It's not that we hadn't noticed it before. It's that we hadn't thought about it before. We all knew from experience that none of us had gotten any sort of tan

It's not that we hadn't noticed it before. It's that we hadn't thought about it before. We all knew from experience that none of us had gotten any sort of tan through glass when asked. We just never thought to think about why. And before that day, we didn't know enough to answer the question. The fact that we were "primed" is just happenstance because the question came up during the learning process. Once we knew the physics (which all HS students in the US learn), the same question(s) could have been asked on another day when we weren't "primed" with the discussion and we would have been able to deduce the answer. For example - if that anecdotal evidence never came up the teacher could have put it on the final exam and we should have been able to figure it out. Again, my point is that anyone who went through the US school system and theoretically has the capability of answering the question if they actually thought about it. But most don't. That was my only point, really. It should be common sense, but isn't because no one actually gives it any consideration.