(May 10, 2019 at 11:15 am)polymath257 Wrote: Let's do this. Suppose that technological civilizations pop up in large spiral galaxies every 50 million years or so. Suppose that they last, say, 500,000 years. Suppose that the signal they send out is strong enough to be detected to a distance of 100 million light years and they do so continuously for that 500,000 years. There are about 200 galaxies within that distance from us and about a 1 in 100 chance of overlap. So we would, in this extreme case, be able to detect 2 other civilizations.
ONLY if they use some system that we can detect.
