One reason that it seems essential to leave the known for the unknown is that it is only bypursuing the unknown that we achieve a greater sense of how much we both do and do not know. Consider, for example, the development of ever-more-sensitive scientific instruments, such as microscopes. We can only know as much about tiny things as our microscopes allow us to see; the more we can enhance our ability to see, the more we are likely to know about things and processes that are often extremely important, even though they are literally invisible to the naked eye. The same is true, of course, of telescopes as well; the more we refine our abilities to see into the universe, the more we are likely to know about such matters as the potential existence of life on other planets, potential dangers from approaching asteroids, etc. etc.