On Sun, 3 Oct 1999, Robert Owen wrote:
> > Hal:
> > This leads to number 5, the classical approach of looking for beamed
> > or leaked signals. This really only makes sense if there are obstacles
> > which make interstellar travel infeasible. We can't rule this out, but
> > from what we understand it should be possible to travel to the stars,
> > although it may not be easy.
Precisely, if you can *see* where "aliens" are (likely), then it becomes a question of what do you want to do, communicate & learn or grow (colonize). One would expect that you may do both -- you colonize uncolonized places, which may occur slowly because you have to make sure that there isn't anyone else in the neighborhood who may beat you to the place you want to colonize. You have a lot more to lose in a failed colonization expedition than you do in simply sending signals to probable ETC and waiting for their response.
For humans, we might colonize stars within a 10 ly radius, but we wouldn't colonize out to the 2000 ly radius unless we can determine those worlds would not develop a competing intelligent ETC within the next 2000 years. There is clearly going to be a difference between colonization and exploration. Colonization (if you intend to send people, materials, etc. is expensive), exploration should be much less expensive. If both exploration & colonization come down to sending nanobots at high %c speeds to neighboring systems then the question shifts entirely to exploration and not colonization. It benefits me little to develop a remote star system unless "I" am in it to enjoy those benefits. It may benefit me a lot to send probes on exploratory missions that beam back information about the remote star system that is difficult to gather locally. However, the real limits of what you can gather locally vs. remotely needs to be rethought in term of nanotechnology growth rates.
>
> Again, I agree that optical and radio scans must be considered only a
> temporary expedient (with the possible exception of the placement of
> detection devices on the dark side of the moon). Dr. Tough, in fact,
> isn't entirely convinced of the ultimate effectiveness of RA SETI or
> OSETI.
Perhaps in part as a result of comments by Robert Freitas and myself.
>
> > Ultimately, it seems that there are three possibilities. Either there
> > are no (advanced) aliens, in which case SETI is not going to work.
If you make that assertion, you immediately are put in the position that the evolution of intelligent technological civilizations is very very difficult.
> > Or there are aliens and they are trying to talk to us, in which case we
> > have to wonder why SETI hasn't worked yet.
There are two answers to this -- we look at shining stars and shining stars are those not surrounded by ETC or evolution of intelligent ETC is difficult and there are only a very few or no ETC around our level around nearby stars. Current radio searches could only detect emissions from civilizations at our levels around stars out to a few dozen or hundred light years.
> > Or, third, there are aliens
> > and they are avoiding talking to us, in which case SETI is likely not
> > to work until they want to talk.
This seems probable unless there is a big piece of evolutionary history/probability that we are curently missing. But Allen's approach is worth considering. If they don't want to talk to you under normal circumstances, perhaps begging them will work...
> Not a good bet, but what other technological alternative to we have
> at this time, assuming that we did not choose to search, rather the
> search chose us.
Well, we could shift the emphasis from listening in radio & optical to "surveying" in the infrared. The surveys are what will tell us where there are "hot"/"warm" objects that do not fit standard stellar models. They are strong candidates for objects to whom we should beam signals, saying "Heaaalllooo, we believe you are watching us, so why don't you talk to us?"
Robert