>I'm personally doubtful we could detect our own civilization today if we had a clone of humanity orbiting Alpha Centauri, and that's still well within our RF l

>I'm personally doubtful we could detect our own civilization today if we had a clone of humanity orbiting Alpha Centauri, and that's still well within our RF light cone. Why would we not be able to detect a clone of our civilization around Alpha Centauri? They're only 4 light-years away, so we should pretty easily be able to detect their TV broadcasts and other RF emissions at that distance. The main problem with SETI's approach I think is that it assumes RF emissions are strong enough to detect from huge distances (AC is the closest system to ours, everything else is farther), and that the ETs are at a similar level technologically and use strong RF transmitters rather than short-range spread-spectrum stuff, so that's a pretty short time window technologically, combined with the distance (it takes decades or centuries for signals to travel here from other star systems). But for a hypothetical humanity clone in the AC system, these problems don't hold, and we really should be able to detect them I think. The problem is, in all likelihood, any real civilizations are likely to be at a different developmental stage, and also to be much, much farther away than our closest neighbor.