In 1950, Nobel prizewinning physicist Enrico Fermi posed his famous paradox: if extraterrestrial intelligence exists, why haven't we found it?
Why indeed? It is not as if we haven't been trying. The search for extraterrestrial intelligence (SETI) has been going on for over half a century. It has mostly drawn a blank. But once in a while there is a flurry of excitement. Here are some of the highlights.To read more, click here.