Well...there are simple physical reasons why no alien civilization will cover the known universe; basically, the universe isn't old enough! You'd have to start waaay back, back when gravity was just starting to decouple, if you mean to have today's colonies out at the observable edge. Unless you violate light speed, which as an implicit violation of causality opens up a whole new can of worms... However. Moore's Law is but one of the observations that technological progress is at least geometric. That's inherent in Freeman Dyson's thinking, and also speaks to Moravec and his machine intelligences. The argument is as follows; double the time since the industrial revolution and we will be in a position to send generation ships and seed far systems with robotics. Repeat that interval, and we'll be dismantling stars for material. Repeat that interval again (always assuming we haven't destroyed ourselves) and we are in a position to make dramatic changes to the very look of the Local Group. Now recall that we spent tens of thousands of years playing with pointed sticks, and tens of millions of years being pond scum, and of course a good four billion years just waiting for the planet to cool down a little. Compared to the piddling thousand years needed to develop a truly stomping technology, if there are other civilizations out there the odds are that one of them woke up a little earlier in their historical morning and has already been there, done that. Hence Dyson's "Why the heck do we still see stars?" Of course, there are intriguing questions on whether our particular philosophical make-up is some unusual co-incidence of the evolution to intelligence of a competative omnivore. Or whether there are natural checks that occur a little further along the evolution of society and thought, that prevent the technological expansion out into the stars (or at least make it a little more eco-friendly). You touch apon the problem of information theory above. I think of it as the "pulsar problem" myself. Information theory basically says the higher the information density, the closer in form it comes to noise. Anything that repeats, pulses, shows any form of mathematic regularity, is a fit subject for compression algorithms to be applied to surpress the pattern. If there are civilizations out there choosing to have twenty-year pauses in their instant messaging chats, what little trickle of radio energy comes our way is going to be very hard to decipher from noise. And, of course, given certain theoretical limits (say, the natural RF noise of our stormy little envelope of air, and the static of cosmic rays dancing in the magnetosphere), reception gets efficient faster than transmission gains in power. Early radios pumped hella power into the air. Spirit and Oppy, on the other hand, are dependent on us doing some pretty sophisticated massaging of their miniscule signals. So, really, the only targets worth pointing an OZMA at are intentional ones. And as Sagan himself mentioned a time or two, it isn't like WE are sending a nice clear signal to possible friends out there. One hopes the aliens are a tad more altruistic. Or less practical than we are. Sounds like we've read many of the same sources, Kuroyume! (Now why don't we ever get into interesting stuff like this in chat?)