Somebody just read "The Mote in God's Eye."
Biven a civilization with the leisure, wealth, technology, and desire to tell others it has arrived. That is already a stupid idea. The wealthy keep a low profile lest the poor and motivated show up to seize a fat piece.
Remarkably, you it doesn't have emitters between deep radio and short microwave. Will it pop a laser at selected targets? First, it's a stupid idea: One target/emission. Second, it's a stupid idea: What if they are looking the other way when the light pulses arrive?
Third, there is no reason for SETI to seek unnatural IR or visible emissions against a star's background emissions. Standard astronomy, expecially the search for exoplanets, is already busting its hump exactly doing that to incredible sensitivity.
Here's the straight skinny: Physics is the same everywhere. High-powered (megawatt) radio and microwave are available to even primitive cultures. The Earth is sitting at the center of a loud EMF bubble more than 60 lightyears in radius. That is 905,000 cubic lightyears. We've already sent out our calling card. Nobody has RSVP.
SETI sees nothing. Perhaps technological civilizations very rarely arise. Perhaps they are common but suffocate themsleves in eventual compassion, diveristy, and god - losing the cutting edge that elevated them from the muck. The universe is undoubtedy dripping with life, almost all of it no better than sub-Saharan Africa.
When Terran First World civilization crashes between 2015 (Baby Boomer retirement) and 2050 (end of petroleum), it is not coming back.
