In 1950, Enrico Fermi asked a question.  It became known as the Fermi paradox.  He said that the size of the universe suggests that there should be many extraterrestrial civilizations.  So why had we never met them?  For over two centuries, we asked why.  Was Earth the only living planet?  Did other civilizations kill themselves off?  Where they avoiding us?  Had they been here and we didn’t recognize them?  There were so many questions.  We still ask many of them.