Actually, Sciencegeekgirl.com adds VERY MUCH to the article, namely a highly interesting discussion of WHY students give these wrong answers. No, it's not because they're stupid or ignorant.
Obviously, anyone who answers a question incorrectly is ignorant of the correct answer, but the point is that in many cases the wrong answer seems to be logically based on a wrong mental model of how gravity works. Just like Aristotelian physics. And Newtonian physics as well. Would you call Aristotle and Newton ignorant?
The interesting part is the discussion of what these wrong mental models look like and how you can teach a correct one.
Absolutely. There was much they did not know, as is true of anyone. "Ignorant" is not an insult, it simply means you do not know something. Would you say Aristotle and Newton knew everything about everything? If not, then they would be, by definition, ignorant of the things they did not know.
The problem is that they may know that the Moon has gravity, but they don't understand what that concretely means when it comes to questions like this.
I would dispute the validity of calling that state of mind "knowing that the moon has gravity". I would instead call it "memorized a couple of correlated keywords".
