6004818 If the age of the earth was represented by the total number of letters in a book four times the size of this, the last letter would be roughly equivalent to the number of years man has inhabited the world (litho) by English School, (20th century); Private Collection; (add.info.: If the age of the earth was represented by the total number of letters in a book four times the size of this, the last letter would be roughly equivalent to the number of years man has inhabited the world. Illustration for General Knowledge Course (Odhams, c 1945).); by Look and Learn; English, out of copyright.