Thirty two years and counting - that is the length of time since the launch of Vayager II and with it earth's message in a bottle to the extraterrestrial aliens that if you are out there, say something. This was Carl Sagan's idea. he thought that while we are at it, sending space junk out beyond the solar system, we ought to see if someone is out there listening. More on the message.
We are still waiting.
When you think about it, the lack of response from the aliens out there is quite staggering. The earth after all, is over 4 billion years old and the universe itself, is 14 plus billion years old. Enough, already. Forget time travel, parallel universes, and worm holes. If someone, intelligent enough as we are, has been working on this problem of contacting intelligent life out there, and has failed for 10 billion years more or less, then the likelihood of finding intelligent life anywhere is slim.
Still, we keep trying.
I am reminded of Sisyphus, who was doomed to roll a heavy rock up a hill for eternity, only to have it roll back during the night so that he could start all over again. It is an existential nightmare, but it is our nightmare, and so we embrace it.