Frank Drake became famous with his equation, in which he tried to estimate the number of "intelligent" civilisations in the universe. An intelligent civilisation would be a form of life that would be creative and curious enough to develop the technology to explore the universe and see whether other intelligent civilisations exist. The equation starts from the total number of stars, derives the stars with planets, derives the planets with the right conditions,etc. He came to the conclusion that the total number of intelligent civilisations in the universe was actually quite high, but that the different civilisations would live on average very remotely from each other.
Drake also started to work on a radio ground station (Arecibo) that could send messages into the universe and that could listen to signals from other stars that may contain an "intelligent" message.
Well after 40 years, the SETI work is not over yet. National Geographic reported in its July edition on the latest evolutions. The good news is that recent astronomy research revealed that there are actually much more suited planets than Drake conservatively estimated years ago. Moreover, recent biology research revealed that life can occur and flourish in much more severe conditions and on a much broader range of planets than we anticipated 40 years ago. The search for complex molecules on Mars and Jupiter's moons continues. Frank Drake, now 84, is still active (admirable) and would like to look for optical signals to pursue his quest for signs of extra-terrestrial life.
It is a fascinating thought but seen the distances, it remains unlikely we will receive a visit soon, let alone make a visit. On the other hand, every encounter of two civilations has always led to the destruction of the civilation being visited and to the success of the visiting civilisation. In other words, if we go there, it could happen we destroy another civilisation. If we are found here on Earth by another civilisation, we are likely to end up like the Indians after they had been found in Amerika in the 16th century. I refer to earlier blogs like Biosphere 2 and Guns, Germs and Steel.
