> Alien civilizations have found such a vastly superior method of communications that they have given up on electromagnetism as a method. There are a lot of pr

> Alien civilizations have found such a vastly superior method of communications that they have given up on electromagnetism as a method. There are a lot of problems with this idea and it comes up predictably in every SETI discussion ever. For starters the inverse square law makes it extremely unlikely any two civilizations would ever detect each other's spurious emissions. Omnidirectional sources of EM radiation readily detectable at interstellar distances are called stars. If you tried to build an omnidirectional gigawatt TV transmitter it would melt itself rather than transmit anything. So the only way any civilization will have a signal detected by another is if they send an intentional and high gain (highly directional) signal towards other stars. To that end the universe is filled with natural EM sources. Everything from the Big Bang to stars to giant clouds of gas emit some EM radiation. Even a planet like Earth with a strong magnetic field and a dense relatively moist atmosphere can see a large number of EM bands from the surface. Even if some alien civilization uses sub-etha quantum blockchain to send e-mail it doesn't matter in terms of interstellar signals. Even on Earth a majority of our communication happens over cables (copper or fiber) or transmitters optimized for terrestrial reception. Our terrestrial communication systems might as well be sub-etha quantum blockchain since they're not useful at all for interstellar communication or detection. Unless there's lots of natural sources of sub-etha quantum blockchain radiation there's not going to be many sub-etha quantum blockchain astronomers. There will be radio and visible (IR and UV included) EM astronomers because the universe is full of that radiation. If a civilization wants to send a detectable signal it's more likely to do so in the EM spectrum than some spectrum where alien astronomers are unlikely. Of the EM spectrum it's also most likely intelligent civilizations would pick bands near natural sources. That way another civilization mapping has clouds or surveying pulsars might stumble across the signal. It's entirely possible a civilization only broadcasts on sub-etha quantum blockchain because they're only interested in other civilizations with that same technology. It's pointless to wonder about them. They might as well not exist as far as we're concerned. You might as well try to deduce the mating habits of unicorn dragons. They have the same level of influence on humanity as the sub-etha quantum blockchain aliens.