People thinking about the social and physical world around them are influenced by the social milieu in which they are born and raised. At one time there was a general consensus that the world was flat and that it was circled by the sun. Today the earth is seen as being a sphere which orbits the sun. In most societies only a small number of persons have the time necessary to confirm their perceptions. While given knowledge may be broadly shared by nearly all members of a particular society, it is not uncommon for the generation of such knowledge to be entrusted to a few persons, with its truth being accepted by other members of society merely on the word of the elected few. At the same time, the insistence of a very small number of people, which is generally accepted as fact or even as common sense in one era, is rejected in the next.