I tell my students that I supremely hope that they have the experience of one of their cherished ideas shown to be wrong. I was recently confronted with a perception mistake on my part which I found to be pretty interesting, even if the consequences are pretty mundane. So, I'm learning how to swim, and I take lessons at the local YMCA. I have recently started practicing a little at the university pool. When I first started swimming at the university pool I noticed that it was significantly longer than the one at the YMCA…at least that is what I thought. I had told a number of people this, particularly how much longer it looked and how much longer it felt swimming to the other side.
I was told this past weekend that they are the same length, which I totally didn't believe. The swim instructor insisted that they are both 25 yards long, and that she has swim meets in both pools. Still skeptical, I did some digging. The university pool seemed, to me, to be 1.5 to 2 times longer! No way I could make a mistake of that magnitude! It felt much longer! It took longer to swim across!
They are the same length.
What I find very interesting is how certain I was of a completely physical measurement, that later turned out to be incorrect. There is something about how the pool had very few people at the university or had glass on each end, compared to the crowded YMCA pool which is walled in by cinderblock, combined with my inexperience with swimming which probably gives rise to the illusion. Or perhaps the fact that the YMCA pool is narrower adds to the illusion. Whatever it is, it was a completely obvious, visceral estimate of the length of an object that turned out to be completely wrong.
It reminds me of the sort of arguments that people make like "Air Force pilots will not make mistakes in observing things in the sky, which bolsters the UFO claim" or "Doctors will not make mistakes in observing medical effects, which bolsters this miracle claim." Arguments from authority fail because authorities can be mistaken, even on basic things.