Frontiers and Controversies in Astrophysics: Lecture 5 Transcript
January 30, 2007
Professor Charles Bailyn:
I have spent a very enjoyable weekend reading your Pluto comments. No, that
was fun. It is a surprisingly--it's a surprisingly deep topic. There are technical issues about how orbits of
planets work. There are these interesting cultural and political currents that underlie the whole thing. And
also some sort of deep philosophy, or what the literary professors like to call "theory," about what it
means--what it means to name something, and what the consequences of particular names are. And so I
thought I would make a couple comments on the Pluto thing first, before we get back to the Hot Jupiters.
Let's see. The first thing I would say--let me encourage you all, when you get this kind of a question--answer
the question that's asked. The biggest problem in the answers that I saw was that sometimes you just didn't
address the specific question that was asked. What I asked was, "To what extent is the Pluto controversy a
scientific controversy?" You don't answer that by a narrative describing what happens. If you say, "Well, they
discovered Eris, and then that threw the scientific world into confusion, and then they had this big meeting
and there was all this fuss, and then people started to get involved who weren't scientists," and so forth--that
doesn't answer the question. Because the question was, "To what extent is this a scientific controversy?"
There are two possible categories of answer to that question. One is, "Yes, it is primarily a scientific
controversy." And the other category is, "No. It was primarily not a scientific controversy." And if you didn't
say one of those things, or something somewhere in between, then that's not kind of responsive to the
question. I would say that you could answer that particular question in this case, in both directions, perfectly
well. If you want to make a case that it's a scientific issue, you say, "Look, classification is very important to
science." I made that point in class on--a week ago, and that, you know--you've got to have your
classifications right in order to understand what's going on. And what has happened? Here is--new data has
come in, which has thrown the old classifications into question. Although, it should be noted that there wasn't
officially a definition of "planet" that goes back to antiquity. And one of the things they were trying to do was
to create one. But that--as new data came in from the outer parts of the Solar System, we had to revise our
classifications. And this is a key point of science, and therefore the whole thing is, at root, a scientific issue.
But you could also argue the opposite, in that, you know, the scientific issue was not really in doubt. Nobody
was questioning whether Pluto and Eris and all those things ought to be in the same category as Jupiter.