I think especially as a science educator I feel pressure to always know things all the time. I have become very comfortable with saying "I don't know" and I do love to talk about uncertainty in science and things that even the great body of knowledge we call "science" has not yet learned. But still, whenever I do say those three words "I don't know" I strive to remember what it was that I didn't know and then learn it.
That's a very different experience from actively telling someone something that you, in the moment, believe to be true and then finding out later that you were wrong. I certainly try not to dwell on it but thinking about it I've found that this kind of mistake has one very beneficial side effect: there is no way I'm going to forget that information that I was wrong about. I'll remember it in a year. I'll remember it, I'm willing to bet, in fifty years.
This also ties in with a topic I think about a lot: misinformation and misconception. These are the science educators strongest opponents. And the strong negative feeling I have after making this kind of mistake is that I have, hopefully in a very small way, added to that great body of misunderstanding and misinformation instead of confronting and sorting through it.
Young children misunderstand stuff all the time though. So hopefully they'll just have forgotten.
What's your experience of factual mistakes in the classroom?