[UnderseaLcpl]

@ Gargamel - Alright, I promised an explanation when I had time, and now it seems I have the time, so here it goes.

You say that SETI is searching for normal, everyday communications from other cultures. Any culture that would use any practical form of instant communication would be forced to rely upon electromagnetic waves.

Nothing in the universe, not even the most powerful stars or black hole mass-jets, can accelerate anything beyond the speed of light,and we can detect those, once they have travelled to us. If there were such a thing as an alien civilization that could project tight-beam comms without us intercepting their radiation bleed-off, we would have long since detected their thermal output. There is no such thing as undetectable energy output in space, especially when it requires exceeding the energy output to accelerate even a light particle-wave beyond the speed of light.