You do realize that signals we have sent out (Aricebo being the main one) haven’t even made it out of our arm of the galaxy yet? And wasn’t it SETI or some group that said any signals we have sent would have been reduced to background radiation levels around four light years out?
Also, assuming lightspeed is the fastest one can go, it would take a crazy long time to develop that technology, and as long to manage to send out signals (physical or EM) to a significant part of a galaxy. And then tens of thousands of light-years to the nearest galaxies to ours. The sheer distance makes any kind of expansion or contact very unlikely unless faster-than-light travel is possible.
Thanks for you comments. What you say is certainly true.
But I’m not talking about communications. I’m talking about signals from civilizations 10,000 or 100,000 more advanced than we are. Your point about a signal being in the noise 4 to 5 years out may well be true. But you may be able to increase the transmit pulse arbitrarily high with sources that we may have in 10,000 years.
And as I understand it you can pul a signal out of the noise at a s/n of 0 dB by integrating since the signal is correlated in some fashion while the noise isn’t.