Not everything that is obvious today was obvious in the fifth century BC; for example, it took until the third century for Archimedes to point out that the numb

Not everything that is obvious today was obvious in the fifth century BC; for example, it took until the third century for Archimedes to point out that the number of grains of sand on the earth is finite. One could say that continuity and related concepts was not properly understood until the 19th century. In some ways, the knowledge of the average high school student today far exceeds that of the greatest geniuses of history.