I wrote:
> To be effective you would want to send out multiple beams from deep space, > repeated for thousands of years, from an antenna orbiting the star or on the > surface of an airless planet . . . Even something as elaborate as this will > eventually cost a trivial amount. It seems to me that an intelligent species > would be motivated to do this as a favor to alien astronomers and > biologists. To help your distant intellectual colleagues. Bear in mind also that if there were, say, ~1 million civilizations doing this, many of them would have found one-another long ago. This would motivate them to redouble their efforts to find other alien civilizations, and take a census of the galaxy. Some would be within ~100 ly of one another, which in a sense is close enough for real-time communication. I mean they would not forget about one-another, and even if the species were as short-lived as we are, groups of experts would find it worthwhile to compose and transmit messages although they would not live to read the responses. People have conducted architectural and scientific projects that take centuries, such as building cathedrals. I assume these civilizations would eventually exchange huge amounts of information, including language. They might set up cooperative reverse-SETI projects. This would enhance the likelihood of finding still other civilizations because: They would have practice contacting alien civilizations, and they would be good at it. They would split up assigned areas of the galaxy. Each would re-broadcast messages from the other. Perhaps eventually dozens or hundreds of civilizations might join in an organized effort. If anything like this scenario was occurring, I think it is likely that we would have detected a "hello galaxy!" signal by now. - Jed
