As you read in the title, I have been thinking these things quite for a long time. What if a bigger catstrophic event happen to earth with unimaginable kind of disaster leaving only some people on earth and destroying all that man made technologies and books. How many years will it take man to be restored to this stage of technology and knowledge? I.e if man starts from scratch can he realy make it to reach this time's level of technology? Having this Idea, I always thought that every kind of knowledge needs to be reserved may be in an audiovisual format describing how to do things from scratch. Say how can we ever make metal? This knowledge needs to be put into audiovisual format describing every bit of the process of making metal. And this knowledge needs to be stored in a safe place on earth and on space. This I think can help restore the knowledge and level of growth on planet earth. This catastrophic event may never happen but if it does anyways, what do you say?