Norm has a pop here at people, particularly those of a scientific bent, who can't accept the evidence of their own eyes. It's an important point. While a certain amount of curiousity about the world is charming, and perhaps even useful, it can too easily lead people to waste their time in fruitless speculation. Some things clearly speak for themselves: the sun self-evidently goes round the earth; light necessarily moves through a luminiferous aether; ill-health is unquestionably a result of imbalance among the four humours.
To even question whether what appears to be the case actually is the case can only ever be an exercise in futility.