So many things we take for granted and consider sacrosanct are, in fact, simply wrong. For example, Napoleon was not particularly short. He was about 5' 7" and while not particularly "tall" was certainly not far from average.
Wikipedia has a very interesting collection of common misconceptions. A few are offered below and many more at the link.
- Searing meat does not "seal in" moisture, and in fact may actually cause meat to lose moisture.
- Microwave ovens do not cook food from the inside out. Microwave radiation penetrates food and causes direct heating only a short distance from the surface.
- Shaving does not cause terminal hair to grow back thicker or coarser or darker.
- Prolonged exposure to cold weather such as rain or winter conditions does not increase the likelihood of catching a cold.