I have recently listened to the tapes of the "Journey through the Tenth Dimension" lecture, given by Michio Kaku in 1989 (I think). He gave his idea of why we haven't found intelligent, extra terrestrial life. He used an illustration of an ant-hill. If you see an ant-hill, do you feel compelled to bend down to the ants' level, and teach them about technology, science, philosophy, and art? An intelligent extra terrestrial with space flight capability, is probably as far beyond us as we are beyond an ant. It's something to think about anyway (and I definitely suggest getting ahold of a copy of the "Journey Through The Tenth Dimension" lecture).