Are we alone?
I have always been fascinated with the idea that we may not be the only intelligent life in the universe. The trouble is, we have absolutely zero evidence for any life beyond Earth, let alone intelligent life. But that doesn't stop me wondering about it. I spend a lot of time talking to SETI people who are actually looking for intelligent aliens using radio telescopes. I am even on the SETI post-detection committee, so if these people succeed, I'll be among the first to know! My own personal wacky idea is that ET may have left a message for us encoded in the genomes of terrestrial organisms, delivered by viruses, and that we should use gene sequencing to search for 'something fishy.'