Astronomy frustrates me. I love physics, but I have little or no interest in astronomy and it really bugs me that when someone says ‘physics’ everyone seems to either think of ‘stars and planets’ or ‘photons and quarks’.
I recently listened to an episode of the ‘Science and City’ podcast from the NYAS which had a forum-style discussion on the topic titled “From Planets to Plutoids” (Mar 27, 2009). Discussed was the difficulty of defining objects in space, the history of the debate, various contemporary points of view and why (whether?) the debate is important.
It’s a mess. There are planets, planetoids, stars, asteroids, Kuiper Belt objects. They’ve been defined by their current physical properties, by their history, by location, by their orbit, by their relationship to nearby objects. Some planetary scientists care about defining objects from one perspective (perhaps the way in which they were formed, or their composition) and they fight against others such as dynamicists who care about the creating definitions from a wholly different perspective. Attempts by organizations (IAU) are considered by some to have failed and are, at best, reluctantly accepted by others for lack of better alternatives.
This type of problem must have been approached many times before in science. The analogy that struck me was that of attempting to categorize elements. As natural scientists from the perspective of physics and chemistry looked at the ever increasing number of elements in the world, they must have been similarly confused in their attempts to name and categorize them.
From that single podcast — I am happy to confess I am far from well-read on this subject — it seems to me that what astronomers are attempting to do is akin to as if we had attempted to categorize elements by their physical state at room temperature, or some similarly ‘intuitive’ but ultimately inappropriate approach. The problem seems to be approached in a haphazardly, ignored until a new class of objects is found and throws everything asunder. Imagine if a physicist attempted to change the very definition of an element so that he could cement his legacy by claiming to have found one.
Why has there yet been no Mendeleev in the world of astronomy? Are we so far from understanding our universe that a periodic table of objects is beyond our grasp? Or are there truly no fundamental properties — the equivalent of quantum numbers — to make such an attempt?