there are over 1.3 million users in the group. I used to be one of them until I read more and found out just how different Pluto is from the rest of the bodies in our solar system that we call planets.

According to Resolution B5 by the International Astronomical Union (IAU), the definition of a planet is as follows:

A planet is a celestial body that

  • (a) is in orbit around the Sun

  • (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and 

  • (c) has cleared the neighbourhood around its orbit. 

Further down in the resolution, Pluto is specifically reclassified as a "Dwarf Planet" by the established definitions. Thus Pluto is not currently a planet, but Pluto WAS a planet at one point. As the above comic illustrates though, perhaps Pluto never should have been called a planet. As Neil deGrasse Tyson points out in a transcript from Nova ScienceNow, we have faced this problem before:

NEIL deGRASSE TYSON: Did you know that in 1801 a new planet was discovered orbiting between Mars and Jupiter?
ROBERT KRULWICH: Neil deGrasse Tyson is director of New York's Hayden Planetarium.
NEIL deGRASSE TYSON: They called it Ceres. And they looked some more, and they found another planet, and another and another. The count of planets in the early 1800s was greater than it is today, thirteen planets in the solar system. And they kept looking, and the numbers kept growing. And they were running out of names, and they realized that, rather than counting new planets, they had discovered a new swath of real estate in the solar system called the asteroid belt.
ROBERT KRULWICH: So Ceres became an unplanet, and was re-designated to a new class. And it became the biggest asteroid.
NEIL deGRASSE TYSON: So we've been there before. We know how to demote something.

Of course, back in the 1800s, we presumably hadn't established the mnemonic devices those of us learned in elementary school and hold onto so dearly. Don't lie - you remember the one you were taught. Mine was "My Very Eager Mother Just Served Us Nine Pizzas." I guess now it should be changed to "My Very Eager Mother Just Served Us Nothing." The 'P' in Pluto now stands for the period in the sentence. Pluto has become nothing more than punctuation, but without that punctuation we'd have an incomplete thought, so it still plays a vital role in the structure of our Solar Sentence System. I suggest that in the future we all take a scientifc approach to similar events should they happen again. We should be light hearted and not become angry with science when an idea or notion we cherish has been changed. That just means science is doing its job in establishing logical rules that we can follow in the classification of objects instead of catering to people that love a cartoon dog so much that it bled into astronomy.

Of course, I wonder how the world will react when more people realize that When I was your age, the Brontosaurus was a dinosaur.

1 comment:

Steneub said...

Okay, now you're just stirring the pot with that Brontosaurus comment.