If one in 20 billion signals is transmitting a message in an encoding we don’t understand, on a time scale potentially completely different from our own.... I’m not confident.
If an intelligent life form exists out there and is advanced enough to ponder the meaning of life and if there is other life... and is intelligent enough to know how to send messages across the universe... and to encode them...
They would therefore be intelligent enough to know to/how to broadcast such a message in a way that can be universally understood.
Assuming it's possible both mathematically - in terms of an arbitrary encoding that we cannot explain away using standard physical phenomena e.g. quasars, and more importantly assuming it's actually possible from an engineering standpoint. All radio signals we send become indistinguishable from noise quite quickly.
I don't think we can realistically expect to detect anything beyond our galactic neighborhood- what could someone in another galaxy do to catch our attention? Trigger supernovas at an interval representing the Planck constant?
