This hour, we’re talking about the challenge of being tiny Earthlings alone on a little planet in a corner of a vast and invisible universe. Of course there’s always the chance — maybe even a good probability — that we’re not alone. For more than 30 years, the scientists at the SETI Institute have been looking and listening for signs of extraterrestrial intelligence. Recently, some of them decided to get a bit more proactive. To find out how, Doug Gordon tracked down SETI’s senior astronomer, Seth Shostak.